Our power station size calculator answers how big a battery to buy. This one answers the question that comes the morning after the outage starts: how long until it is full again? A power station is only as good as its refill, and the refill depends on three numbers most listings hide — how many watts of panel you own, how many of those watts the station can actually accept, and how many good sun hours your sky gives you. Enter yours.
Run your recharge
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Two of those inputs deserve a spotlight. The first is the acceptance cap — the spec almost nobody reads. The Jackery in the list above is a fine station, but it only accepts 400 watts of solar no matter how many panels you wire to it: hang 1,000 watts of panels on it and the extra 600 are decoration. The second is the difference between rated watts and real watts. A panel stamped 400 watts makes that power on a cool, clear noon facing the sun dead-on in a lab. On your roof or your lawn it makes about three-quarters of that across a good day, which is why this calculator counts every panel at 75% before it does anything else.
Worked example: the starting numbers — an EcoFlow DELTA 2 Max at 2,048 watt-hours, 400 watts of panels, and 4.5 good sun hours a day — fill the station in about 6.8 hours of good sun: about a day and a half of real weather.
Questions people ask
How long does it take to charge a power station with solar panels? Divide the battery by what your panels really deliver. A 2,000Wh station behind 400 honest watts of input needs about five hours of good sun — a full clear day in most places, once clouds, angles, and mornings are counted. The same station behind a 100-watt folding panel needs the better part of a week. Panel watts, not battery size, set the pace.
Why do my panels show less going in than they are rated for? Three reasons, in order: the station’s acceptance cap (above), the 75% reality of heat and angle, and the sun simply not being at noon. If your display shows roughly three-quarters of the panels’ rating at midday under a clear sky, everything is working exactly as it should.
How many panels do I need to run a fridge indefinitely? A modern fridge uses roughly 1,000–1,500 watt-hours a day. At 4.5 good sun hours and the 75% factor, about 400 rated watts of panel replaces that on an average day — more in winter or further north. The calculator’s last line runs exactly this check against your numbers.
Shopping with these numbers in hand? Our solar generator comparison scores the three stations above on exactly this — solar acceptance, refill speed, and what owners report — and the Bluetti vs Jackery head-to-head settles the two closest rivals.
The three stations in this calculator
The fuel side of the same question
Solar tells you how fast a battery refills. If part of your backup plan burns gasoline instead, the companion question is how long the fuel lasts — our Generator Fuel & Runtime Calculator turns tank size and stored gallons into days of runtime, so you can size your fuel storage the same way you sized your panels.
EcoFlow DELTA 2 Max
The fast refill of the three: up to 1,000W of solar accepted, so a typical home array never reaches its ceiling.
Bluetti Elite 200 V2
Accepts up to 1,200W of solar — the highest cap of the three — in the same 2,000Wh class.
Jackery Explorer 2000 v2
Same battery class, but capped at 400W of solar in. Buy it for the price, not the refill speed.
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