Can a power station be a UPS?

UPS, EPS and pass-through: what the words mean

A true online UPS (uninterruptible power supply) runs your devices from its inverter all the time and keeps the battery charged from the wall, so a power cut changes nothing on the output: 0 ms. An offline or standby UPS, the kind sold for a desk, passes wall power through and switches to its inverter when the wall drops. Power station makers use UPS and EPS (emergency power supply) for that second kind; EcoFlow, for instance, calls the RIVER 2 Pro's 30 ms switch an EPS. Pass-through is the same arrangement described from the other side: wall power reaches the outlets while the battery charges.

So the number to compare is the stated switchover. Read it as a maker's ceiling ("under 10 ms"), stated in the maker's own test, not a figure we measured. Three units state 0 ms: Jackery Explorer 5000 Plus, Zendure SuperBase V4600 and Zendure SuperBase V6400; Jackery states 0 ms for the 5000 Plus in its online UPS mode and under 20 ms in its backup mode. BLUETTI's Apex 300 page headlines 0 ms, but its manual gives 0 ms only on 240 V output; on the 120 V outlets a US buyer uses it is 20 ms, the figure in the table.

Which devices notice a 10 to 30 ms gap

• Refrigerators, freezers, lights, fans and phone chargers do not care. A compressor that stops for a few hundredths of a second simply carries on or restarts.
• Routers, modems and Starlink usually ride through a short gap on the charge held in their power adapters. If yours restarts, the cost is a minute or two offline, not damage.
• Desktop computers and network drives are the ones that matter. The ATX design guide asks a desktop power supply to hold its output for at least 16 ms at full load, so a 10 ms switchover is inside it and a 20 to 30 ms one may not be, especially near full load. For a computer, choose 10 ms or less, or 0 ms, and save your work anyway.
• CPAP machines differ by model. Whether a short gap restarts therapy is a question for your machine's maker; the CPAP page sizes the night itself.
• Medical equipment that a person depends on needs the device maker's approved backup, not a general-purpose station.

Three limits beyond the switchover

The pass-through ceiling. Some units pass less power through from the wall than their inverter delivers from the battery. OUPES states its Mega 3's UPS output at 2,200 W against a 3,600 W inverter, and Goal Zero rates the Yeti 1000 and 1500's AC pass-through at 1,752 W against 2,000 W inverters. Keep the plugged-in load under the pass-through figure in the manual.

Living on the charger. A unit kept at 100% on the wall for months ages faster than one kept part-charged. Many apps let you cap the charge level while it waits; the manual says what the maker allows.

Runtime still decides. The switch only buys you the battery's hours. A router and a modem at about 35 W run for roughly a day on a 1 kWh unit; a desktop computer at 300 W, under three hours. The calculator adds up your own devices, and the home backup page sizes an outage.