The simple version

On a flat plan every unit of power costs the same whatever time it is. On this kind of plan the clock sets the price instead.

The day is cut into named windows and each window carries its own price. Late afternoon into the evening is normally the dearest one.

Two households using an identical total can pay different amounts. The difference is timing, not quantity.

The numbers

• On the plan named TOU-D 4 PM to 9 PM, summer weekday prices are 33 cents off-peak and 59 cents on-peak from 4pm (Southern California Edison, residential time-of-use rate plans page, read October 12, 2026, figures before the baseline credit)
• On the same plan, winter prices are 36 cents off-peak, 32 cents super-off-peak from 8am, and 50 cents mid-peak from 4pm (same page)
• This utility defines summer as June through September and winter as October through May, and gives no specific calendar day for the boundary (same page)
• In winter that plan has no window named on-peak at all. Its highest winter tier is named mid-peak (same page)
• On a second plan, TOU-D 5 PM to 8 PM, the summer on-peak price from 5pm is 72 cents against 34 cents off-peak (same page)
• The page also prints a lower set of figures described as after the baseline credit, for example 24 cents off-peak and 50 cents on-peak in summer on the first plan (same page)
• The page carries no effective date and no last-updated date for these plans, so all figures here are as read on October 12, 2026 (same page)

What changes when the season turns

The schedule has two settings, one for the warm months and one for the rest of the year. On this utility's published plan the first runs June through September and the second runs October through May.

When it flipped, the dearest window got cheaper and the cheapest ordinary window got more expensive. The dearest band also stopped being called on-peak and became mid-peak, so the label moved along with the price.

Winter then adds a window priced below the one named off-peak. So in winter the hours named off-peak are not the cheapest hours, which is the reverse of what the name suggests.

The actual math on 26 and 14

Under the June to September schedule the dearest window runs at 59 and the cheapest ordinary one at 33, on the per-kilowatt-hour prices above. The gap is 26.

Under the October to May one those two become 50 and 36, so the gap is 14. It has narrowed by 12, a little under half.

That gap is the whole value of shifting when you use power. Halve it and you halve what moving the laundry to a different hour is worth.

What this means

The useful question is not whether a plan looks cheap but how wide its gap is at the moment. A wide gap pays you to move things, a narrow one barely bothers.

The cheapest hours are not always the ones labelled off-peak. On this utility's winter schedule a separate daytime window, from 8am to 4pm, undercuts it by four cents.

Every utility publishes its own windows and its own prices and they are not alike. The figures here belong to one company and were read on one day.

What this is NOT

This article explains what a time of use rate is and what changed when one utility's published schedule moved from its summer season to its winter season, using Southern California Edison's residential time-of-use rate plans page as the example, read on October 12, 2026. It is not advice about which rate plan to choose, when to use power, or whether to switch plans, and it is not a recommendation for or against this utility or any other. It does not predict prices. The figures quoted are the ones the page prints before the baseline credit, and the page also prints a lower set after that credit, which this article names but does not use in its arithmetic. The page says its prices are for customers who get both delivery and generation from this utility, and that customers whose generation comes from another provider may pay different rates. The page carries no effective date and no last-updated date, so the prices may have changed since it was read, and prices, windows and season definitions differ by utility and by plan. The two arithmetic steps are ours on the page's own figures: the 26 cent and 14 cent gaps, and the 12 cent narrowing between them. This is not a political endorsement or criticism of anyone, and it takes no position on how power is priced or regulated.

Sources

• Southern California Edison, "Time-of-Use Residential Rate Plans," read October 12, 2026 (plan names, on-peak windows, season definitions, and per-kilowatt-hour prices before and after the baseline credit)