How many solar panels do you need to recharge a power station, and how long will it take? Choose your region and season, and this calculator works it out using peak sun hours and real-world panel losses.
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Work out how many solar watts you need to recharge a power station or battery, or how long your panels will take.
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Quick answer
- Solar watts needed = Wh to recharge ÷ (peak sun hours × 0.75).
- To refill a 1,000Wh power station in one sunny day in most of the US, plan on about 250–350W of panels.
- Check your power station’s maximum solar input. Panels beyond that limit will not charge it any faster.
What are peak sun hours?
A “peak sun hour” is one hour of sunlight at full strength (1,000 watts per square meter). A summer day might have 14 hours of daylight but only 5–6 peak sun hours, because morning, evening and cloudy sunlight is much weaker. Solar maths always uses peak sun hours, not daylight hours.
The regions in the calculator use rough year-round averages for the US. For your exact ZIP code, NREL’s free PVWatts calculator gives detailed local data.
Why panels never hit their rated watts
A 200W panel is rated in perfect lab conditions. Outside, heat, dust, the sun’s angle, cable losses and the charge controller all take a share. Portable panels propped up by hand usually deliver around 70–80% of their rating, which is why the calculator defaults to 75%. A panel lying flat on the ground in partial shade can drop to 60% or lower.
Tilting portable panels to face the sun directly, and turning them two or three times a day, can noticeably improve output compared with leaving them flat.
Example: recharging a 1,000Wh power station
| Location | Peak sun hours | Solar watts for a full daily recharge |
|---|---|---|
| Arizona, summer | about 7.2 | about 200W |
| Texas, year-round | about 5 | about 300W |
| Ohio, year-round | about 4.5 | about 300W |
| Washington State, winter | about 2.3 | about 600W |
Based on 75% real-world efficiency. Winter needs roughly double the panels of summer in most northern states.
Check your power station’s solar input limits
Every power station has a maximum solar input, listed in watts along with a voltage range (for example “500W max, 12–60V”). Two rules:
- Watts: extra panel watts above the limit are simply wasted. Some people deliberately go slightly over to get closer to the limit on cloudy days.
- Voltage: panels wired in series add their voltages together. Going above the maximum voltage can damage the power station, so always check the panel’s open-circuit voltage (Voc) before wiring panels in series.
Never exceed your power station’s maximum input voltage. Cold weather raises panel voltage, so leave a margin of at least 10–20% below the limit.
Portable vs rooftop panels
Folding portable panels are light and easy to aim, which makes them ideal for camping and occasional outages. Rigid panels cost less per watt and last longer, which suits RV roofs, sheds and permanent setups. Either works with most power stations, as long as the connector and voltage match.
Frequently asked questions
How many solar panels do I need for a 2,000Wh power station?
For a full recharge in one day with about 5 peak sun hours, you need roughly 550W of panels, for example three 200W panels. In winter or northern states, plan on more, or accept that a full recharge takes two days.
Can I charge a power station with solar on a cloudy day?
Yes, but output can fall to 10–25% of normal under heavy cloud. Light, bright cloud has less effect. Expect charging to take several times longer.
Can I use more solar watts than my power station allows?
The power station only takes up to its maximum solar input in watts, so extra watts are not harmful on their own. The voltage limit is what matters for safety; never exceed it.