Solar on a rowhome
Single-attached rowhomes are 55.6 percent of the housing stock, the dominant form in the city, and they change the design problem in three ways. The roof is usually smaller than a detached house's, so the ceiling on system size is lower and every square foot counts. It is often flat or close to it, which means a tilted or ballasted mounting frame rather than panels laid on a pitch. And it meets the neighbour at a party wall, so where your roof ends is a question with a legal answer as well as a physical one.
None of that rules solar out. It does mean the survey matters more than the sales visit. Ask for the roof area to be measured on site, for the structure to be assessed for the added load of a ballasted array, and for the property line to be established rather than estimated from an aerial image. A flat roof also raises questions a pitched one does not: how the array is secured against wind, how water still drains, and whether the membrane is penetrated.
Roof condition deserves its own conversation on an older rowhome. If the covering is near the end of its life, putting an array on it means paying to remove and reinstall the panels when it is replaced. Ask what that costs and whether doing the roof first is the cheaper sequence.
When the roof is not yours to decide about
Buildings of 20 or more units hold 15.1 percent of the city's housing. There the roof belongs to the building owner or the condominium association, a resident cannot commission an installation alone, and an array on the building normally offsets a building account rather than an individual apartment.
Two-unit buildings hold 7.9 percent and three and four unit buildings 6.5 percent. In those the obstacle is smaller but specific: roof rights may involve more than one owner, and an array feeds a single electrical service, so it reduces one household's bill rather than splitting between them. Both points are cheaper to settle in advance than to discover at commissioning.
If you are in one of these buildings, the useful move is to bring the question to whoever does control the roof, with the numbers attached: what the roof can carry, what full retail net metering is worth against the building's own consumption, and what the array would cost. That is a more productive conversation than asking whether solar is allowed.
Full retail net metering, and the annual reconciliation
Pennsylvania's Public Utility Commission sets net metering at the full retail rate. Excess generation is credited kWh for kWh against your usage in each billing period, which is the simplest arrangement a solar owner can be on: a kilowatt-hour you export is worth a kilowatt-hour you draw back later.
The catch arrives once a year. Any credit still banked at the annual reconciliation is settled at the regulated Price to Compare rate rather than at full retail, and the Price to Compare is a narrower number. So credit you actually use during the year is worth full retail, and credit you never use is worth less.
That is the sizing argument in Pennsylvania, and it is a gentler one than in states without full retail crediting. A system matched to your annual consumption captures full value. A system built well beyond it banks credit that gets cashed out at the lower rate at reconciliation. Bring twelve months of bills, and ask your installer to confirm the current net metering tariff for PECO specifically, since terms are set per utility.
Alternative Energy Credits, and how much to count on them
On top of net metering, Pennsylvania's Alternative Energy Portfolio Standards Act lets the owner of a certified solar system earn one Alternative Energy Credit for every 1,000 kWh generated. Those credits can be sold to utilities and suppliers that need them for compliance, which makes them a second stream of value separate from bill savings.
To participate you register the system and connect it to the PJM Generation Attribute Tracking System through the Pennsylvania AEPS portal, either directly or through an aggregator or broker. It is administrative work rather than difficult work, but it is work, and it does not happen automatically when the array is switched on.
The important qualification is that AEC prices are set by supply and demand on an open market and fluctuate. They should not be treated as a reliable income stream, and a quote that builds a fixed annual AEC figure into a payback calculation is presenting a market price as though it were a tariff. Ask any installer who mentions AECs what price they assumed and where it came from, and contact an aggregator to confirm current rates before registering.
Output, and the credit that no longer applies
Plan on roughly 1,298 kWh a year for every kW installed. The figure is derived from satellite irradiance data with a standard performance ratio applied rather than measured on local roofs, so it is a screening number rather than a promise. On a rowhome the binding constraint is usually usable area rather than sun, so the more useful question is how many panels fit well, not how many fit.
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 Philadelphia cannot claim it. Be aware that several widely used sources have not been updated and still carry the old text, so a quote or a guide showing it is not necessarily dishonest, just out of date. Either way the payback figure that follows from it is wrong.
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 pass part of that value through in the rate they offer. Ask them what they claim and what reaches you, and confirm it with a tax advisor rather than with the sales material.