Using the methods described below, you can determine the overall power usage of your home and use it to figure out the number of solar panels and batteries you'll need. It does involve a bit of math, which isn't always everyone's favorite thing to do, but it's pretty simple and easy to understand!

How much power does your home consume?

Method 1

The wattage of an appliance can usually be found on a label attached to the power cord. It’s listed in either amps or watts; you want to know the watts — don’t worry if it doesn’t tell you there is a simple formula for figuring it out.

Volts x Amps = Watts.

For simplicity sake, the average household wiring is 120 volts; chances are, your appliances and anything you plug into the wall runs at 120 volts.

So let’s say the tag on your appliance says it draws three amps; you simply multiply 120 x 3 giving you 360 Watts!

So we take the 360 watts and multiply that by the hours a day we run that specific device and come up with a daily wattage figure.

In the case of something like a refrigerator which may draw 400 watts an hour, we need to multiply the number by 24 hours coming up with 9,600 watts a day.

Method 2: This is the method I suggest.

For $20 you can buy a device that will measure exactly how much power your appliance uses throughout the day. Run this on each appliance for a week and you have real world data.

How many batteries do you need to run your off-grid system?

Ok, so I hope I don’t lose you here; but when we are looking at batteries, we need to calculate what we need in AMP hours (AH).

Amp Hour (AH) gives you a measurement of battery capacity.

So to come up with the number, we are going to divide the total battery capacity required by the voltage of the battery. So in the case of a 12-volt deep cycle battery, we are going to divide our 9,600 number (watts a day for the refrigerator) by 12 (volts) which tells us we need 800 amp hours.

These are all rough estimates. In the example above I’m going to want to add at least another battery to account for things like discharge, days where the sun might not be shining, etc.

There is a phenomenon referred to as Peukert’s Law. To get the real storage capacity of the battery, you need to understand that the amount of energy stored is dependent on the battery’s discharge rate. The greater the rate of discharge, the lower the delivered capacity will be.

Now consider Peukert’s Law can be affected by things like temperature and battery age, and you can throw your estimates right out the window.

So for people that don’t want to get to bogged down in the equations, I always suggest overestimating your needs a bit.

How many Solar Panels do you need to run an off-grid system?

Let’s say you have a 100-watt panel. You want to take that number and multiply it by the number of direct sunlight hours you have in a day. So let’s say you average about 6 hours of direct sun a day, that one panel can produce 600 watts a day.

Panel watts x hours of sun = Daily Output

Next, take your daily wattage needs, in the case above 9600, and divide it by the daily panel output.

Daily Need divided by Daily Output = Number of Panels

For the 9600 watt system, I need sixteen 100-watt panels and four 200-AH batteries.

Have you created your own solar panel system? Do you have any advice for people who are trying to live off the grid?

Article Source: Off Grid Survival