Replacing your roof before installing solar: how to decide

If your roof needs repairs, removing and reinstalling solar panels is an added expense you want to avoid. Here are some tips on how to make the decision.

Closeup photo of asphalt roof shingles.

About 98% of residential solar installations are installed on a rooftop, with the remaining 2% using a ground-mounted system.

For a homeowner who is thinking of going solar, one of the most important issues is deciding if your roof is in the right condition for solar. You can expect home solar panels to operate for 25 years or even more. If you install solar panels on a roof that later needs to be replaced, you’ll have to shoulder the extra expense of having the panels removed and reinstalled before the roofing can be done.

On the other hand, if you replace your roof too soon, you will effectively be “throwing away” years of service life and wasting money.

Because of the long operating life of solar panels, knowing whether your roof is in the right condition for a solar installation can be a tricky decision, especially if your roof is mid-life. I wrote this guide to offer some tips that might help you make the right decision.

How do you fix a roof with solar panels?

If you have solar panels and your roof needs extensive repairs or a full replacement, you will need to do what’s called a remove-and-replace. A solar installer will remove the solar panels and racking, store them, and reinstall them onto your roof after your roof work is done.

This is labor intensive. It requires multiple trips by the installation team, and the reinstallation involves the same amount of labor as a brand new solar installation.

What will it cost? You will find that the quoted prices will vary substantially, especially these days when labor shortages are a real concern for the solar industry. As a very rough guide, the price will be about $100 per panel. A typical system might be 20 panels, in which case you would be looking at roughly $2,000 for a remove-and-replace. If you have space in your garage, you can sometimes save a little money by storing them yourself.

However, the cost will vary substantially depending on the type of roof you have. In any case, this is expensive, and will prolong the payback period of your system if you end up needing it.

Some roofs are easier to work with than others

Some roofing materials are easier (and less expensive) to work with than others. Here’s a list from most expensive to least:

  • Most expensive: clay and lightweight concrete tile
  • Expensive: standard weight concrete and composition tile
  • Average expense: asphalt shingles, corrugated metal, ribbed metal
  • Least expensive: standing seam metal

Tile roofs, especially those made with brittle clay or lightweight concrete, are the hardest material for solar installers to work with. The most common method for installing solar on tile roofs is to remove the tiles, install a new asphalt roof, install the solar array on top of that, and finally reinstall the tiles around the array for aesthetics.

That’s an expensive process. If means that if you have a tile roof, you’ll want to make sure that you have a full 25 years of life left before you install solar.

The most common type of roof in the United States is asphalt shingle, and that’s what the $100 per panel estimate mentioned earlier is based on.

At the least expensive end of the spectrum are standing seam metal roofs. These are the easiest roofs to work with because there are no penetrations required. The solar racking system is clamped onto the metal seams. No holes in the roof are required, saving the installer from the additional step of making sure that the installation doesn’t leak. The clamping system is also a much faster removal and reinstallation.

However, metal roofs often have a 40 year or longer warranty, so the risk of needing a repair during the life of your system is less.

You want at least 15 years of life in your roof before installing solar

Once you have a better idea of what’s on your roof, you can make a decision about whether you can install solar panels right away, perform a roof replacement now, or wait a few years before doing a roof replacment and solar installation at the same time.

As a general guide, it would be a good idea to have at least 15 years of life remaining in your roof before installing solar panels. This is based on the fact that most good solar installers won’t recommend a solar array if the payback period is much longer than 15 years.

This means that if you get to 15 years, the solar array will have paid for itself. Even if you need to repair your roof and pay an installer for a remove-and-reinstall, the remaining service life of your solar panels should mean that the system will end up being a net financial benefit once it reaches its end of life.

Who to call if you need a roof replacement

If you’re thinking of going solar but also need a roof replacement, think about working with a solar company that specializes in both. While many solar companies subcontract their roofing work to other companies, there are roofing companies that have added solar installation to the work they do.

A good roofing company that installs solar will ensure that proper fasteners and waterproofing techniques are used for the installation, as well as doing a proper engineering evaluation of the weight-bearing capacity of the roof.

Finally, by using the same company for both the solar installation and roof repair, you can likely negotiate some cost savings versus using two separate companies.

Think about ground mounted solar

One more thing to mention: you can avoid this problem entirely by going with a ground mounted solar installation. While not everybody has a yard with the space needed for a ground mounted array, if you do have the room, you should seriously consider that option.

Costs can vary substantially, but on average a ground mounted array will add about 40 cents per watt to the final system price. This means that you get a 6 kW system, you can expect that using ground mounting will add roughly $2,400 to the price. While that’s a pretty big cost, it’s also roughly the same cost as a remove-and-replace of a rooftop system. This means that ground mounting works out to about the same price as a roof-mounted array if your roof needs servicing during the life of the system.

There are other advantages of putting your solar panels in your yard instead of your roof, such as making it easy to keep your panels clean. Read our article on ground mounted solar to learn more.

Final advice

You’ll have extra expenses down the road if you install solar panels on a roof that needs repairs during the 25 year lifespan of the array. If you’re not sure about its condition, have a local roofer perform an inspection for you. If it happens that you need a roof replacement, consider a standing seam metal roof, which is very durable and makes a solar installation easier.

Finally, if you have a big enough yard, a ground mounted array will be a more expensive option at first, but will eliminate the need to worry about the condition of your roof.

TAGS:
#Roofing

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