Planning to power a cabin with the sun? Good idea, and one of the first questions you’ll face is how many panels to buy. There’s no single answer, but there’s a simple way to work it out. Figuring out how many solar panels a cabin needs starts with your energy use, not the panels.
Here’s the quick version. Add up how many watt-hours your cabin uses in a day, divide by your area’s peak sun hours, then add a cushion of about 20 to 30 percent for losses. The result is the panel wattage you need, and dividing by each panel’s wattage gives the count. Let’s do it step by step.
Start with how much energy your cabin uses
Make a list of everything you’ll run. For each item, find its wattage on the label and estimate how many hours a day you’ll use it. Multiply watts by hours to get watt-hours (Wh). If those terms are new, our guide to watts versus watt-hours explains them in plain words.
Here’s an example with made-up numbers, just to show the method:
- LED lights, 30 watts for 5 hours: 150 Wh
- Small fridge, 60 watts while running, about 8 hours of running time a day: 480 Wh
- Laptop and phone charging, 60 watts for 4 hours: 240 Wh
- Water pump, 100 watts for 1 hour: 100 Wh
Add those up and you get 970 Wh a day. Your cabin will be different, so use your own list. Appliances with motors or heaters can use far more than you’d guess, which is why a list is better than a guess.
Find your peak sun hours
Peak sun hours aren’t the same as daylight hours. They measure how many hours a day the sunshine is strong enough to equal full-strength sun. Many places get roughly 3 to 6 peak sun hours a day, but it varies with location and season.
Look up your area’s average, and use the lowest season you plan to use the cabin. If you’re up there in winter, plan around winter’s short, weak days, or your system will fall short just when you need it.
How many solar panels do you need? Turn energy use into a count
Now for the math. Follow these steps:
- Take your daily watt-hours (say, 970).
- Divide by peak sun hours (say, 4). That gives about 243 watts.
- Multiply by about 1.25 to cover system losses. That gives roughly 300 watts of panels.
- Divide by each panel’s rated watts. Three 100-watt panels would be 300 watts.
Those numbers are only an example, and your own results may be quite different. Why the extra margin? Wiring, controllers, inverters and batteries all lose a little power, and panels rarely hit their rated output.
Don’t forget batteries, controllers and inverters
Panels are only part of the picture. You’ll need batteries to store energy for nights and cloudy days, a charge controller to protect them, and usually an inverter if you want to run regular household plugs. Sizing the battery bank is a separate job, and our guide to sizing an off-grid battery bank helps with it.
A good rule is to plan for at least a day or two of use in the battery, so a few poor-weather days don’t leave you in the dark. Larger systems also tend to use higher voltage, which keeps wiring thinner and losses lower.
How many solar panels for a weekend cabin or a full-time home?
How you use the cabin changes the whole calculation. A weekend getaway with lights, a phone charger and a small fridge needs a modest setup. A full-time home with a well pump, power tools and electronics needs a lot more.
If you’re just starting out, build for what you use now and leave room to add panels later. Many systems can grow, as long as the controller and wiring can handle extra panels.
Placement and shading tips
Where you put the panels matters nearly as much as how many you have. Aim for a spot with clear sun all day, with no shade from trees or buildings, especially between mid-morning and mid-afternoon. In the northern hemisphere, panels usually face south, and in the southern hemisphere, north.
Tilt them for the season you rely on most, and keep snow and dust off. Because even partial shade can reduce output a lot, it’s worth walking the site at different times of day before you mount anything.
Frequently asked questions
How many panels does a small cabin need?
It depends on what you run. A cabin with a few lights and a phone charger might need only a couple of panels, while one with a fridge and a pump needs more. Work from your own watt-hour list.
Can I run an air conditioner on cabin solar?
Possibly, but cooling and heating use lots of power, so you’d need a much bigger system. It’s usually wise to cut those loads first.
Do I need a permit?
Rules vary by area, especially for larger or grid-tied setups. Check with your local authority and consider a licensed electrician for the wiring.
The bottom line
Working out how many solar panels a cabin needs is simple once you’ve got your daily energy use and sun hours. When you’re ready to buy, our guide to the best off grid solar kits for cabins is a good start, the roundup of the best 60 amp MPPT solar charge controllers helps with controllers, and the list of the best 48V lithium batteries for solar systems covers storage.