Generally, every square foot of roof space has the potential to generate about 15 watts of solar energy. Thus, a solar panel installation on a small home might only need around 200 square feet of roof space, while a larger home can require more than 1,000 square feet of roof space to properly offset electricity usage.

The Amount of Energy Your Household Uses

No two households are exactly alike in their energy use, and what’s even more interesting is that the size of your house does not actually always factor into the amount of energy you use. What is more important is lifestyle factors, such as the number of appliances that you use, the frequency with which you operate these appliances, and the energy efficiency of these appliances.

Of course, it’s not just appliances, either — also determining your energy usage is the amount of lighting that you use, how much your house needs to be heated or cooled, and how much hot water you use on a regular basis.

All this being said, it may be helpful for us to share some average numbers. In Canada, for example, the average resident uses 11,135 kWh  of energy in any given year. This is higher than the average American, who uses 10,909 kWh, or the average Australian, who uses 9,044 kWh.

Calculating How Much Solar Roof Area You Need

First you’ll need to know the dimensions of the solar panels and the size of the system. Sometimes, when designing a solar system, you need to work out whether a landscape or a portrait orientation is needed. What you need to know first? The first things you need to know are:

1. The size of the system you are wanting to install

2. The type of solar panel (and the dimensions – you can get these from the solar panel datasheet)

3. The spacings between solar panels

4. The orientation of the panels. Once you have this information you can work out how much roof space is needed for your system.

Now you’re ready. Here’s how you calculate the area required:

Size of the system (in Watts – e.g. 5kW = 5,000 Watts) ÷ Size of the solar panel (in Watts) = number of panels required Work out how many square meters each panel takes up.

For example, a panel which is 996mm wide and 1680mm long takes up 1.68 x 0.996 = 1.67 sqm. A 5kW system will be 20 x 250W solar panels which would take up 33.4 sqm. A little bit of space will also be needed in between each panel for fixing the panels to the racks—this will depend on what type of racking system is used.