How long will a power station actually run your stuff?
Generic calculators just ask for watts. This one starts with your situation — a CPAP at night, a fridge in an outage, a camping trip, a home backup plan — and tells you the exact size class to buy, with the maths shown.
The humidifier is the single biggest runtime killer. Turning it off roughly doubles your nights.
A 12V DC cable skips the inverter loss and adds back about a third of your runtime.
Averages already include the compressor cycling on and off (about a 35% duty cycle). A fridge does not draw its label watts all day.
35% is typical. Hot garage or old seals: 50-60%.
Big appliances are listed too — pick one and we will be honest with you about it.
Wi-Fi router + modem (15W) is always included.
Prices are approximate US street prices and change often. As an Amazon Associate, Aindlix earns from qualifying purchases made through these links, at no extra cost to you.
Thinking of adding a solar panel?
A panel can double or triple your runtime in good sun — but the wrong panel voltage can damage a station, and some pairings barely charge at all. Our upcoming Solar Compatibility Checker will verify your exact panel + station pairing before you buy. Check your panel pairing (coming soon)
Get this sizing as a worksheet
Optional, and it never blocks your result: leave an email and we will send the one-page sizing worksheet with your numbers filled in.
Why scenario maths beats a generic watts calculator
Two people can both type “100 watts” into a generic calculator and need completely different stations. A 100W load that runs for one hour needs a snack. A 100W load that must run for 24 hours needs a feast. What decides your station size is not the watts on a label — it is watts multiplied by hours, adjusted for how the device really behaves:
- A fridge cycles. Its compressor runs roughly 35% of the time, so a “180W” fridge averages about 63W across a day. Size for the average, but check the surge for the peaks.
- A CPAP’s humidifier dominates. The therapy motor sips about 35W. Add a heated humidifier and a heated tube and you are near 90W — the same station suddenly lasts a third as long.
- The inverter takes a cut. Every AC watt you pull costs about 15% in conversion loss. A 12V DC cable avoids most of that, which is why DC CPAP setups last about a third longer.
- Surge is a separate gate. A station can have enough capacity (Wh) and still fail, if its surge rating cannot start your fridge’s compressor. We check both, every time.
Watts vs watt-hours, in one breath
Watts (W) are speed: how fast a device drinks power right now. Watt-hours (Wh) are the size of the tank: how much energy the station holds. Runtime is tank divided by speed. A 1,000Wh station running a 100W load does not last exactly 10 hours, because of the conversion losses below — plan on about 8.5.
The humidifier effect, with real numbers
On a 1,000Wh station through the AC plug: no humidifier (35W) gives you about 24 hours of therapy — roughly 3 nights. Humidifier on (60W) drops that to about 14 hours. Humidifier plus heated tube (90W) drops it to about 9.4 hours — barely one long night. Same station, same machine, three completely different answers. That is why this tool asks about the humidifier first.
The maths we use (published openly, check it yourself)
The 0.85 factor is the same one EcoFlow, Oukitel and other manufacturers use in their own runtime examples: inverter and conversion losses are real, and any calculator that ignores them is flattering you. Size classes are the standard lithium (LFP) steps: 300, 500, 700, 1,000, 1,500, 2,000, 3,000 and 3,600Wh. We always round up to the next class and keep a 10% reserve in hand — a battery planned to absolute zero is a battery that dies early on a cold night — and we add one more class of headroom when other devices share the station, because in a real outage something extra always gets plugged in.
Surge: the number that actually starts your fridge
When a fridge compressor kicks on, it can draw 3 times its running watts for a split second — typically 400 to 800W of surge on a full-size fridge. If a station’s surge rating is below that, the station trips and your food warms up, no matter how big its battery is. Every fridge verdict above includes the minimum surge your fridge needs, and we flag it when a size class typically falls short.
Frequently asked questions
How long will a 1,000Wh power station run a CPAP?
About 3 nights with the humidifier off (35W, AC plug), about 1.7 nights with the humidifier on (60W), and about 1 night with humidifier plus heated tube (90W). With a 12V DC cable instead of the AC plug, add roughly a third: the no-humidifier case stretches past 4 nights. Use the CPAP tab above with your exact settings.
How long will a 1,000Wh power station run a full-size fridge?
Around 13 to 14 hours for a typical full-size fridge averaging 63W. A mini fridge (29W average) stretches to about 29 hours; an older fridge (126W average) drains it in roughly 6 to 7 hours. For a full 24-hour outage with a typical fridge, you need the 2,000Wh class.
Why does this tool recommend a bigger station than other calculators?
Three honest reasons. First, we include the roughly 15% inverter loss that many calculators quietly skip. Second, we keep a 10% reserve, because a battery should never be planned to absolute zero. Third, we round up to the next real size class you can actually buy, instead of quoting a precise-sounding number of watt-hours that no product matches. A slightly bigger station that works beats a perfect-on-paper one that dies at 3am.
Can a portable power station run a space heater, kettle or air conditioner?
Technically it can start one; practically it is empty in under an hour. A 1,500W heater drains even a 3,600Wh station in about 2 hours, and a small station in minutes. Heating and cooling are the most energy-hungry jobs in a home. For those, the honest answers are a generator, a large fixed home battery, or riding out the outage without them. This tool will refuse to size a portable station for those loads rather than sell you a disappointment.
Does a 12V DC cable really make a CPAP last longer?
Yes — measurably. Through the AC inverter you keep about 85% of the battery; through DC you keep about 95%. That is roughly a third of the lost energy handed back to you, which on multi-night trips is often the difference between carrying one station and carrying two.
What size power station do I need for Starlink?
Starlink Standard averages about 75W, so a 1,000Wh station runs it for roughly 11 to 12 hours; a full 12-hour day needs about 1,060Wh of rated capacity once losses are counted, which lands in the 1,500Wh class if you want the whole 12 hours guaranteed. Starlink Mini (about 30W) runs roughly 28 hours on the same 1,000Wh station.
What does “duty cycle” mean for a fridge?
It is the share of time the compressor is actually running. A typical fridge runs about 35% of the time and rests the other 65%, which is why its average draw (about 63W) is far below its label watts (about 180W). Hot rooms, old door seals and frequent opening push the duty cycle up — the custom mode in the Fridge tab lets you plan for that.
Runtime Finder by Aindlix. Estimates use manufacturer-standard efficiency factors; real runtimes vary with temperature, battery age and exact device settings.