How to use it
- Start from a preset. "Load essentials" ticks a fridge, a freezer, the modem and router, a phone charger and two LED bulbs.
- Tick or untick rows until the list matches what you would really run.
- Replace the example numbers. Change watts and hours per day to your own readings where you have them.
- Set the outage length. The battery target rises in step with the hours you want to cover.
Two example plans for 24 hours
| Plan | What is included | Battery at 85% usable |
|---|---|---|
| Essentials only | Fridge, separate freezer, modem and router, phone charger, two LED bulbs | 3,000 Wh |
| Add comfort | Essentials plus a gas furnace blower, laptop, television and a short microwave use | 8,950 Wh |
The comfort plan needs roughly three times the battery. Most of the difference is the furnace blower, which is why heating deserves its own plan.
How the numbers are worked out
daily energy (Wh) = watts × hours per day, added up for every ticked row
battery target = daily energy × outage hours ÷ 24 ÷ usable share
The battery target is rounded up to the next 50 Wh.
Reading the result
| Battery target | What that usually means |
|---|---|
| Under 1,000 Wh | A small portable power station covers it. Good for internet, phones and lights. |
| 1,000 to 4,000 Wh | A large power station, possibly with an expansion battery. Typical for a fridge and freezer. |
| Over 4,000 Wh | Several batteries, a recharge plan, or a fuel generator. Check which rows are driving the total. |
Limits
- This is an energy total. It does not check whether an inverter can run everything at once or start a motor. Use the generator sizing calculator for running and starting watts.
- Solar recharging is left out. Add it separately with the solar recharge calculator.
- The presets are illustrations, not averages for a typical household.
Common questions
Why is the fridge only 50 W?
That row is the average over 24 hours. A fridge might draw 150 to 200 W while the compressor runs, but it runs only part of the time. Multiplying running watts by 24 hours would overstate its use several times over.
What should I cut first?
Look at the bar chart. Anything that makes heat (a kettle, a heater, a coffee maker) or runs a large motor for hours uses far more than electronics and lights.
Can I add an appliance that is not listed?
Reuse a row you are not using: tick it and type in your own watts and hours. The label in that row will not change, but the maths will be right.
Related
Reviewed October 2026. Results are planning estimates. Check them against your equipment's specifications. Report a problem.