How Many Solar Panels Will Fit on My Roof?

One of the common concerns for most people we talk to, is how many solar panels they can fit on their roof and if that space is actually enough. 

Below we'll cover everything you need to know including: 

How Many Solar Panels Will Fit On Your Roof (Calculator)

We’ve explained how to work out how many solar panels your roof will hold below, as well as what that equates to in terms of system size (in kW). 

However, for simplicity, you can use our solar panel calculator here. 

Our tool can scan your roof and determine how many panels will fit on your roof, as well as what size system is the most suitable for your property based on: 

• Roof pitch and orientation
• Your household electricity consumption
• Any shading from neighbouring properties, chimneys, trees and hedgerows

Work Out Your Usable Roof Space

If you want to work out your usable roof space accurately, simply use this formula below:

Usable roof area (m²) ÷ Panel area (m²) = Estimated number of panels

If we work on a basis of 1.7m² per panel and each panel being 350W, we’d get the following: 

Roof Size vs Number of 350W Panels

A typical 3-bedroom semi-detached house is going to have a roof square footage of around 60-70 m². Alongside this, a solar panel system in the region of 4-7kW is going to be more than enough. 

With one side of your roof offering much higher electricity production than the other, the optimum usable space (assuming no flat roof), is going to be 30-35 m². 

In summary, a typical property will have the perfect amount of roof space available for a suitable solar panel system!

Solar Panel Installation Rules

Do I Need Planning Permission For Solar Panels?

It's rare you'll need planning permission for a solar panel install, unless you live in a listed building. 

If you live in a listed building, it’s worth contacting your local planning office. You may need planning permission and they should offer guidelines as to where and what type of panels you can install, to be in keeping with the local area. 

If you’re not living in a listed building, installations are usually covered by permitted development rights. 

However, there are some considerations to take into account, mainly, your roof's structure. With a full solar panel system weighing 200 kg or more, you'll need an engineer to ensure your roof can take the weight. 

Use our free solar panel calculator here, or, contact one of our experts here if you need advice.

For further reading, check out our detailed guide covering roof suitability for solar panels here. 

How Close To The Roof’s Edge Can Solar Panels Be?

Although there aren’t rules on how many solar panels you can install, how they are installed is a different matter. 

Typically, you won’t have solar panels installed within 30cm of your roof’s edge; the edge of a roof isn’t its strongest point. 

They’ll also need to be spaced out so that they don’t shade each other, otherwise you’re going to see a huge drop in overall electricity production. 

In fact, for those systems using a string inverter, a drop in efficiency from the shading of one panel, would actually drop the efficiency of the whole system. 

That won’t be a problem with any system we install. Our systems incorporate micro or hybrid inverters. Essentially, if one panel is broken or shaded, its drop in efficiency won’t affect the efficiency of the whole system. 

You can get quotes on solar panel systems using a micro or hybrid inverter here.

Example: How Many Solar Panels Will Fit on A 3-Bedroom House?

With an average 3-bedroom semi detached property having around 60-70 m² of roof space, you’ll be able to fit around 12 solar panels. 

Whilst the total roof space available is likely to be in the region of 60-70 m² for a 3-bedroom house, one side of your property will be absorbing a lot more sunlight than the other. Ultimately, this means that it only makes sense to install solar panels on one side of the roof. 

This drops your ideal and usable roof space to 30-35 m², which is more than enough to accommodate a 12-panel solar panel system. 

Of course, this doesn’t factor in obstructions. Obstructions such as hedges, trees, chimneys and neighbouring properties may mean that on certain parts of your roof, it’s not cost efficient to fit solar panels.

Use our free roof scan tool here, that’s going to determine the most cost efficient setup for your property.

What Size Solar Panel System Do I Need?

Now you know how many solar panels you can fit on your roof, is that actually enough? 

Below we’ll explain what size solar panel system you need for your property, and what that’s likely to mean in terms of savings on your electricity bill.

For a 3-bedroom semi-detached property, you’d want a system that’s in the region of 4-6kW. The system mentioned above is almost perfect, giving a maximum output of 5.16kW. 

For a household that's spending around £1,000 per year on electricity, you'd expect to save around 25% by using this 5.16kWh solar panel system. The savings will be made of using electricity directly from your system, as well as selling excess electricity back to the grid. 

Of course, there is another option rather than selling back to the grid, only to buy it back at a higher price at a later date; a solar storage battery. You can check if a solar battery is worth it here. 

By using even a small solar storage battery (say, 5kWh) you'd expect your savings to jump to somewhere in the region of 50%. 

We offer solar panel systems in a range of sizes, and can customise your system to suit your: roof space, electricity demand and which size storage battery you'd prefer. 

Costs vary from system to system, but a basic 5.16kWh setup without a storage battery starts from as little as £5,893.

Use our solar panel calculator to work out which is the perfect system for you and get fixed prices on-screen.

Should I Fit As Many Solar Panels As I Can?

As you can see above, a 5.16kWh system won’t cover all the electricity needs of a 3-bedroom property. Typically, you’d expect it to cover around 50%, for those that use a small (5kWh) solar panel storage battery. 

If you have additional space and cash available, it’s likely that a combination of more solar panels and a larger battery are going to be a great addition to your system, not to mention reducing your reliance on electricity from the grid. 

Interested in reading more before going ahead with a purchase? 

Check out our complete guide to solar panel installation here.