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Solar EV Energy and Charging Overlap Calculator

Compare annual EV energy offset and interval solar charging availability using vehicle acceptance, charging losses, other loads and actual site output.

Use this result well

Inputs that matter
Annual driving distance (miles), Battery-side driving efficiency (miles/kWh), AC-to-battery charging efficiency (%), Site annual AC yield (kWh per DC kW), and 8 more
Output to expect
Annual EV energy offset, Solar and EV charging overlap
  • Check the units and required inputs before comparing results.
  • Keep the assumptions with a copied result so you can reproduce the calculation later.
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Reference & details

How it works

Annual EV energy offset

Estimate annual AC charging energy and the DC array nameplate needed to produce that amount using an actual site-specific annual AC yield. Battery-side driving efficiency and AC-to-battery charging efficiency are separate. Annual matching does not prove solar-only charging at a particular time.

Battery kWh = annual miles / battery-side miles per kWh; charging AC kWh = battery kWh / charging efficiency; required DC kW = AC kWh / annual AC kWh per DC kW.

Solar and EV charging overlap

Compare AC solar surplus with an available charging window interval by interval. Solar-only mode assumes a compatible controller that can modulate from the entered minimum to maximum power; grid-assist mode charges at maximum power. No storage or import/export compensation is modeled.

Surplus = max(PV AC − other AC loads, 0). Charge power is capped at EV/EVSE acceptance; solar contribution cannot exceed surplus. Stop when the battery energy target is met.

Updated: September 2026

Example Scenarios

Try this example to see the calculation, then enter actual documented values and preserve the measurement conditions. A failed or unresolved comparison is part of the record.

→ 2.380952 kW DC for annual EV energy offset

Try this example to see the calculation, then enter actual documented values and preserve the measurement conditions. A failed or unresolved comparison is part of the record.

→ 12 of 12 battery kWh added

FAQ

Estimate annual AC charging energy and the DC array nameplate needed to produce that amount using an actual site-specific annual AC yield. Battery-side driving efficiency and AC-to-battery charging efficiency are separate. Annual matching does not prove solar-only charging at a particular time. Compare AC solar surplus with an available charging window interval by interval. Solar-only mode assumes a compatible controller that can modulate from the entered minimum to maximum power; grid-assist mode charges at maximum power. No storage or import/export compensation is modeled.

Use the exact equipment data, measurement point, operating conditions and units described in the selected mode. Record source documents, dates and unresolved conditions in Sources and assumptions. Built-in examples illustrate arithmetic; they are not manufacturer ratings or approved designs.

Use Save planning case for an explicit local history entry. Copy MD keeps current inputs and notes; Download CSV exports the result breakdown. Export portable copies before clearing storage and save a separate case after changing equipment, conditions or measurements.

About Solar EV Energy and Charging Overlap Calculator

Estimate annual AC charging energy and the DC array nameplate needed to produce that amount using an actual site-specific annual AC yield. Battery-side driving efficiency and AC-to-battery charging efficiency are separate. Annual matching does not prove solar-only charging at a particular time. Compare AC solar surplus with an available charging window interval by interval. Solar-only mode assumes a compatible controller that can modulate from the entered minimum to maximum power; grid-assist mode charges at maximum power. No storage or import/export compensation is modeled.