Portable power stations: how to choose one that really lasts
Usable capacity, inverter draw, battery chemistry and cost per stored kWh explained with measured data.
The number on the box is not what you get
Independent tests show that power stations deliver about 85 to 90 percent of their rated watt hours to a strong load such as a 380 W dehumidifier. With a small load of around 35 W, the same units deliver only 52 to 70 percent, because the inverter itself draws 10 to 16 W the whole time.
For small devices such as a router, a lamp or a CPAP machine, use the DC or USB outputs where possible: they skip the conversion to 230 V and run much longer.
LFP, NMC or sodium
Almost all larger power stations now use lithium iron phosphate (LFP) cells. They are harder to bring into thermal runaway than NMC cells and last more cycles. A 2024 review of fire gases found that NMC cells release about ten times more carbon monoxide per kWh, while LFP releases more hydrogen fluoride. LFP is the safer choice, but no lithium battery belongs in an escape route or a bedroom.
Sodium ion cells are new in this class. The first model charges down to minus 15 degrees and works down to minus 25 degrees, at the cost of lower energy density.
Compare the cost per stored kWh
Price per watt hour hides a lot. We divide the price by the usable kWh, the rated cycles and the average state of health over the battery's life. That shows what each stored kWh really costs, and it is how our product list is ranked.