When you’re living off-grid, it’s important to have an inexpensive source of power to keep your overhead costs low. That’s why so many people who live off-grid turn to solar power for most of their energy needs.
In this guide, we’re going to look at how many solar panels you should install, how you should house your battery, where you should install your solar panels, and a whole lot more. There’s a lot to cover, so let’s get right into it.
How many solar panels do you need?
Figuring out how many solar panels you’re going to need is fairly simple, but there are a lot of variables involved. Let’s start by looking at your energy consumption.
The easiest way to go about this is usually to look at your power bill. Your utility will typically tell you how much power you’ve used each month - you can simply divide the number of kWh you see on your bill by the number of days in the month. Divide that by 24, and you know how much power you use an hour.
Things usually aren’t that simple when you’re off-the-grid - there are no utilities to report your power usage to you. That means you’re going to need to do research. You should look at your lighting, appliances, HVAC, and other electric-powered devices, and figure out what their kWh usage is. From there, you’ll want to determine how often you use those devices in a typical day.
If you can’t figure out how much power an appliance uses, check out Silicon Valley Power’s Appliance Energy Usage Chart for some average power usage. Wherever possible, however, we recommend finding out exactly how much power your device uses. Precision is powerful when it comes to solar arrays.
Once you’ve figured out your energy needs, you can conduct the following calculation:
Your hourly energy requirements (kWh) x peak sunlight hours in your area / wattage of your panel (kW)
Let’s say your off-grid home uses .83 kWh per hour. You’ve got 4 peak sunlight hours a day, and your panel produces 300 watts. 300 watts is .300 kW. That means our calculation is:
.83 x 4/.300 = ~11 panels.
Of course, solar power generation isn’t always optimized. Clouds, for example, can obscure the sun and reduce (though not eliminate) solar power generation. As such, it’s usually a good idea to include about 25% more panels in your array than the calculations above yield.
The full formula, then, is:
Hourly energy requirements (kWh) x peak sunlight hours / solar panel wattage (kW) x 1.25.
Mounting your solar panels
When it comes to mounting solar panels, you’ve got a lot of great options. A-frame houses are perfect for roof-mounted solar panels - the 60° angle means you have a lot of space, and the panels will be quite well positioned to absorb as much sunlight as possible - especially in the winter.
That’s true, at least, for people at higher latitudes. At lower latitudes, you want lower angles. In these cases, or in the case that your roof is obscured by trees, you may want to use a fixed ground solar installation. Tracking installations are also possible, but they’re generally not worth the extra cost.
Fixed ground installations are handy if you’ve installed your A-frame close to the equator because you can tilt the panels at a shallower angle than your A-frame might allow. It’s quite a bit of extra labor, however - you’ll need to pound metal poles into the ground, then create a framework of metal beams, supported by the poles, to install your panels.
Whether you’re going for a ground or roof-based installation, how you’ll install the panels will depend on the solar modules or kits you’ve purchased. For roof installations, a roof rack can help you maintain consistent power generation. Roof racks allow the wind to cool both sides of your solar array - solar panels work better when they’re cooler.
A question many would-be solar adopters get stuck on is this: “How do I get power at night?”. When you’re grid-tied, the solution is simple - at night, you get power from the grid. For off-grid solar, you’ll need a solar battery.
There are three competitors in the solar battery world: lead acid, lithium ion, and saltwater. Saltwater batteries are currently prohibitively expensive, so let’s look at lead acid and lithium ion.
A few quick notes before we go
The best way to keep your costs relatively low is to use AC power in your A-frame home. That means you’re going to need an inverter to switch your solar array’s output from DC to AC. Almost all modern homes are AC - that means DC-powered devices are much more expensive. There are inefficiencies when converting DC to AC, however, so you may want to add an extra panel or two to your array.
You’ll also want a backup source of power for the winter - solar panels can do a lot, but they can’t do everything. A diesel generator is a good place to start.