Enter EV and solar design data
Results appear above this form after calculation.
Worked engineering example
| Battery | SoC | Charger | Sun hours | Panel | System efficiency | Solar target | Required PV | Recommended panels | Daily solar output |
|---|---|---|---|---|---|---|---|---|---|
| 75 kWh | 20% → 80% | 7.4 kW at 92% | 5.5 h/day | 450 W | 80% | 80% of charge | 8.89 kW | 20 | 39.60 kWh/day |
In this scenario, the array can offset roughly 232.94 km of driving energy per sunny day when the vehicle consumes 170 Wh/km.
Engineering formulas behind the calculator
Energy to battery (kWh) = Battery capacity × (Target SoC − Start SoC) ÷ 100
AC energy (kWh) = Battery energy added ÷ Charger efficiency
Solar target energy (kWh) = AC energy required × Solar contribution fraction
Required PV size (kW) = Solar target energy ÷ (Peak sun hours × System efficiency)
Panel count = Ceiling[(Required PV size × 1000) ÷ Panel wattage]
Daily solar energy (kWh/day) = Installed PV size × Peak sun hours × System efficiency
Solar km/day = Daily solar energy × 1000 ÷ EV energy use
CO₂ avoided = Solar energy displaced × Grid emission factor
How to use this calculator
- Enter your EV battery size and the charging window using starting and target state of charge.
- Add charger power and charger efficiency to reflect realistic AC charging losses.
- Provide daily distance and EV energy use to estimate how much solar range recovery you want.
- Enter peak sun hours, panel wattage, panel area, and full system efficiency for your location and hardware.
- Set the desired solar contribution percentage, then click the calculate button.
- Review the result cards, detailed table, and Plotly graph. Export the summary as CSV or PDF when needed.
Frequently asked questions
1) What does peak sun hours mean?
Peak sun hours represent equivalent full solar irradiance hours per day. They simplify variable sunlight into one useful design value for daily solar energy estimation.
2) Why is charger efficiency included?
Not all AC energy reaches the battery. Charger efficiency accounts for conversion losses, wiring losses, and thermal losses, giving a more realistic energy requirement.
3) Does this calculator size storage batteries too?
No. This version focuses on EV charging energy, charger load, and solar array sizing. Stationary storage can be added later as a separate design layer.
4) Can I use it for off-grid charging?
Yes, for first-pass estimation. However, true off-grid design also needs battery storage autonomy, inverter surge limits, weather margins, and seasonal solar variability.
5) Why might actual output differ from results?
Real systems change with temperature, shading, dirt, cable length, inverter loading, orientation, and seasonal weather. This tool uses averaged engineering assumptions.
6) What is daily solar coverage?
It compares estimated daily solar production against your daily driving energy demand. A value above 100% means solar exceeds that daily driving requirement.
7) How should I choose solar contribution percentage?
Choose 100% for full solar offset goals. Use lower values when roof area is limited, grid support is acceptable, or lower installation cost matters more.
8) Is the carbon estimate exact?
No. It is an engineering estimate based on the emission factor you enter. Grid carbon intensity changes by region, season, and time of use.