Solar Panels on House Roof

One of the most common questions that is asked about solar panel installations is how much roof space you need to install the panels. This is a crucial thing to know before you install solar panels. So how is it worked out? What do you need to know about solar panels to figure this out? Is there anything else you need to know before installing panels?

How to work out the roof area you need for solar panels?

There are a number of different things you need to know before working out the roof space required for solar panel installations. 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. 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.

Which direction do your panels need to face?

If you don’t have enough roof space on a single roof face, you can consider splitting your system into 2 different orientations. The best orientation for panels (in the Southern hemisphere) is North. East and West are slightly less efficient (around 9% less). South is around 20% less efficient so should be avoided when possible. If you split your panels between your East roof and your North roof evenly, you would only lose around 4.5% of your overall system capacity (in kW).

Is there a minimum number of panels facing in one direction?

Yes! This depends entirely on the inverter you choose. Most inverters will have a minimum voltage in order to work. The more panels in one “string”, the higher the voltage will go. Usually at least 6 panels will be needed to get the inverter functioning correctly.

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