Backup time calculator
Backup time calculator
Pick your appliances, set quantities and move the capacity slider. The calculator shows the runtime and catalog products that fit your load.
Devices & quantity
- Router + ONU15 W
- Laptop60 W
- LED lights20 W
- Fridge70 W
- Gas boiler90 W
- TV90 W
- Water pump400 W
- CPAP / medical40 W
- 3D printer180 W
Source capacity
Backup time
How we calculate
Formula & tips
How do I work out how long a power station lasts?
Runtime = capacity (Wh) × inverter efficiency × depth of discharge ÷ total appliance power. We use 90% efficiency and 95% depth of discharge.
Why does a fridge use less than its label says?
Power is the hourly average. Fridges and boilers cycle on and off, so their average draw is lower than the peak.
What inverter power do I need?
The inverter must handle start-up surges: for a pump or fridge allow 2–3× power headroom.
How many hours will a 3 kWh power station last?
Usable energy is 3000 Wh × 90% × 95% ≈ 2565 Wh. At a 150 W load (fridge, router, lights) that is about 17 hours; at 400 W, about 6.4 hours.
LiFePO4 or Li-ion: which battery is better for a power station?
For home use, LiFePO4: 3000–6000 cycles versus a few hundred for most Li-ion, a lower overheating risk and a flat voltage until nearly empty. Li-ion is lighter, so it goes into drones and e-transport.
What else does an inverter need besides a battery?
Correctly sized cables, circuit breakers on the battery and grid side and, for solar, panels. A hybrid inverter connects between the incoming supply and the switchboard; the inverter model sets the battery voltage (12, 24 or 48 V).