Usable watt-hours: why you get less than the rated Wh

Jackery's own formula

Jackery prints a runtime formula on its US pages for the Explorer 1000 v2. It takes capacity in Wh, multiplies by 0.85, and divides by the watts the appliance draws. For an 80 W laptop it gives 11.3 hours. The runtime calculator describes 0.85 as an allowance for inverter and battery losses. So 1,070 Wh behaves like about 910 Wh once an AC outlet is involved.

Jackery's warranty page adds that the runtimes it quotes are for reference only. Actual runtime varies with conditions. The factor is a planning figure. The runtime calculator uses the same 0.85 unless a maker prints its own usable figure.

What 0.85 does to three stations

Multiply the rated Wh by 0.85, then divide by the load.

A heavy load shows the gap best. A 1,070 Wh station sounds like it should run a 1,500 W load for 43 minutes. The 0.85 factor trims that to about 36.

What the factor leaves out

Age is the first omission. The Explorer 1000 v2 is rated for 4,000 cycles to 70 percent. Near the end of that rating its 1,070 Wh is about 749 Wh before the 0.85 factor. A 100 W load would then run about 6.4 hours. The DELTA 3 is rated for 4,000 cycles to 80 percent, which leaves about 819 Wh at the same point. The two ratings use different thresholds, so they are not directly comparable.

Cold is the second. Jackery's manual for the Explorer 1500 v2 lists 2,000 W of output. It states that output drops to 1,200 W between -4 and 14 °F. A lower output ceiling limits what a load can draw, even if the stored energy is intact.

Cycling loads and average draw

Some appliances draw their running watts only part of the time. Whirlpool's tech sheet puts a full-size refrigerator at 86 to 104 W while it runs. Its compressor cycles, and ENERGY STAR certified models use 305 to 805 kWh a year. That averages out to about 35 to 92 W.

Divide the Explorer 1000 v2's 909.5 usable Wh by that average and the answer is roughly 10 to 26 hours. Dividing by the running watts alone would say about 9 to 11. The longer range is the one a cycling compressor earns.

Where rated numbers come from

A station's Wh is a nominal figure, often amp-hours times nominal volts. The Explorer 1000 Plus lists 1,264.64 Wh from a 30.4 Ah, 41.6 V pack. So rated Wh can carry decimals that come straight from a cell spec. A station's name is only a rough guide to its capacity. The Wh line in the specifications is the number to start from before applying 0.85.

The HomePower 3600 Plus lists 3,584 Wh. EcoFlow's own backup checklist ends with a live test of runtime under a real load. That is the check no formula replaces.