How to work out what size power station you need
Updated
Start with a list
Write down what has to run, how many of each and for how many hours a day. The worked example below is the outage essentials setup, a short list for a power cut:
| Appliance | How many | Running | Hours a day | Energy a day |
|---|---|---|---|---|
| Refrigerator (modern, full size) | 1 | 275 W | 24 | 1,300 Wh |
| Wi-Fi router and modem | 1 | 28 W | 24 | 672 Wh |
| Phone charging | 2 | 20 W | 2 | 80 Wh |
| LED bulb, 60 W equivalent (800 lumens) | 3 | 8.5 W | 5 | 128 Wh |
Check 1: running watts against output
Add the running watts of everything that could be on at the same moment: 369 W for this list. The station's continuous AC output has to be at least that. 50 of the 54 stations in the data pass, because nothing on the list heats or cooks. A microwave, a kettle or a space heater adds 1,500 W to 1,530 W and changes that at once; their appliance pages give the figures.
Check 2: the largest start against surge
Motors and compressors draw several times their running watts for a moment as they start. The refrigerator here needs about 1,000 W, so the list needs 1,094 W: everything else running plus the fridge starting. 6 stations have enough output for the list and still fail on this start. Where a maker publishes no surge rating, we check the start against the continuous output. The starting watts guide explains the spike.
Check 3: watt hours against usable capacity
The list uses 2,180 Wh a day. A station delivers about 85% of its rated capacity at the outlets, after inverter and conversion losses, so divide by 0.85: one full day takes about 2,564 Wh of rated capacity, two days 5,128 Wh. Why you get less than the rated capacity covers the losses.
17 of the 54 stations pass all three checks for a full day of this list, and the smallest of them is the BLUETTI Apex 300 (2,765 Wh), with 25.9 h of the routine. That is the closest fit: the smallest capacity that is enough, then the lower price, then the lighter unit.
Size classes at a glance
Each class below counts the appliance types in our data that every model in it runs on its own, out of 79. The class pages list the models and the running time for each appliance.
| Class | Capacity | Models | Runs on every model | Usable at the nominal size |
|---|---|---|---|---|
| 300 Wh | under 400 Wh | 6 | 27 of 79 | 255 Wh |
| 500 Wh | from 400 to 749 Wh | 4 | 40 of 79 | 425 Wh |
| 1,000 Wh | from 750 to 1,499 Wh | 13 | 43 of 79 | 850 Wh |
| 2,000 Wh | from 1,500 to 2,499 Wh | 13 | 69 of 79 | 1,700 Wh |
| 3,000 Wh | from 2,500 to 3,999 Wh | 13 | 71 of 79 | 2,550 Wh |
| 5,000 Wh | of 4,000 Wh and more | 5 | 78 of 79 | 4,250 Wh |
Common setups, already worked out
These setups run the same three checks against every station. Each page lists the stations that are enough and the ones that fall short, with the numbers they fail on.
| Setup | Energy a day | Goal | Closest fit |
|---|---|---|---|
| A CPAP for two nights | 88 Wh | 48 h | Jackery Explorer 240 v2 (256 Wh) |
| A refrigerator overnight | 1,300 Wh | 8 h | DJI Power 500 (512 Wh) |
| Outage essentials | 2,180 Wh | 24 h | BLUETTI Apex 300 (2,765 Wh) |
| Well pump backup | 1,750 Wh | 24 h | BLUETTI Elite 200 V2 (2,074 Wh) |
| Van life | 1,199 Wh | 24 h | Goal Zero Yeti 1500 (1,505 Wh) |
| A space heater | 12,000 Wh | 24 h | none in the data |
What moves the answer
- Your own labels. Watts vary by model and age; the label guide shows where to read them.
- Recharging. A station that refills from solar every day can be smaller than one that has to last the whole outage; the solar guide sizes the panels at 4 peak sun hours and 75% of the panel rating.
- Expansion batteries. Some stations take extra packs, which add watt hours but never add output or surge.
- 240 V loads. A well pump or a dryer on 240 V needs a station that supplies split phase power; 8 of the 54 in the data do so on their own. The well pump guide works one out.
Check your own label
Watts vary by model and age. Check the label on your own appliance and enter it for an exact answer.