The honest answer to “how much solar do I need?” is: it depends entirely on what you draw and how you travel. There’s no universal panel size. A backpacker keeping a power bank alive needs almost nothing; a family running a fridge, lights, devices, and Starlink needs a roof full of panels — or a different charging strategy altogether.
This guide gives you the method to figure out your number. Run the math with the solar sizing calculator to get a tailored figure, then use the steps below to interpret it.
Step 1: Calculate your daily energy budget (watt-hours)
Everything starts here. List every device, its wattage, and the hours per day it runs. Multiply and sum.
- Fridge — your biggest constant load. A 12V fridge averages roughly 30–50Wh per hour over a day, depending on heat and how often it’s opened.
- Lights — small, but they add up over a long evening.
- Device charging — phones, tablets, a laptop.
- High-draw gear — this is where budgets blow up. Starlink pulls 20–40W continuously; over a day that’s hundreds of watt-hours on its own. Induction cooking and 12V air conditioning are even heavier.
Add it all up. That daily watt-hour total is the number everything else is sized against. The solar sizing calculator does this for you based on your electronics and family size.
Step 2: Convert daily draw into solar watts
A solar panel’s rated wattage is its output under ideal sun. In the real world you get far less — clouds, angle, heat, and short winter days all cut into it. A useful rule of thumb is that a panel produces roughly 3–5 times its rated wattage in watt-hours over a good day (a 100W panel might yield 300–500Wh), but this swings hard with season and latitude.
So if your daily budget is 600Wh and you expect modest sun, you may need 150–200W of panel just to break even — and more to also recover overnight drain. When in doubt, size up; undersizing leaves you slowly falling behind day after day.
Step 3: Match the scale to your setup
Backpacking / small power banks
A minimum of a 30–40W panel is enough to keep portable power banks topped off. That’s the floor for any solar at all.
Weekend camping with a power station
A folding 100–200W panel typically keeps a mid-size power station ahead of a fridge plus devices if you park in sun. Pair the panel to the station’s solar input — see best portable solar panels.
Full-time rig with a fridge and high-draw gear
Now you’re looking at several hundred watts of panel, ideally feeding a DC-DC charger with an MPPT solar input as part of a dual-battery system. And even then, solar alone may not keep up in winter or under tree cover.
Step 4: Decide if solar should even be your primary source
This is the decision people skip. Solar is ideal for stationary camping — when you park for days, panels quietly refill the bank. But if you drive most days, a DC-DC charger pulling from the alternator (or a high-output secondary alternator) refills a large bank faster and more reliably than any roof of panels. Many efficient builds use the alternator as the primary source and solar as a top-up for the days they sit still.
If your travel style is “drive a few hours, camp one night, repeat,” lean on alternator charging. If it’s “park for a week and explore on foot,” lean on solar.
Common mistakes
- Sizing solar before calculating draw. You can’t size the input until you know the output. Do Step 1 first.
- Trusting the rated watt number. Real-world yield is a fraction of the rating. Always derate.
- Ignoring high-draw gear. Starlink and induction cooking quietly double many people’s budgets.
- Solar-only for daily drivers. If you’re moving every day, the alternator is usually the smarter primary source.
- No headroom. Size to recover overnight drain and the day’s use, not just break even.
Bottom line
Calculate your daily watt-hours, derate the panel rating to real-world output, then match the scale to how you travel — and decide whether solar or the alternator should carry the load. Start with the solar sizing calculator for your number, then see the power hub to fit solar into the whole system.