Battery Runtime
Calculator
Results
- Usable capacity (kWh)
- 9
- Energy delivered to the load (kWh)
- 8.28
- Runtime (hours)
- 11.04
- Runtime (minutes)
- 662.4
Energy results
| Usable capacity (kWh) | 9 |
| Energy delivered to the load (kWh) | 8.28 |
| Runtime (hours) | 11.04 |
| Runtime (minutes) | 662.4 |
formula-map diagram
- Usable capacity (kWh)
- 9
- Energy delivered to the load (kWh)
- 8.28
- Runtime (hours)
- 11.04
- Runtime (minutes)
- 662.4
Energy relationship
Formula
t(h) = (kWh × DoD × η) ÷ (load W ÷ 1000)= 9
Note
This is a simplified model: it applies the standard equation to the numbers you entered and ignores real-world losses, weather variation, tariff structures and equipment tolerances. Wind power assumes air density 1.225 kg/m³ at ISA sea level and the power coefficient you enter (Betz limit 0.593). Verify with measured data or a professional energy audit before making purchasing decisions.
More in Energy and environment
See all →Frequently asked questions
What's the basic formula behind the runtime estimate?+
Runtime in hours equals battery capacity (in watt-hours or amp-hours times voltage) divided by the load's power draw in watts. A 1000Wh battery powering a 100W device, for example, gives roughly 10 hours of runtime.
Why is actual runtime shorter than the calculated figure?+
Inverter and conversion losses, the battery's usable depth of discharge, and reduced efficiency at high discharge rates all cut into the theoretical runtime. It's common for real-world runtime to come in 10-20% below a simple capacity-divided-by-load calculation.
Does the load need to be constant for this to work?+
The basic formula assumes constant power draw, so for loads that vary, like a refrigerator cycling its compressor, you should use average power draw over time rather than peak wattage for a more realistic estimate.
How does depth of discharge change my runtime?+
If you only want to use, say, 80% of a battery's capacity to preserve its lifespan, you should multiply the rated capacity by 0.8 before dividing by the load, which proportionally shortens the safe runtime versus draining it fully.
Why does discharging faster reduce total available energy?+
This is the Peukert effect: batteries, especially lead-acid, deliver less total energy when discharged at high current than at low current, because internal resistance wastes more energy as heat at higher rates. Lithium batteries are less affected but still see some efficiency loss at very high discharge rates.