How AER Works

So how, exactly, does AER work?

AER is a validated and powerful combination of scientific data paired with mighty computer algorithms and machine learning. The result is a few actionable lines of small, but mighty, emissions-reducing code.

AER 101

WattTime’s AER software pulls information from different power plants and grid operator data to calculate which moments have lower marginal emissions rates. It then “talks” via the cloud to individual smart devices that are signed up for AER. The software system lets these devices know when to use electricity—and when not to—to reduce emissions, automatically. We simply “move” flexible energy consumption to better times. And we do this seamlessly, without impacting the end use.

For example, most people think refrigerators are always consuming power. But in fact, refrigerators only have to consume power in little bursts of cooling that happen about every 30 minutes or so. Within any 30-minute window, the power grid’s marginal emissions can vary greatly. It might be powered by a very dirty marginal power plant in the first 5 minutes, while the second 5 minutes will be powered by a very clean one such as a wind or solar farm… or vice-versa.

AER works by deliberating syncing electricity consumption to cleaner times, but always making sure to stick within whatever limits are needed for a particular device to operate as its designed. 

Optimal Refrigeration Control For Soda Vending Machines

by Z. Dewitt and M. Roeschke 2015

Automated Demand Response Refrigerator Project

by J. Tran, J. Gilles, R. Mann, and V. Murthy 2015

Electricity Generation and Demand Working Better Together

Electricity Generation is Naturally Variable

The electricity grid is like a living organism. From moment to moment, hour to hour, and day to day its “breathing” fluctuates, depending whether wind farms or solar energy or fossil-fueled power plants are supplying the electricity.

That breathing comes to life as emissions. As electricity demand rises and falls, certain power plants in certain places turn on and off at certain times in response. Their associated emissions are known as marginal emissions. Marginal emissions change every 5 minutes opening up room for small adjustments in timing energy use that add up.

Electricity Demand is Increasingly Flexible

Did you know that according to our research, around 70% of U.S. electricity demand could be flexible? In many cases, the exact timing of electricity use can vary without impacting the end use. For example, if you plug in an electric vehicle to charge overnight, it doesn’t so much matter precisely when the EV is pulling power, as long as you have a full battery in the morning.

Such flexible demand, when paired with the grid’s variable emissions rate, unlocks enormous opportunities. This is the power of AER.

Methodology and Validation

AER relies on real-time and location based marginal emissions rate. The method for determining these emissions rates builds on the approach summarized in these academic papers, including one written by our founder, Gavin McCormick. Additionally, RMI conducted further validation of this work.

Location, Location, Location: The Variable Value of Renewable Energy and Demand-Side Efficiency Resources

by Duncan S. Callaway, Meredith Fowlie, and Gavin McCormick

Spatial and Temporal Heterogeneity of Marginal Emissions: Implications for Electric Cars and Other Electricity-Shifting Policies

by Joshua S. Graff Zivin, Matthew Kotchen, and Erin T. Mansur

Marginal Emissions Factors for the U.S. Electricity System

by Kyle Siler-Evans, Ines Lima Azevedo, and M. Granger Morgan

WattTime Validation and Technology Primer

by Jamie Mandel and Mark Dyson