Offset California EV Charging Costs with Plug-In Solar
- Bright Saver
- Mar 17
- 4 min read
California EV Owners: Offset Your Charging Costs with Plug-In Solar
In short: A plug-in solar expansion kit can offset 33-61% of your annual EV home charging costs in California. A 2-panel kit offsets about 1,200 kWh/year (~33% of typical EV charging), while a 4-panel kit offsets about 2,200 kWh/year (~61%). Both pay for themselves in under 5 years.
For a side-by-side comparison with traditional solar add-ons, see Plug-In Solar vs. Traditional. For the legal framework, see NEM Expansion Rules.
You made the switch to electric. But if you're charging at home in California, your electricity bill went up. A lot.
California has some of the highest electricity rates in the country. The good news: if you already have rooftop solar on NEM 1.0 or NEM 2.0, a plug-in NEM Expansion Kit can help claw back a meaningful portion of that charging cost — and the extra energy earns NEM credits at your existing rate.
What Does It Cost to Charge an EV in California?
Using 12,000 miles/year at 30 kWh/100 miles = 3,600 kWh of charging per year:
Utility | Avg. Rate | Annual EV Charging Cost | Monthly |
PG&E | $0.42/kWh | $1,512 | $126 |
SCE | $0.345/kWh | $1,242 | $104 |
SDG&E | $0.457/kWh | $1,645 | $137 |
That's on top of your regular household electricity. If your rooftop solar was sized before you got the EV, your true-up bill is climbing.
How NEM Expansion Helps EV Owners
California's NEM expansion rule lets you add up to 1 kW or 10% of your original system size without losing your existing NEM rate. A Bright Saver NEM Expansion Kit plugs into a standard outlet after a little Ikea-style assembly, and starts generating electricity the same day.
Every kilowatt-hour your expansion kit produces either powers your home directly (offsetting your EV charging) or flows back through your meter as NEM credits. Either way, your bill goes down.
Savings for EV Owners
At conservative NEM rates (~$0.30/kWh), here's what an expansion kit offsets:
System | Annual kWh | Annual NEM Credits | % of EV Charging Offset | Payback |
NEM 2-Panel ($1,649 incl. tax) | ~1,200 kWh | $360/year | ~33% of EV charging | 4.6 years |
NEM 4-Panel ($2,583 incl. tax) | ~2,200 kWh | $660/year | ~61% of EV charging | 3.9 years |
A 4-panel kit offsets roughly 61% of a typical EV's annual charging needs. The remaining 39% still comes from the grid, but your net cost drops significantly.
The Full Picture: Gas vs. Electric vs. Electric + Solar
Fuel Source | Annual Cost (PG&E area) |
Gasoline (30 MPG, $4.50/gal) | $1,800 |
EV home charging (no expansion) | $1,512 |
EV + 2-panel NEM expansion | $1,152 |
EV + 4-panel NEM expansion | $852 |
With a 4-panel kit, your annual "fuel" cost drops to $852 — less than half what you'd pay for gasoline, and $660 less than EV charging alone.
Why It Gets Better Over Time
California electricity rates have been rising 5 to 8% per year. Your EV charging costs will keep climbing, but your NEM Expansion Kit cost is locked in at day one.
Year | Est. NEM Rate | 2-Panel Annual Credits | 4-Panel Annual Credits |
Year 1 | $0.30/kWh | $360 | $660 |
Year 5 | $0.37/kWh | $444 | $814 |
Year 10 | $0.47/kWh | $564 | $1,034 |
Year 20 | $0.76/kWh | $912 | $1,672 |
Over 20 years, a 4-panel kit generates over $21,000 in cumulative NEM credits on a $2,583 investment.
Solar Production vs. EV Charging Timing
Solar production happens during the day. If you charge at night, the solar electricity offsets other household usage during the day, and you draw from the grid at night for charging. Your NEM credits from daytime production offset your nighttime usage at true-up.
If you can charge during daytime hours (while at home or with a timer), the solar electricity directly powers the charger — maximum efficiency.
Environmental Impact
System | Annual CO2 Prevented |
2-panel kit | ~850 lbs CO2/year |
4-panel kit | ~1,560 lbs CO2/year |
Over 20 years, a 4-panel kit prevents roughly 15 tons of CO2 — equivalent to taking a car off the road for 3 years.
Real-World EV Charging Scenarios
Daily commuter, 40 miles/day:
At roughly 30 kWh per 100 miles, a 40-mile daily commute uses about 12 kWh/day or 4,380 kWh/year. A 4-panel kit producing 2,200 kWh/year offsets roughly half your commute charging. At PG&E rates, that saves $660/year in NEM credits.
Weekend driver, 100 miles/week:
About 1,560 kWh/year of charging. A 2-panel kit (1,200 kWh/year) covers 77% of your charging needs. At SDG&E rates ($0.36/kWh), that's $432/year in credits — the kit pays for itself in 3.8 years.
Two-EV household:
If both cars charge at home, total charging can exceed 7,000 kWh/year. A 4-panel kit won't cover all of it, but $660-$792/year in NEM credits still makes a meaningful dent. Combined with your rooftop system, plug-in solar helps close the gap between your original system sizing and your current usage.
FAQ
Can plug-in solar fully power my EV?
A 4-panel kit produces about 2,200 kWh/year, covering roughly 61% of typical EV charging needs (3,600 kWh/year). It significantly reduces your charging cost but won't eliminate it entirely.
How does this work with my existing rooftop solar?
Your NEM Expansion Kit works alongside your rooftop system. Both contribute to your NEM credits through the same bi-directional meter. The expansion rule lets you add up to 1 kW or 10% without losing your existing NEM rate.
Does this replace a Level 2 charger?
No. Plug-in solar generates electricity — it doesn't replace charging equipment. It makes your charger cheaper to operate by offsetting the electricity cost.
What if I charge at night?
Your solar panels produce during the day, earning NEM credits. Those credits offset your nighttime grid usage at true-up. The net effect on your bill is the same whether you charge day or night.
Stop paying full price to charge your EV.
NEM 2-Panel Kit: $1,499 (+ tax) — Offset ~33% of EV charging
NEM 4-Panel Kit: $2,348 (+ tax) — Offset ~61% of EV charging
Free pickup from our Oakland or Los Angeles warehouses. Delivery + installation support available within 50 miles of Oakland for $349.
Bright Saver is a 501(c)(3) nonprofit. Our mission: Help Americans save on electricity bills by making plug-in solar affordable and accessible to all.