Time-of-use plans explained

A time-of-use plan prices a kilowatt-hour differently depending on when it is used. The meter, or a portion of the meter, has to know the clock. A flat residential schedule uses one energy price around the clock. This guide explains the difference with two sources that were read in full: Seattle City Light's residential rates effective January 1, 2026, and the Public Utility Commission of Texas Power to Choose export retrieved October 10, 2026. Peak hours are whatever that utility publishes. Each company sets its own window, and the hours belong in the comparison.

A flat rate has one energy price

Seattle City Light's default residential flat schedule, RSC, for customers in the city of Seattle is $0.3945 per day plus $0.1338 per kilowatt-hour, effective January 1, 2026. On a 30-day bill, the daily charge is $11.835. One thousand kilowatt-hours at 13.38¢ is $133.80. Added and rounded to the cent, the total is $145.64, before the taxes the rate page leaves outside the energy charge. Every kilowatt-hour on that schedule costs the same 13.38¢, whether it falls at 3 p.m. or 3 a.m. The 2025 EIA-861 bundled average for Seattle City Light is a different measurement: 14.74¢, an $87.48 average bill, and 593.6 kilowatt-hours a month, across 472,309 customers. The annual average spreads the fixed charge and a year of sales into one cents figure. The January 2026 flat tariff is the current schedule.

Suburban cities served by Seattle City Light use different rates from the Seattle schedule. The $0.1338 figure is the Seattle city rate. Other jurisdictions have their own schedules on City Light's rate page.

The Seattle time-of-use periods

Seattle also publishes a residential time-of-use option. The energy prices effective January 1, 2026, for Seattle are 16.10¢ on peak, 14.09¢ mid-peak, and 8.05¢ off-peak. Peak is 5 p.m. to 9 p.m. Monday through Saturday, excluding city-observed holidays. Off-peak is midnight to 6 a.m. every day. The remaining hours are mid-peak. City Light lists the time-of-use energy prices on their own. The comparison below prices those energy rates. The flat schedule's $0.3945 daily charge belongs to the flat option.

Shift 10 kilowatt-hours from peak to off-peak and the energy charge for those 10 kilowatt-hours moves from $1.61 to $0.805, a difference of $0.805. Shift 100 kilowatt-hours and the difference is $8.05. The rest of the bill is unchanged by that shift. A time-of-use option changes the bill on the kilowatt-hours that actually move, by the gap between the periods. If the household already uses little energy between 5 p.m. and 9 p.m., little is left to move. If a dryer or a car charger stays in those hours, those kilowatt-hours take the peak price.

The flat 13.38¢ price sits between the mid-peak 14.09¢ and the off-peak 8.05¢. A household whose usage is concentrated overnight can beat the flat energy price. A household whose usage is concentrated from 5 p.m. to 9 p.m. can pay more than the flat energy price. The arithmetic is the share of kilowatt-hours in each bucket. Seattle's page defines the buckets. Another utility's peak can be a summer afternoon or a winter morning, so the hours have to come from that utility's tariff.

Texas uses a flag, and the hours are on the label

The Power to Choose file retrieved October 10, 2026, contains 1,857 plan rows, counting English and Spanish listings. Ninety-three of them are marked time of use. The export includes an average price in dollars per kilowatt-hour at 500, 1,000, and 2,000 kilowatt-hours, the delivery utility, the retail provider, the term, and a set of flags. A time-of-use flag means the offer was disclosed as time-varying. The clock itself, including whether peak is four hours or twelve, and what share of a typical month the disclosure assumed, is on the electricity facts label.

The plan checker multiplies the disclosed average. If you enter 1,000 kilowatt-hours, the estimate uses the 1,000-kilowatt-hour price. If you enter 800, the nearest standard level is still 1,000, and the tool says which level it used. Weekday and weekend buckets live on the facts label, which is linked from the row. The label is the PUCT document. The flag is the filter.

Ninety-three time-of-use rows are about one in twenty of the rows in that export. The rest are unmarked for time of use. A fixed-rate flag and a time-of-use flag answer different questions. Fixed, in this file, refers to the product type the provider submitted. It can still sit next to a bill credit that makes the 500-kilowatt-hour price much higher than the 1,000-kilowatt-hour price. The bill-credit guide covers that pattern. A time-of-use plan can also carry a credit. Read both flags.

What to ask before you switch

Ask which hours are peak, mid, and off, including weekends and holidays. Ask whether the daily or monthly customer charge changes when you leave the flat schedule. Ask how the 1,000-kilowatt-hour average on a Texas facts label was weighted across periods. Ask what happens to an EV charging session that starts off-peak and ends on-peak. An interval meter splits the session. A meter that records only the total will not. Those answers live on the tariff or the facts label. The U.S. residential average of 17.23¢ for 2025 is a revenue-over-sales figure for the year. It has one price for the whole year.

If you are comparing a time-of-use offer with a flat offer, price the same kilowatt-hours in the same hours. Seattle's published gap, 16.10¢ against 8.05¢, is $0.0805 per kilowatt-hour moved from peak to off-peak. That is the scale of the Seattle option checked for this page. Another city's gap is whatever its tariff says.

Salt River Project's E-23 price plan varies by billing cycle rather than by hour of the day. The ratebook checked here, the November 2025 cycle with the January 2026 transmission cost adjustment of minus 0.06¢, prices every kilowatt-hour at 12.04¢ in the May, June, September, and October cycles, 13.98¢ in July and August, and 10.97¢ from November through April. The monthly service charge is $20, $30, or $40 depending on the dwelling and the service amperage. A January bill at the $30 tier and 1,000 kilowatt-hours is $139.70. A July bill at the same tier and the same usage is $30 plus $139.80, or $169.80. The season is the whole billing cycle, which is a different design from Seattle's 5 p.m. window. Taxes outside the E-23 per-kilowatt-hour total sit outside both of those bills. SRP's 2025 EIA average, 13.98¢ across 1,074,095 residential customers, matches the summer-peak energy total on the sheet and remains an annual revenue figure. The July tariff is the July tariff.

Where to look next

The bill calculator's Seattle schedule is the flat RSC rate, the default residential service. The three time-of-use prices are here so the periods are specific. The Texas plan tool can filter to the time-of-use flag, and the hours stay on the facts label. The rate-history chart is the annual EIA-861 series. Use the chart for the year. Use the tariff for the hour. A useful comparison prices the same kilowatt-hours on the flat schedule and on the time-of-use schedule, with the hours taken from the utility that would bill them.