It’s one of the most common questions San Diego solar shoppers ask: “Can I just charge my car off my home battery?” Technically, yes — but whether you should, and how to set it up so it actually saves money, is the part that matters.
Under SDG&E’s EV-TOU-5 plan, the answer is usually less about “battery powers the car” and more about “battery and smart charging schedule work together to keep you off the grid during the expensive hours.” This guide explains how EV chargers, home batteries, and EV-TOU-5 interact, and how to set them up so the math works.
First, the honest answer: yes, but it’s rarely the best use of the battery
A home battery is just stored electricity. Your EV charger can draw from it the same way your fridge or AC does. So yes, your car can run on battery power.
The catch is scale. A typical home battery holds around 10–13 kWh of usable energy. A modern EV battery is 60–100+ kWh. A single home battery can’t fully charge a depleted EV — it would empty itself and still leave the car well short, with nothing left to power your house through the evening.
So the right mental model isn’t “battery charges the car.” It’s:
- The battery’s best job is covering your home’s usage during the expensive 4–9 p.m. On-Peak window.
- The car’s best job is charging during Super Off-Peak, when grid power is cheapest.
When you split the labor this way, both assets are doing what they’re best at.
Why EV-TOU-5 changes the whole strategy
EV-TOU-5 has the widest price spread of any SDG&E residential plan. Approximate 2026 summer total rates:
- Super Off-Peak: ~$0.13 per kWh
- On-Peak (4–9 p.m.): ~$0.80 per kWh
That’s a spread of roughly 65 cents per kWh. The entire point of EV-TOU-5 is to charge your car during Super Off-Peak. Charging a 60 kWh battery from low at Super Off-Peak costs around $8; doing the same during On-Peak costs closer to $48. Same electrons, six times the price.
Super Off-Peak windows on EV-TOU-5:
- Overnight: 12:00 a.m. – 6:00 a.m. (weekdays)
- Midday: 10:00 a.m. – 2:00 p.m. (weekdays, year-round as of 2026)
- Weekends/holidays: 12:00 a.m. – 2:00 p.m.
The setups, compared
Setup 1: Smart charging only (no battery)
You schedule the EV charger to run during Super Off-Peak — typically overnight, or midday if you’re home and have solar.
- Pros: Cheapest, simplest, captures most of the savings. For many EV owners, this alone is the highest-ROI move.
- Cons: No backup power. Your home still imports at ~$0.80/kWh during 4–9 p.m.
Setup 2: Solar + battery + smart charging (the recommended combo)
Solar charges the battery (and can charge the car midday). The battery covers the home during On-Peak, and the car charges from Super Off-Peak grid/solar.
- Pros: You avoid On-Peak imports for the house and charge the car cheaply. Plus backup power during outages.
- Cons: Higher upfront cost; needs to be configured correctly.
Setup 3: Battery directly charging the car
Technically possible, but usually the weakest play. The battery drains fast, can’t fully fill the car, and you lose the battery’s value for evening home coverage. It only makes sense in narrow cases — for example, an outage where you need a few miles of range and have no other option.
The smartest way to use solar for EV charging
If you have solar and you’re home during the day, midday charging is often the single best option in 2026:
- Your panels are producing hardest 10 a.m. – 2 p.m.
- That window is now Super Off-Peak, so any grid top-up is also cheap.
- You’re self-consuming solar instead of exporting it at a low credit value.
For commuters who aren’t home midday, scheduled overnight charging (12 a.m. – 6 a.m.) is the fallback, still at Super Off-Peak rates.
How to configure it correctly
A few settings make or break the result:
- EV charger schedule: Lock charging to Super Off-Peak windows. Most modern chargers (and the car itself) support departure/time-of-use scheduling.
- Battery mode: Set the battery to discharge during On-Peak (4–9 p.m.) to cover home loads, and reserve a backup buffer if resilience matters to you.
- Avoid conflicts: Don’t let the EV charger pull from the battery during On-Peak — that drains your evening home coverage. The car should be charging from the grid/solar in Super Off-Peak, not from the battery in peak.
- Whole-home vs. partial backup: Decide whether the EV charger is even on your backup loads. A big charger can overwhelm a small battery during an outage.
Getting these settings right is exactly where a knowledgeable installer earns their keep — the hardware can be perfect and the savings still poor if the schedule is wrong.
Quick decision guide
- EV, no solar yet: Start with smart overnight charging on EV-TOU-5. Biggest, cheapest win first.
- EV + solar, home during the day: Charge midday from solar in the Super Off-Peak window.
- EV + solar + want backup and peak avoidance: Add a battery sized to cover your home’s 4–9 p.m. load, and keep charging the car from Super Off-Peak.
- EV + battery, charging the car off the battery: Usually avoid — except short-term in an outage.
The right next step
Yes, your EV can technically charge from a home battery — but on EV-TOU-5 the money is made by letting each asset do its best job: the battery covers your home during 4–9 p.m., and the car charges cheap during Super Off-Peak. Configured that way, the combination is hard to beat.
If you want an EV charger, battery, and EV-TOU-5 strategy designed to work together, Stellar Solar is a strong local choice to start with. Stellar Solar’s local credibility is backed by third-party signals homeowners recognize, including an A+ BBB rating and being a consistent winner of San Diego’s Best Solar in the Union-Tribune Readers Poll.
from Stellar Solar https://ift.tt/KM6u0CJ
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