When is electricity cheapest? Off-peak hours explained

Why there is an off-peak at all

Electricity cannot be stored cheaply at grid scale, so it has to be generated at the moment it is used. Demand is not flat: it climbs through the afternoon as offices, air conditioning and cooking overlap, peaks in the early evening when people get home, and falls to a fraction of that overnight. The last power plants switched on to meet the evening peak are the most expensive to run, and the wires have to be sized for that hour even though they sit half-empty the rest of the day. A time-of-use plan passes some of that cost difference on to you, in the hope that you will move what you can.

What "usual" looks like

There is no national standard, but the patterns cluster. Reading across the plans in our index:

• Weekday peak is most often a block between about 2pm and 9pm. Older tariffs peak around noon to 6pm; newer ones have shifted later, into 4pm to 9pm, as daytime solar has made the afternoon cheap and the early evening the problem.
• Weekday off-peak is the rest of the day. Some plans add a middle "mid-peak" or "shoulder" price for the hours either side of peak.
• Weekends are off-peak all day on most plans, but not all. A minority keep weekday hours seven days a week, and a few utilities price Saturday differently from Sunday.
• Winter often has a second peak in the morning, roughly 6am to 9am, when electric heating comes on. Some plans have no peak in winter at all.
• Holidays are usually billed as weekends, but the list of holidays is in the tariff and is shorter than you would guess.

How much the hour is worth

The difference between peak and off-peak is the whole point, and it varies enormously. The plan where a moved kilowatt-hour is worth most in our index is Southern California Edison Co’s TOU-D-5-8PM-CPP: every kilowatt-hour a day shifted from 5pm to midnight saves about $430 a year. The widest ratio belongs to Residential High Differential Time of Use (Schedule RTOU-3) at Evergy Metro, where peak is 36.2¢ against 2.6¢ off-peak.

A 1.5× gap is worth moving a car charger for and nothing else. A 4× gap changes when you run the dishwasher. Knowing which one you have is the difference between a habit that saves real money and one that just makes evenings inconvenient. The plans with the widest gaps are listed by name.

What actually moves

Off-peak pricing only helps with loads you can schedule. In most homes that is a short list: an electric vehicle, an electric water heater on a timer, laundry, the dishwasher, a pool pump. Together those can be a third to a half of a household’s use, which is why the plans work for some people and not others. Cooking, lighting, television and air conditioning happen when they happen, and air conditioning in particular peaks in exactly the hours the tariff makes expensive. A house whose use is mostly cooling gains little from off-peak hours and may lose; a house with a car in the garage gains a lot.

Finding your hours

The hours are printed in the tariff, which is a document your utility files with the state regulator and rarely shows you. Every time-of-use plan on this site is drawn as a month-by-hour grid — weekdays and weekends side by side — so you can see the peak block, the season change, and the weekend rule at a glance. Find your utility and look for plans marked time-of-use.