How solar and EV savings work
Solar payback is simple division. Take the quote, subtract combined incentives such as the 30% federal credit, then divide by what you save on bills each year. After that point the panels keep producing for 25 years or more with no fuel bill. EV math runs the same way. Compare yearly gas cost with yearly charging cost for the same miles. When the car charges from your own roof, fuel cost stays low for every year after payback.
Payback = Net cost ÷ Annual bill savings · EV/yr = Miles/100 × kWh/100mi × Rate
Net cost = Quote × (1 − Incentive%) · Gas/yr = Miles ÷ MPG × Price/gal
Worked example
Scenario: $18,000 system with 30% incentive. Bill drops from $180 to $20 a month. Driving 12k miles a year at 28 MPG and $3.60 a gallon, versus 30 kWh per 100 miles at $0.16.
Solar Payback
~6.6 years
25-Yr Solar Savings
~$35,400
Gas vs EV / Year
$1,543 vs $576
EV Fuel Saved / Year
~$967
If an EV is coming, size solar for that load now so you do not have to add panels later. Incentives and net metering vary by utility, so confirm with a local installer.
What the calculator shows
- Net solar cost after your combined incentive percent
- Years until bill savings repay the system
- Lifetime bill savings minus net cost across 25 years
- Yearly fuel cost for gas next to yearly charging cost for electric
- Dollars kept each year by switching fuel
Where solar and EV fit in your home plan
An order that works for many homes is insulation and heat pumps first (see our Heat Pump Calculator), then solar sized for that added load, then the EV. That way you do not undersize the array. To track emissions as well as money, try our Carbon Footprint Calculator.