Why your roof might not be suitable for solar panels

Interest in solar panels is rising as householders seek out ways to lower their sky-high energy bills and help save the planet.

There are roughly 1.2 million UK homes with solar panel installations, according to the latest data from the renewables industry-led quality assurance scheme MCS, and the number is rising.

But, as everyone explores their renewable options. there are also many homes that are unsuitable for the low-carbon tech. We spoke to solar panel experts about what homeowners need to know before making the eco-friendly switch.

What if your roof isn’t large enough for solar?

The amount of space required for solar panels is dependent on the desired size and power output of the system, according to Heatable co-founder Ben Price.

The number of solar panels required to power a typical UK home will depend on the home's energy demands and the size and orientation of the roof. In the UK, a single solar panel typically has a size of around 1.6 square metres (17.2 square feet) to two square metres (21.5 square feet) and has a power output of between 250 and 400 watts.

For example, a typical 3-4 kW solar panel system in the UK may require around 20-25 square metres (215-270 square feet) of roof space, and a 4-5 kW system may require around 30-35 square metres (322-377 square feet) of roof space. However, Ben warns that the shape and features of the roof, such as dormer windows, can affect installation. 

“Bear in mind that these are estimates only as unfortunately there is no one size fits all approach and there are many different variables between solar panel system installation scenarios," he said. “If there is not enough space on the roof to meet the desired power output goals then property owners can potentially use other locations including ground-mounted solar, as well as the sides of buildings, or shed and garage roofs,” Ben adds. “It's worth noting that solar panels can also be installed on other surfaces, such as ground mounts or on the sides of buildings, which can provide additional space for installation.”

Fred Lowe, director of electrical and mechanical contractors Lowe & Oliver, says the critical question to ask is if your roof is structurally sound. 

“Without a stable platform no infrastructure can be installed. When was it last inspected for leaks? Can the building withstand the pressure?" he said. “It might not be large enough and if it’s too small, you simply won’t produce enough to wake the inverter up. Roof obstacles such as dormer windows do pose a problem, but it’s possible for multiple systems to be used across a roof to suit layouts as required. Installers can be flexible to meet your needs - on various occasions panels we have installed in an unorthodox fashion to widen the square footage.”

Be aware you may need planning permission for solar panels if you are not installing them on the roof.

What if your tiles are made of clay?

Ben says clay tiles are not a complete barrier to installing solar panels – but it does mean additional considerations that need to be considered.

He said: “For example, some clay roofs are only designed to take the weight of the tiles, so a structural assessment will need to be conducted to determine if the roof can bear the weight of the panels.

“Additionally, clay tiles tend to be more fragile than other roofs, so the mounting equipment and procedure are also adapted in such scenarios.”

He adds that homeowners should seek the advice of a solar company with experience in dealing with tile roofs.

What if your roof is not south facing?

A south-facing roof is an ideal scenario, since this direction receives the most direct sunlight during the day, however, east and west-facing roofs can still generate a significant amount of energy so solar can still be well worth it.

Fred said: “If the roof is not south facing, it’s not a total disaster. Optimisers can be installed on panels to optimise peak periods, so it’s still worth speaking to an established installer. Shading is a huge factor though from trees and other obstacles, so conduct a pre-site survey using a solar PV fisheye lens to factor all shading into the design criteria.”

Ben adds that some shading is OK, but trees that cast heavy shade may need to be removed or trimmed.

“Additionally, there are several ways to maximize the electricity generation of a solar panel system installed on an east or west-facing roof, as well as creating a system optimised for low light conditions,” Ben said.

For example, a solar tracking system, which moves the solar panels to face the sun throughout the day, can also increase the system's energy production.

What if your property is a listed building or in a conservation area?

In the case of listed buildings or buildings within a conservation area, there are additional rules and restrictions to be aware of.

Unlike a regular solar installation, it is not considered “permitted development” so applying for planning permission is essential.

In addition, if planning permission is granted, there may still be additional rules to abide by, which may restrict the solar installation location and design.

For instance, it’s common for the restrictions to stipulate that the panels themselves must not be visible from nearby roads and must not distract from the not detract from the building's appearance.

What if you don’t have space for an inverter?

The solar inverter has a major role in converting the electricity generated from your panels from a direct current (DC) to an alternating current (AC).

Typically, people have these installed in the garage or utility room because they need a clearance area of around 60 cm² for the ventilation openings, but this varies depending on the exact size.

Ben adds: “For people who are struggling to find adequate space to house an inverter, one solution is to use a microinverter or power optimizer system, which allows for the conversion of DC to AC power locally at the solar panel itself.

“This means that a small inverter is installed on the back of each solar panel, which allows for greater flexibility in terms of installation location and orientation.”

Fred adds that new fire regulations are soon to be bought in banning batteries and inverters from loft and stairwell spaces, so keep an eye on those developments.

Ben Price

Ben Price is a co-founder of Heatable.co.uk, a website that offers solar installation and other home services to customers throughout the country. With his team, Ben has worked to establish Heatable as a trusted and reliable provider of renewable energy solutions, helping homeowners to reduce their carbon footprint and save money on energy costs.

Fred Lowe

Fred Lowe is a Director of Lowe & Oliver Ltd who celebrate their centenary this year. Established nationwide, Lowe & Oliver provides a comprehensive portfolio of electrical and mechanical services. Fred Lowe heads up the Special Works Department which focuses on a range of carbon reduction & energy saving solutions.