Thermostat settings for SDG&E time-of-use rates

On SDG&E time-of-use plans, electricity costs the most from 4 to 9 p.m. every day. The best thermostat settings pre-cool your home a few degrees in the early afternoon, and let it drift a few degrees warmer during on-peak hours. If you have a heat pump, keep heating setbacks small so the backup electric heat doesn't kick in.

Fallbrook, Bonsall and the inland valleys of North County run hotter than the coast, so AC is often the largest electric load in the house on a summer evening. That's exactly when SDG&E prices are highest. Below is how Fallbrook Heating & Air sets thermostats for customers on time-of-use (TOU) rates. These are the same points we explain at the kitchen table after a tune-up.

What are SDG&E's time-of-use hours?

SDG&E's residential time-of-use plans, including TOU-DR1, TOU-DR2, TOU-ELEC and EV-TOU-5, all have on-peak pricing from 4 p.m. to 9 p.m. every day, including weekends and holidays. Rates within each period change over time, so check SDG&E's rate pages for current prices rather than relying on old figures.

We checked SDG&E's pricing plan page on October 16, 2026. It lists these residential plans:

On TOU-DR1, SDG&E lists super off-peak as midnight to 6 a.m. on weekdays and midnight to 2 p.m. on weekends and holidays. The page also shows some weekday midday super off-peak hours, so check your plan's details. Off-peak covers the remaining hours outside 4–9 p.m. SDG&E also offers EV-TOU (separate EV meter) and DR-SES (for some solar customers). For current prices, see SDG&E's Total Electric Rates page.

How does pre-cooling before 4 p.m. work?

Pre-cooling means running your AC harder before the on-peak window, so your home starts 4 p.m. a few degrees cooler than usual. Walls, floors and furniture store some of that coolness, and the AC then runs less from 4 to 9 p.m. A typical approach is 2–4°F below your normal setting from about 1 or 2 p.m.

For example, if you're comfortable at 76°F:

1. Early afternoon (about 1–4 p.m.). Set the thermostat to 73–74°F. If your plan has midday super off-peak hours, use those first.
2. On-peak (4–9 p.m.). Set it to 77–78°F. The house warms slowly from its cooler start, and the AC runs less often.
3. Evening (after 9 p.m.). Return to 76°F, or whatever you sleep well at.

Pre-cooling works best in homes with decent insulation, tight windows and sealed ducts. In a leaky house, the stored coolness escapes before it does much good. Leaky ducts in a hot Fallbrook attic waste cooling at any hour. Ducts are tested and sealed when equipment is replaced under California's Energy Code; see our Title 24 duct testing page.

How much should I set the thermostat back?

For cooling, a 2–4°F rise during on-peak hours is a good starting point for most homes. Bigger setbacks look tempting but often backfire: the house heats up quickly, comfort drops, and the AC runs flat out at 9 p.m. trying to catch up. Start small, check your next bill, and adjust.

A few rules of thumb we share with customers:

• Don't switch the AC off on a hot afternoon. Recovering from 90°F indoors takes far longer than holding 78°F.
• Turning the thermostat lower doesn't cool the house faster. Many systems deliver cool air at one fixed speed.
• Close blinds on west- and south-facing windows before the afternoon sun hits them.
• Run the dishwasher, dryer and other big loads before 4 p.m. or after 9 p.m.
• If upstairs rooms overheat, zoning can direct cooling where it's needed.

Can a smart thermostat handle time-of-use scheduling?

Yes. A programmable or smart thermostat can run your pre-cool and on-peak settings automatically every day. ENERGY STAR notes that smart thermostats can learn your schedule, adjust when you're away using your phone's location, and be controlled remotely. Set your schedule around 4–9 p.m. and check that weekends follow the same pattern.

When you set up a schedule:

• Program the 4–9 p.m. window every day. SDG&E's on-peak hours apply on weekends too.
• Check that the thermostat's equipment setting matches your system (AC with furnace, or heat pump).
• Turn off "early start" or "smart recovery" features that start cooling just before 9 p.m. if they push run time into the on-peak window.
• Keep the thermostat out of direct sun and away from supply registers so it reads the room accurately.

Fallbrook Heating & Air can check your thermostat wiring and settings during a tune-up, install a smart thermostat, or move a thermostat that sits in a sunny or drafty spot.

What changes if I have a heat pump?

In heating mode, keep setbacks small, around 2°F. When a heat pump has to recover from a big setback, many thermostats call for the auxiliary electric heat strips, which use far more electricity than the heat pump itself. That can wipe out your savings, especially if recovery runs into the 4–9 p.m. window.

Heat pumps heat and cool, so they're on time-of-use rates year-round. SDG&E says its TOU-ELEC plan is designed for homes with an electric heat pump, among other electric equipment. Whatever plan you're on:

• Use a thermostat set up for heat pumps, with the auxiliary or emergency heat wired and labeled correctly.
• On winter afternoons, warm the house slightly before 4 p.m. rather than letting it cool a lot and recovering on-peak.
• Avoid big overnight setbacks on cold nights. Inland Fallbrook averages lows around 41°F in December.
• If "AUX" or "EM HEAT" shows on the thermostat often, have the system checked.

If your heat pump runs but doesn't heat, see our guide to a heat pump not heating, or our heat pump service page.

Does maintenance affect my time-of-use bill?

Yes. A clean filter, clean outdoor coil and correct refrigerant charge let your system cool the house quickly during your pre-cool window. A neglected system runs longer to do the same job, often right into on-peak hours. ENERGY STAR recommends checking your filter monthly and having a yearly tune-up.

A yearly tune-up ($169 per system) covers the routine. SDG&E also lists current rebates on its rebates page; see our SDG&E rebates guide. Programs change; we'll check current eligibility with you.