Building Energy Technology: Non-Intrusive Appliance Load Monitoring

Fraunhofer Center for Sustainable Energy Systems

Image of a fusebox. Picture courtesy of Phil Landowski /

Project Motivation

Non-intrusive appliance load monitoring (NIALM) is a way for homeowners and building managers to monitor energy consumption on an appliance-by-appliance basis without having to install dedicated sensors across an entire house or office building. NIALM is not a new concept – the first non-intrusive devices date back almost twenty years to processes developed at MIT. But those early devices were far from user-friendly: setting them up required installation by a trained electrician and a manual, one-by-one synchronization with every appliance in the household.


Growing public interest in smart meters has put NIALM back into the limelight. Smart meters build on conventional energy meters by giving them the ability to communicate with the central office of whichever utility company would normally read them. On one level, this allows utilities to track – and manage – customer energy consumption for their demand response programs. But it has benefits for the end user as well, offering consumers information on their energy consumption in a way that’s easily accessible even to a technical layman.


Smarter-than-Smart Meters

Fraunhofer CSE’s patented monitoring process builds on the basic principles of smart metering by adding another layer of technical sophistication.


In a household, each appliance has a unique energy “signature” called a power jump: the increase in energy consumption when an appliance is turned on. By analyzing power jumps, CSE’s NIALM process identifies a signature for each device in the household, then uses a sophisticated algorithm to separate those signatures from the overall energy consumption.


Instead of a single aggregate total for energy consumption, meter users can now see just how much their toaster oven or flatscreen TV is tacking onto their monthly electricity bill. Beyond the obvious advantages, there are other benefits to NIALM:

  • A user can tag and track individual appliances over time. This makes it possible to determine which devices consume the most power, and how much energy is wasted by leaving devices powered on for longer than necessary.
  • This process can also help identify inefficient or malfunctioning appliances, and allows users to determine whether or not replacing them will ultimately be a cost-effective decision.
  • Users on a plan where energy expense varies with time of day can use this information to plot the most cost-effective time to use particularly energy-intensive appliances.
  • Utilities can also use NIALM data to quickly detect and identify outages in their grids.

With 10 million smart meters already deployed in the US and 50 million expected to be installed in households by 2020, public demand for more detailed and actionable consumption information will only grow over time. NIALM taps into this demand by making smart meters truly intelligent, giving energy-savvy users the tools to predict, monitor, and manage their own power consumption and efficiency on a very granular level.