As I plan for my dream homestead, my projects have a few different scopes. Sometimes I make plans that are immediate – think, “this is the cutest thing I’ve ever seen, how can I make this RIGHT NOW?!” Then there are the short-term plans that I can start adopting in the next few months. And then there are the plans that are so long-term that it’s sort of insane to be thinking about them right now when I have 100 different things to do in the next two months as we prepare to move.

Enter solar power, a plan that I may need in two years… or I may not need for another ten years. And by the time I do need it, the decrease in solar panel cost and the (still unknown) impact of climate change means that this information is subject to change often! And yet, it’s what my brain decided we absolutely needed to do this afternoon, so… here’s what I’ve found about solar energy to help you prepare for a solar power system in WNC.

This is the second post in my Homestead Power Series. I highly recommend you read the first post, which covers some tips about reducing your overall power usage to reduce the total cost of your solar system.

I started with this great link from SunPower: How Many Solar Panels Do I Need in My Home? As you’d expect, there’s no straightforward answer. It depends on your area (enter this area-specific blog!), how much electricity you generate, how efficient your solar panels are, specific details about your roof, etc. The best way to figure out how many solar panels you need is to consult a professional. That said, I’ll walk you through the numbers I generated. A solar professional might give you slightly different numbers, but these calculations should at least give you somewhere to start. (For additional research, I also recommend Solar Power Authority’s guide, “How Much Does it Cost to Install Solar on an Average US House?

PV vs CSP solar panels

There are two basic types of solar panels: photovoltaic (PV) and concentrated solar power (CSP). You can read more about the differences here. However, the important takeaway is that for a residential system, you’re usually going to be looking at PV solar panels.

Your Energy Requirements

The best way to find out how much energy you need for your current system is to take a look at your energy bill for the past few months. You should see your energy usage per year, month, or day, shown in kilowatts per hour (kWh).

(If you need some brushing up from science class: Watts are the standard unit of measurement for energy/power usage over time. 1 watt = 1,000 kilowatts.)

  • Per SunPower’s report, you need your daily energy usage.
  • If your energy company gives you monthly, weekly, or yearly energy usage, divide this accordingly to get your daily number.
    • For example, my power company tells me that the average monthly usage in my apartment community is 700 kWh
    • It also tells me that this is over a 28 day period; thus, we’re using 25 kWh per day, on average.
  • I also recommend averaging this usage over the past three months to get a more accurate view of your energy needs.
    • When I account for those cold winter months, our community average is closer to 32 kWh.
    • If you wanted to give yourself plenty of cushion, you could also take the energy estimate for your most expensive bill this year (probably in the coldest winter or hottest summer month).
  • Because solar panel efficiency varies based on weather and hardware failures, SunPower recommends that you add a 25% cushion to whatever your final number is.
    • With this cushion added, the average apartment in my community uses 39.5 kWh per day.

It’s worth noting that my apartment community does not have gas appliances or offer fireplaces. These numbers are electric-only. (We’ll have a wood fireplace in our apartment next month, and I’m eager to see how this will affect our average bill.)

Peak Sunlight Hours

Per SunPower:

The peak sunlight hours for your particular location will have a direct impact on the energy you can expect your solar system to produce. For example, if you live in Phoenix you can expect to have a greater number of peak sunlight hours than if you lived in Seattle.

This where a regional blog like mine comes in handy. You need to know the peak sunlight hours for your area specifically, using PV solar panels. You can search for your area here, but if you live in WNC, I’ve looked it up for you: a few portions of Yancey, Mitchell, Avery, Watauga, and Ashe counties have 4.0-4.5 kWh peak sunlight hours per day. All the other counties in WNC get 4.5-5.0 peak sunlight hours per day.

  • Now we need to divide to find out how much energy you need to generate in each of those peak hours to meet your daily usage requirement.
    • I’m pulling energy data from my current apartment in mid-Ohio, but for these purposes I’m going to pretend it’s already June and I live in Buncombe County.
    • I need 39.5 kWh per day, and I need to get this from about 4.5 hours of sunlight in a day.
    • 39.5 divided by 4.5 = approximately 8.8 kWh needed for each peak hour of sunlight.
  • The final step is to convert this hourly power generation figure to watts (multiply by 1,000).
    • So the average apartment in my community needs a solar system of about 8,800 watts to meet their power requirement each day.

Efficiency of Your Solar Panels

Let’s go back to SunPower’s guide:

There’s tremendous variation in solar panel capabilities and performance. PV solar panels (most commonly used in residential installations) come in wattages ranging from about 150 watts to 345 watts per panel, depending on the panel size and the cell technology used to manufacture the modules.

SunPower wants us to come up with a low-wattage and high-wattage figure to discover how many panels we need and how much that might cost. (Consider also that these prices don’t include installation, wiring, inverters, batteries, or any other solar accessories you’ll need, although Amazon does have several solar starter kits that include many of these features.) Let’s take a look.

Low-wattage system

  • Amazon recommends “Renogy 100 Watts 12 Volts Monocrystalline Solar Panel” when I search for solar panels. You have tons of options here, and this may be much cheaper or more expensive than a system you might find; I’m just choosing this one to get some numbers to punch!
  • Renogy offers a small discount on a 4-pack of their 100 Watt panels, at $556.99.
    • That’s 400 watts, but remember that our hypothetical apartment system needs 8,800 watts.
    • So we would need 88 solar panels, which would mean we would have to purchase this kit 22 times for a final total of $12,011.78. 
    • (That’s also assuming you could fit 88 solar panels on the roof of this hypothetical apartment!)

Higher-wattage system

These numbers will vary a lot based on your individual situation, especially if you’re able to reduce your dependence upon electricity by taking advantage of some of the tips outlined in this post.

Once you buy your solar panels, you’ll have to install them, too (or hire someone else to do it)… but that’s outside the scope of this post… for now.

Readers, please chime in with the following answers, if you have them:

  • Do you have solar power established in your home? Or, are you planning to have solar power?
  • How much of your home’s energy is powered by solar?
  • Any tips about setting up your solar system, or brand recommendations?
  • If you’re comfortable sharing, how much did your solar system cost?

(An asterisk* in the middle of text means that I plan on expanding on this topic later.)