The Power Sizer
Pick what must stay on. We'll work out your peak watts and watt-hours and show which products can genuinely run it — including the ones that can't, and why.
Your devices
Add your own device
Check the label on the plug or power brick for its wattage.
What fits
Estimates use typical wattages and the assumptions below. Check your own devices' labels and the maker's runtime chart before buying.
How the maths works
Peak draw
Everything that runs continuously, plus your single biggest short-burst appliance (like a kettle). The inverter must supply this, and we add 20% headroom.
Energy
Watts × hours for each device. Fridges and freezers cycle on and off, so we use their average draw rather than their running figure.
Losses & reserve
We assume about 85% of a lithium battery's rated capacity reaches your devices once inverter losses and battery reserve are counted.
Lead-acid UPS
Traditional UPS batteries deliver less energy the harder they're worked, so their runtimes drop sharply at high loads. We model that too.