Homeowner Blog

Can I install Solar Panels on an Old Roof?

Luke Pemberton · 30 Jan 2024

To find out what constraints having an older roof puts on your potential solar installation, we asked Tok Charles, a Technical Designer here at Spirit some questions that anyone might have.

Installing Solar Panels on Old Tiles

  • Risk of tile breakage during installation; extra care required, potentially prolonging installation time.
  • Option to install an integrated solar system when replacing the roof, which replaces roof tiles with solar panels.
  • Old tiles are manageable, but require careful handling.

Solar Panels on Weak Roofs

  • Structural reinforcement, such as installing 'W-beams', is necessary for weak roofs.
  • A full structural survey is conducted to assess roof strength before installation.

Solar Panels on Listed Buildings

  • Installation not permitted on Grade 1 or 2 listed buildings.
  • Options include installing on nearby structures or ground-mounted systems away from the listed building.

Maintenance of Solar Panels on Older Roofs

  • Solar systems have low maintenance, lasting over 25 years.
  • Roof repairs should be done before solar panel installation to avoid higher costs later.

Safety Concerns for Old Roofs

  • No additional safety concerns, but a structural survey is conducted for assurance.
  • Care is taken with old tiles to prevent breakage during installation.

Condition of Roof for Solar Installation

  • Roof should be clear, with solutions available for obstructions like chimneys.
  • Cleanliness is not crucial; moss or similar is acceptable.

In-Roof Systems on Old Roofs

  • Ideal for old roofs, allowing roof replacement with an integrated solar system.
  • Saves on tile costs and labour, making installation quicker.

Solar Panel Longevity on Old Roofs

  • Solar panels last as long on old roofs as on new, with warranties typically at least 25 years.

Effect of Old Roofs on Solar Efficiency

  • The condition of the roof does not impact the operational efficiency of solar panels.

Incentives for Solar on Older Roofs

  • Beneficial for older properties with poor energy efficiency.
  • Can improve the building's Energy Performance Certificate (EPC) rating and property value.

Cost of Installing Solar on Older Roofs

  • Not inherently more expensive; costs can be offset by savings from integrated in-roof systems and roof strengthening during solar installation.

Warranties for Solar Panels on Older Roofs

  • Standard warranty of 25+ years, similar to installations on newer roofs.

Can I Install Solar Panels if I Have Old Tiles?

“The risk with installing solar when you have old tiles is that they can break when we come to fit the system on the roof.

What you could potentially do is, if you were considering replacing your roof, you could get a roofer to strip back all your tiles, at which point we could install an integrated (solar) system. In this sort of system, the panels effectively replace the roof tiles.

If you don’t want to do that, old tiles aren’t necessarily a problem; the system just could take longer to install as we’d need to take extra care when we’re up on your roof.”


Can I install Solar Panels on a Weak Roof?

“If you have a roof that’s been structurally tested and needs reinforcement, you should go down this route and get reinforcement. ‘W-beams’ will be installed on your roof trusses, strengthening your roof.

If you aren’t sure whether you have a weak roof, don’t worry; we always carry out a full structural survey with our Head of Installations, Justin, for every one of our installations. This way, you don’t have to guess whether your roof is too weak.


Can you Install Solar Panels on a Listed Building?

“It depends on how listed the building is. If the building is Grade 1 or 2, then we can’t go anywhere near it within the curtilage of the listed building.

What we could do is install solar panels on a neighbouring building, such as a barn or an outhouse. Alternatively, we could install a ‘ground-mounted’ system away from the listed building itself, which would sit on the ground in your garden or field.


Is the Maintenance of Solar Panels on Old Roofs Different?

“Solar systems don’t need much maintenance at all; they last 25-years or more.

If you think your roof may need repairing in that time, however, you should carry this out beforehand. Doing it while the panels are up will mean that they’ll have to take the panels down, fix the roof, then put them back up, incurring a significantly higher cost.

Doing it while you install solar is probably the most cost-effective option, as you’ll be able to share the cost of the scaffolding, roofing labour, and some tiles between the repairs and the solar installation.”


Safety Concerns Installing Solar Panels on an Old Roof

“There aren’t really any additional safety concerns when installing solar panels on an old roof. If you’re worried about the strength of the roof, we’d always do a structural survey before going ahead with any installation.

If the tiles are particularly old, then they may break. If this were the case, then we’d figure it out very quickly, and we’d take extra care.”


What Condition Should my Roof be in to Install Solar?

“Preferably, your roof should be nice and clear. If there is a chimney in the way, then we can either work around this or help you organise taking it down.

It doesn’t need to be particularly clean; if there’s moss or anything, that’s fine. We’d just be installing above the roof.”


Can I get an In-Roof System on an Old Roof?

“Yes absolutely. In fact, an in-roof system is actually quite a good idea if you have an old roof. You can replace that old roof, and then instead of re-tiling the whole roof then putting a system on top of the tiles, you can install an integrated in-roof system, saving on tile costs, and it would be a quicker installation for the solar, saving on labour.”


How Long do Solar Panels Last on an Old Roof?

“The solar panels will last the same amount of time they would on any other roof; it really comes down to the warranty of the panels. The industry standard for panel warranty is a minimum of 25-years, with some panels going up to 40-years. But there’s no reason why they couldn’t go on much longer than this. The warranty just guarantees they’ll work at a good level at the end of their period.”


Do Older Roofs Affect the Efficiency of the Solar Panels?

“No. This won’t make a difference. The solar panels will operate completely independently of the situation of the roof.”


Are There any Incentives for Solar Panels on Older Roofs?

“When it comes to solar for older properties, it’s actually a very good thing to consider. Older properties tend to have bad energy efficiency rating, and bad heat loss ratings. Solar panels can really make a difference. How much solar makes a difference to the EPC rating depends on the building and the solar installation themselves. But it’s a great way to help a building’s EPC rating and, therefore, increase its property value.”


Is it More Expensive to Install Solar Panels on an Older Roof?

“No, it’s not more expensive to install solar panels on an older roof. If you opt to replace the roof at the same time, you can install an integrated in-roof system, saving money on tiles and labour.

If your roof is structurally weak, you might as well strengthen it, then install solar while you’re there. The price of the installation won’t increase because you’re strengthening your roof. In fact, it will be cheaper because it’s quicker to install on a new roof than an older one.”


What Warranties are Available for Solar Panels on Older Roofs?

“The warranty would be 25-years plus. Which is very standard and the same as any other roof.”

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Topics: Maintenance, Solar PV