When you have a solar power system you will have days when you won’t be able to charge your batteries so you need to know how big to build the power storage. If you know your watt hour usage and sunlight exposure it will help you determine this.
In order to do this you need to add up all the wattage hours used in your house. To determine how many amp hours are being used all you have to do is look at the wattage rating on your appliances and multiply it by the hours of use each day. If there isn’t a wattage rating just use the amps rating and multiply it by 120 volts ,that will give you the watts. ( amps x volts = watts) (Side note) you won’t be able to power large wattage appliances because it will drain your battery bank too fast . anything over 1500 watts shouldn’t be included in your configuration.
Then you add all the appliances wattage hours together. Remember this is for each day of use separately. Then multiply it by 3 because if your power is out for three days you’ll need to determine what size you need for that length of time.
To find battery capacity multiply daily watt hours usage by 2 that way you will use only 50% of the battery capacity.
To determine the size of the battery bank in hours you will divide the total watt hours by whatever size battery system you’re using 12,24,48 volts. The larger the voltage system you have the better because you will be able to power more and longer.
For instance if you have 25,200 watt hours take that 25,200/12volts=2100 amp hours then divide that by whatever your batteries amp hour rating is and you’ll get how many batteries you’ll need to use to have enough energy to run your appliances comfortably if you didn’t have 3 days of power or three days of no charging your batteries.
For example your house uses 25,200 watt hours of power and you use 12 volt batteries in your battery bank so you divide 25,200/12 =2100 amp hours then divide that by the batteries amp hour rating. which in this case is 105 amp hours for the 12 volt batteries you’re using. This comes out to 20 batteries in your battery bank. This number will vary on the size of your battery.
Now you know how many batteries you’ll want to have in your solar powered system. In our next article we’ll discuss what kind of battery is the best for you and how you can hook them up to get maximum power.