What a Detroit roof makes in a year
The planning figure for Detroit is about 1,203 kWh a year for every kW of panels you install. It is derived rather than measured: a standard performance ratio applied to satellite irradiance for the area, not a number DTE or the city publishes. Use it to decide whether the idea is worth pursuing at all, and let a site survey produce the number that goes into a contract.
What moves it on a specific house is orientation, pitch, usable area and shade. A south-facing plane generates across the whole day, while east and west faces concentrate their output at one end of it. Pitch affects both production and how fast snow clears. Usable area is what remains after vents, stacks, chimneys and setbacks are subtracted, and it is usually smaller than the roof looks from the street. Shade is the factor people underestimate, because a winter sun sits low enough to reach under branches that clear the roof easily in July.
Ask for the model broken out plane by plane rather than as one house total. Panels on a compromised face still raise the headline annual figure while earning less per dollar spent, and that breakdown is what lets you compare two quotes as though they were the same product rather than two different ones with similar totals.
Rider 18, and what DTE pays for the power you export
Michigan does not have traditional one-for-one net metering. The Michigan Public Service Commission replaced it with a Distributed Generation program, and DTE's version is Rider 18, open to systems up to 550 kW. Under it, the power you draw from the grid, your inflow, is billed at the retail rate of whichever schedule Rider 18 attaches to. The power you send back, your outflow, is valued on a separate basis.
Outflow is valued at the power supply component of that retail rate, including Power Supply Cost Recovery. That is deliberately narrower than the full retail rate, because the retail rate also carries delivery and other charges that an exported kilowatt-hour does not earn. The practical result is that a kilowatt-hour you send to the grid is worth less than a kilowatt-hour you avoid buying, and that is the single most important sentence here for anyone modelling a payback.
That gap is why the order of operations matters more in Michigan than in a full net metering state. Using your own generation as it is produced, or storing it to use later, is worth more than exporting it. Ask your installer to show the split between self-consumed and exported production in the model behind the quote, because two systems with identical annual output can be worth different amounts depending on where that split falls.
What happens to credit you do not use
The credit your outflow earns offsets all electric charges at the premise except securitization charges. That is broader than it first sounds, because it is not confined to the energy line on the bill: the credit reaches the delivery charges too, with securitization the one carve-out.
Anything left over is carried forward in what DTE calls an Excess Generation Bank. A bank is genuinely useful in a climate with long summer days and a weak December, because surplus from June is still available against the months when the array produces least. It also means a system that runs ahead of your consumption every month of the year is accumulating credit rather than money.
Which is the sizing argument. Michigan's 2023 Public Act 235 lets a customer build up to 110 percent of their prior 12 months of usage, and that is a ceiling rather than a target. Because export is valued below retail and unused credit sits in a bank, the useful size for most households is the one that matches their own consumption, not the one that fills the available roof. Bring twelve months of bills to the first conversation and size against those.
Who actually controls the roof in Detroit
Detroit has 329,393 housing units and 64.3 percent of them are single-detached houses. If you are in one, you own the decision from end to end: the design, the Rider 18 application, the interconnection and the inspection. That is the simplest version of this process, and here it is the majority case.
Apartments in buildings of 20 or more units are 13.4 percent of the stock. An array on one of those is a building-owner project rather than a resident one, and it normally offsets a building account rather than any individual apartment, so the person who benefits is not automatically the person under the roof. Two-unit buildings are a further 6.4 percent, and they raise a narrower question: an array feeds one electrical service, so which meter it connects to decides whose bill it reduces. Settle that with the other household before anyone signs anything.
Single-attached row houses are 7.1 percent. They share a roofline and a wall with the neighbouring unit, which does not rule solar out but does mean the roof plane, the fire separation and the mounting all need looking at on site rather than from an aerial image. Ask whether the installer has surveyed the actual property line or has been working from a satellite view.
Paying for it in 2026
The 30 percent federal residential tax credit under Section 25D applied through December 31, 2025 and is not available for a purchased home system placed in service after that date. A 2026 purchase in Detroit cannot claim it. Any quote, payback calculation or online calculator that still includes it is describing a year that has ended, and the figure it produces is wrong by a wide margin.
If you go solar through a lease or a power purchase agreement rather than buying, the provider may still claim the business version of the credit under Section 48E and pass part of that value through in the rate they offer you. That is a question to put to the provider directly and to check with a tax advisor, not an assumption to build into your own budget.
On financing, Michigan Saves is a nonprofit green bank that connects homeowners with participating credit unions for qualifying improvements, solar photovoltaic systems, battery storage and EV chargers among them. Rates start at 5.99 percent APR with terms up to 180 months, you have to use an authorized contractor, and the application runs through the Michigan Saves portal. Lender rates and the contractor list both change, so check the current terms at the point you are quoted rather than relying on a number someone gave you last year.