Your utility is the city, so ask the city
Rochester Public Utilities is municipally owned, which puts it in a different category from the investor-owned utilities most Minnesota solar material describes. Under Minnesota's net metering statute, a qualifying facility under 40 kW interconnected to a public utility may elect compensation at the average retail utility energy rate for net excess generation. That is a good arrangement, and it is the framework you will find quoted in general guides.
What we are not going to do is assume it describes RPU. A municipal utility sets its own terms for customer generation, and the gap between a statutory framework for investor-owned utilities and a municipal utility's own tariff is exactly the sort of thing that turns a payback calculation into fiction. This page will tell you what to ask rather than what to expect.
Put these questions to RPU in writing before you accept a quote: may a customer-owned generator connect, what is the application process and what documents does it need, what interconnection and metering equipment is required and at what cost, how is net excess generation compensated and at what rate, and does that rate have an end date or an annual reconciliation. Ask whether there is a system size limit as well.
Do not accept an installer's assurance in place of RPU's answer. An installer working mostly in the Twin Cities may be quoting Xcel terms without noticing which utility serves your address, and you carry the consequences if that assumption is wrong. Ask them directly which Rochester installations they have interconnected and when.
A notable townhouse share, and what a shared roofline means
Single-family detached homes are 58.5 percent of Rochester's 54,492 housing units, so most households control their own roof outright and can go straight to quotes.
The distinctive figure is the 8.9 percent in single-unit attached townhouse-style homes, a larger share than in most comparable Minnesota cities. A townhouse shares a roofline and a wall with the units beside it, and that changes the project in two ways worth knowing before a design exists.
First, the usable roof area on your section is often narrower than it looks from the street, and the ridge may not run the way a satellite image suggests. Ask for an installer to look at the actual planes rather than quoting from imagery. Second, fixings, penetrations and future access to the roof affect the structure your neighbours share, so there is usually an association or an agreement governing what may be attached. Find the governing document and read it before you commission a design.
Buildings of 20 or more units are 17.6 percent of the stock, where the roof belongs to the building owner. There the route is a written proposal covering cost, ownership of the equipment, insurance and roof replacement, put to the owner rather than to an installer.
What a Rochester roof produces
Plan on roughly 1,260 kilowatt hours a year for every kilowatt installed on a well oriented, unshaded array. That is a good figure for the upper Midwest, and it is a screening number derived from irradiance data rather than a measurement from local roofs, so treat it as a ceiling for your address.
Orientation erodes it first and cannot be recovered with better equipment. A south-facing plane produces the most, east and west planes produce usefully but give up output, and a north plane rarely repays the hardware. On a townhouse, plane choice may be constrained by which section of roof is yours, which is another reason to establish the ownership question first.
Shading erodes it most, because it removes production in the middle of the day when the array would otherwise be strongest. Ask for an assessment that considers the whole year rather than the hour of the site visit. Then check the roof covering age: panels outlast most coverings, so one within a few years of replacement should be replaced before the array goes on rather than paying later to remove and reinstall it.
Minnesota winters take days of production out entirely when snow sits on the glass, and a steeper plane clears faster than a shallow one. That does not change the annual figure much, but it does change when the production arrives, which matters if your utility reconciles a credit balance at a fixed point in the year.
The federal credit no longer applies to a purchase
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 purchase in Rochester now cannot claim it.
That is a large change rather than a technicality. The credit was big enough to carry a substantial share of a residential project, so removing it lengthens payback, raises the effective cost of each kilowatt hour saved, and weakens the case for adding a battery.
A great deal of published material has not been updated, so a quote, guide or online calculator that still applies the credit may be out of date rather than dishonest. The payback figure it produces is wrong either way. Ask any installer to show the arithmetic without it.
Rebuild it instead from what you can actually verify: RPU's own compensation terms for net excess generation, the electricity you stop buying, and the installed cost including interconnection and metering charges. If you take a lease or a power purchase agreement rather than buying, the provider may claim the business version of the credit under Section 48E and reflect part of that value in the rate they offer, which is a question for the provider and a tax advisor rather than an assumption for your budget.