On the standard residential rate plan at PG&E, SCE and SDG&E, the hours from 4 to 9 p.m. are priced highest. Those are also the hours when rooftop panels make little or no power, because the sun goes down. A battery stores daytime solar power so a home can use it then.
1. Which utilities price 4 to 9 p.m. highest?
All three of California's big utilities do, on their standard residential rate plan.
PG&E's E-TOU-C plan is named “Time-of-Use Peak Pricing 4-9 p.m. Every Day.” It prices 4 to 9 p.m. above all other hours, on weekdays and weekends.1
SCE's TOU-D 4-9PM plan lists its highest rates on summer weekdays from 4 to 9 p.m. Its TOU-D-PRIME plan lists its highest rates from 4 p.m. to 9 p.m.1
SDG&E's peak pricing runs from 4 p.m. to 9 p.m.1
2. Is every plan priced this way?
No. All three utilities also sell a plan whose peak runs from 5 to 8 p.m., so the window on your bill may be different.1 Your bill names your rate plan.
3. Why can't solar panels cover those hours?
Solar panels make electricity from sunlight.2 The sun goes down inside the 4 to 9 p.m. window, so panels make little or no power for most of the hours that cost the most.
4. How does a battery help?
A battery stores energy for later.2 Paired with solar, it holds power your panels make during the day, so a home can run in the evening on what its roof made earlier.
SDG&E says its Solar Billing Plan is built to pair solar with a battery, because evening demand is high when the sun is down.3
5. What should you ask about your own plan?
Ask which plan a quote assumes and when that plan's peak hours are. Those hours are the ones a battery would need to cover.
Quick answers.
Does 4 to 9 p.m. peak pricing apply on weekends?
On PG&E's E-TOU-C plan, yes: it applies every day. SCE's TOU-D 4-9PM plan lists its highest rates on summer weekdays. Check your own plan on your bill.
Does every California utility have a 4 to 9 p.m. peak?
PG&E, SCE and SDG&E all price 4 to 9 p.m. highest on their standard residential rate plan. Each also sells a plan with a 5 to 8 p.m. peak. Other utilities set their own plans.
Can solar panels cover the evening peak on their own?
Mostly no. Panels make power from sunlight, and the sun sets during the 4 to 9 p.m. window. A battery is what stores daytime solar power for those hours.
Sources.
- PG&E, time-of-use rate plans, SCE, time-of-use plans and SDG&E, pricing plans, checked September 2026.
- US Department of Energy, solar integration: solar energy and storage basics, checked September 2026.
- SDG&E, Solar Billing Plan, checked September 2026.
