NREL is a national laboratory of the U.S. Department of Energy, Office of Energy 

Efficiency & Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

Contract No. DE-AC36-08GO28308

NILM Applications for the 

Energy-Efficient Home

D. Christensen, L. Earle, and B. Sparn

Technical Report

NREL/TP-5500-55291

November 2012
NREL is a national laboratory of the U.S. Department of Energy, Office of Energy 

Efficiency & Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

National Renewable Energy Laboratory

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Contract No. DE-AC36-08GO28308

NILM Applications for the 

Energy-Efficient Home

D. Christensen, L. Earle, and B. Sparn

Prepared under Task No. BE12.0203

Technical Report

NREL/TP-5500-55291

November 2012
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1

NILM Applications for the Energy-Efficient Home

Dane Christensen†

National Renewable Energy Laboratory

15013 Denver West Parkway

Golden, CO 80401

dane.christensen@nrel.gov

Lieko Earle

National Renewable Energy Laboratory

15013 Denver West Parkway

Golden, CO 80401

lieko.earle@nrel.gov

Bethany Sparn

National Renewable Energy Laboratory

15013 Denver West Parkway

Golden, CO 80401

bethany.sparn@nrel.gov

ABSTRACT

Research in non-intrusive load monitoring (NILM) has exploded 

in recent years, enabling innovative and significant technological 

advances. Few products are yet available, but development is 

underway at universities and corporations worldwide. In this 

presentation we discuss our vision of how these products will 

enable energy efficiency, improve comfort, and provide positive 

cash flow in the U.S. housing sector. Specifically, we forecast

products that serve the greater systems – the energy management, 

whole-house, and community energy systems.

Keywords

Efficiency, Residential, AHEM, Energy Management, Analysis, 

Fault Detection, Diagnostics, Measurement, Load Disaggregation

1. INTRODUCTION

The National Renewable Energy Laboratory’s (NREL)

Residential Buildings Group serves as technical lead to the U.S.

Department of Energy’s Building America program1, the nation’s 

leading research effort for systems integration delivering

residential building energy efficiency. The program’s research 

innovations have enabled builders to achieve cost-effective energy 

savings in excess of 60% relative to circa-1995 code construction.

As built-in efficiency opportunities have been leveraged, energy 

consumption by lighting, electronics, and “other” end-uses – most 

of which the designer/builder can neither control nor effectively 

predict – has surpassed every other category and now accounts for 

roughly 40% of electricity costs in U.S. homes

2

. That proportion 

is forecasted to grow for the foreseeable future. To meet the 

nation’s energy needs, these diverse and complex energy uses 

must be moderated. Reducing these loads is challenging because

they are poorly understood, unmonitored, and uncontrolled.

In this presentation, we discuss the immediate and near-term 

applications where we predict NILM’s greatest impact will be 

achieved, and identify other opportunities where NILM will 

enable systems innovations. NILM technologies promise to 

deliver valuable data on what, when, and how end-uses are 

consuming energy. To create “killer apps” based on these data, 

you must first determine who will use them and why.

2. CONSIDER THE CUSTOMERS

Potential customers for a residential NILM application include:

• The homeowner or building manager, who is using energy and 

has various motivations for seeking out a NILM application;

• The technology sector, which will incorporate NILM

technology into an existing or new product; 

• The service sector, which will use NILM tools to deliver home 

maintenance, retrofits, advertising, or security services; and

• The utility, which sells the energy and receives regulatory 

incentives to cost-effectively implement efficiency.

A residential application built on NILM will serve one or more of 

these customers and will meet that customer’s specific needs.

3. DEFINE THE NEEDS

3.1 Homeowner Needs

Homeowners do not know where their energy “goes” – i.e., how,

when, and why their devices, lighting, and appliances are using 

energy3

. They are similarly naïve about the savings potential and 

comfort enhancements available from usage and retrofit changes4

. 

Homeowners struggle to maintain appliances, and have very 

limited tools to manage their energy use, costs, and comfort.

3.2 Technology Sector Needs

The technology sector is devising many uses for NILM output that 

deliver features and lifestyle enhancements. Many companies are 

entering this sector, typically seeking to add NILM features into 

existing mobility, security, audiovisual, and comfort product lines.

Because of business sector silos, the broader applications of 

NILM have not been fully realized. There is no standard for 

NILM data and data access, so each company is using proprietary 

formats for its products.

3.3 Service Sector Needs

The service sector is challenged with legacy audit and analysis 

methods5

. Many small businesses with thin profit margins 

struggle to guarantee value and savings to their customers. Larger 

companies also struggle to maintain high-quality service. Overall,

few technologies exist to support process improvement.

3.4 Utility Needs

Because of the regulatory environment and a highly diverse 

residential customer base, utilities have limited tools to effectively 

deliver residential energy savings and peak reductions. They 

actively seek new tools to reduce the cost and duration of 

efficiency pilots, and have difficulty demonstrating that efficiency 

programs have saved energy6

. Utilities are challenged to generate 

sufficient energy during peak consumption hours and to maintain

grid stability at acceptable costs.

4. MEET THE NEEDS

Many products can be devised with these diverse needs, goals,

and interests in mind. The most successful and innovative will be 

designed to simultaneously meet needs of multiple stakeholders. 

An example is a NILM system built into a utility meter to verify 

demand response. This meter provides added value by making 

data available to the homeowner’s energy management devices.

Technology manufacturers could build products around that data 

stream and service technicians could access it for diagnostic 

purposes. Although this example appears to meet most customer 

needs, it represents an “infrastructure” application, which is a 

slow path to market for NILM.

Alternatively, NILM can be packaged as a standalone consumer 

product. Early market products have not been widely successful 

for several reasons – primarily cost and installation requirements.

Although market analysis would be necessary for a given product,

we expect products that cost a few hundred dollars or less, and 

can be installed very simply, have a higher chance of being 

adopted.
2

From a systems perspective, NILM applications should deliver 

both energy savings (with associated cost savings) and non-energy 

lifestyle benefits. Our research focuses on energy savings and 

energy-related lifestyle benefits such as thermal comfort, indoor 

air quality, lighting, maintenance, and building durability.

5. NEAR-TERM APPLICATIONS

We expect NILM products entering the market in the next 3–5 

years will be targeted largely at specific individual needs.

Feedback on energy consumption, with device-level breakdown, 

is a clear opportunity. Studies show that visualization alone has 

minimal effect on persistence7

. Yet these products are likely to

educate customers and lay a foundation for later efficiency 

product opportunities.

Use of NILM by utilities to verify specific device-level 

performance as part of an efficiency program is a key opportunity. 

NILM will allow the impact of the new technology on other 

household systems, and on occupant use, to be measured more 

effectively, quickly, and cheaply than current methods permit. 

Measuring the persistence of energy savings is a significant issue.

Thermostats have traditionally operated as open-loop devices. 

Manufacturers such as Nest, Honeywell, and Trane/iLink have 

recently incorporated networking and novel decision-making

techniques; however they do not predict in advance of the load. If 

NILM allowed a thermostat to see that all the lights, the 

entertainment center, the oven, and the refrigerator turned on, the 

air conditioner could turn on in advance of the temperature rising, 

and the system could direct cooling to occupied rooms, thus 

delivering substantial savings and better comfort.

Utilities struggle to maintain power delivery during the hottest 

hours of the year, because of high air conditioning demand.

During times of very low demand (mild winter nights), utilities

cannot throttle generating stations enough, so they must dump 

energy into large resistor banks. Both “load shed” and “load add” 

needs present an opportunity for smart home controls, enabled by 

NILM. By knowing a home’s typical usage by device, an energy 

management system can perform device-specific demand 

response much more effectively. Many utilities provide incentives 

for demand response, a trend that will certainly grow.

6. LONG-TERM APPLICATIONS

Highly advanced whole-house control systems are possible, but 

current designs require placement of numerous sensors throughout 

the house. NILM is a key enabling technology to improving these 

products. The near-term opportunity of device modulation to meet 

utility cost incentives will transition into a toolkit for automating

whole-house energy use, cost, and comfort. Additional features 

(security, audiovisual) will likely be incorporated into successful 

automated home energy management (AHEM) products, to 

become a class of home automation systems.

NILM-based analysis can identify poor appliance performance. 

Fault detection and diagnostics (FDD) based on runtimes, event 

and operational signatures, and energy consumption trends will 

also begin to incorporate prognostics (FDD/P). Applications will 

then be able to forecast imminent problems, deliver maintenance 

reminders, and identify when professional service is needed.

Similar to equipment-focused FDD/P, NILM can also be used as a 

continuous home audit. Currently, audits provide a snapshot-intime view of the building asset, and cannot account for occupant 

usage effects. Applications using NILM to suggest cost-effective 

retrofits or consumer goods replacement, to enhance federal, local 

and utility rebate programs, and to monitor for significant building 

changes, are most likely to find a strong market.

Finally, the cost to install an electric vehicle charging station is 

nearly prohibitive, and many utilities are beginning to charge a 

different rate for electric vehicle charging, thus requiring a second 

meter. Both utilities and homeowners will benefit from 

applications that use NILM to submeter this and similar emerging 

products.

7. CONCLUSION

The future for NILM is very bright, and a system-level view of

application design will maximize its impact and accelerate its 

market adoption. NILM is expected to have a significant impact 

on our energy economy by enabling energy efficiency, utility cost 

savings, and other non-energy benefits.

8. REFERENCES

[1] http://www.buildingamerica.gov

[2] Buildings Energy Data Book 2010, Table 2.1.6.

[3] Ehrhardt-Martinez, K (2009) Pursuing Energy-Efficient 

Behavior in a Regulatory Environment: Motivating Contexts 

for Policymakers, Program Administrators, and Program 

Implementers. Prepared for the California Public Utilities 

Commission. Washington, DC.

[4] Attari SZ, DeKay ML, Davidson CI, de Bruin WB (2010) 

Public perceptions of energy consumption and savings. Proc 

Natl Acad Sci USA 107:16054–16059.

[5] Bianchi M (2011) Technical Barriers, Gaps, and 

Opportunities Related to Home Energy Upgrade Market 

Delivery. NREL Report No. TP-5500-53011.

[6] See, for example, BPA FY13 Technology Innovation FOA, 

Topic 5 at: https://www.bpa.gov/SECURE/TIFO/

[7] Ehrhardt-Martinez K, Donnelly KA, Laitner JA (2010) 

Advanced Metering Initiatives and Residential Feedback 

Programs: A Meta-Review for Household Electricity-Saving 

Opportunities. Washington, DC: ACEEE.

ABOUT THE AUTHORS:

Dane Christensen directs the laboratory program and facilities 

for NREL’s Residential Building Group. His research efforts and 

interests include HVAC, hot water, building envelopes, demand 

response, and AHEM. Dane supports technical efforts for the 

Building America program and related energy efficiency 

initiatives. Dane received a PhD in mechanical engineering from 

University of California, Berkeley and a BS in mechanical 

engineering from Rice University.

Lieko Earle leads field testing efforts for Building America and 

conducts laboratory- and field-based research on automated home 

energy management devices and control strategies. Her interests 

include advanced monitoring efforts such as real-time energy-use 

feedback for occupants and non-intrusive load-disaggregation 

techniques. Lieko received a PhD in physics from University of 

Colorado and a Sc.B in physics from Brown University.

Bethany Sparn led the construction of NREL’s Automated Home 

Energy Management laboratory (AHEM Lab) and is coordinating 

innovative demand response, HVAC, and hot water system 

research. She is an expert at data acquisition and control systems.

Bethany received an MS in mechanical engineering from

Colorado State University. She also holds a BS in mechanical 

engineering from Columbia University and a BS in physics and 

mathematics from University of Puget Sound.

† Corresponding author
NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

NILM Applications for the 

Energy-Efficient Home

Dane Christensen, PhD

Lieko Earle, PhD and Bethany Sparn

National Renewable Energy Laboratory

Golden, Colorado

1st International Workshop on 

Non-Intrusive Load Monitoring

7 May 2012

Image credit: Dennis Schroeder, NREL PIX#19029
2

Image credit: Dennis Schroeder, NREL PIX#17612

National Renewable Energy Laboratory

Among the national laboratories, we are unique 

• Dedicated solely to energy efficiency & renewable energy technologies

• Highest number of patents, copyrights, and technology transfers (absolute & per capita)

• We develop next-generation energy technologies and practices, advance 

related science and engineering, and transfer knowledge and innovations 

to address the nation's energy and environmental goals
3

Image credit: Dennis Schroeder, NREL PIX#20160

Technical Lead for U.S. Department of Energy’s Building America program

• Develop cost-effective efficiency solutions for residential retrofit & construction

• Demonstrated in over 45,000 homes over past 20 years, across all US climate regions

• View buildings as a system – components consume energy to serve system functions

• Targets: 50% energy savings in new construction by 2015 and in retrofit by 2017

NREL Residential Buildings
4

Need Technology Enabling Persistent Energy Use Reduction by 20% 

across Lighting, Appliances & MELs, at Installed Cost of $2000

Significance of NILM

Space Heating

9%

Space

Cooling

22%

Water 

Heating

9% Lighting

14%

Refrigeration

9%

Electronics

7%

Ventilation

6%

Cooking

2%

Wet 

Cleaning

4%

Other

18%

2010 Residential Site Electrical Splits

(5.0 site Quads, 15.6 primary)

Sources:

Buildings Energy Data Book 2010, Table 2.1.6

EIA Annual Energy Outlook 2011

“Maximizing Residential Energy Savings: Net Zero Energy House Technology Pathways,” NREL TP-550-44547

32.0%

34.0%

36.0%

38.0%

40.0%

42.0%

44.0%

46.0%

48.0%

2

2.2

2.4

2.6

2.8

3

3.2

2000 2010 2020 2030 2040

Energy Consumption (Quadrillion BTU)

Residential: Lighting & MELs 

Energy Trends

L&MELs Energy

L&MELs % of Electric
5

Customers for NILM Technologies

Homeowner or building manager – responsible for 

energy use and has various motivations for seeking out 

NILM applications, products and tools

Technology sector – will incorporate NILM technology 

into an existing or new product

Service sector – will use NILM tools to deliver home 

maintenance, retrofits, advertising or security services

Utility – sells the energy and receives regulatory 

incentives to cost-effectively implement efficiency
6

Application: Measurement & Verification

• Deliver Feedback & Visualization

• Identify High-Consuming End-Uses

• Verification of Savings at Replacement

• Understand Occupancy 

& Usage Profiles

Near-Term

Image credit: Bethany Sparn, NREL PIX#20576
7

Application: Climate Controls

• Smart, Learning Capabilities

• Respond to Occupancy

• Pre-Cool for Greater Efficiency

• React to Loads, not just to Measured Temperature 

Change

• Deliver Heat &

Cooling only to

Occupied Zones

• Provide Better

Thermal 

Comfort and

Efficiency

Near-Term

68

70

72

74

76

78

80

82

0 5 10 15 20 25 30

Ttstat ( ̊F)

time (min.)

0 10 20 30 40 50 60

Standard Tstat Control

NILM-enabled Tstat Control

Indoor Temperature, measured at Thermostat
8

Application: Automated Home Energy 

Management (AHEM)

• Automate Energy Savings

o Turn off devices that are not in use

o Modulate lighting based on daylight

o Enable more flexible appliance scheduling

o Meet utility bill budgets

• Provide Dynamic Demand Response

• Automatic “Vacation Mode”

Long-Term
9

Application: End-Use Fault Detection 

And Diagnostics

• Recognize Maintenance Needs

• Provide Early Notification of Problems

o Impending Equipment Failure

o Envelope Degradation (water, air leaks, etc)

o Windows, Doors Left Open

• Reduce Service Call Time and Cost

• Verify Quality Installation/Workmanship 

by Contractor or Technician

Long-Term
NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

How Can NREL Help?
11

Investigate Technology/Product Performance

• Neutral, Third-Party Experts

• AHEM Lab: Robust & Accurate Test Bed for 

Product Evaluation

• Study Interactions

with other Home

Components &

Systems

• Develop Models 

for WholeBuilding Analysis

& Optimization

Image credit: Dennis Schroeder, NREL PIX#20007
12

Optimizing System Interactions

Source: BEopt v.1.2

Reference

Building
13

Example: Break-Even Cost for HPWH, installed in conditioned space 

in an all-electric home

Technology Opportunity Assessment

Example: Energy Savings estimated for HPWH replacing Electric Water Heater

installed within conditioned space

Source: “Heat Pump Water Heater Technology Assessment Based on Laboratory Research 

 and Energy Simulation Models.” NREL Report No. CP-5500-51433
NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

Thank You!

Dane Christensen

dane.christensen@nrel.gov