If you’re considering going off-grid with solar and a battery bank, you’re probably wading through a jungle of questions and research. To decide if off-grid solar survival is right for you, let’s set the ultra-technical aspects aside (mostly) for a moment, and work through the top 5 questions to ask yourself before diving in, getting off-grid, and soaking up the rays!
Off-Grid Solar Survival: Important Things to Keep In Mind
1. What is Your “Payback Period”?
“Payback period” is a phrase that’s thrown around a lot in regard to solar. So first, we need to break that down. Solar materials and labor cost (X) and your current electric bill cost you (Y) each month/year. What we want to know is: How soon will the solar system start saving me money? To determine how long that will take we just divide (X) by (Y).
For example, let’s say solar costs $1,000 (X), and your current monthly electric bill is $100 (Y). Because you paid $1,000 up front and you don’t have an electric bill anymore, after your 10th month you’ll be saving $100 per month. So in this example, your payback period is 10 months. (Hint: Solar prices have dropped dramatically in the past 10 years, but your payback period almost definitely going to be quite a bit longer than 10 months)
2. Am I in a Location That’s Viable for Solar?
Location, location, location. The more hours of sunlight that your solar panels can receive, the better. A big mistake that’s made all too often with solar is failing to consider an object like a tree, or chimney, or nearby pole that will cast a shadow on your solar array at some point during the day. Even though that shadow might only be covering a tiny portion of the one panel it can drastically reduce the performance of the whole array.
As the sun tracks from east to west throughout the day, and throughout the seasons, you want to make sure your array is in a location where it can receive maximum sunlight. A quick google search for “distribution of solar radiation in _______ (your country)” should show you what you’re looking for and you can narrow in from there.
3. Are You Self-Installing or Hiring an Installer?
Depending on your local laws, having a certified installer may be the only legal option. This comes with huge benefits of having someone to contact in the event of a malfunction, having an expert help determine your needs, and it will certainly decrease the time you have to wait before going off-grid. Even at the prices solar is now available for, this is not an investment you want to have to make twice if you make a mistake.
If you are free to do what you please on your land, you could save a significant amount of money by self-installing. Remember, that the self-installing route will involve a lot of research, and it can be extremely dangerous to work with electricity, but it can absolutely be done. It’s probably from growing up with an ultra safety conscious father, but I feel compelled to reiterate that working with electricity can be deadly and it is critical to inform yourself on how to safely work with it before attempting a project like a solar install.
4. Is the Amount of Electricity you use is Compatible With the Amount of Solar System you can Afford?
Stick with me on this one; there’s an armful of important things to consider, but it’s worth in the end. A good way to determine this is to take a close look at your current electric bill. It should show you how many kW (which stands for kilowatt, or 1,000 watts) you use each month. The key here is balancing energy efficiency with convenience and comfort.
Heating and cooling will likely make up the majority of your electricity use. That includes your air conditioning, your heating, your washer and dryer, your fridge, your cooking etc. Generally, unless you’re planning a truly monstrous system, your air conditioning and home heating won’t be able to be on electricity from your solar system. You can do workarounds by having non-electric forms of air conditioning and heating to solve this issue. Having energy efficient appliances, reducing overall use, and insulating extremely well will all be important steps on your path to energy independence.
Next, let’s get familiar with how much electricity each appliance uses. Each appliance will have the W (watts) and the V (volts) as well as some other information listed on the appliance itself or on a tag on the cord. Once you get down to the nitty-gritty details of knowing not only how much energy you use per day, but roughly how much each electrical appliance uses, then you can really narrow in on how big your battery bank will need to be.
There are a variety of battery chemistries at varying prices (deep-cycle lead acid (non-sealed), sealed AGM, Lithium etc.). In most instances, the most affordable and available option will be a deep-cycle lead-acid battery. Keep in mind that, for most battery chemistries you will not want to discharge your battery more than 50% at any time. For example, if you have 600 Amp Hours total of battery capacity, you should only ever use 300 Amp Hours. This helps keep your batteries healthy and performing for you day after day.
As a brief technical note, you’ll often hear people talking about watts, kilowatts, volts, amps, and amp hours. The basics of what you really need to know here are a kilowatt is one thousand watts, volts X amps = watts, and while all are important to understanding, when you get right down to it Amp Hours are the most logical way to think about electricity you have on hand. For a more in-depth explanation on why, check out this article: Volts, Amps and Watts Oh My! Explaining The Basics Of Electricity.
Lastly, you’ll want to do some rough figuring on how many hours of sunlight your location receives per day. Then, use that to determine how many panels you’ll need in your array to be able to put the energy you use throughout the day back into your batteries through your solar panels.
I get 4 hours of peak sunlight per day, I can put 50 amps into my batteries per hour peak production. So I can usually count on 200 amp hours being available to recharge my batteries each day.
It may be slightly more because there will be an hour or two before and after “peak hours” that give me a little electricity, but it may also be slightly less if it is raining or cloudy. So, if you need more power per day, you’ll need to add more panels, or perhaps increase your battery bank size, and likely increase your controller size (your controller is the brains of the operation that essentially makes the “varied” power coming from the panels play nice with the batteries). I recommend doing a “back-of-the-envelope” calculation before going too far in-depth. This way you get an idea of how much your electrical use will cost you in terms of your solar system.
5. Do you Have Space for All This Stuff!?
The solar panels will need quite a bit of real estate if you are trying to get off-grid completely. Consider whether you’ll have space for this on your roof. Also, consider whether your roof is facing the right direction for maximum sunlight. Alternatively, you could mount the panels in your yard. You could even put them on something like a large cart you could roll to the best sunlight location in your yard throughout the different seasons.
Keep in mind also that the batteries are quite heavy. You don’t want them in an area that can accumulate fumes from off-gassing (not an issue with sealed batteries). You do want your batteries to be in a location that is decently temperature controlled. This is important because they will lose capacity when they are cold and should never be allowed to freeze.
You’ll want your batteries to be as close as possible to your controller and inverter, as well as the solar panels themselves. The cables you will use to connect these various components will most likely be made of copper. They will also be thick so that they can move a large current safely without overheating. That all adds up to increased cost for every foot further away that your batteries are from the rest of the system. In short, keep your cables as short as possible.
Watch this awesome video by TinHatRanch for an ultimate guide to DIY off-grid solar power:
There is no doubt more questions to be asking yourself before you roll up your sleeves on an off-grid solar build, but these five are a solid start to get the ball rolling. Take your time to think through each piece carefully and it will pay off nicely down the road. And remember, others before you have taken this leap! Do your research, reach out to people with experience, be patient, and you can do this!
Do you have any experience in building an off-grid solar power system? Let us know in the comments section below!
Editor’s Note: This post was originally published on February 1, 2017, and has been updated for quality and relevancy.