What Size Portable Power Station Do You Actually Need?

Start With Watt-Hours, Not Watts

Our September scan of Amazon's power-station bestsellers found units from 88Wh to 2,010Wh all selling at 900 or more per month. Buyers are not converging on one size because there isn't one. There is only your load, your number of days, and a short piece of arithmetic.

The two numbers on the box answer different questions. Watts describe how big a load the station can carry at one moment. Watt-hours describe the fuel tank. A 600W unit with 288Wh is a sprinter; a 500W unit with 519Wh is a distance runner, and for most buyers the tank is what decides satisfaction. Sizing mistakes come from reading the sprint number and ignoring the tank.

Here is the whole formula up front: add up the watt-hours you use per day, multiply by the days you need to run, divide by 0.85 for inverter losses, then add about 25% headroom. That result is the capacity you shop for. The sections below apply it to the five loads that cover nearly every first-time buyer.

What Size Power Station for Camping, Outages and Work

Almost every first-time purchase lands in one of the five classes below, and the scan's sales ranks say so: the 288Wh class and the 1-2kWh class are where the volume lives, while the extremes thin out fast. Find your class first, then let the arithmetic pick the exact unit.

Phones, lights, and a fan: under 300Wh

A phone charge costs 10-15Wh. Four phones topped up daily is under 60Wh. An LED lantern at 8W for five hours adds 40Wh, and string lights less. The item that breaks this class is the fan: a table fan at 30W for eight hours burns 240Wh on its own. Electronics-only camping, tailgating, or a desk setup lands here, and a 250-300Wh unit covers it with room to spare.

A 12V fridge on a camping trip: 300-600Wh

A portable fridge compressor draws around 40W and cycles roughly a quarter to a third of the time in mild weather, which works out to 240-340Wh per day. One fridge night plus daytime electronics fits comfortably in the 300Wh class. A two-night weekend pushes 500-700Wh before corrections, which sits at the top of this class. Sustained heat changes the math: duty cycle climbs past 50% and the daily figure nearly doubles. If your trips involve heat and a fridge, be honest about it and shop the next class up. The full camping power math is worked through separately.

A CPAP through the night: 300-500Wh

A CPAP machine draws 6-20W with the humidifier off and 30-50W+ with it on, per the range printed across manufacturer manuals. That is 50-160Wh per night dry, and 240-400Wh per night humidified. The 300-500Wh class covers humidified nights with margin, and smaller units work if you travel with the humidifier chamber unplugged. The CPAP runtime breakdown does this night by night.

An evening of TV and internet: 500-1,000Wh

A 55-inch LED TV draws 60-100W, and a router plus streaming box add about 20W. Call it 80-120W combined. A five-hour evening costs 400-600Wh, so the 500-1,000Wh class buys one comfortable evening or two frugal ones per charge. This is also the class where a fridge weekend lands once the corrections below are applied.

An RV air conditioner: 2,000Wh and a reality check

A 13,500-15,000 BTU rooftop unit draws 1,300-2,000W running. A 2,000Wh tank at 85% efficiency holds about 1,700 usable Wh, which is 1-2 hours of compressor time. This is a different purchase conversation, and the RV AC numbers deserve their own post.

Two Corrections Before You Shop

The first is inverter efficiency. The tank stores DC; your outlets deliver AC; the conversion costs around 15%. Every runtime estimate you make from a spec sheet should be multiplied by 0.85. The wattage and runtime math shows the worked examples.

The second is headroom. Ratings are measured on healthy new packs at room temperature, and your battery will be neither, forever after year one. Cold weather alone can cut usable capacity by a fifth. Add 20-30% on top of the corrected total so the unit you buy in 2026 still covers the job in 2029.

Worked example: two fridge nights at 300Wh per day plus 80Wh of electronics is 680Wh. Divided by 0.85, that is 800Wh. Add 25% and you are shopping in the 1kWh class, not the 600Wh class. This is the step most buyers skip, and it is why so many used units end up for sale.

Where Spec Sheets Stretch

Two habits inflate the printed numbers. Peak watts get headline billing: a peak rating sustains for seconds, exists to start motors, and cannot hold a resistive load through a cup of tea. Match your biggest continuous load to the rated output, not the peak.

The second is mAh inflation. Some listings advertise capacity in mAh counted at the 3.7V cell voltage, which produces a flattering number before any conversion loss. Two units quoting 200,000mAh and 740Wh may hold the same energy; only one label is honest about the unit that matters. Compare watt-hours, always.

The Decision Path

Line up your loads, sum the daily watt-hours, multiply by days, divide by 0.85, add a quarter. Then check output: the station's rated watts must clear your biggest single appliance, with surge room for anything that has a motor or compressor. Surge specs deserve a squint in the budget tier, where peak numbers do the headline work: the scan's small units advertise 200-240W peaks, which start a fan motor for a second and nothing more.

One worked pass through the path: an electronics camper with a drone kit totals about 450Wh a day for two days, divides 900 by 0.85 to get 1,060, adds 25%, and lands just over 1,300Wh. That buyer shops the 1-2kWh class regardless of what any roundup recommends. A phones-and-lantern camper runs the same arithmetic and stops at 300Wh. Same formula, opposite corners of the market, and both are right.

When two classes both fit your arithmetic, buy the smaller expandable unit rather than the bigger sealed one. Capacity you add later costs less than capacity you carry idle. The scan's bestseller list quietly confirms that buyers settle into two answers: the 288Wh class and the 1-2kWh class both move 900 to 3,000 units a month, with little middle traffic.

Frequently Asked Questions

What size power station do I need for a 12V fridge?

One night runs on 300Wh with margin in mild weather. Two nights need the 500-600Wh class before corrections, and real heat pushes a fridge weekend into the 1kWh class once inverter losses and headroom are counted.

Will a 300W station run a TV?

Output is not the problem: any home TV draws 60-150W, well under 300W. Runtime depends on the tank. A 288Wh unit delivers about 245Wh after inverter losses, which is three to four hours of a 70W TV.

What happens if I undersize?

Nothing dramatic. The inverter trips and shuts off if a load exceeds the rated watts, or the tank empties before you are done. Both are annoying, neither is dangerous, and both are prevented by the 0.85-and-headroom math above.

Is a bigger battery always better?

No. Every extra 500Wh adds weight, price, and capacity that sits unused most of the year. Buy for your real load with headroom, prefer expandable over oversized, and spend the difference on the output quality you will notice.

Once the math lands you in a class and two models are left on the shortlist, put both into Ask Versa AI and let the scorecard break the tie.