Methodology
How we calculate
The exact arithmetic behind every 'can it power' answer on this site: how running and starting watts are added, where the runtime factor comes from, why generator run time is never extrapolated, and how cycle life is normalised.
We do not test products. Every figure on this site is quoted from a manufacturer or retailer page, a CPSC notice or an ENERGY STAR record, and the link sits next to the number. This page explains what we do with those figures.
1. Your load
Running watts are the sum of each appliance's running draw times quantity. Starting watts add, on top of that sum, the single largest difference between an appliance's starting and running draw — because in practice one compressor or pump motor starts while everything else is already running, and two motors rarely start in the same instant. Size for starting the largest motor, then add the running watts of everything else that is connected. Generac GP Series Portable Generator Owner’s Manual (GP18000EFI), p. 17 “Don’t Overload the Generator”.
Energy per day multiplies each appliance's average draw by hours of use. For appliances that cycle (refrigerators, freezers, well pumps) the average is far below the running figure; we take it only from a published annual-consumption number (ENERGY STAR or EnergyGuide kWh/year ÷ 8,760 h) or a maker's spec. When no such figure exists we use the running draw, which overstates energy and understates runtime — the conservative direction.
2. Does it fit?
A power station passes when its continuous AC output is at least your running watts and its peak output is at least your starting watts. A generator passes when its running (rated) watts on the chosen fuel cover your running load and its starting (peak) watts cover your starting load. The headline number on a generator box — “12,500 W” — is almost always the starting figure; we never present it as continuous. Boost modes that let a station run a higher-wattage resistive load (EcoFlow X-Boost and similar) are noted on the card but excluded from the fit test, because they work only for some appliances.
3. Station runtime
Runtime = battery capacity (Wh) × runtime factor ÷ load (W). The runtime factor accounts for inverter losses and the capacity the battery protects at the bottom of discharge. Where a manufacturer publishes its own formula (Jackery and EcoFlow both print “× 0.85” in their buying guides, linked below) we use that maker's factor and link to it. When a maker publishes no factor we use 0.85 Jackery — What Can Jackery 290 Run? (buying advice, modified 2026-08-19) (Jackery's and EcoFlow's own published factor; applied to brands that publish none.), and the result row says so. Runtime is shown two ways: at the running draw (everything on, continuously) and, where an average figure exists, at the average draw. Real results vary with temperature, battery age and the load's power factor; treat the number as a planning figure, not a promise.
4. Generator run time
Makers publish run time per tank at one or two load points, usually 25 % and 50 %. We show those points, compute what percentage of the rated load your appliances represent, and say whether your load sits below, between or above the published points. We do not draw a curve through two points and read off an answer; fuel consumption is not linear in load and the honest statement is a bracket.
5. Cycle life
“4,000 cycles” means nothing without the capacity the battery is promised to retain. Jackery's figure is to 70 % of original capacity, EcoFlow's to 80 %. We always print the threshold with the number, and when a maker does not define one we say so rather than compare it with those that do.
6. Prices
We show the manufacturer's list price on the date we read it, with a link, and derive $ per Wh (stations) or $ per running watt (generators) from it. Amazon's price is not displayed because Amazon's rules only allow prices fetched through its API, which this site does not yet have; the Amazon button leads to the current listing.
7. Safety
Fuel generators produce carbon monoxide; every generator page carries the CPSC rule on where to run one, and the card states whether the maker lists a CO sensor and quotes how the maker describes it (some say “with automatic shutdown”, others only “CO sensor”). For medical devices (CPAP, oxygen concentrators) we show the published wattage only with a notice to confirm it with the device maker; we give no medical advice. Models under a current CPSC recall are flagged on their card and in lists; closed recalls from earlier years that covered only a serial range of a model still sold are not shown.
Updated 2026-10-31.