Battery runtime calculator
Estimate capacity-based runtime for sustained average loads. This does not convert a finite equipment timetable into “all devices last this long.”
Estimated runtime
Enter your sustained average load and calculate.
Choose inputs that describe the same load
Enter the station's nominal capacity in Wh. Starting charge and stopping reserve define the part of that capacity you plan to use; the capacity factor allows for an assumed reduction in available capacity. These are planning inputs, not a battery-health diagnosis.
Add the sustained average watts on each output route. A reading at an appliance's AC plug includes its adapter, while a reading at a USB or DC input belongs on that route. Use zero only for a route with no load. Do not enter the station's inverter rating as the appliance's consumption.
Keep AC enabled when an AC appliance needs power, including pauses between compressor cycles. The idle draw is added separately from the load divided by conversion efficiency. USB-only or DC-only use can be modeled with AC disabled.
How the result is calculated
Available energy = nominal capacity × capacity factor × (starting charge − reserve). Battery-side power = AC watts ÷ AC efficiency + USB watts ÷ USB efficiency + DC watts ÷ DC efficiency + enabled AC idle draw. Runtime = available energy ÷ battery-side power.
Worked example
A 1,000 Wh battery at 100% assumed health, starting full and stopping at 10%, supplies a sustained 100 W AC load for 8.1 calculated hours at 90% AC efficiency and zero assumed idle draw. An actual inverter can add idle consumption; enter an appropriate value for your plan.
Calculated with the same formulas as the interactive tool. Inputs are illustrative and results are rounded for display.
Can I use a daily energy reading?
The main sizing calculator accepts measured daily kWh directly and is better for multiple devices with different schedules. This tool assumes the entered average load continues throughout the runtime estimate. It does not simulate a timetable or enforce device switching.
Why is no-load runtime blank?
With no battery-side demand, the model reports that there is no meaningful runtime estimate. It does not model long-term storage discharge. If AC is enabled with a positive idle draw, that draw still uses energy even when appliance watts are zero.
Does sufficient runtime mean a device will work?
No. Check continuous output, startup magnitude and duration, supply voltage and frequency, and the intended ports separately. For cycling appliances, also check low-load shutdown behavior. Read why nominal Wh differs from usable runtime.