Power station specs list a headline capacity in watt-hours, but what you can actually use is lower. This checklist uses an independent test, credited below, and applies it to a real store.
1. Plan around usable capacity
StorageReview's DELTA 3 Max Plus and Ultra Plus review measured the DELTA 3 Max Plus at 1.64 kWh of discharge against a rated 2,048 Wh, about 80%, and 2.33 kWh of recharge energy, about 88%. Losses in the inverter and battery mean you should multiply the rating by roughly 0.8 when estimating runtime.
2. Check continuous and surge output
The review lists 3000 W continuous and 6000 W surge for the Max Plus. Add up the watts of what you want to run, including start-up surges for motors, and compare with the continuous figure.
3. Check UPS switchover if you want backup
The review measured an 8 ms UPS transfer. If you want the unit to keep a computer or router running during a cut, look for a stated switchover time and a test that confirms it.
4. Check weight and expandability
The review gives expandability to roughly 10 kWh for the Max Plus and a heavier 33.7 kg for the larger Ultra Plus. Think about who will carry it and whether you will add batteries later.
5. Read the return costs
Heavy items cost a lot to ship back. Check who pays return shipping, any card fees on cancellation and what happens to bundles if you keep part of an order.
An example: checking a store against the list
In our EcoFlow Europe review we applied these questions. The store offers a 30-day return and a published fee table, but the customer pays return shipping and cancellation fees, and the measured capacity was about 80% of the rating.
A note on the sources
StorageReview disclosed that EcoFlow sent the units it tested and tested the US models. We wrote this article in our own words. Some links to brands on this site are affiliate links; see our affiliate disclosure.