DECISION TOOL
How big a power station do you actually need?
Capacity on the box is not capacity at the outlet. List what has to stay on and for how long, and the arithmetic gives you a battery size with the losses already counted.
How the arithmetic works
Each row is watts times hours times quantity, which gives watt-hours. Those are added, your headroom percentage is applied, and the total is divided by 0.85 to account for inverter conversion and standby losses. That is a conservative planning figure, not a manufacturer specification — real efficiency varies by unit and by load.
This is why a 1,024 Wh label does not deliver 1,024 Wh from the AC outlets. The gap is the part most outage plans miss.
Continuous draw is a separate constraint from capacity. A battery large enough to run your list for a day can still refuse a device whose start-up surge exceeds the inverter. Motor-driven appliances — fridges, pumps, power tools — are where that bites.