The short answer
Match watt-hours to your hours, AC watts to your running load, surge to your biggest motor, and check recharge limits. Then compare chemistry, weight and warranty.
The five numbers
| Number | What it tells you | How to use it |
|---|---|---|
| Capacity (Wh) | How long it runs | Your average watts × hours ÷ 0.85 |
| AC output (W) | What you can run at once | Above your running total |
| Surge (W) | Whether motors start | Above your starting total; ask if not stated |
| Recharge (W in) | How fast it refills | Wall, solar and car limits differ |
| Weight (lb) | Whether you can move it | Heavy units live in one place |
Total your load first with the load calculator; then use the specifications table to shortlist.
Then check
- Chemistry: LiFePO4 units list long cycle life; see LiFePO4 vs. other lithium.
- Expansion: can you add batteries later, and do output watts rise?
- Outlets: the plug types and USB-C power you need; 240 V if a 240 V load matters.
- UPS function: some units switch over in milliseconds so a router or computer does not drop.
- Warranty and support: length and what it covers.
- Indoor use: the maker's temperature and ventilation rules.
Common mistakes
- Buying on watt-hours alone and discovering the inverter cannot start a pump.
- Assuming the headline capacity is all usable; about 85% reaches the load by our assumption.
- Expecting solar to refill a big battery in a day in winter or under storm clouds.
- Plugging a house into the unit or skipping an electrician for a home connection.
Figures marked as Wattstanding calculations show their working; product figures come from the sources on each product page. How we work