Roof age and solar: when to replace the roof first, and what the codes say about the roof itself

The roof decision is a timing decision

Panels stay on the roof for as long as the system runs. If the roof under the array has to be replaced in that time, the panels come off and go back on, and that removal and reinstall is its own job with its own cost line. When to remove or reinstall panels covers that job in each state.

So the question a homeowner can settle before signing is one of order: roof first, or panels now and a removal later. None of the code pages or utility pages this site cites gives a roof age or a remaining-life figure, so ask the company to state in writing whether its quote assumes your current roof stays. What those pages do give is what each state’s code expects of the roof, and the decisions below rest on that and on ordinary contract questions.

There’s no federal credit attached to the timing either way. The IRS says the Residential Clean Energy Credit “is not available for any property placed in service after December 31, 2025,” and that includes battery storage.

Michigan: what the code expects of the roof

The 2015 Michigan Residential Code is the current edition as of LARA’s notice, and Michigan’s rule R 408.30521a adds a rooftop PV section to it:

• PV panel systems mounted on or above the roof covering must comply with the code, Section R324 and NFPA 70.
• The roof must support the loads.
• The system is installed per the manufacturer’s instructions, with roof penetrations flashed and sealed.

Section R324 covers access and ventilation. As one city’s checklist reproduces the residential code, pathways at least 3 ft wide run from eave to ridge, single-ridge roofs need two of them, panels sit at least 18 in. from a hip or valley when they’re on both sides, and panels stay at least 3 ft below the ridge. The same checklist caps arrays at 150 ft by 150 ft, exempts roofs at 2:12 or flatter, and says ground mounts follow local fire separation. It’s a city document, not LARA’s text, so read those numbers as the shape of the rule and let the building office give the exact ones.

Midland shows how one city asks for this. It publishes separate Photovoltaic Systems Building and Photovoltaic Systems Electrical forms. They ask whether the system is on the roof or the ground, and they want structural calculations along with three-foot access paths, 18-inch valley clearance and 3 ft below the ridge.

The Michigan Public Service Commission’s consumer tips put rooftop panels at about 100 sq ft of roof per kW. They also say city or county rules may require a permit and inspection. The permit is pulled under the contractor’s state license number, and how solar permits work in Michigan sets out who does what.

Decisions for a Michigan roof

If the roof will need replacing during the system’s life, there are three options, and each company can price all of them:

1. Replace the roof first, then install the system.
2. Install now and plan a removal and reinstall when the roof is replaced, with that cost as its own line. The Michigan panel removal and reinstall page describes the job.
3. Put the array on the ground instead. The ground mount page covers that job, and the checklist above says ground mounts follow local fire separation.

If your roof was replaced recently, bring its paperwork to the quote. Whatever you choose, ask the solar company for its warranty on the roof penetrations in writing, along with who’s responsible if one leaks.

California: what the code expects of the roof

Government Code section 65850.5 says a city or county shall administratively approve applications to install solar energy systems through a building permit or similar nondiscretionary permit, with review limited to health and safety.

Access is set in the 2022 California Residential Code, R324.6. It calls for not fewer than two pathways on separate roof planes from the lowest roof edge to the ridge, each not less than 36 inches wide, and at least one of them on the street or driveway side. At a horizontal ridge the clear setback is 18 inches on both sides for arrays covering 33 percent or less of the plan-view roof area, and 36 inches above that. Where sprinklers are installed under NFPA 13D or R313, the threshold becomes 66 percent. Roofs with a slope of 2:12 (17 percent) or less are exempt, and so are detached non-habitable structures.

Those values come from the 2022 edition. The 2025 code took effect January 1, 2026, and its requirements may differ, so ask your building department which edition it’s applying.

Decisions for a California roof

The same choice of order applies. Ask each company whether its quote assumes the existing roof stays, includes a new roof, or prices a removal and reinstall later; the California removal and reinstall page describes that job.

California adds one date. Revenue and Taxation Code section 73 excludes a new active solar energy system from reassessment only for systems completed before January 1, 2027. A system completed on or after that date falls outside the exclusion as the statute stands.

A newly built single-family home is a different case. The 2025 Building Energy Efficiency Standards, effective January 1, 2026, require solar PV on newly constructed single-family homes under section 150.1(c)14, with five exceptions, and the required size depends on the solar-access roof area. That standard doesn’t cover additions or alterations, so it doesn’t decide anything about the roof on an existing house.

Questions to put to the company

These work on any roof, in either state:

1. Does the quote assume the current roof stays, and for how long?
2. If the roof is replaced while the panels are up, who removes and reinstalls them, and what does that line cost?
3. What warranty covers the roof penetrations, and who answers if one leaks?
4. Which layout drawing goes to the permit office, and does it show the access pathways?

Lay the quotes side by side and keep the ones that price the roof options in writing.