To: Anthony Balducci, DOE

From: Diane Fisher and Isaac Turiel, LBNL

Subject: Distribution of Green Lights ballasts vs. operating hours, and Xenergy ballasts vs.

operating hours.

Date: April 1, 1998

Introduction

This memo explains how distributions of the fraction of ballasts vs. annual operating hours were

derived, using two different data sets, one from EPA's Green Lights program, and the other from

Xenergy, a private firm which conducts energy audits. We are looking at the Green Lights

Program to gain some insight into the range of operating hours found for fluorescent lamp ballasts

in facilities which participate in voluntary lighting energy efficiency programs. Ideally, we would

like to compare this distribution to the distribution of lighting hours for commercial fluorescent

ballasts in all commercial buildings. However, the only source of such data we have been able to

find' is dated (it's based on 1986 CBECS data), and uses a method for calculating lighting

operating hours which is different from our method and may not be directly comparable. We are

therefore using the Xenergy database as described below.

Data Sources

Xenergy, Inc., conducts energy audits of buildings at the request of either the building owner or

the local utility. We obtained an extract of Xenergy's database of its audits in late January of

1995. The data obtained were for 1979 through early 1995. We used data from 1990-1995.

The extract aggregated the data to the 3-digit zip code level and for each zip code included the

number of buildings, building types (e.g. office, industrial, etc.), the quantity of fixtures installed

by equipment types, lamps per fixture, and the average weekly lighting operating hours for each

equipment type.

We obtained an extract of EPA's database on its Green Lights program in late August of 1997.

This database is based on reports submitted by Green Lights program participants on completed

upgrades. The data obtained were for the beginning of the program in 1990 through July 1997.

Data were reported separately by project and by fixture type and included the facility type (e.g.

office building, industrial), upgrade type (e.g. reballasting, relamping, delamping, etc.), lamp type,

ballast type, fixture quantity, lamps per fixture, lamps per ballast, lamp watts, and lighting

operating hours.

'EIA (1992) Lighting Consumption in Commercial Buildings. Energy Information

Administration, U.S. Department of Energy, Washington DC. DOE/EIA 0555(92)/1.

EE-RM-97-500 COMMENT 20F

) 

MEMO#c2-

To: Anthony Balducci, DOE 

From: Diane Fisher and Isaac Turiel, LBNL 

SUbject: Distribution of Green Lights ballasts vs. operating hours, and Xenergy ballasts vs. 

operating hours. 

Date: April 1, 1998 

Introduction 

This memo explains how distributions of the fraction of ballasts vs. annual operating hours were 

derived, using two different data sets, one from EPA's Green Lights program, and the other from 

Xenergy, a private firm which conducts energy audits. We are looking at the Green Lights 

Program to gain some irisight into the range of operating hours found for fluorescent lamp ballasts 

in facilities which participate in voluntary lighting energy efficiency programs. Ideally, we would 

like to compare this distribution to the distribution of lighting hours for commercial fluorescent 

ballasts in all commercial buildings. However, the only source of such data we have been able to 

find! is dated (it's based on 1986 CBECS data), and uses a method for calculating lighting 

operating hours which is different from our method and may not be directly comparable. We are 

therefore using the Xenergy database as described below. 

Data Sources 

Xenergy, Inc., conducts energy audits of buildings at the request of either the building owner or 

the local utility. We obtained an extract ofXenergy's database of its audits in late January of 

1995. The data obtained were for 1979 through early 1995. We used data from 1990-1995. 

The extract aggregated the data to the 3-digit zip code level and for each zip code included the 

number of buildings, building types (e.g. office, industrial, etc.), the quantity of fixtures installed 

by equipment types, lamps per fixture, and the average weekly lighting operating hours for each 

equipment type. 

We obtained an extract of EPA's database on its Green Lights program in late August of 1997. 

This database is based on reports submitted by Green Lights program participants on completed 

upgrades. The data obtained were for the beginning of the program in 1990 through July 1997. 

Data were reported separately by project and by fixture type and included the facility type (e.g. 

office building, industrial), upgrade type (e.g. reballasting, relamping, delamping, etc.), lamp type, 

ballast type, fixture quantity, lamps per fixture, lamps per ballast, lamp watts, and lighting 

operating h~urs. 

!EIA (1992) Lighting Consumption in Commercial Buildings. Energy Information 

Administration, U.S. Department of Energy, Washington DC. DOEIEIA 0555(92)/1. 
Page 2

April 1, 1998

Derivation of Distributions

The distributions from the two data sets were derived in very similar ways. In both data sets, the

number of ballasts is not reported directly, but can be estimated based on other quantities. In the

case of the Xenergy data, we used the number of fixtures and the. number of lamps per fixture to

approximate the number of ballasts using the following assumptions: For electronic ballasts, we

assumed that the number of ballasts was equal to the number of fixtures. For magnetic ballasts,

we assumed that fixtures with 1 or 2 lamps per fixture contained one ballast per fixture, and that

fixtures with 3 or 4 lamps per fixture contained 2 ballasts per fixture.

The Green Lights data included the fixture quantity, the number of lamps per fixture, and the

number of lamps per ballast. We calculated the number of ballasts per fixture by dividing the

number of lamps per fixture by the number of lamps per ballast. We then multiplied ballasts per

fixture by fixture quantity to obtain the ballast quantity for each record in the database. In a small

number of records in the database, the number of lamps per ballast was not reported. In these

cases, we used the number of fixtures and the lamps per fixture to estimate the number of ballasts,

using the same assumptions described above for the Xenergy dataset.

For each data set, we used information on technology types to group the ballasts into those which

operate 4-foot lamps, 8-foot lamps, and 8-foot high output (HO) lamps. Ballasts that did not fit

into these three categories were classed as "other". Since the Xenergy data included information

about lamp lengths, separating ballasts into these three categories was straightforward. Since the

Green Lights data did not report lamp lengths, we used the reported lamp types (e.g. T8, T12

slimline, etc.) and lamp watts to assign lamps and the ballasts which operate them into the three

categories. For the Green Lights data, we included only new electronic ballasts installed in the

retrofit, i.e. we did not include data for fixtures in which only the lamp was changed, or other

upgrade types which do not result in the installation of a new electronic ballast (e.g. improved

controls, delamping).

For both data sets, we then summed the number of ballasts in each of 21 lighting operating hour

"bins", 0-8 hrs/week, 8-16 hrs/week, etc. (or approximately 0-417 hrs/year, 418-834 hrs/year,

etc.). We did the sums separately for each facility type, and for each of our three ballast

categories (4ft, 8ft, and 8ftHO). We then combined the results for all commercial ballasts

together, and in the case of the Xenergy data we weighted the results for each facility type by the

square footage of that building type in the CBECS survey.' We then divided the number of

ballasts in each bin by the total number of ballasts to get the fraction of ballasts in each bin. We

then plotted the fraction of ballasts vs annual operating hours.

2 Weighting the Xenergy results by the CBECS square footage is done to make the Xenergy results, which we

are using as a baseline, more representative of the general population of commercial buildings.

EE-RM-97-500 COMMENT 20F

Page 2 

April 1, 1998 

Derivation of Distributions 

The distributions from the two data sets were derived in very similar ways. In both data sets, the 

number of ballasts is not reported directly, but can be estimated based on other quantities. In the 

case of the Xenergy data, we used the number of fixtures and the number of lamps per fixture to 

approximate the number of ballasts using the following assumptions: For electronic ballasts, we 

assumed that the number of ballasts was equal to the number of fixtures. For magnetic ballasts, 

we assumed that fixtures with 1 or 2 lamps per fixture contained one ballast per fixture, and that 

fixtures with 3 or 4 lamps per fixture contained 2 ballasts per fixture. 

The Green Lights data included the fixture quantity, the number oflamps per fixture, and the . 

number of lamps per ballast. We calculated the number of ballasts per fixture by dividing the 

number oflamps per fixture by the number oflamps per ballast. We then multiplied ballasts per 

fixture by fixture quantity to obtain the ballast quantity for each record in the database. In a small 

number of records in the database, the number of lamps per ballast was not reported. In these 

cases, we used the number of fixtures and the lamps per fixture to estimate the number of ballasts, 

using the same assumptions described above for the Xenergy dataset. 

For each data set, we used information on technology types to group the ballasts into those which 

operate 4-foot lamps, 8-foot lamps, and 8-foot high output (HO) lamps. Ballasts that did not fit 

into these three categories were classed as "other". Since the Xenergy data included information 

about lamp lengths, separating ballasts into these three categories was straightforward. Since the 

Green Lights data did not report lamp lengths, we used the reported lamp types (e.g. T8, T12 

slimline, etc.) and lamp watts to assign lamps and the ballasts which operate them into the three 

categories. For the Green Lights data, we included only new electronic ballasts installed in the 

retrofit, i.e. we did not include data for fixtures in which only the lamp was changed, or other 

upgrade types which do not result in the installation of a new electronic ballast (e.g. imprOVed 

controls, delamping). 

F or both data sets, we then summed the number of ballasts in each of 21 lighting operating hour 

"bins", 0-8 hrs/week, 8-16 hrs/week, etc. (or approximately 0-417 hrs/year, 418-834 hrs/year, 

etc.). We did the sums separately for each facility type, and for each of our three ballast 

categories (4ft, 8ft, and 8ftHO). We then combined the results for all commercial ballasts 

together, and in the case of the Xenergy data we weighted the results for each facility type by the 

square footage of that building type in the CBECS survey. 2 We then divided the number of 

. ballasts in each bin by the total number of ballasts to get the fraction of ballasts in each bin. We 

then plotted the fraction of ballasts vs annual operating hours. 

2 Weighting the Xenergy results by the CBECS square footage is done to make the Xenergy results, which we 

are using as a baseline, more representative of the general population of commercial buildings. 
Page 3

April 1, 1998

Discussion of Results

The results are summarized in Table 1 and the distributions are shown in Figure 1. In all cases,

the Green Lights distributions appear to be shifted to somewhat higher operating hours than the

Xenergy distributions. For 8ft and 8ftHO ballasts, the Green Lights distributions are dominated

by a few large peaks. This is because the total number of ballasts are small, and the distributions

are dominated by the results for a few large projects.

For all cases except 8ft commercial ballasts, the Green Lights distribution includes a large peak at

8760 hours/year (continuous operation) which is not seen in the Xenergy data.. EPA staff are not

aware of any reason why this value would be over-reported, and it is not used anywhere as a

default. On the other hand, since Green Lights data is self-reported there is a higher probability of

error, and there may also be incentives for project managers to make their projects look good

(higher lighting operating hours would lead to higher calculated energy savings ). It is also

possible that Xenergy data somewhat under-reports fixtures operating at 8760 hours/year.

According to their staff, if the lighting hours of most fixtures in a particular area of a building

were operating at one lighting hour level (say 60 hrs/week), but a small fraction (say less than

10%) were operating at a different level (say 168 hrs/week, or 8760 hrs/year), it was considered

acceptable practice for the auditor to ignore the small fraction and report the same operating

hours for all of the fixtures in the area. If most fixtures that operate continuously are located in

areas where they are a small fraction of all of the fixtures in that area, such fixtures would b

undercounted by Xenergy. If EPA data over-reports or Xenergy under-reports ballasts at 8760

hrs/year, then correcting for this would make the Green Lights averages closer to Xenergy

averages. For example, if the 8760 peak is left out of the Green Lights averages, they become,

for Oft, 8ft, and 8ftHO ballasts, respectively, 3900, 5200, and 4100 hrs/year. For industrial Oft,

8ft, and 8fHO ballasts, respectively, the averages become 4800, 5600, and 5200 hrs/year.

EE-RM-97-500 COMMENT 20F

Page 3 

April 1, 1998 

Discussion of Results 

The results are summarized in Table 1 and the distributions are shown in Figure 1. In all cases, 

the Green Lights distributions appear to be shifted to somewhat higher operating hours than the 

Xenergy distributions. For 8ft and 8ftHO ballasts, the Green Lights distributions are dominated 

by a few large peaks. This is because the total number of ballasts are small, and the distributions 

are dominated by the results for a few large projects. 

For all cases except 8ft commercial ballasts, the Green Lights distribution includes a large peak at 

8760 hours/year (continuous operation) which is not seen in the Xenergy data.. EPA staff are not 

aware of any reason why this value woUld be over-reported, and it is not used anywhere as a 

default. On the other hand, since Green Lights data is self-reported there is a higher probability of 

error, and there may also be incentives for project managers to make their projects look good 

(higher lighting operating hours would lead to higher calculated energy savings). It is also 

possible that Xenergy data somewhat under-reports fixtures operating at 8760 hours/year. 

According to their staff, if the lighting hours of most fixtures in a particular area of a building 

were operating at one lighting hour level (say 60 hrs/week), but a small fraction (say less than 

10%) were operating at a different level (say 168 hrs/week, or 8760 hrs/year), it was considered 

acceptable practice for the auditor to ignore the small fraction and report the same operating 

hours for all of the fixtures in the area. If most fixtures that operate continuously are located in 

areas where they are a small fraction of all of the fixtures in that area, such fixtures wouldb 

undercounted by Xenergy. If EPA data over-:reports or Xenergy under-reports ballasts at 8760 

hrs/year, then correcting for this would make the Green Lights averages closer to Xenergy 

averages. For example, if the 8760 peak is left out of the Green Lights averages, they become, 

for 4ft, 8ft, and 8ftHO ballasts, respectively, 3900, 5200, and 4100 hrs/year. For industrial 4ft, 

8ft, and 8ftHO ballasts, respectively, the averages become 4800,5600, and 5200 hrs/year. 
Page 4

April 1, 1998

Table 1. Average Annual Operating Hours and Ballast Quantities For Xenergy and Green

Lights Data.

Xenergy Green Lights

Commercial Quantity (000) 1 Operating Hours Quantity (000) Operating Hours

4FT 63601 3600 9085 4300

8FT 572 1 3600 161 5300

8FTHO 85 1 4000 14 4700

Industrial,

4FT 774 4200 673 5800

8FT 306 4000 41 6300

8FTHO 59 5000' 19 5600

EE-RM-97-500 COMMENT 20F

Page 4 

April 1, 1998 

Table 1. Average Annual Operating Hours and Ballast Quantities For Xenergy and Green 

Lights Data. 

Xenergy Green Lights 

Commercial Quantity (000) I Operating Hours Quantity (000) Operating Hours 

4FT 6360 3600 9085 4300 

8FT 572 3600 161 5300 

8FTHO 85 4000 14 4700 

Industrial 

4FT 774 4200 673 5800 

8FT 306 4000 41 6300 

8FTHO 59 5000 19 5600 
0

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8343

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EE-RM-97-500 COMMENT 20F

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