Energy Decision # 57 - Rooftop Solar Structural Explained: Re-Roof or Walk Away

Now, let's talk about the lifespan mismatch for a second.

So what is this lifespan mismatch? Here's what it looks like from where you sit.

A solar proposal shows up with a 25-year savings projection.

Your roof already has 12 years on it.

And nowhere in that projection is there a line for what happens when the roof has to be replaced with the panels sitting on it.

The lifespan mismatches the gap between how long solar panels last and how long the roof under them lasts.

Panels are built for about 25 to 30 years.

The membrane on a typical commercial flat roof, which is the waterproof sheet that keeps water out of the building, commonly lasts 15 to 20 years.

Here's why it happens.

Solar usually gets considered on a roof that's already partway through its life.

Tri-Van Roofing, a commercial roofing firm, notes that many commercial roofs are already 8 to 15 years old when solar first comes up.

So, the roof wears out while the panels still have years of production left.

And when that happens, somebody pays a crew to take the panels down, replace the roof, and put the panels back.

That work is called removal and reinstallation.

So how do you measure the lifespan mismatch? The number to know is remaining useful life.

Remaining useful life is how many more years a roofing professional judges your roof will keep the water out.

Roof age is only a starting point.

A 15-year-old roof may have 20 years left.

A 12-year-old roof may have serious problems developing under the surface.

The warranty end date is a reference point, but it doesn't tell you the roof's condition.

Compare your remaining useful life against the 25 to 30 years the panels will sit up there.

Firms that do this work put the cutoff in slightly different places.

The line most of them land on is about 10 to 15 years.

If your roof has less remaining useful life than that, re-roofing before solar is generally the right call.

When those two numbers don't line up, the fix is to re-roof first and design the solar around the new roof.

Now, let's talk about the lifespan mismatch for a second.

So what is this lifespan mismatch? Here's what it looks like from where you sit.

A solar proposal shows up with a 25-year savings projection.

Your roof already has 12 years on it.

And nowhere in that projection is there a line for what happens when the roof has to be replaced with the panels sitting on it.

The lifespan mismatches the gap between how long solar panels last and how long the roof under them lasts.

Panels are built for about 25 to 30 years.

The membrane on a typical commercial flat roof, which is the waterproof sheet that keeps water out of the building, commonly lasts 15 to 20 years.

Here's why it happens.

Solar usually gets considered on a roof that's already partway through its life.

Tri-Van Roofing, a commercial roofing firm, notes that many commercial roofs are already 8 to 15 years old when solar first comes up.

So, the roof wears out while the panels still have years of production left.

And when that happens, somebody pays a crew to take the panels down, replace the roof, and put the panels back.

That work is called removal and reinstallation.

So how do you measure the lifespan mismatch? The number to know is remaining useful life.

Remaining useful life is how many more years a roofing professional judges your roof will keep the water out.

Roof age is only a starting point.

A 15-year-old roof may have 20 years left.

A 12-year-old roof may have serious problems developing under the surface.

The warranty end date is a reference point, but it doesn't tell you the roof's condition.

Compare your remaining useful life against the 25 to 30 years the panels will sit up there.

Firms that do this work put the cutoff in slightly different places.

The line most of them land on is about 10 to 15 years.

If your roof has less remaining useful life than that, re-roofing before solar is generally the right call.

When those two numbers don't line up, the fix is to re-roof first and design the solar around the new roof.