Off Grid Solar Power – How to Calculate Your Needs

hi everyone Matt here from exploring alternatives if you’re thinking of setting up an off-grid solar power system but you’re not sure exactly how much power you how many watts how many solar panels what kind of batteries what kind of inverter this can all be very confusing at first so keep watching and I’m going to explain everything in this video so the first and most important thing is to figure out what you want to use your solar system for so what appliances and electronics are you going to be using for example are you going to be using a small fridge maybe with a few LED lights running seven days a week all day or maybe you want a solar system just to run a few lights when the Sun goes down for a few hours at night so this makes a big difference and how are you going to calculate everything

so I’m going to use the solar system setup that we put together in our campervan as an example to help you understand everything so first of all we determined that with our solar power system we want it to be able to power two laptops one small USB fan like this we also want it to be able to charge camera batteries every once in a while we also wanted to be able to charge our iPod Touch and some double-a batteries and we wanted to make sure that we could power all these electronics for about eight hours a day seven days a week so the first thing we needed to do was to figure out what was the energy consumption of each item every electronic device every appliance every item has a power consumption rating it’s often on the power adapter itself sometimes it can also be directly on the item there’s a little sticker in the back and this can be found on every single item that you look at what is most important is that you want to find the output wattage of every item so in this case it clearly says output sixty watts and if you look at this fan it also says clearly 2.

5 watts but for some items like this camera battery charger for example it doesn’t actually give me the output wattage of the item unfortunately it’s only giving me the output volt and milliamps so there’s an easy conversion for this all you have to do is do volts times amps and you get the wattage in this case as you can see it says milliamps often it’ll say amps but in this case it’s milliamps thousand milliamps gives you 1 amp so in this case 500 milliamps means that it’s point five amps so you’re going to do 8.

4 times 0.5 and you’re going to get a total of 4.2 that means that this item takes 4.2 watts so we figured out that our first laptop would take 60 watts our second laptop would take 45 watts our camera battery charger would take 4.

2 watts charging our iPod would take about 4 watts and our little fan would take 2.5 watts so that would give us a total of 115 point 7 so we rounded it out to 120 just to be safe then we just had to figure out for how long we wanted to use all of this so in our case we wanted to use everything for about eight hours a day seven days a week we probably wouldn’t actually use all of this eight hours a day seven days a week but that gives us a little bit of leeway in case we want to use other things like an electric shaver anything like that once you have all those numbers figured out all you have to do is input them into a solar power calculator that you can easily find online and to make it easier for you I put a link to a very good calculator in the description of this video first we’re going to go to this website right here Rena G calm and this is really the best calculator I’ve found yet online

so we’re going to go to the calculator section right here click calculator it’s going to bring us to this page with a few different options we’re going to select solar sizing calculator and click right here you’ll see at the top there’s a calculator for on grid systems we’re going to ignore that and go to the off grid section down here make that a bit bigger so first we’re going to input what is the total wattage that we’re thinking of using so in our case like we mentioned earlier it was 120 so I’m going to input that in right here 120 then for how long are we planning on using these devices in our case it’s approximately 8 hours a day so I’m going to put 8 in this box right here now the charge controller there’s at PWM and MPPT they have different efficiency numbers so in our case we have an MPPT charge controller

so I’m going to input 92 percent right here then you have to figure out approximately how much Sun you get how many hours of sunlight you get in your area per day where we live we get about five hours a day of sunlight so I just input five in this box right here and once I have all these numbers inputted I just press calculate right here and I get my totals so you can see minimum system size so how many watts of solar panels do I need they recommend about two oh eight point seven recommended battery size if it’s 12 volt 160 amp hours and recommended battery size if it’s two if they’re 24 volts 80 amp hours so as you can see it’s not very complicated once you figure out the output wattage of every item and for how long you want to use them for in our case we actually didn’t do exactly what the calculator was telling us to do we had some restrictions in terms of budget and available space in our campervan so we altered things a little bit we actually got 300 watts of solar panels and only a hundred fifty amp hour battery but for our needs the system is working really really well

so I think it was okay in our case to vary the results a little bit one last thing to keep in mind for your solar power system is the inverter and in the case of the inverter bigger is not actually better usually smaller is better so again I’ll use our system as an example we figured out that we would use about 120 watts at a time so with the when you’re trying to pick an inverter you have to figure out what is the maximum amount of wattage that you’re going to be using at the same time so if you have a 500 watt inverter and you’re thinking of using a thousand Watts all at the same time while your inverter the fuse in it is going to blow and it’s not going to work you’re going to need a 1500 watt inverter or anything above a thousand in our case we knew we were only going to need 120 watts

so we picked a pretty small inverter our inverters 500 Watts that gives us some room to add some more electronics on there and we were comfortable with that but we probably could have went down to even 300 watts this is more efficient because your inverter actually takes power it’s a machine that’s running off your solar system also so the bigger it is the more power it takes and if you don’t need that amount of power you’re actually wasting energy so thanks for watching I hope this helps you calculate how much you need for your solar system and I hope it clarifies things you can also click the link right there in the corner if you want to check out our other video about our solar power system in our campervan that shows you how we set up everything and all the different components thanks for watching and good luck setting up your system