NBS MONOGRAPH 51

|. Q_ TTV A

Analysis of Electric Energy

Usage in Air Force Houses

Equipped With Air -to -Air

Heat Pumps

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
THE NATIONAL BUREAU OF STANDARDS

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Documents, Government Printing Office, Washington 25, D.C.
UNITED STATES DEPARTMENT OF COMMERCE • Luther H. Hodges, Secretary

NATIONAL BUREAU OF STANDARDS • A. V. Astin, Director

Analysis of Electric Energy Usage in

Air Force Houses Equipped With Air-to -Air Heat Pumps

Paul R. Achenbach, Joseph C. Davis, and William T. Smith

National Bureau of Standards Monograph 51

Issued July 13, 1962

For sale by the Superintendent of Documents, U.S. Government Printing Office Washington 25, D.C. - Price 30 cents

Contents

Page

1. Introduction 1 2. Description of sample houses 2

3. Analysis of data 3

3.1. Monthly electric energy use 3

3.2. House heating by range, water heater, and miscellaneous

devices 5

3.3. Correlation of energy requirements for heating and heating

degree-days 6

3.4. Correlation of energy requirements for cooling and cooling

degree-days 8

3.5. Conditions affecting maximum power demand for the housing

area 10

a. Load factor 10

b. Daily pattern of power demand 12

c. Coincidence of component and total power demands in the sample houses 15

d. Frequency distribution of power demand values 28

3.6. Relation of maximum demand for the entire airbase to that

for the housing area only 30

4. Summary and conclusions 31

5. Methods of limiting maximum power demand in the housing area 32

6. Comparison of annual energy use in 16 sample houses with other

published information 33

(in)

Analysis of Electric Energy Usage in Air Force Houses Equipped With

Air-to-Air Heat Pumps

Paul R. Achenbach, Joseph C. Davis, and William T. Smith *

An analysis was made of the electric energy usage for all purposes in 16 samples houses

selected from a total of 1,535 houses constructed at Little Rock Air Force Base to domicile

Air Force personnel. Of principal interest was the energy used by the air-to-air heat pumps

installed for all-year air conditioning and the effect of electric energy used by other appliances on the heating and cooling loads in the houses. The data revealed that the annual energy

usage in the 16-house sample averaged 25,300 kilowatt-hours per house, of which approximately half was used by the heat pump and its auxiliary resistance heaters, about one-fourth was used for water heating, and the remaining one-fourth was used for the electric range and

miscellaneous devices. It was determined that the energy used by appliances, other than the

heat pump, which contributed toward heating the house was about half the amount used by

the heat pump during the winter months. An analysis of the demand charts revealed that the monthly maximum power demand for the entire housing area was probably caused by

a moderately high sustained demand in many houses rather than a coincidence of the maximum demands in a smaller number of houses. The effect of several types of programing

devices on the pattern of power demand is discussed.

1. Introduction

A significant number of the new homes in the

United States now employ some air conditioning

in them for summer cooling. The use of a heat

pump for year-round air conditioning is naturally

of interest to any homeowner who has decided

upon, or is considering, cooling for his entire

house. Within the last few years air-to-air heat pumps of the remote type have been installed

in a number of large housing projects at U.S.

Air Force bases in several Southern States. The National Bureau of Standards conducted a study of the heat-pump sA'stems at three airbases

and of the gas heating and separate air-conditioning systems at three additional airbases, under the

sponsorship of the U.S. Air Force, the Office

of the Chief of Engineers, and the Bureau of Yards

and Docks, to obtain data on energy usage, system

performance, house heating and cooling requirements, and other design data. One part of this study, which is presented in this Monograph,

consists of an analysis of electric energy usage and

electric power demand data obtained from a sample group of occupied houses at Little Rock

Air Force Base in Arkansas, equipped with heat

pumps, water heaters, cooking ranges, clothes

dryers, and miscellaneous appliances all operated

by electricity.

The Arkansas Power and Light Company, the

electric utility that serves the Little Rock Air

Force Base, collected electric energy consumption

data on 16 houses in the housing area from October

1958 until the spring of 1961, using four or more demand meters on each house to record separately

the energy and the power demand used for the

electric range, the electric water heater, the heat

pump, including supplementary heaters, and the

total for the house on a 15-min demand interval.

*Mc-chaniail Engineering Consultant for Refrigeration and Air Conditioning, Directorate of Civil Engineering. Headquarters, U.S. Air Force.

Also recorded were the indoor air temperatures

in each of the houses and outdoor air temperatures

at three separate stations in the housing area. The total monthly energy use indicated by these

four meters in each of the 16 houses has been summarized by Arkansas Power and Light Company

personnel.

The monthly summaries of the energy usage,

the original charts from the recording demand

meters, and the temperature records were made

available to the National Bureau of Standards for further analysis. The purpose of this analysis was to develop the following information for the

sample houses from these records:

(a) The amount of electric energy used by the

occupants for cooking, water heating, house heating and cooling, and miscellaneous purposes;

(b) an electric energy usage factor relating the

energy used for heating or cooling, the average

severity of the weather as indicated by degree-days,

and the inside floor area of the house

;

(c) a computation of the contribution of the

electrical equipment, other than the heat pump,

to the heating of the house in the winter and to the cooling load in the summer, based on metered

energy values and some assumptions regarding the

fraction of the metered energy that was effective

in warming the house;

(d) the components of the electrical equipment

that contributed significantly to the monthly

maximum 15-min power demands in the 16 sample

houses ; (e) the frequency of recurrence of 15-min power

demands of various magnitudes;

(f ) one or more ways to effectively reduce the

maximum power demands for the entire bousing

area without unduly altering the living habits of

the house occupants.

1
2. Description of Sample Houses

The identification of the 16 houses used for the

study with respect to location, type of house, floor area, exterior gross wall area, window and door

area, number of bedrooms, and nominal capacit}*

of the supplementary resistance heaters is summarized in table 1. House t}7pes A, Ai, B, and

Bi were used to domicile airmen., and house types

C, D, E, F, and G were used primarily to domicile

officers. House types A! and Bi were of duplex

construction with carports adjoining, as illustrated

in figure 1 ; house types A, B, C, and D were of

duplex construction with living quarters adjoining

and carports at either end; and the remainder were of detached design. All houses were of

single-story construction built on concrete slabs on grade. Perimeter insulation of the floor slab

consisted of 2 in. of rigid polyst}Tene foam. The

insulation in the walls and ceiling consisted of 4

and 6 in. of glass fiber, respectively. All of the

sample houses were equipped with a single heat

pump having a nominal cooling capacity of 27,000

Btu/hr, except houses numbered 467 and 468,

which had two such heat pumps in them.

There were 1,535 houses in the housing area, so the sample that was used for this study repre- sented about one percent of the total. The sample

included six 2-bedroom units, eight 3-bedroom

units, and two 4-bedroom units. The entire

housing area was comprised of 465 2-bedroom

units, 1,067 3-bedroom units, and twelve 4-bed- room units. It is evident from these figures that

the proportion of 4-bedroom units was much greater in the sample group of houses than for the entire housing area and that the proportion of 2-bedroom houses was somewhat greater in the

sample than for the entire group.

The occupancy of the sample houses for the

period from June 8, 1959, to March 8, 1960, as reported by the housing officer at the airbase, is summarized in table 2.

Table 2. Occupancy of sample houses

House

No.

Period Occupied or vacant Rank of occupant

Size of family

4 June 8, 1959 to Mar. 8, 1960- Occupied M/Sgt... 2 adults.

14 June 8, 1959 to Mar. 8, 1960. Occupied M/Sgt... 2 adults.

1 child.

74 •> Hill Ot lifUf L'J . O, AlJUU- W( I. u pit U, 9 Orlllltc 9 children.

163 U( i

1 1 | 1 fbgl 9 o rl 1 1 1 f c 9 £, (Kill US, J children.

172 Time 8 IQ^Q In "NTnv 9t

1959 Nov. 25, 1959 to Dec. 1,

Vyl_l tlJ'H U. . Vacant.

9 i (1 nit

o

i, :' lull -.

1959. Dec. 1, 1959 to Mar. 8, 1960. Occupied M/Sgt... 2 adults, 5 children.

180 June 8, 1959 to Mar. 8, 1960. Occupied... T/Sgt... 2 adults, 1 child.

263 June 8, 1959 to Mar. 8. 1960. Occupied T/Sgt... 2 adults, 2 children.

301 June 8, 1959 to Mar. 8, 1960. Occupied S/Sgt.— 2 adults, 2

children.

467 June 8, 1959 to Mar. 8, 1960 Occupied Col 2 adults, 3

children.

468 June 8, 1959 to Mar. 8, 1960. Occupied Col 2 adults, 3 children.

577 .Tune 8, 1959 to Mar. 8, 1960. Occupied Col 2 adults, 3 children.

585 June 8, 1959 to June 30, 1959. June 30, 1959 to Aug. 4, 1959.

j\. A no- u A IQ^Q fn TTol-» A 10fiH ji . iyoy lo r e u. iyou Feb. 4, I960 to Mar. 8, 1960 June 8, 1959 to Mar. 8, 1960

Occupied.... Vacant

Capt— - 2 adults, 2 ch ildrcn

.

Occupied Vacant

i;t t

587 Occupied cwo... 2 adults.

656 June 8, 1959 to Oct. 30, Vacant

Oct. 30, 1959 to Mar. 8, 1960. Occupied 1/Lt 2 adults, 3 children.

770 June 8, 1959 to Mar. 8, 1960 Occupied Capt 2 adults, 2 children.

843 June 8, 1959 to Nov. 7, 1959 Nov. 7, 1959 to Mar. 8,

Occupied Vacant

1/Lt 2 adults, 1 child.

1960.

Table 1. Identification of sample houses

Street address of house

114 Minnesota Circle... 122 Mississippi Loop...

110 Missouri Circle 129 Georgia Avenue

189 Pennsylvania Drive

102 Florida Avenue

115 Idaho Circle

126 Montana Circle 103 Arizona Drive

105 Arizona Drive

102 Alabama Drive

122 Illinois Drive

130 Illinois Drive

129 Iowa Circle

123 Louisiana Drive

127 Michigan Circle

Contractor

identifica- tion No.

4 H

14 A,

74 B

163 Bi

172 B

180 A

263 A

301 A,

467 F

468 G

577 E

585 C

587 D

656 D

770 E

843 C

House type No. of bed- rooms

Floor area

Gross

ft 2 1,070 970 1,070

1,070

1,070

970

970

970

1, 680

2, 050

1, 190 1,050

1,100

1,100

1, 190 1,050

Ill-Mr

891 1,013 999

1,013

891

891

891 1,553 1,900

1,115 999

1,046

1,046

1, 115 999

Ext. gross wall area

ft2 1,056

992 832

1,056 832

768

768 992

1,456 1,604

1, 176 832

916 916

1,176 832

Window

and door

area

ft2 219

180

193 219

193

153

153 180 266 267

267

166

193 193 267

166

Nominal ca- pacity of sup- plementary re- sistance heaters

kw

5.4

3.6

5.4 5.4

5.4

3.6

3.6 5.4

7.2

7.2

7.2 3.6

5.4

5.4

7.2

3 6

2
Figure 1. A typical type Bi 3-bedroom house with carports adjoining.

3. Analysis of Data

3.1. Monthly Electric Energy Use

The average monthly electric energy use per

house for each of the major components comprising the load and for the entire house was

determined for the sample houses as a group and

also for the 2-bedroom, 3-bedroom, and 4-bedroom

houses as subgroups. These monthly averages

have been summarized in table 3 for the period

from October 1958 to March 1960, inclusive. The

sample consisted of 11 to 15 houses prior to June

1959, since not ah of the 16 houses chosen for

study were initially occupied. The average

monthly energy use for the heat pump, the water

heater, the kitchen range, and miscellaneous

devices in each subgroup and for the entire sample

are also shown as a percentage of the corresponding average total house energ3T use. Since the

miscellaneous devices of the house such as lights,

television, clothes dryer, and resistance heater in

the bathroom were not metered separately, the

energy use of these devices was determined by

subtracting the sum of the usages of the heat

pump, the water heater, and the range from the

total energy use of the house.

The average monthly energy use for the several

components of the total load in the sample houses

is plotted in figure 2 for the period from October

1958 to February 1960. The average monthly

energy use per house for the entire housing area is

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also plotted as a dashed line in figure 2 for comparison. This latter average represents an in- creasing number of occupied houses starting with

about half of the total in October 1958 and

increasing to 1,535 in June 1959.

It will be noted in figure 2 that the energy use for the heat pump and for the entire house reached an

annual maximum in the middle of the winter and a smaller maximum during July and August. Two

minimums of energy usage for the heat pump and

for the house as a whole occurred during the year,

in April and October, approximately, when little heating or cooling was required. The winter maximum use of energy was approximately twice the

summer maximum. The energy use for the water

heater, the kitchen range, and the miscellaneous

devices was relatively more stable throughout the

year, although the minimum use of energy for water heating and the miscellaneous devices oc- curred in July and the maximums occurred in the

colder months of the year. Figure 2 shows that the average monthly energy

use per house for the 16 houses was very close to that for 1,535 houses for the period from July 1959

to February 1960 when the base was fully occupied, despite the disproportionate number of large

houses in the 16-house sample.

Considering the average values for all the sample

houses after March 1959, table 3 shows that the

energy used for the heat pump ranged from a low

value of about 30 percent of the total load during

spring and fall to a value between 50 and 60 per- cent during the middle of the summer and winter;

the energy used for water heating ranged from

about 15 percent in the middle of the winter to a

little over 30 percent in the spring and fall; the

energy used for the kitchen range was 5 percent or

less of the total throughout the year; and the

energy used for miscellaneous devices ranged from

20 to 30 percent of the total most of the time.

Considering the 2-bedroom, 3-bedroom, and 4- bedroom houses as separate subgroups, table 3 shows that for most months of the year the energy

used for the heat pump and for water heating in- creased with the number of rooms, whereas the

energy used by the electric range was usually the

greatest in the 3-bedroom houses, and the energy

used for miscellaneous devices was rather inconsistent with respect to house size. The energy used in the sample houses for each

component of the total load and the percent of the

total represented by each component is summarized in table 4 for the 12-month period from

March 1959 to February 1960, inclusive. It should

be noted that only 15 houses were occupied during some months of this period.

Table 4 shows that the total energy used by

the heat pump for heating and cooling on an

annual basis was slightly less than that used for

all other devices combined. The annual energy

usages for water heating and miscellaneous devices were each about half as large as that for the heat pump.

Table 4. Average annual energy use in sample houses

Component of load Total energy used

Percent of

total

Heat pump .__ .__ kw-hr

12, 290

6, 135

965 5,905

48.6

24.3 3.8

23.3

Water heater _ _ . _ Range - — Miscellaneous (by difference) Total _ 25, 295 100.0

3.2. House Heating by Range, Water Heater,

and Miscellaneous Devices

It is known from experience that the energy

used by an electric range, an electric water heater,

and the miscellaneous devices in a house makes

some contribution toward warming the house in

any season of the year. This auxiliary heating

reduces the load on the heating system in cold

weather and increases the load on the cooling

s}^stem in hot weather.

It is probable that all of the energy input to the cooking range assists in warming the house

with very little time lag except for the water

vapor, generated by the cooking processes, that

escapes from the house in the wintertime without

being condensed. During the cooling season the

water vapor produced by cooking would add to the latent cooling load on the heat pump and the

sensible heat emitted from the range would add

to the sensible cooling load of the heat pump.

For this analysis it was assumed that all of the

electric energy used by the cooking range was

effective in warming the house.

The jacket heat losses from the water heater

would warm the house winter and summer, if the

heater were located in the occupied space, and a

variable fraction of the heat in the warm water

used for bathing, dishwashing, and laundry would

be transferred to the air in the house as sensible or latent heat. Observations of the electric energy

required to maintain storage temperatures in the

water tank in some of the sample houses during

the night when no water was being drawn indicate

that the jacket loss of these water heaters was

8 to 10 percent of the total monthly energy used

for water heating. To make some allowance for the heat transferred to the air in the house from

the hot water during use, it was assumed for this analysis that 15 percent of all the electric energy

supplied to the water heater was effective in

warming the house.

It is probable that all of the electric energy

used by electric lights, resistance heaters, toasters,

radio and television sets, and nearly all of the

energy used by an electric iron would be converted

into heat that would assist in warming a house.

The situation with respect to an electric clothes

dryer is less definite. Although there would be some heat transferred to the room from the jacket

of the dryer, these devices are usually equipped

with a small blower which uses room ah- to carry

the water vapor and some sensible heat outside

635728—62 2 5
during the clothes-drying process. Such a blower,

when in operation, would increase the infiltration into the house, and create a heating requirement

that would probably more than offset the jacket

heat loss in cold weather. In summer the clothes

dryer would increase the cooling load somewhat.

For the purpose of this analysis, it was assumed

that the clothes dryer contributed nothing toward

heating the sample houses and that all of the

remainder of the energy used by miscellaneous

devices was converted into heat within the house.

The electric energ3r used by the electric clothes

dryers at Little Rock Air Force Base was not

metered separately from the other miscellaneous

loads. However, the energ}7 used for this purpose

in 15 sample houses at 3 other airbases where

it was metered separately averaged about 100

kw-hr per house per month. Accordingly, the

energy used for miscellaneous devices in the

houses at Little Rock An1 Force Base was cor- rected by subtracting 100 kw-hr from the monthly

totals reported in each case where the monthly

total exceeded 100 kw-hr.

On the basis of the foregoing assumptions, the

monthly contribution of the electric range, water

heater, and miscellaneous devices to house heating was determined by the following expression

:

kw-lirA =kw-hrR +0.15 kw-hrw + (kw-hrM— 100)

where kw-hrA is the computed contribution of

all appliances, other than the heat pump, to house heating in kw-hr/month, kw-hrR is the

metered electric energy use of the electric range

in kw-hr/month, kw-hrw is the metered electric

energy use of the electric water heater in kw-hr/

month, kw-hrM is the electric energy used by

miscellaneous devices in kw-hr/month.

This formula has been used later in this report

for deriving one of the three factors for energy

used per degree-day per 1 ,000 ft2 of floor area for the sample houses at Little Rock Air Force Base.

It is recognized that this formula could probably

be improved in accuracy by a careful study of

the heat dissipation characteristics of the various

electrical appliances, as used in a house.

3.3 Correlation of Energy Requirements for

Heating and Heating Degree-Days

Heat requirements for residences of similar

construction in different climates and for different

months in the same climate have often been

compared on the basis of the number of degreedays occurring in each locality or in each time

period. The heat requirements of houses of

similar size and construction are related to the

length of the exterior walls and to the inside floor area. In an effort to correlate the energy re- quirements of the 16 sample houses at Little

Rock Air Force Base during the heating season,

3 different energy-usage factors were determined

for the months of October, November, and

December of 1959 and for January and February

of 1960. These factors relate the electric energy

used and the inside floor area for each of the

sample houses to the degree-days and have the

units kw-hr/degree-day (1,000 ft2). The data

involved in determining the factors and the factors

themselves are summarized in tables 5 to 9, inclusive, for the 5 months studied.

The three energy-usage factors shown in tables

5 to 9 each involved the inside floor area of the

house, but employed different values for the

electric energy used for heating the house or

different bases for computing the degree-days.

The first factor was computed from the electric energy used by the heat pump plus the contribution to heating made by all other appliances and

the degree-days related to a 65 °F base. The

second factor was computed from the electric

energy used by the heat pump only and the degreedays related to a 65 °F base. The third factor was computed from the electric energy used by the

heat pump plus the contribution to heating made

by all other appliances and the degree-daj^s based on the difference between the monthly average

indoor and outdoor temperatures.

Degree-days based on an indoor temperature

of 65 °F were determined by one or both of

the following two methods. In one method the

maximum and minimum outdoor temperatures

for each clay were taken from the temperature

recorder charts and averaged. Each daily aver- age was subtracted from the value 65 °F, and all such differences for the month were added to determine the degree-days for the month. In the

other method the degree-days were determined by

evaluating the hourly differences between the

recorded outdoor temperature and the 65 °F base.

Good agreement was found between the two

methods in the several instances when both

methods were used for a given month.

An examination of tables 5 to 9 indicates that

the methods used to obtain the energy-usage

factors provided reasonable consistency among the

average values for the 2-, 3-, and 4-bedroom

houses as subgroups. Considering all the sample

houses as a group, the second factor, obtained

from the energy consumption of the heat pump

only and the degree-days related to a 65 °F base,

did not differ by more than 13 percent in 4 of the

5 months from the third factor, obtained from the

total energy used for heating and degree-days

based on average indoor-outdoor temperature

difference. For the 5 months studied, the second

energy-usage factor averaged 2.14 kw-hr/degreeday (1,000 ft2 ) whereas the third factor averaged

2.20 in the same units for all the sample houses.

The near equality of these two factors indicates

that the total energy for heating, including the

quantity kw-hrA, bore the same relationship to the degree-days based on indoor-outdoor temperature difference as the heat-pump energy did to the

degree-days based on a 65 °F reference value.

Or in other words, it tends to corroborate the

validity of the 65 °F base for computing degreedays in relation to the energy used by the heat

6
pump for heating. The second and third energyusage factors were somewhat more consistent from

month to month than the first energy-usage factor,

but this was due principally to the high values of

the first factor during the month of October when

heating was more intermittent.

It will be noted that the appliance contribution,

kw-hrA , in tables 5 to 9 ranged from 84 percent of

the heat-pump energy in October down to about

40 percent of this item in February based on the

averages for 16 houses. Considering the 5 months

from October 1959 to February 1960, inclusive,

the computed appliance contribution toward

heating the houses, kw-hrA, averaged 51.6 percent

of the energy used by the heat pump and 34.0

percent of all the energy used for heating the

houses.

In those instances where the indoor temperature

and the energy usage in tables 5 to 9 indicated that a particular house was probably not occupied during a month, the data for that house were not

included in the average. It will be noted that the

occupancy, as indicated by the data in tables 5 to

9, was not always consistent with the occupancy

information summarized in table 2. Coefficients of variation are shown in tables 5

to 9 for the three energy-usage factors for the 2-,

3-, and 4-bedroom houses as subgroups and for all the sample houses for the months from October

1959 to February 1960, inclusive. The coefficient

of variation is defined as the standard deviation

divided by the average of the group of values under

consideration and is one method of indicating the

consistency within a group of values. Based on

the 5-month average from October 1959 to February I960, the coefficients of variation indi- cate that the consistency among the individual

houses of a given subgroup and within the 16-

house sample was about the same for the first and third energy-usage factors, whereas the consistency was a little poorer for the second energyusage factor. The first and third energy-usage

factors involve the total energy used for heating

and two different methods for evaluating degreeTable 5. Relation of energy usage and degree-days under heating conditions for October 1959, Little Rock Air Force Base

Contractor's house number

Energy consumption

Ave indoor tempAvg out- door temp

Degree-days

Inside floor area

Energy-usage factor, kw-hr/degree- days (1, 000 ft*)

Heat pump

Appliance

contribution, kw-hrATotal for heating Based on

05° F

reference

Based on

avg indoor- outdoor temp

Total

energy,

65 °F base

Heat pump

energy,

65 °F base

Total

energy, indoor-outdoor, AT

2-bedroom houses

kw-hr kw-hr kw-hr °F °F ft 2 14 440 469 909 78 59 214 589 891 4.8 2.3 1.7

180 380 529 909 74 59 214 465 891 4.8 2.0 2.2

263 380 484 864 75 59 214 496 891 4.5 2.0 2.0

301- 360 423 783 73 59 214 434 891 4.

1

1.9 2.0

585 640 366 1,006 78 59 214 589 999 4.7 3.0 1.7 843 440 240 680 70 59 214 341 999 3.2 2.1 2.0

440 419 859 75 59 214 486 927 4.4 2.2 1.9

Coefficient of variat ion-. 0. 13 0. 16 0.11

3-bedroom houses

4 520 385 905 75 59 214 496 999 4.2 2.4 1.8 74 580 295 875 76 59 214 527 1,013 999

4.0 2.7 1.6

163 1,240

680 607 1, 847 76 59 214 527 8.6 5.8 3.5172 240 920 .77 h 59 214 558 1,013 4.2 3.1 i.e

577 400 623 1,023 74 59 214 465 1, 115 4.3 1.7 2.0

587 500 380 880 73 59 214 434 1,046 3.9 2.2 1.9 656 560 486 1,046 77 59 214 558 1,046 4.7 2.5 1.8 770 680 618 1,298 74 59 214 465 1, 115 5.4 2.8 2.5 Average 645 454 1,099 75 59 214 504 1,043 4.9 2.9 2.

1

Coefficient of variation 0.30 0. 39 0.28

4-bedroom houses

467 468 Average380

960

782

699 1,1621,659 7673

59

59 214

214

527

434

1,553

1, 900

3.5

4.

1

1.2 2.4

1.4

2.0

670 741 1,411 75 59 214 481 1, 727 3.8 1.8 1.7

Coefficient of variat 0. 08 0. 41 0.18

Average for 16 houses 571 477 1,048 75 59 214 494 1,085 4.6 2.5 2.0

Coefficient of variation, 16 house 0. 26 0. 38 0.24

7
days, whereas the second energy-usage factor is derived from the energy used by the heat pump

only. Thus it appears that the energy-usage

factors which include the contribution of appliances other than the heat pump to the househeating function provide a greater consistency in

results among a group of houses in the same month

I han that which makes use of only the heat-pump

energy consumption.

3.4. Correlation of Energy Requirements for

Cooling and Cooling Degree-Days

A similar relation of energy usage, floor area, and cooling degree-days was determined for the

months of June, July, and August 1959 for the

sample houses. These data are summarized in

tables 10, 11, and 12. The degree-day concept has been used to some

extent for estimating the energy required for airconditioning residences during the cooling season. However, it has not had the same measure of

acceptance for cooling conditions as for heating

conditions. Under cooling conditions, the heat

contributed by electrical appliances added to the

summer cooling load rather than assisting the heal

l)uni]) as it did during the winter. Also, in the

summertime, the outdoor temperature frequently

crossed the reference value used for degree-day

determinations whether the reference value chosen was 65 or 75 °F. Solar radiation on a house is a much greater factor in the total cooling load than

it is for the heating load, and its effect is only

partly and indirectly reflected in the indooroutdoor temperature difference during the summer.

In addition, the degree-day concept makes no

allowance for the cooling load represented by the

humidity in the outdoor air used for ventilation.

Three energy-usage factors were computed based on three different computations of the cooling dcTable 6. Relation of energy usage and degree-days under heating conditions for November 1959, Little Rock Air Force Base

Energy consumption Degree-days Energy-usage factor, kw-lir/degree- day s o.oon IV)

Contractor's house Appliance Ave indoor Avg out- door temp

Based on Inside floor number Heat contribu- Total for temp Based on avg indoor- area Total Heat Total pump tion, heating 65 °F outdoor energy,

C>5 °E base pump energy, kw-hrA reference temp energy, indoor-out - 65 °F base door, AT

2-bedroom houses

kw-hr kw-hr kw-hr "F °F m 14 1, 140 495 1, 635 76 45 610 930 891 2.9 2.0 2.0

180 920 668 1.588 74 45 640 870 891 2.8 1.6 2.0

263 860 805 1.665 76 45 640 930 891 2.9 1.5 2.0

.301 1,600 492 2, 092 72 45 640 810 891 3.7 2.8 2.9

585 1,420 529 1.949 77 45 640 960 999 3.0 2.2 2.0

843 "620 »3 "623 "60 45 640 M50 "999 1.0 •1.0 1.4

Average 1, 188 598 1,786 75 45 640 900 927 3.1 2.0 2.2

Coefficient of varial ion 0.11 0.23 0.17

3-bedroom houses

4 1, 220 502 1,722 73 45 640 840 999 2. 7 1.9 2. 1 74 1, 180 597 1, 777 77 45 640 960 1,013 999 2.7 1.8 1.8

163 2, 180 766 2, 946 71 45 640 780 4.6 3.4 3.8

172 1, 320 338 1,658 76 45 640 930 • 1.013 2.6 2.0 1.8

577 1.300 781 2, 081 72 45 640 810 1, 115 2.9 1.8 2.3

587 _ 1,060 729 1,789 73 45 640 840 1,046 2 7 1.6 2.0

656 1,160 618 1,778 78 45 640 990 1, 046 2. 7 1.7 1.7

770 _ 1,520 856 2, 376 72 45 640 810 1,115 3.3 2.1 2.6 Average 1,368 648 2, 016 74 45 640 870 1, 013 3.0 2.0 2.3

Coefficient of variat ion 0.20 0.26 0.29

4-bedroom houses

467 468 Average

1.810

1,760 837

837

2,677

2, 597

73

73 4545 640640

840

840

1.553

1.900

2.7

2.1 1.91.4 2.1

1.6

1,800 837 2, 637 73 45 640 840 1,727 2.4 1.7 1.9

Coefficient of variat ion 0. 13 0. 16 0. 14

Average for 15 houses.. 1,365 657 2, 022 74 45 610 876 1,091 3.0 2.0 2.2

Coefficient of variation, 15 house 0. 19 0.25 0.25

» House 843 apparently not occupied. These data not included in the averages.

8
gree-days. The degree-day values in columns 6 and

7 of tables 10, 11, and 12 are based on the differ- ences between hourly values of outdoor temperature taken from the temperature recorder charts

and the reference values of 65 and 75 °F, respectively. The degree-day values in column 8 of the

tables were computed from the mean of the daily

maximum and minimum outdoor temperatures

and the daily average indoor temperature.

It will be noted in tables 10 to 12 that the

energy-usage factor for cooling varied over a considerable range depending on the basis selected for determining the degree-daj^s of cooling. An examination indicates that the first two energy-usage

factors were fairly consistent from month to month

in the 2-, 3-, and 4-bedroom houses as subgroups.

The percentage variation in each of these two

factors in any given month for any group of houses was the same because the factors were related to each other by a fixed ratio : the ratio of the degreedays based on reference temperatures of 65 and

75 °F, respectively. However, the first factor dif- fered less among the 3 separate months than did

the second factor. Considering all the sample

houses as a group, the three monthly values of the

first factor differed by only 10 percent of the aver- age whereas the three monthly values of the second

factor differed by 25 percent of the average.

The third energy-usage factor varied more among house subgroups and from month to month

than did the other two factors. Basing the

degree-days on the difference between mean daily

outdoor temperature and average indoor temperature is probably the least suitable of the three

methods employed for correlating energy usage,

first, because this temperature difference can be- come vanishingly small, or even negative, and yet

the house can have a cooling requirement, and

secondly, because a house probably responds with

respect to the need for cooling or heating on a cycle

of less than 24 hr. Note that tbe degree-day

value for house 585 as used for the third factor was

Table 7. Relation of energy usage and degree-days under heating conditions for December 1959, Little Rock Air Force Base

Energy consumption Degree-days Energy-usage factor, kw-hr/degree- davs (1.000 ft 2]

Contractor's house Appliance Avg indoor Avg out- Based on Based on Inside floor number Heat contribu- Total for temp door temp 65 °F avg indoor- area Total Heat Total pump tion, heating reference outdoor energy, pump energy,

indoor-outdoor, AT

kw-hrA temp 65 °F base energy,

65 °F base

2-bedroom houses

kw-hr kw-hr kw-hr op °F ft> 14 1.140 535 1, 675 77 43 643 1, 054 891 2.9 2.0 1.8

180 760 732 1,492 73 43 643 930 891 2.6 1.3 1.8

263 1.080 859 1.939 77 43 643 1, 054 891 3.4 1.9 2.1 301 - 1, 712 529 2, 271 73 43 643 930 891 4.0 3.0 2.7

585 1,200 560 1, 760 43 643 1,054 999 2.7 1.9 1.7 843 » 1,000 •306 » 1, 306 »69 43 643 "806 "999 •2.0 »1.6 • 1.6 Averaee 1,184 643 1,827 75 43 643 1,004 927 3.1 2.0 2.0

Coefficient of variation 0. 17 0. 27 0.18

3-bedroom houses

4 1,320 390 1, 710 74 43 643 961 999 2.7 2.1 1.8 74 980 677 1,657 75 43 643 992 1,013

999 2.5 1.5 1.6

1, 700 720 2,420 74 43 643 961 3.8 2.6 2.5 172.. 980 278 1,258 71 43 643 868 1,013 1.9 1.5 1.4

577 1,140 1, 016 2, 156 71 43 643 868 1,115 3.0 1.6 2.2

587. 720 824 1,544 72 43 643 899 1,046 2.3 1.1 1.6 656 1, 140 735 1,875 78 43 643 1,085 1,046 2.8 1.7 1.7 770 1,340 1,036 2, 376 72 43 643 899 1, 115 3.3 1.9 2.4 Average 1,165 710 1,875 73 43 643 942 1,043 2.8 1.8 1.9

Coefficient of variation _ 0.20 0. 24 0. 21

4-bedroom houses

467

468

1, 540 1,920 926

1,293

2, 466

3, 213

727443

43

643

643 899

961

1,553

1,900

2.5 2.6

1.5

1.6

1.8

1.8 Average 1,730 1,110 2,840 73 43 643 930 1, 727 2.6 1.6 1.8

0.04 0. 06 0.00

Average for 15 houses.. 1,247 741 1,987 74 43 643 961 1,091 2.9 1.8 1.9

0.18 0.27 0.18

» House 843 apparently not occupied. These data not included in the averages.
negative during August because the average indoor

temperature was 1 °F higher than the mean daily

outdoor temperature even though the heat pump

used 380 kw-hr of electric energy during the

month, causing the corresponding energy-usage

factor to be negative.

The coefficients of variation of the energ3"-usage

factors during cooling operation, defined in the same way as for heating operation, are shown in tables 10 to 12 for the months of June, July, and

August 1959, respectively. These coefficients were

the same for the first two energy-usage factors

except for differences .caused by the arithmetical

rounding-off process because the factors themselves for any given house were related to each

other in the same ratio as the degree-days based

on reference temperatures of 65 and 75 °F, respectively. The coefficient of variation was la'-ger for the third energy-usage factor than for the other

two, and especially so in August for the group of 2-bedroom houses because of the one negative

value of the energy-usage factor for house 585.

3.5. Conditions Affecting Maximum Power

Demand for the Housing Area

The unit rate for electric energy at the Little

Rock Ah Force Base was related by sliding scales

to the following three quantities: (1) the total

monthly usage of electric energy; (2) the magnitude

of the maximum 15-min power demand during the

month ; and (3) the load factor, i.e., the ratio of the

monthly average use of the electric power to the

maximum 15-min demand of power for the month.

For this type of rate structure, a reduction of the

maximum 15-min demand in any mont h would tend

to lower the unit rate by virtue of its effect on the

second and third quantities above, even if the

total energy usage remained unchanged.

a. Load Factor

Figure 3 shows the average monthly power use

of all the occupied houses from April 1959 to February 1960, inclusive. It also shows the average

Table 8. Relation of energy usage and degree-days under heating conditions for January I960, Little Rock Air Force Base

Energy consumption Degree-days Energy-usage factor, kw-hr/degree- Uays (1, 000 ft?)

Contractor's house Appliance Avg indoor Avg out- Based on Based on Inside floor number Heat contribu- Total for temp door temp C5 °F avg indoor- area Total TTeat Total pump tion, heating reference outdoor energy, pump energy, kw-hra temp 05 °F base energy, indoor-out65 °F base door, AT

2-bedroom houses

kw-hr kw-hr kw-hr °F °F ft 2 14 1,440 458 \,S'J\ 76 42 694 1,054 891 3.1 2.3 2.0

180 1,160 601 1,761 73 42 694 961 891 2.8 1.9 2.1

263 _ 1,160 694 1, 854 75 42 694 1,023 992891 3.0 1.9 2.0

301 2,040 658 2,698 74 42 694 891 4.4 3.3 3.1

585 1,400 595 1,995 76 42 694 1, 054 999 2.9 2.0 1.9

843 1, 380 613 1, 993 73 42 694 961 999 2.9 2.0 2.1 Averaee 1,430 603 2, 033 75 42 694 1,008 927 3.2 2.2 2.2

Coefficient of variation 0.18 0.23 0. 19

3-bedroom houses

4 1,400 825 2,225 74 42 694 992 999 3.2 2.0 2.2

74 1,020 934 1, 954 73 42 694 961 1,013

999

2.8 1.5 2.0

163 2, 580 858 3,438 74 42 694. 992 5.0 3.7 3.5

172 1,800 609 2,409 74 42 694 992 1,013 3.4 2.6 2.4

577 1,400 1,076 2,476 71 42 694 899 1,115 3.2 1.8 2.5

587 840 1,040 1,880 73 42 694 961 1,046 2.6 1.2 1.9

65C 1,340 729 j.nO'j 77 42 694 1,085 1, 046 2.9 1.8 1.8

770 1, 6S0 1,019 2,699 73 42 694 961 1. 115 3.5 2.2 2.5 Average 1,508 886 2, 394 74 42 694 980 1, 043 3.3 2. 1 2.4

Coefficient of variat 0.20 0.34 0.22

4-bedroom bouses

467... - 2,180 1,418 3, 598 74 42 694 992 1,553 3.3 2.0 2.3

468 2, 600 1,265 3. 865 73 42 694 961 1,900 2.9 2.0 2.1 Average 2, 390 1,342 3,732 74 42 694 977 1,727 3.1 2.0 2.2

0. 06 0.00 0.05

Average for 16 houses.. 1, 589 837 2, 426 74 42 694 990 1,085 3.2 2.3

Coefficient of variation. 16 houses . _ . . '.. 0. 19 0.28 0. 18

]()
15-min demand of all the occupied houses occurring

at the time of monthly maximum 15-min demand

for the entire housing area. The load factor for the

entire housing area was determined month by

month from these data and plotted in figure 3 for the same period.

Figure 3 shows that the monthly load factor

approximated 0.50 from April 1959 to December

1959, with two exceptions, and then rose sharply

until it reached a value of about 0.60 during February 1960. That is, the monthly average power

demand was about one-half the maximum 15-min

demand much of the time, with a higher ratio

occurring during the colder months of the winter.

A low load factor occurs for a given house when the

various pieces of electrical equipment are energized

for only a small percentage of the total time, but

occasionally many or all of them are simultaneously energized for periods up to 15 min. When

the short periods of simultaneous use of many

components of the load in a number of houses

APR. OUN. AUG. OCT. DEC. FEB. 1959 I960

Figure 3. The average monthly -power use of all the occupied

houses, the average 15-min power demand at the time of the monthly maximum power demand for all occupied houses and the average monthly load factor, for the period April

1959-February 1960.

Table 9. Relation of energy usage and degree-days under heating conditions for February 1960, Little Rock Air Force Base

Energy consumption Degree-days

Contractor's house number Heat pump

Appliance

contribution, kw-hrATotal for heating

Avg indoor temp Avg out- door temp Based on

65 °F

reference

Based on

avg indoor- outdoor temp

Inside floor area

Energy-usage factor, kw-hr/degree- days (1, 000 ft-')

Total

energy,

65 °F base

Heat pump

energy,

65 °P base

Total

.energy, indoor-outdoor, AT

2-bedroom houses

kw-hr kw-hr kw-hr °F »P ft* 14. 1,780 670 2, 450 75 34 908 1, 189 891 3.0 2.2 2.3

180 1,800 504 2,304 73 34 908 1,131 891 2.8 2.2 2.3 263 1,720 528 2,248 73 34 908 1, 131 891 2.8 2.1 2.2 301.. 3, 140 735 3,875 72 34 908 1,102 891 4.8 3.9 3.9

585 1,760 716 2, 476 75 34 908 1,189 999 2.7 1.9 2.

1

843 1,800 816 2, 616 74 34 908 1,160 999 2.9 2.0 2.3

Average... . 2, 000 662 2, 662 74 34 908 1, 150 927 3.2 2.4 2.5

Coefficient of variation 0.23 0.29 0.24

3-bedroom houses

4 3,000 842 3,842 74 34 908 1,160 999 4.2 3.3 3.3

74. 1,540 1,158 803

2, 698 73 34 908 1, 131 1,013 2.9 1.7 2.4

163 2,800 3, 603 73 34 908 1, 131 999 4.0 3.1 3.2

172 2,080 712 2, 792 (*) 34 908 O) 1,013 3.0 2.3 C)

' 577 2, 160 1,196 968

3, 356 69 34 908 1, 015 1,115 3.3 2.1 3.0

587 1,200 2, 168 71 34 908 1, 073 1,046 2.3 1.3 1.9 656 1,740 757 2, 497 75 34 908 1,189 1,046 2.6 1.8 2.0

770 2, 180 1,099 3, 279 72 34 908 1,102 1, 115 3.2 2.2 2.7 Average 2, 088 942 3, 029 72 34 908 1,114 1,043 3.2 2.2 2.6

Coefficient of varia lion 0. 18 0.28 0.20

4-bedroom houses

467 2,720

3, 800

1,072

1,546 3,792 74 34 908

908

1, 160 1,0731, 553 1,900 2.7 1.9 2.1 468 5,346 71 34 3.

1

2.2 2.6 Average 3,260 1,309 4,569 73 34 908 1, 117 1,727 2.9 2.1 2.4

Coefficient of variation . . 0. 07 0.08 0.11

Average for 16 houses 2,201 883 3,084 73 34 908 1, 129 1,085 3. 1 2.3 2.6

Coefficient of variation. 16 houses. . .. . . . . . 0. 21 0.28 0.22

a Data not available. 11
occur ;ii t he same time, the load factor for the

entire group is low.

b. Daily Pattern of Power Demand

In order to determine how the power demand

varied throughout the day, the daily pattern of power demand was plotted for 5 of the sample

houses for the months of January 1960 and August

1959. For these 2 months, the power used during

each 15-min period of the day was tabulated for the 5 houses. From these data the maximum and

minimum demands that occurred on any' day of the month and the average demand for all days of

the month were plotted for each 15-min period of

the day. This information is shown in figures 4

to 8, inclusive, for January 1960 and in figures 9 to 13, inclusive, for August 1959.

Of the 5 sample houses evaluated, houses

numbered 14, 263, 468, and 587 revealed similar

changes in the average and maximum power

demands between the day and night hours during

Table 10. Relation of energy usage and degree-days under cooling conditions for June 1959, Little Bock Air Force Base

the month of January. Starting in the morning

at a time ranging from about 0630 to 0900 hr, the

average and maximum power demands rose quickly to about twice that observed earlier in the

morning and remained at a high level until 1 to 3 hr after noon when they decreased to a value only

a little above the night demand. After about 2

hr at a low value, the power demand rose again

to a smaller maximum at about 1800 or 1900 hr

and then gradually decreased to night level,

before midnight in most cases. The daily pattern

of power demand for these 4 houses indicates the

following conclusions regarding the power demand:

(1) The monthly maximum 15-min power

demand often occurred between the hours of

0630 and 2000 and was caused principally by the

activities of the occupants of the house during

their waiving hours.

(2) The monthly maximum 15-min power

demand was not directly caused by the heating

equipment during the coldest hours in the 24-hr

period.

Contractor's house number

Energy consumption

Avg

indoor temp

Avg

outdoor temp

Degree-days

Inside

floor area

Energv-usage factor, k\v-hr/degree- days (1,000 ft2

)

Heat pump

Appliance

contribution k\v-hrA

Hourly

values, 65 °F base

Hourly

values,

75 °F base

Daily mean

above

indoor avg

Hourly

values,

65 °F base

Hourly

values,

75 °F base

Daily mean

above

indoor avg

2-bedroom houses

kw-hr kw-hr °F » F W

14 __ 720 354 76 79 390 146 90 '891 2.1 5.5 9.0

180 900 489 70 79 390 146 270 891 2.6 6.9 3.7

263 900 262 68 79 390 146 330 891 2.6 6.9 3.1

301 720 470 76 79 390 146 90 891 2.1 5.5 9.0

585 "420 "162 »74 79 390 146 "150 "999 "1.1 »2.9 »2.8

843 840 179 73 79 390 146 180 999 2.2 5.8 4.7 Average 816 351 73 79 390 146 192 912 2.3 6. 1 5.9

Coefficient of variat 0. 10 0.11 0.44

3-bedroom houses

4 820 244 75 79 390 146 120 999 2.1 5.6 6.8

74 820 517 71 79 390 146 240 1,013 999

2.1 5.5 3.4

163 960 555 73 79 390 146 180 2.5 6.6 5.3

172 780 289 73 79 390 146 180 1,013 2.0 5.3 4.3 577 660 443 77 79 390 146 60 1,115 1.5 4.1 9.9

587 880 424 71 79 390 146 240 1,046 2.2 5.8 3.5

656 660 562 76 79 390 146 90 1,046 1.6 4.3 7.0

770 900 147 73 79 390 146 180 1, 115 2.1 5.5 4.4 Average 810 398 74 79 390 146 161 1,043 2.0 5.3 5.6

Coefficient of variation 0. 16 0. 14 0. 37

4-bedroom houses

467 1,560 579 74 79 390 146 150 1, 553 2.6 6.9 6.7

468 1,560 688 76 79 390 146 90 1,900 2.1 5.6 9.1 Average 1,560 634 75 79 390 146 120 1, 727 2.4 6.3 7.9

Coefficient of variation 0.11 0.10 0.15

Average for

15 houses.. 912 413 73 79 390 146 166 1,091 2.2 5.7 6.0

Coefficient of variation. 15 houses.. . 0. 15 0. 14 0.38

» House 585 apparently occupied only part of the time. These data not included in the averages.

12
and tables 5 to 9 show that the total monthly

energy use in this house was of the same order of magnitude as for houses 14, 263, and 587 during

the winter months. No reason was found for the

power demand pattern being different for house 74

from that observed in the other four houses. In August, the daily pattern of power demand

was similar in all 5 houses studied, as shown in figures 9 to 13. Starting in the morning between

0600 and 0900 hr, the average and maximum

power demand increased fairly rapidly for about

2 hr, after which it was reasonably stable until

about 1900 hr and then gradually decreased until

several hours after midnight. The daily average

power demand was quite low from 0200 to 0600 hr

ranging from about 0.5 kw in 2 of the houses up to about 1.5 kw in house 263. The daily average

power demand during the period from 1000 to 1900

hr was in the range from 3 to 4 kw in some houses

and up to 6 kw or more in others.

Unlike the most prevalent daily pattern of

power demand in January, there was no period of

Table 11. Relation of energy usage and degree-days under cooling conditions for July 1959, Little Rock Air Force Base

Contractor's house number

Energy consumption

Avg

indoor temp

Avg

outdoor temp

Degree-days

Inside

floor area

Energy-usage factor, kvv-hr/degree- days (1,000 ft2 )

Heat pumpAppliance

contribution kw-hr a

Hourly

values, 65 °F base

Hourly

values, 75 °F base

Daily mean

above

indoor avg

Hourly

values,

65 °F base

Hourly

values,

75 °F base

Daily mean

above

indoor avg

2-bedroom houses

kw-hr kw-hr "F °F

14 _ 840 354 76 81 488 225 155 891 1.9 4.2 6.1

180 -860 "6 "67 81 488 225 -434 •891 "2.0 "4.3 "2.2

263 1. 14(1 169 72 81 488 225 279 891 2.6 5.7 4.6

301 1,04(1 463 76 81 488 225 155 891 2.4 5.2 7. 5 585 "440 •75 •74 81 488 225 "217 -999 "0.9 "2.0 "2.0

843_ 840 183 74 81 488 225 217 999 1.7 3.7 3.9 Average 965 292 75 81 488 225 202 918 2.2 4.7 5.5

Coefficient of variat ion . 0. 17 0. 17 0.25

3-bedroom houses

4 1,140 227 75 81 488 225 186 999 2.3 5.

1

6. 1 74 1, 000 640 72 81 488 225 279 1,013 2.0 4.4 3.5

163 1,360 481 74 81 488 225 217 999 2.8 6.1 6.3

172 720 328 76 81 488 225 155 1,013 1.5 3.2 4.6

577 1, 100 569 76 81 488 225 155 1, 115 2.0 4.4 6.4 587 1, 000 286 72 81 225 279 279 1,040 2.0 4.2 3.4

656 540 276 77 81 488 225 124 1, 046 1.

1

2.3 4.2

770 1,280 434 71 81 488 225 310 1, 115 2.4 5.

1

3.7 Average 1,018 405 74 81 488 225 213 1,043 2.0 4.3 4.8

Coefficient of variat ion... 0.25 0.25 0. 25

4-bedrootn houses

467

468 Average

1, 540

1,560

185 325 74

76

81

81 488488 225225

217

155

1, 553

1, 900

2.0

1.7 4.4 3.6

4.6

5.3

1, 550 255 75 81 488 225 186 1, 727 1.9 4.0 5.0

Coefficient of variat 0.08 0.10 0. 07

Average for 14 houses.. 1, 079 351 74 81 488 225 206 1,105 2.0 4.4 5.0

Coefficient of variation, 14 houst 0.21 0.22 0. 25

" Houses 180 and 585 apparently not occupied. These data not included in the averages. 13

635728—62 3

(3) A fairly stable power demand approximating twice the night level occurred from about

0700 to 1400 hr.

(4) Several high 15-min demands occurred

during the month that approximated the one monthly maximum value in each house.

(5) There was a high degree of similarity in the

daily pattern of power demand in the 4 houses

and therefore a good probability of coincidence

of high or maximum values in a group of houses.

Despite the similarity in the daily patterns of

power demand shown in figures 4 to 7 for houses

numbered 14, 263, 468, and 587, the pattern

shown in figure 8 for house 74 was significantly

different. The variation in power demand between day and night was much less in this house,

the monthly maximum 15-min demand was lower,

and high values in the maximum demand curve were more or less evenly scattered throughout

the 24-hr period. Table 2 indicates that house 74 was not occupied by an unusually small family,
total. It will be noted that about 1 2 percent of the

total daily energy use occurred between the hours

of 2300 and 0700 in 4 of the sample houses during

August, and about 25 percent- of the total daily

energy use occurred in the same period in four of

the sample houses dux-ing January. The fifth house in the group used a higher percent of the

Table 13. Average day and night energy use in 5 sample

houses

Electric energy used, k\v-hr

low demand in the middle of the afternoon in August. This variation is probably explained by

the high solar load at this time of the day and the

fairly steady requirement for heat pump operation.

Figures !) to 1:5 show that there were no high

values of maximum power demand between 2200

hr in the evening and 0600 hr in the morning

that approached the monthly maximum L5-min

power demand in these 5 houses. This pattern

indicates I he high probability that the monthly

maximum power demand in (lie summer months

would also occur during the period of the day when

the occupants are active.

An inspection of figures 4 to 13 indicates that

the load factor for the individual house could be

increased, if some of t he electrical load were shifted

from the daytime hours to the night hours. Table

13 is a summary of the daily average energy use

in 5 sample houses between the hours of 2300 and

0700, and between 0700 and 2300 for the months of

August and January. The energy use in these

two periods is also expressed as a percent of the

Table 12. Relation of energy usage and degree-days under cooling conditions for August 1959, Little Rock Air Force Base

August 1959 January 1960 House

No. 2300- Percent 0700- Percent 2300- Percent 0700- Percent

(170(1 of 2300 of 0700 of 2300 of hr total hr total hr total hr total

14 5.8 11.4 45.

1

88.6 20.0 24.

1

62.9 75.9

74 9.0 12.4 63.7 87.6 10.5 25.2 31.

1

74.8

263 12.7 22.4 44.0 77.6 14.7 17.7 68.3 82.3 468 9.9 11.9 73.6 88.1 38.9 27.5 102.6 72. 5 587 18.4 23.9 58.6 76.

1

656 5.5 10.8 45.4 89.2

Contractor's

Energy consumption

Avg Avg

Degree-days

Inside

Energv-usage factor, degree- days (1,000 ft2

) house number

Heat, pumpAppliance

contribution ku-hiA

indoor temp

outdoor temp Hourly

values,

65 °F base

Hourly

values,

75 °F base

1 )aily mean

above

indoor avg

floor area Hourly

values,

65 °F base

Hourly

values,

75 °F base

Daily mean

above

indoor avg

2-bedroom houses

kw-hr kw-hr op °F ft* 14 840 400 76 79 447 170 93 891 2.1 5.5 10. 1 180 900 380 70 79 447 170 279 891 2.3 5.9 3.6

263 680 68 76 79 447 170 93 891 1.7 4.5 8.2

301 1,040 572 75 79 447 170 124 891 2.6 6.9 9.4

585 380 316 .80 79 447 170 -31 999 0.9 2.2 • -12.3

843... _._ 660 162 76 79 447 170 93 999 1.5 3.9 7.1 Average 750 316 76 79 447 170 111!) 927 1.9 4.8 4.4

Coefficient of variat ion 0.31 0.31 1.78

3-bedroom houses

1, 240

1, 280 1,080

680 880

1,360 800

1,080

1,050

276

583 852

188 543

274

549 454

465

74

7372

7577

73

77

79

7979

79

79

7979

79

447

447 447 447

447

447

447

447

447

170 170

170

170

170 170 170

170

170

155 180 217

12462

18662

217

151

999

1,013 999

1,013

1, 115 1,046

1,046

1, 115

2.8

2.8

2.4

1.5 1.8 2.9

1.7 2.2

1,043

Coefficient of variation.

2.3

0. 23

7.3

7.4

(i. 4 3.9

4.6 7.6

4.5 5.7

5.9

0.24

4-bedroom houses

467 1,740

1,880 438

635

74

77

79

79 447447

170

170

155621,553

1,900 2.5 2.2

6.6

5.8 7.2

468.. 15.9 Average 1,810 537 76 79 447 170 109 1,727 2.4 6.2 11.6

Coefficient of variation . 0. 07 0. 07 0. 38

Average for 16 houses.. 1,033 418 75 79 447 170 130 1,085 2.

1

5.5 6.9

Coefficient, of variation, 16 houses 0.26 0.27 0.84

• Interior temp. 1 °F above exterior temp. Significance of coefficients of variation for 2-bedroom houses and all 16 houses is questionable due to the negative quantity for house 585.

14
total than the others during August and a lower

percent than the average during January in this same time period. If the energy use were uniform, day and night, one-third of the total daily use would have occurred during the 8-hr period

between 2300 and 0700 hr.

c. Coincidence of Component and Total Power

Demands in the Sample Houses

In order to study the contributions of the various

house appliances to the maximum demands for electric power, the simultaneous demands in the sample houses at the time of the maximum demand

for the entire housing area were graphed for a 4-hr

period, bracketing the time of the maximum value

for the months of August 1959 and January 1960.

The data used for these graphs were taken from

the strip recorder charts of the demand meters

which recorded the average power demand in kilowatts in 15-min increments for the heat pump,

the water heater, the range, and the total house

load. The miscellaneous load in the house, which

consisted of the lights, the toaster, the television

and radio sets, the refrigerator, the clothes dryer,

etc., was not metered separately, but was calculated by subtracting the sum of the range, water

0200 0400 0600 0800 1000 1200 I4O0 1600 1800 2000 2200 240(

TIME OF DAY.hr Figure 4. Daily pattern of power demand in house 14, type Ai for the period January 8, 1960-February 8, 1960.

1000 1200

TIME OF DAY.hr Figure 5. Daily pattern of power demand in house 263, type A, for the period January 8, 1960-February 8, 1960

15
heater, and heal pump demands from the total house meter demand.

These graphs for houses numbered 14, 163, and

467 are shown in figure 14 for January 1960 and

in figure L5 for August 1959. The demands of the

various components of the load in each house were plotted againsl the same time scale such thai

the center of the time scale coincided with the

time of the maximum power demand for the entire housing area, i.e., for 1,535 houses. For I he

1-hour period in January, represented in figure

14, it will be, seen that the water heater was

energized continuously lor several hours in each

house, that I lie heat pump was operating inter- mittently on a time cycle that resulted in some

power demand during every 15-min period, that the range contributed very little to the total demand, and thai the power demand of the miscellaneous devices varied widely from one 15-min

period to the next. The total power demand in house 163 varied widely during the 4-hr period,

ranging from 1 to Hi..") kw, whereas it was reason0600 1000 1200 TIME OF DAY.hr Figure 6. Daily pattern of power demand in house 468, type 0, for the period January 8, 1960-February 8, 1960.

0200 1000 1200 1400 TIME OF DAY.hr 1800

Figure 7. Daily pattern of power demand in house 587, type D, for the period January 8, 1960-February 8, I960.

16
ably steady at a high level in house 467, ranging

from 12.5 to 18 kw. One of the three houses had a maximum demand at 1100 hr coincident with the

maximum for the entire housing area.

It should he noted that some of the graphs for miscellaneous power demand show negative values,

which is a physical impossibility. It is believed

that these negative values resulted from imperfect

synchronization of the time clocks and the 15- min demand intervals of the four recorders from

which the miscellaneous demands were determined

by calculation.

In figure 15, the component power demands in the same houses are shown for a 4-hr period

bracketing the time of the monthly maximum demand for the entire housing area on August 24,

1959. In each of these houses the power demand

of the heat pump was fairly steady, ranging from

about 2 to 6 kw for the- 3 houses. The water

heaters in 2 houses were energized for \% to V/2 hr,

the miscellaneous devices varied in demand from

0 to 7 kw, but none of the cooking ranges was used.

The maximum demand in each of these houses

during the 4 hr was noncoincident with that for

the entire housing area.

IOOO 1200 TIME OF DAY.hr Figure 8. Daily pattern of power demand in house 74, type B. for the period January 8, 1960-February 8, 1960.

0200 1000 1200 TIME OF DflY.hr 800

Figure 9. Daily pattern of power demand in house 14, type Ai, for the period August 7, 1959—September 8, 1959.

17
Figure 16 shows the averages of the demands

for the house and each component for all 16 of

the sample houses for I lie same 4-hr periods in January and August. This figure shows thai there w as sufficient diversity, or noneoineidenee of high

demands, within this group to produce a fairly

steady total for each component and for the house

total. On January 18 there was about a 2 kw

variation dining the 4-hr period related to an average value of about 8 kw for the house total,

and on August 24 a variation of about 1 j4 kw re- lated to an average value of about 5% kw. Tins

graph shows how the diversity in a group of houses

reduces the wide variations in demand that are

characteristic of a single house.

In order to study the factors that caused the

monthly maximum demands in individual houses,

the power demands of each component of the

load and of the house as a whole were plotted for a 4-hr period bracketing the time of the monthly

maximum demand for that house. Such graphs

are shown for houses 14, 16:5, and 4(i7 for I winter

month in figure 17 and for I summer month in figure IS. The time at which the monthly maxi-

- MAXIMUM ON ANY DAY A — MINIMUM ON ANY DAY

• — AVERAGE FOR ALL DAYS

0200 1000 1200 TIME OF DAY.hr 1800

Figure 10. Daily pattern of power demand in house 74, type B, for the period August 7, 1959—September 8, 1959.

15 -MINUTE POWER DEMAND BETWEEN

AUGUST 17 AND AUGUST 30 INCLUSIVE WAS USUALLY LOWER THAN 0.2 kw AND ALWAYS LOWER THAN 4.5 kw, INDICATING LITTLE USE OF ELECTRICAL

EQUIPMENT DURING THIS PERIOD. AVERAGE VALUES DETERMINED WITHOUT

THE USE OF DEMAND VALUES FALLING

IN THE PERIOD.

iff •A

0400 0600 1000 1200 TIME OF DAY.hr 1800 2000 2200 2400

Figure 11. Daily pattern of power demand in house 263, type A, for the period August 7, 1959-September 8, 1959.

L8
mum demand occurred in each house was placed

at the center of the 4-hr time scale in each graph. In figure 17 it will be noted that the heat pump,

water heater, and miscellaneous devices contributed significantly to the maximum in each case and that the electric range contributed little or nothing in power demand. The power demand

of the heat pump in houses 163 and 467 was such

that use of the supplementary resistance heaters was indicated even though the outdoor temperature averaged 53 °F in the case of house 163. A sustained demand in excess of 15 kw for 3 hr

occurred in house 163 as a result of long steady

operation of the heat pump and water heater.

The high demands in the other two houses were

of much shorter duration.

A comparison of figures 17 and 18 shows that

the maximum total power demand in each of

the three sample houses was higher during January than during August. However, the same

three components; namely, the heat pump, water

heater, and miscellaneous devices, were the

principal contributors to the maximum power

demands during- both seasons. The water heater

1000 1200 TIME OF DAY.hr Fku.re 12. Daily pattern of power demand in house 1^68, type G, for the period August 7, litoU-September 8, 1959.

0800 1000 1200

TIME OF DAY.hr Figure 13. Daily pattern of power demand in house 656, type D, for the period August 7, 1959-September 8, 1959.

19
HOU

0

SE 14, TYPE 4,

1

1 HOUSE I63 . TYPE B, HOC SE 467, T tpe F

A/

I

i 1 ft h

VI

f

i 1!

) — -

\J

TV

—

V / r

K - —

1 4

-V

1

i/ f0900

DIFFERENCE

1300 0900 1100 TIME OF DAY Figure 14. Total and component 15-min power demands in 3 sample houses for a 4-hr period bracketing the time of maximum demand for the entire housing area which oc- curred during the period January 8-February 8, 1960. Time of maximum demand for the housing area, 1100 hr, on January 18, I960. Average outdoor temperature during 4-hr period, 31.4 °F.

cT 3

«

i

!

JANUARY 18,1960 AUGUST 24.1959

—

W

0900

DIFFERENCE TIME OF DAY Figure 16. Average of the total and component 15-min power demands for 16 sample houses during a 4-hr period bracket- ing the time of maximum demand for the entire housing

area which occurred during the periods January 8-

February 8, 1960, and August 7-September 8, 1959.

HOUSE 14, TYPE A, HOUSE 163. TYPE B, HOUSE 467, TYPE F

tvi

a

z

09 4 3 6t DIFFERENCE

1345 0943 1145 TIME OF DAY Figure 15.—Total and component 15-min power demands in 3 sample houses for a 4-hr period bracketing the lime of maximum demand for the entire housing area which occured during the period August 7-September 8, 1959. Time of maximum demand for the housing area, 1145 hr, on August 24, 1959. Average outdoor temperature during 4-hr period, 92.2 °F.

HOUSE 14, TYPE A, TIME OF MAXIMUM DEMAND.

JAN 17, I960 AT 1200 AVERAGE OUTDOOR

TEMPERATURE. 41* F

HOUSE 163, TYPE B, HME OF MAXIMUM DEMAND, FEB 6, I960 AT 1430 AVERAGE OUTDOOR

TEMPERATURE, 53* f

HOUSE 467. TYPE F

AA

A

1000

8Y DIFFERENCE

1400 1230 1430 TIME OF DAY Figure 17. Total and component 15-min power demands in 3 sample houses for a 4-hr period bracketing the time of maximum total demand for each house occurring during

the period January 8-February 8, 1960.

20
HOUSE 14. TYPE A, TiUE OF MAXIMUM DEMAND

z: ? 5 9

-

' : = -.e = i:-e :_"::: = temperature. bb'f

" I 0

HOUSE 163. TYPE B, riME OF MAXIMUM DEMAND

SEPT 4 1959 AT 1615 AVERAGE OUTDOOR

TEMPERATURE. 76" F

HOUSE 467. TYPE F

riME OF MAXIMUM DEMAND

AUG 21. 1959 AT 1415 AVERAGE OUTDOOR

TEMPERATURE. 9("F

1015

' BY OFFERENCE

1415 1415 ISI5 TIME OF DAY Figure 18. Total and component 15-min power demands in 3

sample houses for a 4-hr period bracketing the time of maximum total demand for each house occurring during

the period August 7-September 8, 1959.

provided a fixed demand whenever it was energized, winter or summer, whereas the heat pump

provided a somewhat lower maximum demand

in the summer because the supplementary resist- ance heaters would ordinarily never be used

during the summer.

Figure 19 shows the type of maximum demands

that would have occurred if the maximum demand

in all of the 15 sample houses represented by the

figure had occurred coincidentally. The data

for house 263 were not continuous throughout

the 4-hr period and for this reason were not

included in the averages plotted in figure 19. Figure 19 shows that the average of the maxima

for the 15 houses was about 17 kw whereas figure

16 shows that the average demand of the 16

houses at the time of the maximum demand for the entire housing area was only about 8 kw

during the month of January I960. During the

month of August 1959, the maximum 15-min

demands in the 16 sample houses averaged about

13 kw whereas the average 15-min demand at the time of the maximum demand in the entire

housing area was about 0)2 kw. Figure 19 shows

a high degree of coincidence between the maximum

demands of each of the components of the load

in the sample houses and the maximum for the

house as a whole during both the winter and

summer months used for illustration. In order to evaluate the magnitude of the component and total power demands in each of the

sample houses in a more comprehensive way than was possible with the limited graphical presenta-

* <

tu V

JM

TO!

ICH

HO 3 \

I ' 3

<£

FOR

El

IMUM

'

EACH

ME

OF

:mano

IF

MAX f

0 JTIME

( ?

<sE

O

. .A. J

«^7

TIME, HOURS

Figube 19. Average of the total and component 15-min power demands for 15 sample houses during a 4-hr period bracket- ing time of maximum total demand for each house which

occurred during the periods January 8-February 8, 1960,

and August 7-September 8, 1959.

tion in figures 14 to 19, tables 14 to 19 were prepared

to show coincident power demands in all the

sample houses for 3 winter months and 3 summer

months at the time of the monthly maximum

power demand for the entire housing area. Considering winter operation first, tables 14 to 16 show that the average total house demand for

the 16-house sample approximated the average for

the entire housing area during 2 of the winter

months studied, viz, January and February.

Based on averages for the 16-house sample, the

heat pump contributed from 48 to 62 percent of the

total house load, the water heater from 19 to 29

percent, the miscellaneous devices from 12 to 21

percent, and the electric range from }{ to 3 percent.

It will be noted that the heat pump in every house

used some energy during the 15-min period

representing the maximum demand for each of the

3 months, and that the average power demand for

the heat pump in all the sample houses ranged

from 3.6 to 5.0 kw for the 3 months. The water

heaters in 5 to 8 houses, in different months, were

energized at the time of the maximum demand,

and in only a few cases were the electric ranges

using a significant amount of energy. Tables 14

to 16 show that the maximum demand for the

entire housing area occurred between 0900 and

1100 hr for the 3 winter months represented.

Tables 17 to 19 show that in the summer months

of June and August 1959 the average total house

demand for the 16-house sample exceeded the

21
average for the entire housing area by amounts

up to 16 percent and was less than the average for

the entire housing area by 17 percent in July.

Based on averages for the 16 sample houses, the

heat pump contributed from 35 to 58 percent of

the total house load, the water heater from 9 to 25 percent, the miscellaneous devices from 20 to 49 percent, and the electric range from 1 to 4

percent. The tables show that the heat pump in a

large majority of the houses operated during a part of the 15-min period representing the maximum demand, water heaters in 3 to 7 houses were

energized at the time of maximum demand, and

veiy few of the electric ranges contributed a

significant amount to the total load. Tables 17

to 19 show that the maximum demand for the

entire housing area occurred between 1000 hr and noon for the 3 summer months studied.

The negative values that appear for the power

demand of the miscellaneous devices in tables 14

to 19 indicate that the demand periods were not

perfectly synchronized and that the reported demand values do not represent simultaneous oc- currences in some cases. However, the demands

reported for the heat pump, water heater, electric range, and the house total are recorded values that

certainly occurred within a few minutes of each

other.

Table 14. Total and component 15-min power demands in

each sample house at the time of monthly maximum demand

for the entire housing area, December 10, 1959-January

8, 1960

(Time of housing area maximum demand: 0915, January 8, 1960)

Contractor's house No. House

total Heat pump

Hot water

heater Range Misc. 1

2-bedroom houses

14 kw

9.5

5.4 3.5

6.0 4.3

t>0

kw

3.5

5.4 2.8

2.4

2.0

l>0.2

kw

4.2

00

0

0

' 0

kw

0

00

00 b0

kw

1.8

00.7 3.6

2.3

b -0.2

180 263

301

585 843

3-bedroom houses

4 3.3

(°) 6.0 3.5

6.5 4.8

2.0

5.1

2.5 M

C)

1.2

5.6 3.6

0.2

3.0

2.7

(.") 0

000

4.2

3.0

0

(°) .01 0

00

0.4

0

-1.9

(

c

) t°) 2.3 0.9

1.2 -2.8

-0.9

74

163

172

577

587 656

770.

4-bedroom houses

467 12.6

8.0 7.9

6.7

4.0

0

000.7 468 1.3 Average for sample houses

Average for 1,535 houses

5.8 3.6 1.3 .03 0.7

7.6

Table 15. Total and component 15-min power demands in

each sample house at the time of monthly maximum demand

for the entire housing area, January 8-February 8, 1960

(Time of housing area maximum demand: 1100, Jan. 18, 1960)

Contractor's house No. House

total Heat pump

Hot water

heater Range Misc."

2-bedroom houses

14.. kw

13.8 1.2 7.5

8.0

4.3

4.4

kw

2.1 3.7

3.5

4.0 2.2

4.0

kw

4.8

04.4

0

0

0

kw

00

00

0

0

kw

6.9 -2.5

-0.4

4.0

2.1 0.4

180 263

301 585 843

3-bedroom houses

4 3.0 2.2

15.5 6.0

10.8 8.5

1.4 7.0

2.7 1.8 3.6

1.8

9.0

1.8

4.0 1.8

0

04.5

4.7

05.0

04.2

00

0.8

0.4

00.2

0.1

0

0.3

0.4

6.6 -0.9

1.8

1.5 -2.7

1.0

74

163

172..

577

587 656

770

4-bedroom houses

467 13.3

13.4 8.03.7

4.0

3.5

00

1.3

468 0.2 Average for sample houses

Average for 1,535 houses

7. 5 3.6 2.2 0.

1

1.6

8.1

Calculated by difference.

Table 16. Total and component 15-min power demands in each sample house at the time of monthly ?naximum demand

for the entire housing area, February 8 to March 8, 1960

(Time of housing area maximum demand: 1015, March 2, 1960)

Contractor's house No. House Heat Hot water Range Mkca total pump heater

2-bedroom houses

kw kw kw kw kw

14 6.7 5.9 0.0 0.0 1.7

180 12.7 3.5 4.7 .0 4.5

263 9.5 8.5 2.4 .0 -1.4

301 14.0 6.0 3.1 .0 4.9

585 7.0 4.2 0.0 .2 2.8

843 — 3.5 3.7 .0 .0 -0.2

3-bedroom houses

4.. 6.0 6.1 0.0 0.0 -0.

1

74 1.2 3.5 .0 3.0 -5.3

163 13.9 2.7 4.0 0.2 7.0

172 13.5 3.5 4.4 .0 5.6

577 8.9 7.0 0.0 1.2 0.7

587 6.4 4.6 .0 0.0 1.8

656 3.2 2.2 .0 .0 1.0

770 11.9 3.4 4.0 .4 4.1

4-bedroom houses

« Calculated by difference,

b House No. 843 apparently not occupied,

average,

o Not available.

These data not included in t he

467.. 10.9

11.4

7.9

7.8 0.24.4

0.0

.0 2.8 468- -0.8

Average for sample houses. Average for 1,535 houses...

8.8 5.0 1.7 0.3 1.8

9.0

Calculated by difference.

22
The total and coincident component 15-min

demands occurring at the thne of the monthly

maximum total demand in each sample house are summarized for 3 winter months in tables 20 to 22

and for 3 summer months in tables 23 to 25. It will be noted in these tables that none of the

maximum demands of the sample houses during

either winter or summer occurred coincidentally

with the maximum demand of the entire housing

area listed in tables 14 to 19. In the 3 winter

months, the average of these maximum values

ranged from 17.2 to 18.2 kw, of which about 35

percent was power used by the heat pump, about

20 percent was used by the water heater, about 5 percent was used by the electric range, and about

39 percent was used by the miscellaneous devices.

Tables 20 to 22 also show that, for the 3 winter

months, the 15-min power demand exceeded 1 kw

for 12 to 16 heat pumps, for 13 to 15 water heaters,

and for 3 to 4 electric ranges in the sample houses

at the time of the maximum 15-min monthly power

demand in each house. At the same time, the

miscellaneous devices in 14 to 16 of the sample

houses were using more than 1 kw of electric power.

For the 3 summer months, the average of the

maximum monthly power demands of the 16

sample bouses ranged from 13.8 to 13.9 kw, of

which about 23 percent was power used by the heat

pump, about 26 percent was used by the water

heater, about 3 percent was used by the electric range, and about 45 percent was used by the misTable 17. Total and component 15-min power demands in

each sample house at the time of monthly maximum demand

for the entire housing area, June 8 to July 7, 1959

(Time of housing area maximum demand: 1045, June 29, 1959)

Contractor's house No. House Heat Hot water Range Misc."

total pump heater

2-bedroom houses

kw kw kw kw kw

14 12.2 1.8 0.6 0.0 9.8

180 3.1 1.5 .0 .0 1.6 263 5.4 0.0 3.4 .0 2.0

301 2.7 2.7 0.0 .0 0.0 3.2 0.0 .0 .0 3.2

843 7.0 2.8 3.8 .0 0.4

3-bedroom houses

4 4.2 2.1 3i6 0.0 -1.5

74 2.5 2.0 0.0 .0 0.

5

163 5.8 3.0 .0 .0 2.8

172 3.3 1.5 .8 .5 0.5

577 2.0 2.0 .0 . 1 —.1

587 3.2 2.1 ' .0

" .0 1.1 656 0.9 1.1 .0 .0 -0.2

770 8.0 0.0 .0 .0 8.0

4-bedroom houses

467 - 9.4 4.2 3.7 0.0 1.5 468 9.4 (") 4.1 0.0 (») Average for sample houses- 5.1 1.8 1.3 0.04 2.0 Average for 1,535 houses 4.9

a Calculated by difference.

b Xot available.

Table 18. Total and component 15-min power demands in

each sample house at the time of monthly maximum demand

for the entire housing area, July 7 to August 7, 1959

(Time of housing area maximum demand: 1145, August 3, 1959)

Contractor's house No. House Heat Hot water Range Mise.»

total pump heater

2-bedroom houses

kw kw kw kw kw

14 8.5 2.1 4.5 0 1.9 180 2.0 2.1 0 0 -0.1

263 7.8 1.9 4.9 0 1.0

301 2.8 2.1 0 0 0.7

585 2.4 2.0 0 0 0.4

843 2.0 0.8 0 0 1.2

3-bedroom houses

4 3.0 2.0 0 0 1.0

74 8.2 2.4 0.7 0.4 4.7

163 4.5 3.0 0 0 1.5

172 2.5 3.0 0 0.5 -1.0

577 ._ 2.8 2.7 (1 0 0.1 587 3.4 2.4 3.0 0.2 -2.2

656_- 0.9 2.3 0 0 —1.4

770 3.4 0 0 0 3.4

4-bedroom houses

467 5.5 3.8 0 0 1.7 468 4.8 4.4 0 0 0.4 Average for sample houses. 4.0 2.3 0.8 0.1 0.8

Average for 1,535 houses. _. 4.8

a Calculated by difference. Table 19. Total and component 15-min power demands in each sample house at the time of monthly maximum demand

for the entire housing area, August 7 to September 8, 1959

(Time of housing area maximum demand: 1145, August 24, 1959)

Contractor's house No. House Heat Hot water Range Misc. * total pump heater

2-bedroom houses

kw kw kw kw kw

14 5.7 2.0 0 0 3.7

180 1.6 2.0 0 0 -0.4

263 3.3 0 0 0 3.3

301 5.3 3.0 0 0 2.3

585 0.4 0 0 0 0.4

843 2.6 2.0 0 0.4 0.2

3-bedroom houses

4 2.8 2.3 0 0 0.5

74..J- 11.4 2.8 0 1.0 7.6 163- . 8.0 3.0 0 0 5.0

172 9.4 2.0 2.0 0.5 4.9

577 4.6 2.4 2.

1

0 0.1

587 656 6.7 3.4 0 0.2 3.1 770 3.2 2.0 0 0 1.2

4-bedroom houses

467 13.5 6.3

5.2

0.7 3.20

01.0 5.1 468 4.6 Average for sample houses.

Average for 1,535 houses.

5.7 2.2 0.5 0.2 2.8

4.9

« Calculated by difference.

23
cellaneous devices. Tables 23 to 25 show thai the

heat pumps in 14 to 15 sample houses, the water

heaters in 13 to 14 sample houses, and the electric ranges in 1 to 2 sample houses were each using more than 1 k\v of electric power at the time of the

maximum summer power demand. At the same

lime the miscellaneous devices in 14 to 16 of the

sample houses were using more than 1 kw of elect l ie power.

The power demand data shown in tables 20 to 25 show that the miscellaneous devices, with one

exception, made a larger contribution to the

monthly maximum demand in the sample houses on the average than any of the other components

of the load during both winter and summer

conditions.

Tables 20 to 25 show that maximum demands

in the individual houses occurred on different

days and at different times of the day in most

cases, both winter and summer. A study of the

demand charts and the charts from the outdoor

temperature recorders also showed that the maximum demands in the individual houses occurred

at various outdoor temperatures. In the period

from January 8 to February 8, 1960, the outdoor

temperatures, rounded to the nearest degree at

the time of the monthly maximum demands in the

16 sample houses, ranged from 21 to 58 °F,

distributed as follows:

Outdoor tempera- Number

lure range, °F of cases 21 to 30 2

31 to 40 8 41 to 50 4

51 to 60 2

In the period from August 7 to September 8, 1959,

the outdoor temperatures, rounded to the nearest

degree, at the time of the monthly maximum

demands in the 16 sample houses, ranged from 78

to 93 °F, distributed as follows

:

Outdoor tempera- Number

lure range, °F of cases 71 to 80 2

81 to 90 10

91 to 100 4

These results indicate that the maximum demands

in individual houses during winter and summer

were not directly related to the magnitude of the

heating and cooling loads and confirm the findings

that the miscellaneous loads contributed more to the maximum demand than do the heat pumps.

Tables 26 to 31 show the monthly maximum

power demand for each of the 16 sample houses

and the monthly maximum power demand of each

of the four components comprising the total house load. The monthly maximum power demands of the components did not necessarily

Table 20. Total and component 15-min power demand

occurring at the time of the monthly maximum total demand

in each sample house, December 10, 1959 to Jan uary 8, 1960

ContracTime of maximumtotal demand for house Maxi- mum

total

Coincident component demand

tor's demand

house for Heat Hot

No. Date Time house pump water Range Mise.°

heater

2-bedroom houses

kw kw kw kw kw

14 Jan. 1, 1960 1130 16.8 5.8 4.5 0.1 6.4

180 Jan. 7, 1960 1730 16.7 4.0 4.5 2.5 5.7 263 Jan. 6, 1960 1230 17.1 7.2 5.0 0 4.9

301 Jan. 1, 1960 0845 17.6 7.0 4.2 0 6.4 585 Dec. Hi. Liij'.l 0600 18.8 7.9 4.4 0.7 5.8

843 Jan. 6, 1960 1145 b 11.6 >>8.4 t>3.7 i>0 "-0.5

3-bedroom houses

4 Jan. S, 1960 0730 16.6 7.6 4.5 3.8 0.7

74 Dee. 18. 1959 0800 12.0 6.0 0 2.9 3.1

163 Jan. 6, 1960 1300 20.8 4.4 2.7 0.

1

13.6 172 Jan. 7, 1960 1145 18.2 7.0 4.8 .4 6.0

577 Jan. 8, 1960 0700 19.2 9.0 3.5 0 6.7

587 Dec. 30, 1959 1015 15.9 2.3 4.9 0 8.7

656 Jan. 5, 1960 1045 17.0 4.6 4.4 0.1 7.9

770 Dec. 30, 1959 2015 16.2 9.1 4.4 .5 2.2

4-bedroom houses

467 Dec. 28, 1959 0830 17.9 9.4 4.2 0.2 4.1 468 Dec. 28, 1959 1045 17.9 4.5 2.9 0 10.5

Average for 15 houses 17.2 6.4 3.9 0.8 6.2

° Calculated by difference.

b House No. 843 apparently not occupied. These data not included in the

average.

Table 21. Total and component 15-min power demand

occurring at the time of the monthly maximum total demand

in each sample house, January 8 to February 8, 1930

Time of maximum Maxi- Coincident component demand

Con- total demand for house mum

trac- total

tor's demand

house for Heat Hot

No. Date Time house pump water Range Misc.»

heater

2-bedroom houses

kw kw kw kw kw

14 Jan. 17,1960 1215 16.1 3.0 4.5 0 8.6

180 Jan. 20,1960 1330 17.9 0 4.5 1.0 12.4 263 Jan. 20,1960 1145 14.8 0 5.0 0 9.8

301 Jan. 29,1960 0915 16.9 2.5 4.2 0 10.2

585 Jan. 20,1960 1715 18.8 6.0 4.8 0.9 7.1 843 Jan. 25,1960 1000 16.2 8.5 0 0 7.7

3-bedroom houses

4 Jan. 31,1960 0900 17.6 1.0 2.4 4.0 10.2

74_ Feb. 5, 1960 1815 12.4 4.0 3.0 3.0 2.4

163 Feb. 6, 1960 1430 19.6 9.2 4.5 1.0 4.9

172 Jan. 16, 1960 1815 18.6 5.9 4.5 4.0 4.2

577 Jan. 17, 1960 0845 19.4 4.0 2.0 2.0 11.4 587 Feb. 6. 1960 0900 16.2 10.0 4.0 1.0 1.2

656 Jan. 25,1960 0915 15.8 1.0 4.5 0.2 10.1

770_ Jan. 18,1960 1300 14.6 4.0 4.0 0.2 6.4

4-bedroom houses

467 Jan. 22,1960 0715 20.8 13.9 3.8 0 3.1 468 Jan. 21,1960 0730 19.4 14.0 2.8 0 2.6

Average for 16 houses. where applicable 17.2 6.4 3.7 1.1 7.0

a Calculated by difference.

24
Table 22. Total and component 15-min power demand

occurring at the time of the monthly maximum total demand

in each sample house, February 8 to March 8, 1960

ContracTime of maximum

total demand for house Maxi- mum

total

Coincident component demand

tor's house No. Date Timedemand

for house Heat pumpHot

water

heater Range Misc.

»

2-bedroom houses

kw kw kw kw kw

14 Mar. 3, 1960 1145 16.7 5.7 4.6 0 6.4

180 Feb. 27, 1960 1030 17.7 7.4 4.5 0 5.8

263 Feb. 19, 1969 1330 18.1 5.5 5.0 0 7.6

301 Feb. 1.5, 1960 0845 17.6 (") (b

) (b

) (b) 585 Feb. 17, 1960 0545 19.1 5.6 4.4 0 9.1 843 Feb. 26, 1960 0700 17.6 8.1 3.4 3.1 3.0

3-bedroom houses

4 Mar. 3, 1960 0730 17.6 2.0 4.7 4.4 6.5

74 Feb. 14. 1969 2145 17.2 13.8 3.0 3.8 -3.4

163 Mar. 3, 1969 1115 18.2 0.4 3.5 0.1 14.2 172 Mar. 3, 1969 1145 17.6 0 4.7 0 12.9 577 Feb. 29, 1969 0715 20.

1

10.2 4.5 (b

) 5.4

587 Mar. 2, 1960 0900 17.2 10.4 0 0 6.8

656 Mar. 6, 1969 1645 17.8 0 4.5 0.4 12.9 770 Feb. 24, 1960 1000 16.8 3.3 0 .4 13.1

4-bedroom houses

467 Feb. 29, 1969 0815 20.8 10.8 4.3 0 5.7 468 Mar. 1. 1960 1115 20.2 7.8 3.0 0 9.4

Average for 15 houses 18.1 6.1 3.6 0.9 7. 7

» Calculated by difference.

t> Xot available.

Table 23. Total and component 15-min power demand

occurring at the time of the monthly maximum total demand

in each sample house, June 8 to July 7, 1959

Time of maximum Maxi- Coincident component demand

Con- total demand for housi/ mum

trac- total

tor's demand

house for Heat Hot NTo. Date Time house pump water Range Misc. 1 heater

2-bedroom houses

kw kw kw kw km

14 Jur.e 21, 1959 1430 13.9 3.1 0.6 0.4 9.8

189 Julv 4, 1959 1230 14.7 2.8 4.9 1.8 5.2

263 June 26, 1959 1100 13.4 2.8 4.4 0 6.2

301 Julv 1, 1959 1630 13.4 3.1 4.5 0 5.8 585 June 10, 1959 1015 13.4 3.0 5.0 0 5.4 843 June 22, 1959 1030 12.2 2.8 4.2 0.2 5.0

3-bedroom houses

4 June 29, 1959 0830 11.8 0.9 4.8 0 6.1

74 Julv 1, 1959 2900 13.4 13.2 3.0 0 -2.8

163 June 8, 1959 1145 15.1 4.8 5.0 0.5 4.8 July 4, 1959 2045 14.4 3.0 4.5 0 6.9 577 June 22, 1959 2030 12.5 1.6 3.3 0 7.6 Julv 6, 1959 1130 14.1 2.6 4.7 0.9 5.9 656 July 5. 1959 1715 13.0 1.3 2.0 0 9.7

770 June 8, 1959 2100 14.2 1.1 4.5 0 8.6

4-bedroom houses

467 June 28, 1959 1430 15.4 5.4 0 0 10.0 468 June 27, 1959 1215 15.9 ( b

) 0 0.5 C)

Average for 16 houses. where applicable 13.8 3.4 3.5 0.3 6.3

a Calculated by difference.

b Xot available.

Table 24. Total and component 15-min power demand

occurring at the time of the monthly maximum total demand

in each sample house, July 7-August 7, 1959

ContracTime of maximumtotal demand for house Maxi- mum

total

Coincident component demand

tor's demand

house for Heat Hot

No. Date Time house pump water Range Misc. a heater

2-bedroom houses

kw kw kw kw km

14 July 20,1959 1145 12.7 2.5 4.2 2.4 3.6

180 Aug. 5, 1959 0900 11.7 1.0 (be) 0 ( b

) 263 Aue. 3, 1959 1230 14.0 2.7 4.8 0 6.5

301 Julv 20,1959 0845 13.8 3.0 4.8 0 6.0

585 Aug. 6, 1959 1800 14.9 2.0 2.4 3.2 7.3

843 July 17,1959 1830 11.7 2.0 2.8 0.5 6.4

3-bedroom houses i— . . Julv 10,1959 1600 13.7 3.7 0 0 10.0 74 Aug. 1, 1959 1145 13.2 3.2 4.2 0 5.8

163 Julv 11,1959 1445 17.7 2.8 0 0.5 14.4

172 Aug. 5, 1959 1145 14.4 2.4 4.2 1.0 6.8

577 Julv 25.1959 1500 14.0 2.5 4.6 0.4 7.5

587 Julv 8. 1959 1900 13.2 6.5 4.6 0 2.1

656 Julv 9.1959 1145 13.6 0.6 4.4 0 8.6

770 Aug. 6, 1959 1330 12.6 2.9 4.0 0 5.7

4-bedroom houses

467 July 16,1959 1130 13.6 2.5 4.0 0.6 6.5

468 Aug. 6, 1959 1630 16.8 6.0 4.0 0.6 6.2

Average for 16 houses, w here applicable 13.9 2.9 3.5 0.6" G.9

a Calculated by difference.

b Not available.

c Water heater not in use.

Table 25. Total and component 15-min power demand

occurring at the time of the monthly maximum total demand

in each sample house, August 7—September 8, 1959

ContracTime of maximumtotal demand for house Maxi- mum

total

Coincident component demand

tor's house No. Date Time

demand

for house Heat pump

Hot

water

heater Range Misc. a

2-bedroom houses

kw kw kw kw kw

14 Aug. 20,1959 1215 12.8 2.0 4.5 0 6.3 180- - Sept. 2,1959 1315 13.4 2.8 4.4 1.4 4.8

263 Sept. 7,1959 1200 13.5 3.0 4.4 0 6.1

301 Aug. 16,1959 1030 14.0 3.0 4.5 0 6.5

585 Aus. 25.1959 1745 13.7 5.0 4.6 2.7 1.4 843 Aug. 28, 1959 1245 11.5 0 0.5 0 11.0

3-bedroom houses

4 Sept. 8,1959 0930 15.6 2.8 0.8 0 12.0

74 Aug. 23.1959 1400 15.3 4.5 4.4 0 6.5

163 Sept. 4,1959 1615 15.6 5.0 4.2 0.5 5.9

172 Aug. 17,1959 1845 12.8 2.0 4.5 1.0 5.3

577 Aug. 20,1959 2015 13.6 2.2 4.6 0.5 6.3

587 Aug. 10,1959 1130 12.4 2.1 4.7 0.5 5.1 656, Sept. 1. 1959 0945 13.4 3.0 4.4 0 6.0

770 Aug. 17,1959 0645 13.2 1.2 4.2 0 7.8

4-bedroom houses

467 Aug. 21,1959 1415 15.2 5.5 4.3 0 5.4

468 Aug. 29,1959 1415 16.8 7.2 4.4 0 5.2

Average for 16 houses 13.9 3.2 4.0 0.4 6.4

a Calculated by difference.

25
coincide1 with the monthly maximums for the house

as a whole. The degree of coincidence between

the monthly component maximums and the

monthly maximum for the entire house is shown

as a coincidence Factor in these tables. For the

purpose of these tables, the coincidence factor is denned as the ratio of the measured maximum

power demand of the house to the sum of the maximum power demands of t he appliance components

in the house over a period of a month. The time

at which the maximum 15-min power demand

occurred for each house is reported in tables 20 to 25, inclusive, for these same months.

Tables 26 to 28, for the 3 winter months used

for analysis, show that the maximum power

demands for the various components were fairly

consistent from month to month when comparing

averages for all of the sample houses. The

maximum power demands for the heat pump

ranged from 5.6 to 14.8 kw in different houses

with the 3-month average for all houses being

9.2 kw. Individual houses cannot reasonably be

compared because different house types were

equipped with different amounts of supplementary resistance heating, and houses 467 and 468 were equipped with two heat pumps whereas the

others in the sample contained only one. The

maximum power demand of the water heaters

varied from 4.4 to 5.4 kw, probabfy due to voltage

variations at different houses. The maximum

Table 26. Maximum total and component 15-min poiver

demands occurring at any time during the month in each sample house, December 10, 1959-January 8, 1960

Contractor's house No.

Maximum noncoincident power demands for month

House

Heat Hot pump water Range

heater Misc.

Monthlycoinci- dence

factor

for the house

2-bedroom houses

kw kw kw kw kw

14 16.8 6.6 4.8 3.7 6.4 .78 180... 16.7 7.7 4.8 4.0 5.2 .77

263 17.1 8.6 5.2 b 1.0 11.7 b.65

301 17.6 7.5 4.5 7.6 7.6 .65

585 18.8 8.4 5.0 3.7 7.4 .77 843 _ <= 11.6 °8.6 « 5.2 "5.0 <=.62

3-bedroom houses

4 16.6 8.4 4.8 5.1 5.1 .71 74 12.0 8.1 4.6 6.2 3.1 .55

163 20.8 11.2 5.2 4.3 4.7 .82

172 18.2 9.3 5.0 4.5 6.1 .73

577 19.2 10.3 5.0 5.6 5.8 .72

587 15.9 10.2 5. 1 4.2 6.9 .60

656. 17.0 9.9 4.8 4.1 9.9 .59

770 16.2 9.8 4.8 3.6 6.7 .65

4-bedroom houses

467 17.9 12.2 4.6 3.0 5.0 .72 468 17.9 14.0 4.8 4.3 5.7 .62 Average for 15 houses 17.2 9.5 4.9 4.6 6.5 .69

» From table 20.

t> Range meter incorrectly wired. These data not included in the average.

" House No. 843 apparently vacant. These data not included in the average.

Table 27. Maximum total and component 15-min power demands occurring at any lime during the month in each sample house, January 8-February 8, I960

Contractor's house No.

Maximum noncoincident power demands for month

House 0 Heat Hot pump water Range

heater Misc.

Monthly

coinci- dence

factor

for the house

2-bcdroom houses

kw kw kw kw kw

14 16.1 6.8 4.8 5.7 8.2 .63

180 17.9 7.7 4.8 2.8 8.5 .75

263 14.8 8.7 5.2 b 0.6 8.8 b .64

301 16.9 7.4 4.6 4.0 7.2 .73

585 18.8 8.4 4.9 3.9 6.0 .81 843 16.2 8.3 5.4 4.2 6.2 .67

3-bedroom houses

4 17.6 8.4 4.8 6.3 6.5 .68

74 12.4 7.6 4.5 5.7 5.2 .54

163 19.6 10.8 5.2 4.9 8.2 .67

172 18.6 6.6 5.0 5.4 6.0 .81 577. 19.4 10.5 4.9 5.0 8.4 .67

587 16.2 10.1 5.1 4.4 5.4 .65

656 15.8 9.7 4.8 4.3 7.4 .60 770 14.6 10.

1

4.6 3.6 7.5 .57

4-bedroom houses

467 20.8 14.0 4.7 3.0 5.8 .76

468 19.4 14.2 4.7 4.0 4.5 .71 Average for 16 houses, where

applicable 17.2 9.3 4.9 4.5 6.9 .68

" From table 21.

b Range meter incorrectly wired. These data not included in the average. Table 28. Maximum total and component 15-min power demands occurring at any time during the month in each sample house, February 8-March 8, 1960

Contractor's house No.

Maximum noncoincident power demands for month

Monthly

coinci- dence

factor

for the House « house Heat pumpHot

water

heater Range Misc.

2-bedroom houses

kw kw kw kw kw

14 16.7 6.6 4.7 3.

1

5.7 .83

180 17.7 7.8 4.7 4. 1 5.3 .81 263 18.1 8.6 5.3 b0.7 9.0 b.77

301 17.6 7.4 4.4 3.8 5.6 .83

585 19.1 8.1 5.0 5.0 4.2 .86

843 17.6 8.6 5.4 4.3 5.2 . 75-

.

3-bedroom houses

4 17.6 7.4 4.8 5.5 9.4 .65

74 17.2 7.5 4.5 5.9 8.8 .64

163... 18.2 5.6 4.6 5.3 9.1 .74

172. 17.6 9.7 5.0 4.6 5.7 .70

577 20.

1

10.6 4.9 5.8 5.1 .76

587 17.2 10.5 5.2 2.8 7.0 .67

656 17.8 9.4 4.7 4.4 7.9 .67

770 _. 16.8 9.5 4.5 3.6 8.2 .65

4-bedroom houses

467 20.8 14.8 4.7 4.0 9.8 .62 468 20.2 8.2 4.7 6.7 9.2 .70 Average for 16 houses, where

applicable 18.1 8.8 4.8 4.6 7.2 .73

» From table 22. b Range meter incorrectly wired. These data not included in the average 26
power demands of the electric ranges varied

widely depending on the habits of the individual

occupant. Probably none of the recorded maximum power demands for the electric ranges

represents the full connected load of this appliance.

The miscellaneous devices provided the second

largest maximum power demand on the average.

The biggest single electrical load included in the

miscellaneous group was the clothes dryer, with a power consumption of about 5 kw. Other significant loads in the miscellaneous group were the

resistance heater in the bathroom, the washing

machine, and such appliances as electric irons

and toasters. The coincidence factor for individual houses

ranged from 0.54 to 0.87 during the 3 winter

months, but the average value for all houses in the

sample varied only between 0.68 and 0.73 in the

3-month period.

Tables 29 to 31, for the 3 summer months used

for analysis, show that the maximum power

demands for the various components were fairly

consistent from month to month based on the

averages for all the sample houses. The average

of the maximum values for the total house load in

all houses was 3 to 4 kw lower for the summer

months than for the winter months, due almost

entirely to a corresponding decrease in the

maximum power demands for the heat pump in

the summer. The maximum power demands of

Table 29. Maximum total and component 15-min -power demands occurring at any time during the month in each sample house, June 8-July 7, 1.959

Maximum nonce-incident power demands for month

Monthly

coinci- No.

House a Heat pump

Hot

water

heater Range Misc.

factor

for the house

2-bedroom houses

kw kw kw kw kw

14 13.9 5.6 4.8 5.0 10.

1

.55

180 14.7 3.2 5.4 3.5 6.8 .78

263- 13.4 3.1 5.

1

b 1.0 6.0 b.88

301 13.4 3.5 5.1 3.5 10.2 .60 585 13.4 3.1 5.0 3.4 5.5 .79

843 12.2 4.4 5.4 3.8 6.3 .61

3-bedroom houses

4 11.8 4.4 5.3 5.4 6.2 .55 74 13.4 3.3 4.7 4.0 7.2 .70

15.1 7.7 5.2 4.4 11.4 .53

172 14.4 3.2 4.8 4.3 6.9 .75 577 _ _ 12.5 3.2 5.1 5.4 7.6 .59

587 14.

1

3.2 5.0 2.9 6.9 .78 656 13.0 7.8 5.0 3.9 7.6 .53

770 14.2 3.1 4.8 2.4 8.1 .77

4-bedroom houses

467 15.4 5.8 4.8 3.4 9.6 .65

468 15.9 5.9 4.8 5.0 6. 1 .73 Average for 16 houses, where

applicable 13.8 4.4 5.0 4.0 7. 7 .66

Table 30. Maximum total and component 15-min power demands occurring at any time during the month in each sample house, July 7-August 7, 1.959

Contractor's house

Maximum noncoincident power demands for monthMonthly

coinci- dence No. House a Heat pump

Hot

water

heater Range Misc.

factor

for the house

2-bcdroom houses

kw kw kw - kw kw

14 12.7 3.2 4.9 4.4 8.8 .60

180 11.7 3.1 b 0 2.0 9.8 .79

263 14.0 3.1 4.9 "1.0 6.4 = .91

301 13.8 3.5 5.1 4.

1

6.1 .73

585 14.9 3.4 4.8 3.2 . 6.2 .85

843 11.7 3.3 5.2 4.8 7.5 .56

3-bedroom houses

4 13.7 5.0 5.1 3.1 10.5 .58

74 13.2 5.5 4.7 4.9 5.9 .63

163 17.7 3.3 5.0 5.3 9.8 .76

172 14.4 3.2 4.6 3.0 5.8 .87

577 14.0 3.4 4.8 6.9 6.5 .65 587 13.2 3.3 4.9 2.7 6.2 .77 656 13.6 3.5 4.7 2.5 8.6 .70

770 12.6 6.4 4.8 3.5 7.1 .58

4-bedroom houses

467 13.6 5.5 4.6 3.0 6.6 .69 468 _ 16.8 6.0 4.7 4.3 5.5 .82 Average for 16 houses, where

applicable 13.9 4.0 4.9 3.8 7.3 . .71

a From table 24.

b House No. 180 apparently unoccupied during most of this period. Water

heater not in use.

0 Range meter incorrectly wired. These data not included in the average.

Table 31. Maximum total and component 15-min power

demands occurring at any time during the month in each sample house, August 7-September 8, 1959

Contractor's house

Maximum noncoincident power demands for month

Monthly

coinci- dence No.

House a Heat pump

Hot

water

heater Range Misc.

factor

for the house

2-bedroom houses

14, kw

12.8 kw3.1 kw

4.9 kw

4.0 kw6.1 .71 180 13.4 3.1 5.1 3.9 4.6 .80 263 13.5 3.1 4.9 i> 0. 5 5.8 b.94

301 14.0 3.5 5.1 3.8 6.3 .75

585 13.7 5.4 4.9 5.1 5.1 .67

843 11.5 1.6 5.2 4.1 7.7 .62

3-bedroom houses

4 15.6 5.0 5.0 3.9 8.4 .70

74 15.3 4.9 4.6 4.2 7.5 .72

163 15.6 5.1 5.0 4.5 6.1 .75

172 12.8 3.2 4.6 3.3 5.6 .77

577 13.6 3.2 4.8 6.1 5.8 .68

587 12.4 5.6 4.9 1.9 5.1 .71 656 13.4 3.4 4.7 4.0 6.2 .73

770 13.2 3.1 4.5 3.8 7.1 . 71

4-bedroom houses

467 15.2 5.8 4.6 4.3 5.4 .76 468 16.8 7.2 4.6 4.6 5.5 .77

Average for 16 houses, where

applicable 13.9 4.1 4.8 4.1 6.1 .72

» From table 23.

b Range meter incorrectly wired. These data not included in the average.

» From table 25.

b Range meter incorrectly wired. These data not included in the average.

27
the water heater, electric range, and miscellaneous

devices were comparable, winter and summer.

Kxcepting house 203, the coincidence factor for

the sample houses ranged from 0.53 to 0.87 during

the 3 summer months, but the monthly average

for all houses varied only from 0.66 to 0.72 for

the 3-month period. It will be noted in tables 29

to 31 that the coincidence factor for house 263 was

significantly higher than those for all other houses

in the sample. Investigation revealed that the

demand meter on the electric range for this house was incorrectly wired causing the meter to indicate a low value most of the tune. Therefore,

the coincidence factors for house 263 were not

used in determining either the summer or winter

average values.

d. Frequency Distribution of Power Demand Values

It was noted in figures 4 to 13 that high 15- min power demand values, somewhat lower than

the monthly maximum value, occurred at various

times throughout the day, usuallv during the

period from 0630 to 2000 hr. The exact number

of these occurrences cannot be counted in figures

4 to 13 because these graphs show only the one

highest value of power demand occurring at each

15-min interval of the day. Information on the

frequency of these high power demands is of importance in determining the requirements of

the distribution system and in selecting possible

devices for limiting the magnitude of the maximum power demand in the houses.

20.0

Figure 20. Frequency distribution of 15-min power demand

greater than 5 kw for 5 houses during the period January 8-

February 8, I960.

Figures 20 and 21, representing data for January

I960 and August 1959, respectively, were plotted

to show the frequency of recurrence of 15-min

power demands at various levels of demand.

The curves are plotted for the same 5 houses for which the daily pattern of power demand was

illustrated in figures 4 to 13. Because the higher

values were of primary interest, only demands

greater than 5 kw were used.

An inspection of figures 20 and 21 indicates that

the frequency distribution curves are approximately exponential in shape for the range of power

demand values of 5 kw and higher. A mathematical expression of the form y=Ce~kT was used

to fit curves to some of the observed data. The

values of constants C and k differed somewhat for different houses; x represented the 15-min power

demand in kilowatts, and y represented the per- cent of the total monthly demand intervals at tin's value of power demand.

The number of 15-min intervals in the month

for which the power demand would be expected

to be at any selected value from 5 kw to the

maximum can be derived from figures 20 and 21

for this group of sample houses. Tables 32 and

33 show the power demands corresponding to frequencies of 0.1, 1.0, and 5.0 percent for the

period January 8, 1960-February 8, 1960, and to frequencies of 0.1, 1.0, and 3.0 percent for the

period August 7, 1959-September 8, 1959, taken

from figures 20 and 21. Since there are ninety-six

15-min periods in a day, a frequency of 1 percent

corresponds to about one 15-min period per day

on the average. These tables show that the demands of houses 14, 263, and 587 were similar

during January and that those for houses 14, 263,

and 656 were similar during August. The de15.0

4.0 6.0 8.0 10.0 I2D 14.0 16.0 18.0 20.0

15 - MINUTE POWER DEMAND, kw Figure 21. Frequency distribution of 15-min power demands

greater than 5 kw for 5 hoxises during the period August 7—

September 8, 1959.

28
rnands for house 468, a 4-bedroom house, were

larger than the others for both months whereas

the demands for house 74 were the lowest of the

group during January and second highest in August.

Table 32. Power demands at selected frequencies of recurrence, January 8, 1960-February 8, 1960

Selected frequenev

of recurrence

15-min power demand, kw, for house No.

14 263 468 587 %

0.1

1.0 5.0

15. 0 9.

2

9. 8 6.

2

5. 8 >5.

0

15.0

10.9 6.8

18.0

15.0

11.5

15.0

10.0 5.8

Table 33. Power demands at selected frequencies of recurrence, August 7, 1959-September 8, 1959

Selected j 15-min power demand, kw, for house Xo.

frequency

of recurrence 14 74 263 468 656 %

0.1 11.6 14.3 13.5 16.0 13.7 1.0 7.9 10.0 8.0 12.0 8.2

3.0 5.5 6.9 5.2 9.3 5.4

The data obtained from house 14 for the months

of January and August were plotted to show the

frequency of recurrence of aU power demands

from zero to the maximum. Exponential curves

of the form y=Ce~la fit the data approximately

for both months over a part or the whole of the

range of demand values. The curve drawn

through the observed data in figure 22 fits the

values calculated from the exponential equation

reasonably well from 6 kw to the maximum of

about 18 kw, but bends to the right of the exponential curve for demand values from 3.5 to 6 kw.

In contrast, the curve in figure 23 fits both

observed and calculated values throughout the

range of power demand.

The reasons for the significant difference in the

shape of the frequency curves for January and

August for demand levels below 3.5 kw are not

fully understood. The double reversal of the

slope of the frequency curve from negative to positive and back to negative again for power

demands below 5 kw in figure 22 was probably

related to the number and size of the more or less fixed components of the house load. Close

examination of the plotted points in figures 20 and

21 for houses 263 and 587 during January and for

houses 263, 14, and 74 during August, indicates

that similar changes in slope of equal or lesser magnitude may have occurred in the frequency

curves for some other houses. Table 34 shows

the frequency of recurrence of outdoor temperatures in consecutive 5-degree temperature bands

from 20 to 75 °F, based on readings to the nearest degree from the chart of one of the outdoor

temperature recorders. This table indicates that

the outdoor temperature was at 40 °F or lower

0 Z 4 6 8 10 12 14 16 18 20 15-MINUTE POWER DEMAND, kw (X) Figure 22. Frequency distribution of 15-min -power demands

for house 14 during the period January 8-February 8, 1960.

15 -MINUTE POWER DEMAND, kw (X) Figure 23. Frequency distribution of 15-min power demands

for house 14 during the period August 7—September 8, 1959.

29
for nearly one-half of the total hours in the

1-month period represented by the table, thus

entailing many L5-mirj demand periods when the

heat pump operated steadily.

Table 34. Frequency of recurrence of outdoor temperatures in selected temperature ranges at Little Rock Air Force

Base, January 8-February 8, 1960

Temperature

range

No. of hours with temperatures in this range

op

20 to 25 45

26 to 30 70

31 to 35 90

36 to 40 150

41 to 45 120

46 to 50 95

51 to 55 75

56 to 60 40

61 to 65 35

66 to 70 20

71 to 75 5

The frequencies of recurrence of 15-min power

demands at or above selected levels of demand

from about 5 kw to the maximum are shown in

figures 24 and 25. The same data were used for

these figures as for figures 20 and 21, but in this case the frequencies shown as ordinates were

plotted on a cumulative basis. The data for 5 houses are sbown in figure 24 for the month of

January 1960, and the data for 4 of the same

houses and 1 other house are shown in figure 25

for the month of August 1959. These curves can

5 7 9 II 13 15 15-MINUTE POWER DEMAND, kw Figure 24. Cumulative frequency of recurrence of 15-min power demands greater than 5 kw for 5 houses during the period January 8-February 8, I960.

5 7 9 || 13 15 15-MINUTE POWER DEMAND, kw Figure 25. Cumulative frequency of recurrence of 15-min

power demands greater than 5 kw for 5 houses during the period August 7-September 8, 1959.

be used to determine what part of a day or a month, on the average, will correspond to 15-min

power demands at any selected value or higher.

For example, figure 24 shows that the 15-min

power demand for house 468 will be 15.2 kw or

higher, 1 percent of the time, or about one 15-min

period per day on the average in the month of

January. In figure 25, it is shown that the 15-min

power demands that will be equaled or exceeded

1 percent of the time in August, range from 9.6

to 13.2 kw in the 5 sample houses. Curves of this type can be used to evaluate the probable amount

of time that the energ}'-use habits in a given

house would be affected by a device which limited

thejl5-min demand to any selected value.

3.6. Relation of Maximum Demand for the

Entire Airbase to That for the Housing

Area Only

Table 35 shows the magnitudes of the monthly

15-min maximum demands from March 1959

through February 1960, for both the housing

area by itself and the entire airbase. It also shows

the times that the monthly maximum demands

occurred for both the housing area and the entire

airbase. Comparison of the magnitude of the

two maximum demands and the time of occurrence

of these demands, shows that the demand of the

housing area was the predominant factor

determining the time of the monthly maximum

demands for the entire airbase. For these months,

the maximum demand for the housing area ranged

30
from 59 percent to 81 percent of that for the entire

airbase, with the higher percentages occurring

in the whiter months. For all months but 5, the time of the maximum demand for the housing

area was coincident with that for the total base.

In four of these five exceptions, both maximum

demands occurred on the same morning.

It should be noted that the lack of coincidence

of the housing area and total airbase maximum

power demands occurred during the summer

months when the power usage for ah conditioning was not as great as for winter operation. In

agreement with much of the data given on the

sample houses, the data in these tables show that

in every instance, except one, the maximum

demand for the housing area occurred during the

morning hours.

Table 35. Maximum 15-min demands for entire airbase and housing area only

Time Period

Magnitude of monthly maximum

demand

Entire

airbase Housing

area only

Ratio of housing de- mand to total demand

Time of monthly maximum demand

Entire airbase Housing area only

Mar. 6-Apr. 7, 1959 Apr. 7-May 7, 1959- May 7-June 8, 1959 - June 8-July 7, 1959 July 7-Aug. 7, 1959 Aug. 7-Sept. 8, 1959 Sept. 8-Oct. 8, 1959

Oct. 8-Nov. 9, 1959 Nov. 9-Dee. 10, 1959 Deo. 10, 1959-Jan. 8, 1960 Jan. 8-Feb. 8, 1960 Feb. 8-Mar. 8, 1960

kw

9,856

7, 728 8,949

10, 600

11,200

11,200 9,968

12, 656

14,448

14, 672

15, 568

17, 024

kw

7, 224

5, 712 5,292

7,560

7, 308

7.476 6,384

10, 080

11, 508

11,676

12, 432

13, 860

%

73

74

59

716567

64

80

80

81

1100 0930

1045 1030

1100 1100

1115 0915 0930

0915

1100

1015

3-6-59 4-9-59

5-29-59

6-29-59 8-3-59 8-24-59 9-28-59 11-6-59

11-17-59

1-8-60

1-18-60 3-2-60

1100 0700

1230

1045 1145

1145

1115 0915 0930

0915

1100

1015

3-6-59

4-13-59

5-29-59 6-29-59 8-3-59 8-24-59 9-28-59

11-6-59 11-17-59

1-8-60

] IS (ill 3-2-60

4. Summary and Conclusions

The more significant data developed by this

analysis and the conclusions derived therefrom

may be summarized as follows

:

(a) The annual use of electric energy by the

sample houses averaged 25,300 kw-hr per house

based on the 12-month period from March 1959

to February 1960, inclusive (table 4). Of this

total, 48.6 percent was used by the heat pmnp,

including the supplementary resistance heaters,

for heating and cooling; 24.3 percent was used for

water heating; 23.3 percent was used for miscellaneous devices, including a resistance heater in the bathroom; and 3.8 percent was used by the

electric range. Annual costs can be derived from

these data by applying appropriate rate schedules.

(b) Three energy-usage factors were computed

to correlate the electric energy used for heating,

the severity of the weather, and the floor area of

the sample houses (tables 5 to 9). These factors were expressed in the units kw-hr/degree-day

(1,000 ft 2 of floor area). The first factor was

based on the total electric energy used for heating,

including the contribution made by appliances

other than the heat pmnp, the degree-days related

to a 65 °F base, and the inside floor area of the

house in thousands of square feet. This factor

averaged 3.4 for the 16 sample houses during the

5-month period from October 1959 through February 1960. The second energy-usage factor was

similar to the first except that only the electric energy used by the heat pump was included. The

third energy-usage factor employed the total electric energy used for heating, as for the first factor,

but the degree-days were based on the average

indoor and outdoor temperatures. The second

and third factors averaged 2.1 and 2.2, respective^, for the same 5-month period. Within a

given month the first and third factors provided

a better correlation of the energy use, the weather,

and the size of the sample houses. However, the

third factor was less variable from month to month

than the other two factors for the 5-month period

used in the comparison.

(c) Three energy-usage factors were computed

to correlate the electric energy used by the heat

pump for cooling, the severity of the weather, and

the floor area of the sample houses (tables 10 to

12). These factors were expressed in the units

kw-hr/degree-day (1,000 ft 2 of floor area) and were

alike except for the method used to determine the

cooling degree-clays. The degree-days were based on hourly values of outdoor temperature and

reference temperatures of 65 and 75 °F for the

first and second factors, respectively, whereas the

degree-days were computed from the mean daily

outdoor temperatures and the average daily

indoor temperatures for the third factor. The

best correlation was obtained by the first energyusage factor employing a 65 °F reference value for

determining degree-days, for which an average

value of 2.1 was observed for the 16 sample houses

from June through August 1959.

(d) Appliances other than the heat pump contributed significantly toward the heating of the

31
sample houses in the tvinter (tables 5 to 9). For

the assumptions made, the computed appliance

contribution toward heating averaged 34 percenl

of all of the energy used for heating in the sample

houses for the period from October 1959 to February I960, inclusive. The computed appliance

contribution to the summer cooling load averaged

about 12.9 kw-hr per day per house, equivalent

to a 24-hr average of about 1,830 Btu/hr (tables

10 to 12).

(e) The maximum electric power demand for the entire housing area was apparently caused by a moderately high average-demand in many houses

lather than a coincidence of the maximum or very

high demand in a minority of the houses, as in- dicated in tallies 14 to 19. None of the 16 sample

houses exhibited a monthly maximum demand

coincident with the monthly maximum demand for the entire housing area, yet the average demand in the sample houses at the time of the monthly

maximum for the entire housing area was about

equal to the average for all of the houses at that

time. These facts suggest that a program device

which simply reduced the individual house

maximum demand by 4 or 5 kw probably would

not have a significant effect on the maximum

demand for the entire housing area.

(f) The average electric power demand during

the hours from about 0630 to 2000 was significantly

higher than during the night hours (figs. 4 to 13).

This difference was more significant in the summer

than in the winter. For 4 of the 5 sample houses on which this comparison was evaluated, the

average rate of energy use during the hours from

0700 to 2300 was about 1% tunes that during the

night hours from 2300 to 0700 in the month of

January, and this day-to-night ratio of energy

use rates was about 4 to 1 for the same time

intervals in the month of August (table 13).

The difference between the day and night rates

of energy use was not as great as this in the fifth house, i.e., house 263 during August and house

46X during January. These results indicate that

a program device which transferred some of the

load from the daytime hours to the night hours

would probably provide a lower maximum demand

for the housing area.

(g) The maximum electric power demands for

the individual houses averaged about 14 lew in the summer and about 17.5 kw in the winter

with the heat pump, water heater, and miscellaneous devices being the principal contributors

to these maximum demands (tables 20 to 25).

The monthly coincidence factors between the

maximum demands of the load components in

each house and the maximum demand for the

entire house load averaged about 0.70 both

winter and summer (tables 26 to 31).

(h) An exponential curve of the form y=

Ce~kx approximated the relation between the

frequency of recurrence, ?/, of power demands

from about 5 kw upward, and the numerical

value of the 15-min power demand, % (figs. 22

and 23). Cumulative curves for frequency of recurrence of high power demands (figs. 24 and

25) showed that power demands of 11.5 kw or more occurred only about 1 percent of the time, or about 15 min per day, on the average, during

a typical summer or winter month, except in the large 4-bedroom houses with two heat pumps.

These cumulative frequency curves also indicated

that power demands in excess of 7 kw occurred

for no more than 3K In' per day, on the average,

except in the large 4-bedroom houses.

5. Methods of Limiting Maximum Power Demand in the Housing Area

Various devices and methods have been used to

limit the power demand in houses designed for

electric heating and all-electric appliances. These

usually take the form of some type of programing

system and could either be administrative or

mechanical-electrical. Certain intermittent operations in a house, such as laundering, could be

staggered throughout the week by administrative

order to provide diversity among a large group of

houses. This type of programing has the advantage that no equipment is required to implement it, but it depends on voluntary cooperation in most

cases and would cause inconvenience at times.

The practicability of administrative programing

can best be evaluated by the personnel at an air- base and will not be further considered in this dis- cussion.

Mechanical-electrical devices for programing a group of component loads in a house might take- any of the following forms:

(1) A nonpreferential total load-limiting device;

(2) a total load-limiting device that gave prefer- ence to certain appliances;

(3) a load selector that permitted either of two

appliances, but not both, to be energized at the same time;

(4) a device which permitted one or more appli- ances to be energized, only if the load already

energized was below some selected value;

(5) an off-peak water heating control on a time

clock

;

(6) a device to reduce the applied voltage, from

230 to 115 v on resistance elements such as the

water heater and the supplementary resistance

heaters in the heat pumps whenever the power

demand reached some selected value;

(7) a control that prevented operation of the

water heater for intervals of 2 hr, more or less, during the time of the day when other loads were

high, but with these 2-hr periods staggered

throughout the period from about 0800 to 2000 hr. In considering the type of programer that would

provide the best combination of reduction of

maximum demand and minimum of inconvenience

to the house occupants, the principal conclusions

indicated by the foregoing analysis of the energy

32
usage and power demand in the sample houses and

the priority of the several load components in the

house from a convenience standpoint should be

taken into account. From a convenience standpoint it is believed

that the various functions occurring in a housethat require electric energy should be placed in the

following order of decreasing priority:

(1) Cooking;

(2) heating and cooling;

(3) miscellaneous uses, laundering, ironing, etc.;

(4) water heating.

Cooking was given priority over heating partly

because it can effectively substitute for heating

for limited periods of time. Heating and cooling were given priority over miscellaneous uses be- cause they are continuous requirements over

rather long periods of time whereas the occupant

has considerable choice in performing the miscellaneous functions of laundering, ironing, etc. Water heating was given the lowest priority

because it is both possible and conventional to provide some storage of hot water whereas only

very limited storage of heating and cooling effect

is practical, and the other functions cannot be

stored.

The foregoing analysis and conclusions, regarding the average pattern of daily power demand,

the coincidence factor within individual houses

and among groups of houses, the probable cause

of the maximum demand for the entire housingarea, the frequency of recurrence of high demands,

and the convenience considerations associated

with the various energy-using activities in a house, indicate that some type of programer

that caused the water heater to be energized

only during periods of low or moderate demand

by other appliances offers the best possibility

of decreasing the maximum 15-min power demands

for the entire housing area. Program devices 3

tlnough 7, listed at the beginning of section 5

of this report, are variations of this type of device.

Of all the devices listed it is believed that a

relay which permitted one or more appliances

to be energized only if the load already energized was below some selected value, identified as (4) in the earlier listing, offers the best possibility

of distributing the total daily energy use evenly

over the 24-hr period. This type of relay, with

a current coil in the lines serving the house, would

interrupt the circuit to the water heater or possibly

to the water heater and dryer, whenever the cm-rent reached some selected value. In this

arrangement the electric service to the water

heater, or water heater and dryer, would be con- nected on the line side of the current relay. This

device would not limit the power demand or time

of use of any component of the load, except the one or two interrupted by the current relay, and

would not prevent these from being energized

except at times of high demand. The data on

frequency of recurrence of high demands indicate

that such a relay should be activated at a load

somewhat above that caused by the compression

system of the heat pump, but somewhat below

the load when the compression system and supplementary resistance heaters were both energized.

That is, in the houses with one heat pump the

relay should be energized at a load somewhere

between 5 and 8 kw and in the houses with two

heat pumps at a load somewhere between 9 and

12 kw. This type of program device might re- quire a water heater sized for off-peak heating to provide greater storage of hot water than is now

possible.

An off-peak water heating schedule controlled

by a time clock could also be used to shift the

water heating load to the night hours, but unless

the horns of water heating were staggered after midnight, the time of maximum demand for the

entire housing area might only be shifted to a new hour without reduction in magnitude. This

device might still be practical, if it were found

that the power demand of the airbase outside the

housing area became quite low at night.

The type of device which permitted either of two devices to be energized as required, but not both simultaneously, would probably reduce the

maximum power demand in each house appreciably, but it might not reduce the high average

that appears to have caused the maximum

demand for the entire housing area. This analysis indicates that water heaters with

storage tanks suited to off-peak heating are desirable and that some types of programing devices

for water heating would probably be better than

others in this installation. The program devices

identified by the numbers (4), (5), (6), and (7) appear to offer the best possibilities for reduction

of maximum power demand.

6. Comparison of Annual Energy Use in 16 Sample Houses With Other Published

Information

Table 36 provides a comparison between annual

energy usage of some of the appliances in the 16

sample houses and of the same type of appliances

in homes elsewhere in the United States. Information is shown for the heat pump, the hot water

heater, and the electric range only. Comparable

information is published for other individual home

appliances, but it has not been included because

the energy use by these appliances was not metered

separately in the sample houses at Little Rock Air

Force Base. A literature search revealed that there are very

few published data available on energy usage for individual appliances obtained by meter readings.

Most of the information on individual appliances

consists of estimates by electric light and power

33
Table 36. Comparison of annual energy use in 16 sample houses with oilier published data

A. Private homes, nonmilitary

Iieating Annual energy usage (kw-hr) Source of information Geographical area degree-days Size of sample Heat pump

Water

heater Range

Edison Electric Institute Study, 1957". Entire nation, without geographical weighting of samples. Unknown. Data from more than 15 450 1, 225 30 electric light and power companies. Edison Electric Institute Study, 1959 b . Edison Electric Institute Study, 1961 °.

Same 14, 635

15, 840

3,675

4, 070

4,475 (Quick re- covery)

1,200 Same Same - 1,225

Southeastern Electric Exchange Eco- nomic Study, June 1958. <• Southeastern States 3, 500 20-40 nonmilitary private homes,

large and small towns.

3,376 1,206

B. 1- and 2-family structures, Little Rock Air Force Base

National Bureau of Standards Study

for period March 1959-March 1960. Arkansas 3,000 16 dwelling units 12, 290 6,135 965

» Edison Electric Institute; Wattage Rating and Estimated Average Annual KWH Consumption of Electrical Household Appliances Assuming Normal

Use, January 1, 1957.

b Ibid., January 1, 1959.

° Ibid., January 1, 1901. d Southeastern Electric Exchange; Economic Study of Electric, Gas and Oil Usage for Capehart and Other Public Housing Projects, June 1958. A study of the table shows that the average

annual energy usage of the heat pumps in the 16

houses at Little Rock Air Force Base was lower

than the estimates published by the Edison Electric Institute by amounts ranging from 16 to 22

percent. The average annual energy usage for

the hot water heaters in the 16 sample houses was

appreciably higher than any of the published

data. The hot water heaters at Little Rock Air

Force Base can probably be considered to be of

the quick-recovery type. Thus, the observed

average energy use of 6,135 kw-hr water heating

at the airbase should be compared with the value

of 4,475 kw-hr published by the Edison Electric

Institute in 1961 for quick-recovery heaters. The

observed annual energy use by the electric ranges

in the 16 sample houses was about 80 percent of

the values cited from the other sources.

companies based on meter readings of the total

house load. The information cited in table 36

from the Edison Electric Institute studies of 1957,

1959, and 1961 is of this type. The estimates are based on information obtained by the Institute

from over 30 different electric light and power

companies, and the data have not been weighted

geographically. Since over 90 percent of the

electric light and power companies in the United

States are members of the Edison Electric Institute, the data from which the estimates were made are probably representative of the entire

nation.

The data shown in table 36 from the Southeastern Electric Exchange study, however, were

obtained from actual meter readings of appliance

energy usage.

34

U.S GOVERNMENT PRINTING OFFICE: 1962


U.S. DEPARTMENT OF COMMERCE

Luther H. Hodges, Secretary

NATIONAL BUREAU OF STANDARDS

A. V. Astin, DirectorTHE NATIONAL BUREAU OF STANDARDS

The scope of activities of the National Bureau of Standards at its major laboratories in Washington, D.C., and Boulder,

Colorado, is suggested in the following listing of the divisions and sections engaged in technical work. In general, each

section carries out specialized research, development, and engineering in the field indicated by its title. A brief descrip- tion of the activities, and of the resultant publications, appears on the inside of the front cover. WASHINGTON, D.C.

Electricity. Resistance and Reactance. Electrochemistry. Electrical Instruments. Magnetic Measurements. Dielectrics. High Voltage.

Metrology. Photometry and Colorimetry. Refractometry. Photographic Research. Length. Engineering Metrology. Mass and Scale. Volumetry and Densimetry.

Heat. Temperature Physics. Heat Measurements. Cryogenic Physics. Equation of State. Statistical Physics.

Radiation Physics. X-ray. Radioactivity. Radiation Theory. High Energy Radiation. Radiological Equipment.

Nucleonic Instrumentation. Neutron Physics.

Analytical and Inorganic Chemistry. Pure Substances. Spectrochemistry. Solution Chemistry. Standard Reference

Materials. Applied Analytical Research. Crystal Chemistry.

Mechanics. Sound. Pressure and Vacuum. Fluid Mechanics. Engineering Mechanics. Rheology. Combustion

Controls. Polymers. Macromolecules: Synthesis and Structure. Polymer Chemistry. Polymer Physics. Polymer Characterization. Polymer Evaluation and Testing. Applied Polymer Standards and Research. Dental Research. Metallurgy. Engineering Metallurgy. Microscopy and Diffraction. Metal Reactions. Metal Physics. Electrolysis

and Metal Deposition.

Inorganic Solids. Engineering Ceramics. Glass. Solid State Chemistry. Crystal Growth. Physical Properties.

Crystallography.

Building Research. Structural Engineering. Fire Research. Mechanical Systems. Organic Building Materials. Codes and Safety Standards. Heat Transfer. Inorganic Building Materials. Metallic Building Materials. Applied Mathematics. Numerical Analysis. Computation. Statistical Engineering. Mathematical Physics. Operations Research. Data Processing Systems. Components and Techniques. Computer Technology. Measurements Automation. Engineering Applications. Systems Analysis.

Atomic Physics. Spectroscopy. Infrared Spectroscopy. Solid State Physics. Electron Physics. Atomic Physics.

Instrumentation. Engineering Electronics. Electron Devices. Electronic Instrumentation. Mechanical Instruments.

Basic Instrumentation.

Physical Chemistry. Thermochemistry. Surface Chemistry. Organic Chemistry. Molecular Spectroscopy. Molecular Kinetics. Mass Spectrometry.

Office of Weights and Measures. BOULDER, COLO.

Cryogenic Engineering. Cryogenic Equipment. Cryogenic Processes. Properties of Materials. Cryogenic Technical

Services. CENTRAL RADIO PROPAGATION LABORATORY

Ionosphere Research and Propagation. Low Frequency and Very Low Frequency Research. Ionosphere Research.

Prediction Services. Sun-Earth Relationships. Field Engineering. Radio Warning Services. Vertical Soundings

Research. Radio Propagation Engineering. Data Reduction Instrumentation. Radio Noise. Tropospheric Measurements

Tropospheric Analysis. Propagation-Terrain Effects. Radio-Meteorology. Lower Atmosphere Physics.

Radio Standards. High Frequency Electrical Standards. Radio Broadcast Service. Radio and Microwave Materials. Atomic Frequency and Time Interval Standards. Electronic Calibration Center. Millimeter-Wave Research. Micro- wave Circuit Standards. Radio Systems. Applied Electromagnetic Theory. High Frequency and Very High Frequency Research. Modulation

Research. Antenna Research. Navigation Systems.

Upper Atmosphere and Space Physics. Upper Atmosphere and Plasma Physics. Ionosphere and Exosphere Scatter. Airglow and Aurora. Ionospheric Radio Astronomy.

RADIO STANDARDS LABORATORY

Radio Physics. Radio Broadcast Service. Radio and Microwave Materials. Atomic Frequency and Time-Interval

Standards. Millimeter-Wave Research.

Circuit Standards. High Frequency Electrical Standards. Microwave Circuit Standards. Electronic Calibration Center.