The calculation, without hidden assumptions
A useful runtime estimate separates nameplate energy from usable energy. MAXScanner lets you start with Wh directly or calculate Wh from Ah × voltage, then reduces that energy by the depth-of-discharge and conversion-efficiency assumptions you enter before dividing by the load.
How to use this calculator
Choose whether the battery is specified in Wh or Ah; Ah mode also requires voltage.
Enter the average load in watts and your usable depth-of-discharge and conversion efficiency assumptions.
Compare ideal and adjusted hours, and treat the result as a planning estimate rather than a guaranteed discharge curve.
Where people use it
- •UPS and inverter backup planning
- •Portable power-station comparisons
- •Solar battery load scenarios
Example: 1,200 Wh battery, 300 W load
The ideal runtime is 4 hours. At 80% usable depth and 90% conversion efficiency, usable energy is 864 Wh and the adjusted estimate is 2.88 hours.
What the result does not assume
- •Real runtime changes with battery chemistry, discharge rate, temperature, inverter standby loss, aging and load variation.
- •Do not treat this arithmetic estimate as a manufacturer discharge curve or emergency-runtime guarantee.
Frequently asked questions
Why is adjusted runtime lower than ideal runtime?+
The adjusted result applies the DoD and efficiency percentages instead of assuming every nameplate watt-hour reaches the load.
What should I use for efficiency?+
Use measured or manufacturer data for the actual inverter/DC converter and load path when available.
Can I enter Ah instead of Wh?+
Yes. Choose Ah mode and enter battery voltage so nominal Wh can be calculated.
Semantic next steps
Continue the calculation
These links move to a different input, formula or project stage rather than a keyword variation of this page.
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Keep the result connected to the real job
MAXScanner keeps the formula and assumptions beside the result so you can verify the number before using it in a drawing, estimate, specification, worksheet or document. Where a supplier, manufacturer, drawing or applicable standard owns a requirement, that source remains authoritative.