PowerRuntime separates stored energy, delivered power and real-world losses. Each calculator shows its inputs and uses transparent electrical relationships rather than a single hidden “capacity ÷ watts” shortcut.
Core runtime model
For a battery supplying an AC load, the general relationship is:
Runtime = usable battery energy ÷ battery-side power draw
Usable energy includes depth of discharge, state of charge, battery health and reserve. Battery-side draw includes conversion efficiency and inverter or UPS idle consumption.
Compatibility checks
- Running watts are checked against continuous output.
- Startup demand is checked against surge output.
- UPS loads are checked against both watt and VA ratings.
- Battery-bank layouts require compatible series voltage.
- Solar charging is limited by the array, controller, battery current limit and active loads.
Device-specific adjustments
Refrigerator estimates can use measured daily energy or compressor duty cycle. UPS estimates can include Peukert high-discharge loss. Generator estimates use a user-provided fuel-rate reference and load curve. CPAP estimates separate therapy load, accessories, reserve and AC/DC conversion.
Rounding and uncertainty
Calculations retain full precision internally and round only displayed results. Planning ranges illustrate normal input variation; they are not statistical confidence intervals. For critical use, verify the result with measured watts and a supervised runtime test.
Open the calculator library or review the calculator disclaimer.