Skip to content

Want to Schedule Your Electricity Use to Reduce Pollution? Here’s How

Some of us occasionally feel the urge to turn off the kitchen/porch/office light as our small step towards addressing global climate change. A Berkeley PhD student – Gavin McCormick – has started a nonprofit to provide information on exactly how our actions impact pollution.

Gavin’s organization, WattTime, is analyzing data from around the US to provide information like the map below. You can hover over an area to get almost live information on CO2 emissions.


It turns out that it’s not straightforward to generate the information behind maps like this – far from it.

Consider two different scenarios. In both, I’m assuming that you’re doing something that you don’t usually do – turning off the porch light earlier, for instance – and that other consumers do not change what they do.

To understand what Gavin is doing, we first need a basic understanding of electricity grid operations. Many readers no doubt understand this better than I do, and this is a highly stylized description, but it works for these purposes.

Wherever you live, there’s a grid operator charged with balancing the electricity system and ensuring that there’s enough power generated at any given time to meet demand. The operator also needs to ensure that the plants are not generating too much as that could damage equipment.


The grid operator communicates with power plant operators in the region about how much they’re producing and with the grid operators in adjacent areas about imports and exports. Much of the communication is automated and, for instance, the grid operator’s “request” for less electricity when you turn off your light would likely be communicated through something called Automatic Generation Control (AGC).

Go back to turning off the porch light. If you live in Ohio and it’s a regular night, it’s possible that the AGC system will instruct a coal plant to reduce production. That’s great if you’re trying to reduce GHGs or other pollutants, as coal plants are as dirty as they come.

Turning off your light in West Texas may not be as helpful for reducing greenhouse gas emissions, especially if it’s windy. In this case, you well might be asking the grid operator to back off on the output from wind plants.

In fact, many wind producers receive subsidies from the federal government that increase in the amount of electricity they produce. This is called the production tax credit, and it was recently $23/MWh. So, wind producers actually want you to keep your lights on in the middle of a windy night. In fact, prices can be negative (though rarely below -$23/MWh), meaning that the wind turbine producers are willing to pay consumers to take their power at that point in time.

West Texas Market Clearing Prices for 2010

One thing that’s great about Gavin’s site is that he’s striving to use a better methodology than what’s out there now. There are other sites that simply report the average emissions in a given hour. So, for the Ohioan turning off the light, the other sites are averaging across zero-GHG-emissions nuclear power plants and the coal plants.

This calculation will provide a misleadingly low estimate of the impact of your actions, though, since the nuclear power plants won’t change their output when you turn off your light. They are not marginal, in the language of economists. So, it doesn’t make sense to account for their emissions, as your actions don’t affect them. While average GHG emissions vary by a small amount throughout the day, the marginal plant can vary a lot – from particularly dirty coal to emissions-free wind. The map above still reflects averages, but WattTime maps reflecting marginal emissions are coming very soon.

My example about a single porch light is actually below WattTime’s aim, as a 100W porch light is 1/5,000,000th of the output of a typical 500 MW plant. They’re really targeting the larger decisions by, for example, designing smart plugs for electric cars and industrial load controllers.

If Gavin’s company takes off, which we’re all cheering for, the calculations get a lot more complicated. If his company accounts for a large and predictable share of electricity demand, grid operators might anticipate that fewer people will turn on their porch lights when polluting plants are marginal, and adjust their decisions about which plants to turn on for the day. Ultimately, planners might anticipate this reaction and adjust the type of power plants they build. Gavin and crew are working on incorporating longer run decisions, so stay tuned for Version 2.0 of their site.

Information will help us make better decisions, and I’m delighted that there are innovators like Gavin out there who are perfecting the information that consumers get, and designing cool websites and apps to put the information in front of us.



Catherine Wolfram View All

Catherine Wolfram is Associate Dean for Academic Affairs and the Cora Jane Flood Professor of Business Administration at the Haas School of Business, University of California, Berkeley. ​She is the Program Director of the National Bureau of Economic Research's Environment and Energy Economics Program, Faculty Director of The E2e Project, a research organization focused on energy efficiency and a research affiliate at the Energy Institute at Haas. She is also an affiliated faculty member of in the Agriculture and Resource Economics department and the Energy and Resources Group at Berkeley.

Wolfram has published extensively on the economics of energy markets. Her work has analyzed rural electrification programs in the developing world, energy efficiency programs in the US, the effects of environmental regulation on energy markets and the impact of privatization and restructuring in the US and UK. She is currently implementing several randomized controlled trials to evaluate energy programs in the U.S., Ghana, and Kenya.

She received a PhD in Economics from MIT in 1996 and an AB from Harvard in 1989. Before joining the faculty at UC Berkeley, she was an Assistant Professor of Economics at Harvard.

23 thoughts on “Want to Schedule Your Electricity Use to Reduce Pollution? Here’s How Leave a comment

%d bloggers like this: