How the calculation works
These are preliminary energy estimates only. Controller current is a screening value based on nominal battery voltage, not a selected controller rating. Actual design must account for charging voltage, inverter and wiring losses, temperature and aging, battery chemistry, PV cold-weather Voc, Isc, string limits, controller input ratings, equipment instructions and applicable code requirements.
Worked example
10 kWh/day, 5 PSH, 80%: 2500 W array; 48 V, 2 days, 80% DoD: 521 Ah; controller current screening estimate approximately 65 A; verify controller selection against manufacturer limits and actual PV/battery configuration.
Common mistakes to avoid
- Leaving out system losses in the array size.
- Using 100% depth of discharge for lead-acid batteries.
- Mixing battery voltage between the bank and the controller.
Frequently asked questions
DoD?
~50% lead-acid, 80–90% lithium.
What are peak sun hours?
Equivalent hours per day at 1,000 W/m². U.S. locations range roughly from 3 to 6; check NREL's PVWatts for your site.
MPPT or PWM controller?
MPPT controllers typically harvest more from higher-voltage arrays and cold weather.
Related calculators
For informational and educational purposes only. Always consult a licensed electrician and local code authority. See our Electrical & Legal Disclaimer. Found an error? Tell us.