An EV and rooftop solar are usually bought as two separate decisions, but on your monthly bill they are really one number. The panels shrink the bill your home already pays, and the charger creates a new load that solar can cover for a fraction of what gasoline or grid power costs. This guide answers the two questions homeowners ask most: how much would I actually save, and what does it cost to charge an EV from solar instead of the grid?
Quick answer: for a typical 1,000-mile month, gasoline costs about $180, grid charging costs about $105, and solar charging costs about $30. Add in the electric bill savings from the panels themselves, and combined monthly savings often land near $300 to $400.
How Much Would You Save? Quick Comparison
| Fuel source | Monthly cost (1,000 miles) | Annual cost |
|---|---|---|
| Gasoline (25 mpg at $4.50/gal) | About $180 | About $2,160 |
| Grid charging (California blended rate) | About $105 | About $1,260 |
| Solar charging (paid-down system) | About $30 | About $360 |
| Savings vs. gasoline | About $150/month | About $1,800/year |
| Savings vs. grid charging | About $75/month | About $900/year |
These are averages. Your real number depends on how many miles you drive, your EV’s efficiency, and your utility rate plan.
What Does It Cost to Charge an EV from Solar?
The Two Bills an EV Driver Is Actually Paying
Before you can estimate savings, you have to name what you are replacing.
- Gasoline: a car that gets 25 miles per gallon at $4.50 per gallon costs about 18 cents per mile, or roughly $180 for 1,000 miles.
- Grid charging: most EVs use about 0.30 kWh per mile, so 1,000 miles is roughly 300 kWh. At a blended California rate near 35 cents per kWh, that is about $105 a month, and it climbs every time the utility raises rates.
- Solar charging: rooftop solar in California produces power at a levelized cost of about 8 to 12 cents per kWh once the system is paid down, roughly a third of the grid rate. That same 300 kWh costs on the order of $30 a month, and the cost stays flat for decades.
See how this compares to your other usage and how much solar panels can save you.
The kWh-Per-Mile Number That Drives Everything
Every estimate starts with two figures:
- Miles driven per month
- kWh your car needs per mile (usually listed on the window sticker as kWh per 100 miles)
Multiply them together, and you get your monthly EV load, typically 200 to 400 kWh. That number is what your solar array has to produce on top of covering the house.
Timing Your Charge Around NEM 3.0
Under NEM 3.0, exporting surplus solar to the grid pays very little, so the real savings come from using your own production directly rather than selling it.
| Charging window | Why it matters |
|---|---|
| 10 a.m. to 3 p.m. (midday) | Your panels produce the most here, and this is exactly when export credits are worst, so charging now uses your own generation instead of exporting it for pennies |
| Overnight | Many drivers can only charge after the solar day ends. A home battery bridges the gap by storing midday production and releasing it after sunset |
This is the practical reason why NEM 3.0 reshapes solar savings matters so much for EV owners specifically. Whether a battery earns its keep depends on your rate plan and mileage, covered in whether battery storage is worth it.
A Worked Example: How Much Would You Save?
Here is the three-step method for a realistic household, using 1,000 EV miles a month and a home that pays $220 a month for electricity before solar.
| Step | Calculation | Result |
|---|---|---|
| 1. Size the EV load | 1,000 miles x 0.30 kWh/mile | 300 kWh/month |
| 2. Price the solar offset | 300 kWh at gas ($180), grid ($105), or solar (about $30) | About $150/month saved vs. gas |
| 3. Add the panel bill savings | $220 electric bill cut to about $40 | About $180/month saved |
| Combined monthly savings | Step 2 + Step 3 | About $330/month, or close to $4,000/year |
You can sanity-check the underlying rate math with a solar savings calculator.
What Changes Your Number Up or Down
- More miles driven raises both the grid-charging cost you are avoiding and the solar system size you need.
- A less efficient EV (higher kWh per mile) increases your monthly load.
- Your utility’s rate plan changes the grid comparison. SDG&E customers, for example, see a bigger gap between grid and solar cost than PG&E or SCE customers.
- System size matters. An array sized only for the house, not the EV, will not capture the full savings above.
- Battery or no battery affects how much of your midday production you can actually use for evening or overnight charging.
What Axia Estimates Factor Into Your Number
A back-of-envelope estimate is a good start, but a real number has to reflect your roof, your rate plan, and your actual driving.
- Sizing the array to carry both the house and the car, not just one or the other.
- Checking your time-of-use windows to see whether midday or battery-backed charging fits your schedule.
- Using your genuine mileage instead of a national average.
- Reconciling the EV load and household load against one system size rather than quoting them separately.
Tracking Your Savings After Install
Once the system is live, watch two things each month: your electric statement and your fuel spend. Together they should track close to the combined figure you estimated. A simple habit is to track your monthly solar savings on a chart and note your gasoline savings alongside it. Comparing that record against your average monthly electric bill with solar confirms the panels are carrying both loads as planned.
The Bottom Line
Solar and an EV charger are two sides of the same monthly bill. The panels erase most of what your home already pays, and the charger converts spare daytime production into miles that would otherwise cost gasoline. Estimated together, combined savings often clear $300 a month and hold steady while gas and grid prices keep rising. Get a combined solar and EV charging estimate built around your roof, your rate plan, and your real driving.
Frequently Asked Questions
How much would I save charging an EV with solar instead of gas?
For a typical 1,000-mile month, gasoline runs about $180, while the same driving on rooftop solar costs roughly $30 in generation. That is around $150 a month in avoided fuel, and unlike the pump price, it stays flat for the life of the system.
What does it cost to charge an EV from solar?
Once a solar system is paid down, it produces power at roughly 8 to 12 cents per kWh in California, compared to about 35 cents per kWh from the grid. For 300 kWh of monthly charging, that is about $30 from solar versus about $105 from the grid.
Is it cheaper to charge an EV with solar than from the grid?
Yes. Grid charging in California costs about 35 cents per kWh, while paid-down rooftop solar produces power closer to 8 to 12 cents. For 300 kWh of monthly charging, that is roughly $105 from the grid versus about $30 from your own panels.
Do I need a bigger solar system to charge an electric car?
Usually yes. An EV adds 200 to 400 kWh of monthly load, so the array has to be sized to cover the house plus that extra charging. Getting the size right is the single most important input in a combined estimate.
When is the best time to charge an EV under NEM 3.0?
Midday, between roughly 10 a.m. and 3 p.m., when your panels produce the most and export credits are worst. Charging then uses your own generation directly. If you can only charge overnight, a home battery lets you store that midday production and use it after sunset.
How do I estimate my combined solar and EV savings?
Size the monthly EV load by multiplying your miles by about 0.30 kWh per mile, price that load against gasoline to find the fuel savings, then add the electric bill savings the panels produce on the rest of your usage. The two halves added together are your combined monthly figure.