Not every kilowatt-hour is made equal. You may see your electric bill and think, “this is the amount of electricity I used, multiplied by the price, and with a few taxes added.” Actually, the true cost of electricity is not that simple. The amount of power you use is very important, but when is also important. Running an appliance at 1 pm is not the same as running it at 9pm. The reason for this is due to the way the power grid works.

• The power being used and the power being generated must be the same.
• Most forms of power generation require time to start up.
• The demand for electricity changes over the course of the year, as well as over the course of the day.

From the above issues, we may notice a few problems. You can’t just produce power thinking it will just be used eventually. At the same time, most of our power does not come from sources you can simply switch on and off. At one extreme, nuclear power is not really turned off, ever. Coal may take approximately 8 hours to fully turn on. Many renewables can’t be used all the time; it might me a cloudy day and the wind may not be blowing.

You can imagine that there is a great deal more electricity used on a summer day than on a winter night. So what do you do? You need to generate extra power for the middle of the day, known as peak demand, when people are working and AC units are on full blast.

So the solution entails much more expensive fuels. The tip of the peak demand for power is generated by burning petroleum fuels. It is a small amount of power but a disproportionally large portion of the emissions related to generating electricity. This means that we need to start thinking about when we use power. Running the washer at 1 PM or 9 PM may use the same amount of power, but the emissions associated are different.

So what can you do?

We won’t propose that you turn the AC off and feel very uncomfortable on the hottest day of the year, but try doing your laundry a little later, maybe run the dishwasher over night, or perhaps turn off your surge protectors. Simply start thinking about which activities can be moved outside the 9AM to 5PM time slot—get creative!