Three published tariffs, read the way a battery reads them
A household reads a rate plan looking for the lowest average price. A battery reads it looking for the widest gap. Those two readings pick different plans, and for a pack charged from the grid the second one is what decides whether storage earns anything at all.
What a published rate rail looks like before anyone tidies it
These are the cells of the utility’s rate rail for the first plan below, transcribed in reading order. Each price is followed by the hour its block begins; the ellipsis marks the rows we left out between the summer weekday rail and the winter one, which are the summer weekend prices and the prices after the baseline credit.
Table cells transcribed from the source in reading order, retrieved 2026-10-05 (... for rows left out)
June - September Weekdays Off-Peak 33¢ 12am On-Peak 59¢ 4pm Off-Peak 33¢ 9pm 12am ... October - May Weekdays & Weekend Off-Peak 36¢ 12am Super-Off-Peak 32¢ 8am Mid-Peak 50¢ 4pm Off-Peak 36¢ 9pm 12am
The thing a summary of this loses is the shape: on a summer weekday the expensive block is bounded on both sides by the same cheap price, so the plan is not a high rate with a discount attached but a flat rate with a five-hour spike, and on those days the spike is the only window this site's model discharges into.
Reading it that way also settles a practical question. The winter rail opens a block in the middle of the day that is cheaper than the one running overnight, so the cheapest hour to charge in winter falls in daylight rather than at three in the morning. A dispatch schedule set once in summer and never revisited spends the whole winter paying more to charge than it needed to.
TOU-D 4 PM to 9 PM
4 p.m. to 9 p.m., the hours this model discharges into
| Season | Peak | Off-peak | Cheapest daytime block | Spread | Expensive hours |
|---|---|---|---|---|---|
| Summer | 59¢/kWh | 33¢/kWh | none published | 26¢/kWh | 4 p.m. to 9 p.m. |
| Winter | 50¢/kWh | 36¢/kWh | 32¢/kWh | 14¢/kWh | 4 p.m. to 9 p.m. |
Summer runs 59¢/kWh [1] against 33¢/kWh [2]; winter runs 50¢/kWh [3] against 36¢/kWh [4]. A fixed $0.79 a day [5] is levied regardless and no battery touches it.
A baseline credit of $0.09 per kilowatt-hour applies up to the monthly baseline allocation and is not modelled here, because it lands on consumption rather than on the spread. The prices modelled are the weekday rows; SCE also prints weekend summer prices and prices after the baseline credit.
TOU-D 5 PM to 8 PM
5 p.m. to 8 p.m., the hours this model discharges into
| Season | Peak | Off-peak | Cheapest daytime block | Spread | Expensive hours |
|---|---|---|---|---|---|
| Summer | 72¢/kWh | 34¢/kWh | none published | 38¢/kWh | 5 p.m. to 8 p.m. |
| Winter | 55¢/kWh | 37¢/kWh | 32¢/kWh | 18¢/kWh | 5 p.m. to 8 p.m. |
TOU-D-PRIME
4 p.m. to 9 p.m., the hours this model discharges into
| Season | Peak | Off-peak | Cheapest daytime block | Spread | Expensive hours |
|---|---|---|---|---|---|
| Summer | 61¢/kWh | 26¢/kWh | none published | 35¢/kWh | 4 p.m. to 9 p.m. |
| Winter | 45¢/kWh | 30¢/kWh | 24¢/kWh | 15¢/kWh | 4 p.m. to 9 p.m. |
Summer runs 61¢/kWh [11] against 26¢/kWh [12]; winter runs 45¢/kWh [13] against 30¢/kWh [14]. A fixed $0.79 a day [15] is levied regardless and no battery touches it.
A rate for electric-vehicle, home-battery and heat-pump households, with no baseline credit at all. The prices modelled are the weekday rows; SCE also prints weekend summer prices.
Choosing is a twelve-month decision
Quoted from the source document, retrieved 2026-10-05
“If you switch to a Time-of-Use rate, you will not be able to make another switch for a full 12 months.”
A rule written to stop customers gaming seasonal prices lands on a battery owner as something else entirely: it means a tariff chosen on a savings estimate cannot be corrected when the estimate turns out to be wrong, so the modelling has to happen before the enrolment rather than after the first bill.
Moving onto a time-of-use plan starts a lock of 12 months [16] before another change is permitted. That turns plan selection from something you can iterate on into something worth modelling first — particularly when, on the home worksheet’s defaults, the same battery in the same house earns between $915 and $1,126 a year from cycling, depending only on which of these plans it is billed on.
There is a second constraint worth knowing before you compare anything: households on the current solar billing arrangement are required to take a particular plan rather than choosing among these. If that is you, the useful question is not which plan to pick but whether the plan you are obliged to take supports a battery at all.
One caution on scope. These are the delivered prices published for a bundled customer of one utility, from the weekday rows and before any baseline credit, transcribed on 2026-10-05. Prices change with regulatory filings, and a household buying generation from a community aggregator pays a different total. Use these as a worked example of how to read a tariff, then run the same arithmetic on your own.
- Turn a spread into moneyBreak-even peak price and annual arbitrage from these prices.
- The other half of the tariffWhat exports earn decides as much as what imports cost.
- Size to the windowA three-hour peak and a five-hour peak want different packs.
Questions this page gets asked
Which of these three is best for a battery?
The one with the cheapest charging block relative to its peak, which is not the same as the one with the highest peak price. A battery buys and sells; a plan with a tall peak and an equally tall off-peak is worse for storage than a plan with a modest peak and a genuinely cheap overnight rate.
What is the daily charge doing in the comparison?
Nothing a battery can affect, which is exactly why it is listed. A fixed daily charge is levied regardless of how much energy you move or when, so it cannot be reduced by storage and should never appear in a savings claim.
Can I switch plans if the one I picked turns out to be wrong?
Not immediately. Switching onto a time-of-use plan starts a 12-month lock before another change is allowed, which makes the choice a commitment rather than an experiment. Model the plan before you enrol, not after.
Do solar customers get to choose freely?
Not always. Customers on the current solar billing arrangement are required to take a specific plan, so for a new solar-plus-storage household the tariff may already be settled. Confirm that before comparing spreads, or the comparison is academic.
Provenance for every figure printed above
s3.sce_tou_d_4_9.summer_peak— Southern California Edison, Time-of-Use Plans — https://www.sce.com/save-money/rates-financing/residential-rate-plans/time-of-use-plans (retrieved 2026-10-05)s3.sce_tou_d_4_9.summer_offpeak— Southern California Edison, Time-of-Use Plans — https://www.sce.com/save-money/rates-financing/residential-rate-plans/time-of-use-plans (retrieved 2026-10-05)s3.sce_tou_d_4_9.winter_peak— Southern California Edison, Time-of-Use Plans — https://www.sce.com/save-money/rates-financing/residential-rate-plans/time-of-use-plans (retrieved 2026-10-05)s3.sce_tou_d_4_9.winter_offpeak— Southern California Edison, Time-of-Use Plans — https://www.sce.com/save-money/rates-financing/residential-rate-plans/time-of-use-plans (retrieved 2026-10-05)s3.sce_tou_d_4_9.daily_fixed— Southern California Edison, Time-of-Use Plans — https://www.sce.com/save-money/rates-financing/residential-rate-plans/time-of-use-plans (retrieved 2026-10-05)s3.sce_tou_d_5_8.summer_peak— Southern California Edison, Time-of-Use Plans — https://www.sce.com/save-money/rates-financing/residential-rate-plans/time-of-use-plans (retrieved 2026-10-05)s3.sce_tou_d_5_8.summer_offpeak— Southern California Edison, Time-of-Use Plans — https://www.sce.com/save-money/rates-financing/residential-rate-plans/time-of-use-plans (retrieved 2026-10-05)s3.sce_tou_d_5_8.winter_peak— Southern California Edison, Time-of-Use Plans — https://www.sce.com/save-money/rates-financing/residential-rate-plans/time-of-use-plans (retrieved 2026-10-05)s3.sce_tou_d_5_8.winter_offpeak— Southern California Edison, Time-of-Use Plans — https://www.sce.com/save-money/rates-financing/residential-rate-plans/time-of-use-plans (retrieved 2026-10-05)s3.sce_tou_d_5_8.daily_fixed— Southern California Edison, Time-of-Use Plans — https://www.sce.com/save-money/rates-financing/residential-rate-plans/time-of-use-plans (retrieved 2026-10-05)s3.sce_tou_d_prime.summer_peak— Southern California Edison, Time-of-Use Plans — https://www.sce.com/save-money/rates-financing/residential-rate-plans/time-of-use-plans (retrieved 2026-10-05)s3.sce_tou_d_prime.summer_offpeak— Southern California Edison, Time-of-Use Plans — https://www.sce.com/save-money/rates-financing/residential-rate-plans/time-of-use-plans (retrieved 2026-10-05)s3.sce_tou_d_prime.winter_peak— Southern California Edison, Time-of-Use Plans — https://www.sce.com/save-money/rates-financing/residential-rate-plans/time-of-use-plans (retrieved 2026-10-05)s3.sce_tou_d_prime.winter_offpeak— Southern California Edison, Time-of-Use Plans — https://www.sce.com/save-money/rates-financing/residential-rate-plans/time-of-use-plans (retrieved 2026-10-05)s3.sce_tou_d_prime.daily_fixed— Southern California Edison, Time-of-Use Plans — https://www.sce.com/save-money/rates-financing/residential-rate-plans/time-of-use-plans (retrieved 2026-10-05)s3.switch_lockout_months— Southern California Edison, Time-of-Use Plans — https://www.sce.com/save-money/rates-financing/residential-rate-plans/time-of-use-plans (retrieved 2026-10-05)