WATFUL
Make every watt count.
Practical power and energy calculators with transparent formulas, editable assumptions and shareable results.
Calculators
Battery
Battery Runtime
How long a battery actually powers your load — after depth of discharge and inverter losses.
Open calculator ›ConverterAh ↔ Wh Converter
Convert between amp-hours and watt-hours at any nominal voltage — the first step of every battery calculation.
Open calculator ›SolarSolar Charge Time
How many peak sun hours and days your panels need to refill a battery, after system losses.
Open calculator ›BatteryBattery Bank Sizing
How big a bank your daily consumption needs, sized for days of autonomy and usable depth of discharge.
Open calculator ›InverterInverter Sizing
The continuous and surge rating your loads need, plus the battery-side current to plan cabling for.
Open calculator ›