When are peak hours for electricity? There is no national answer

Why every utility picks a different window

A peak window exists to move demand away from the hours when the utility’s system is most strained, or when the power it buys is most expensive. Those hours depend on the local climate, on how much solar generation is on the grid, and on what the utility pays for power. A summer-peaking utility in the South sees its system strained in the hottest part of the afternoon. One with a lot of solar sees the strain after sunset, when the panels stop and the air conditioners keep running. A northern utility with electric heating may be stretched hardest on a January morning.

Each utility writes its own answer into its tariff, and regulators approve them one at a time. Nothing coordinates them. The result is that the peak hours at one utility say little about the peak hours across the county line.

The windows that come up most often

Counted by how many utilities use each window, so that a utility filing the same window across dozens of regional plans counts once.

Even the top of this table is thin. Beyond it, 69 of the 83 windows are used by exactly one utility. Some differ only by an hour or a month; others are entirely different shapes — a peak that runs from 9am to 9pm, or two separate peaks on the same winter day.

Three things the usual advice gets wrong

• Peak often starts earlier than 4pm. 126 of the 190 plans (66%) have a peak window that opens before 4pm — some at 2pm or 1pm in summer, some at 6am or 7am in winter. Running laundry at 3pm on the assumption that it is off-peak can put it squarely in the most expensive hours.
• Winter can have its own peak. 43 plans switch windows with the season, usually to a morning peak in the colder months, when heating comes on before work. A household that learned its summer window and never checked again is shifting load to the wrong hours for half the year.
• Weekends are not automatically cheap. Only 49 of the 190 plans treat Saturday and Sunday as off-peak around the clock. On the rest, the weekend has priced hours too.

How much the window is worth

The median time-of-use plan charges 2.6 times as much per kilowatt-hour at peak as off-peak. That ratio is what makes the window worth knowing: every kilowatt-hour moved out of it costs less than half as much. The widest gap in the data is Evergy Metro’s Residential High Differential Time of Use (Schedule RTOU-3), at 36.2¢ against 2.6¢ — 14 times apart. Our ranking of the biggest peak-to-off-peak gaps lists the plans where moving a load pays the most.

How to find your own peak hours

• First, check whether you have peak hours at all. A window only applies to a household on a time-of-use plan. Many households are on a standard plan that charges the same price at every hour, and for them none of this matters. The plan name is printed on the bill, usually near the account number.
• Then look up that plan, not the utility. A utility with several time-of-use plans can give each a different window. Every utility page here lists its plans’ windows side by side in a “peak hours” section, read from the tariff it filed — find yours.
• Check the season. If the plan’s window names months, write down both. Our guide to off-peak hours explains holidays, shoulder periods and the other details tariffs bury.

Method

• Source: the NREL Utility Rate Database, public domain, snapshot 2026-08-27. Every residential plan that is open to new customers, prices energy differently by hour of the day, and is meant for an ordinary home. Variants filed for single- and three-phase service with identical terms are counted once.
• The peak window is the set of hours billed at the plan’s highest energy price, written out the same way as on each plan’s page. Where the highest price applies in different hours in different seasons, both windows are listed.
• Critical-peak events, which a utility calls on a handful of days a year, are not in the database’s schedule and are not counted here.