I recently wrote a blog post all about how we life off the grid using solar power, how much power we use and what exactly our solar power set up looks like. You can read all about our solar power system here but this post is about how you can figure out how much power you use so you know how many solar panels and batteries you need to live off the grid. Because what our family needs is probably different than what your family needs.
Like you've probably heard me say before, anyone can line their big roof with solar panels and supply themselves with power, and even tie into the grid to support it. If this is you, you may want to consider hiring a company to outfit your roof with solar panels and have it done for you. But if you are moving off the grid to support your own power needs AND live more gently on our planet, this post is for you to help you figure out how to do just that! I also do my very best to keep my explanations simple because for myself, it gets so confusing with all the watts, other watts, volts and amps hah! If my words are too simple for you, it's probably because you are more an expert in solar power than I am hah!
Solar is dirty! Read my unpopular opinion here.
For simplicity sake, we're going to touch on three main subjects here: how to calculate how much power you use, how many solar panels and batteries you need, and a list of items to consider based on your location, because I know you all don't live in the Canadian Wilderness of the east coast, do you?
How to calculate your power needs to live off the grid
To build a solar power system for your off grid home, you'll need to start with figuring out how much power you actually use. Depending on your lifestyle, this may be some quick calculations or a lengthly treasure hunt around your home! But basically, you need to take stock of everything that you use and requires power, and add it up. All your kitchen appliances, gadgets, entertainment, internet, dvd, playstation, washer/dryer, night lights, lamps, essential oil diffusers, battery chargers, everything!
For example, if you want to keep your toaster which uses 1500watts and use it every morning for 15 minutes to toast everyone's bread, you'll need at least 375 watts of power to come out of your battery bank. My math looks like this: 1500watts / hour is the same as 375watts / 15 minutes. If you're looking to live with a modest solar power system, this is a lot of power used up on toast but anything that requires heat, and therefore light, will be very power hungry.
Another example, we charge our 4 tablets once daily, which we use for home education and entertainment, 2 cell phones, and occasionally the laptop on days that I am working online. You can google your device to find out how much power they use when they are charging but they typically are 5 running watts each hour they are plugged in charging up. Our 6 handheld devices will use about 60watts a day. My math looks like this: 5watts x 6 devices is 30watts / hour, but let's say everything charges for two hours for good measure 30watts / hour x 2 hours = 60watts.
Once you know how many watts or power you use in a day, you can use this number to figure out the size of your battery bank.
How many batteries you need to live off the grid
Let's say you came up with 3500watts of power consumption in a day, this is more than us and our simple way of living but still, it isn't really a lot. If you are using led acid batteries, or what I call regular batteries, which are most affordable, you will want to double this number because you'll never want to use more than half of your battery bank. This is because there is a point where a lead acid batteries can become so discharged that the reaction is no longer reversible when charging. And batteries are expensive. If you are using lithium batteries, you are able to fully discharge the battery as a form of maintenance, although it still isn't recommended to do so each day.
We now know we need 7000watts in our battery bank each day. There are all different kinds of batteries out there but let's say you are going with a 12v 100ah deep cycle led acid battery, which is pretty standard in the solar power world. 12volts x 100ah = 1200watts from full to empty but we only want to use half of this at the most. 7000watts / 600watts = is approximately 12 of these batteries.
Now that we know we need 12 batteries to store 7000watts to use our daily 3500watts, we can figure out how many solar panels we will need. You can also use this next math for wind power, which is a great way to diversify your power generation. When it is cloudy or during the night hours, you could still have power coming in.
How many solar panels you'll need to power your off grid home
Geography plays a huge part in planning your solar array. If you are in Texas, you are getting much more solar power that us anywhere Canada because you are closer to the equator. You'll need to find out the average amount of hours of sun you get in a day to understand how much power your panels can produce for you in your location. This can be found with a simple google search (average daily sun hours in my location). Where we are on the east coast of Canada it is roughly 3-4 hours of sun per day on average.
We know we use 3500watts each day, this is also what we need in a day to keep our battery bank full. If I have 1000watts of solar panels and get 4 hours of great sun in a day on average, we can generate 4000watts of solar power and that would suffice. Keep in mind that even if a solar panel is rated as a 250watt panel, that is its peak production, at the best angle in the high sun. It is suggested we double the amount of solar panels we actually need in our array because it is unlikely we will get perfect sun, everyday.
I really hope this post helps you figure out how many panels and batteries you'll need to live off the grid. If you'd like to know more about what our solar power system looks like, we have a blog post all about it here.
