EV Charging Solar Calculator: Annual Energy, Direct Solar, Offset, and Cost

Direct answer

Estimate annual EV charging energy, home charging, solar offset, direct-solar opportunity, charging time, and tariff value.

Interpretation

Annual offset is not direct solar charging. This model separates home-charging energy, grid energy, the solar capacity needed for the selected annual target, the portion that can be used directly during the entered schedule, and the value of exported energy.

Decision checks

• PASS means the inputs are internally valid; WARNING identifies an offset/direct-use distinction or a schedule/rate assumption requiring verification.
• The calculator does not promise that a solar array can charge a vehicle directly at the entered percentage.

Formula or method

annual traction energy = miles/day × days/year × vehicle efficiency ÷ 100

annual charging energy = traction energy ÷ charger efficiency ÷ (1 − charging loss)

target solar kW = home charging energy × target offset ÷ annual production per kW

direct-solar opportunity = home charging energy × direct fraction × schedule factor

Assumptions and limitations

• Schedule factor is a transparent approximation based on the entered hours the vehicle is home during solar production; it is not a dispatch simulation.
• Export value and reimport value depend on the tariff, interval data, interconnection rules, and whether exported energy receives the entered credit.
• Vehicle tapering, battery temperature, seasonal production, and charger sharing can change actual charging time.

Worked example

At 35 miles/day, 260 days/year, 30 kWh/100 miles, 10% charging loss, 80% home charging, and a 100% annual offset target, the tool reports annual home-charging energy separately from traction energy and warns if the direct-solar fraction is less than 100%.

Sources

• U.S. Department of Energy Energy Saver — electric vehicles
• U.S. Department of Energy solar production and system-design guide
• NerdVolt EV charging and solar planning guide