What a plan charges by the hour, and what moving a kilowatt-hour is worth

The spread is the whole of it: every kilowatt-hour moved out of the peak hours saves the difference between the two prices, and every one moved into them costs it. On the median plan here that difference is 14.3¢. Shifting 100 kWh a month out of the peak would be worth $172 a year at that spread — the arithmetic, stated at a round figure, not a claim about any particular home.

Which is why these plans reward a household that can move a load and penalise one that cannot. A water heater, a dishwasher or a car charger can wait for the cheap hours; a hot afternoon in a house that needs cooling cannot.

A peak is usually a few hours of the weekday, not the working day: 140 of the 199 plans price 4 hours a day or fewer at the top rate, and the shortest is 0.3 h a day at Oklahoma Electric Coop Inc, averaged over the year.

139 of the 199 plans price no weekend hour at the peak rate at all, so on those the whole of Saturday and Sunday is cheap. 152 of them move the peak with the season, which means the hours to avoid in July are not the hours to avoid in January — a schedule is not something to learn once.

A schedule is only one part of a plan. The fixed charge is billed whatever hour the electricity was used in, and where a plan is also tiered, the prices above are its first tier, so a household well into a higher tier faces different numbers. What the fixed part comes to is the subject of a separate guide.

The obvious table to put here would be each utility’s cheapest time-of-use plan against its cheapest plan without one. It was computed, and then left out, because it would have misled. A tariff record carries no service zone, so inside a single utility the two cheapest schedules are frequently not offers the same household can choose between: one pair came out as a New York City rate against a Westchester one, another as a coastal rate against a low-income inland one. The difference would have read as a saving, and part of it was a difference of territory.

The second reason is the profile. This site prices a time-of-use plan on the typical hour-by-hour pattern of homes in its state, from NREL’s ResStock (the methodology page explains it). A typical home is an average of many, and yours is not it: whether a schedule would lower your bill depends on when you use electricity, and this site does not know that.

What it does know is on this page. Take the spread and the peak hours to your own bill: multiply the kilowatt-hours you could genuinely move out of those hours by the gap, and weigh that against everything else the plan charges. The rate comparator prices any published plan at the consumption you give it.

• How much electricity a home uses, state by state, and what it pays
• What uses the most electricity in a home
• Why electricity rates change, filing by filing

Every figure here is computed when the site is built, from the records named below, by the same code that fills the state, utility and cost-to-run pages this guide links to. When those records are refreshed, the figures change with them; the words around them do not, which is why no sentence here states a direction the data has not been checked for.

The methodology page sets out what the rate engine assumes and where its figures stop being reliable.