Detached or attached, and why the quote should look different
Single-detached houses are 36 percent of Bethlehem's 32,348 housing units and single-attached rowhome-style units 27.9 percent, so the city is close to evenly divided between the two. That is unusual, and it means general advice written for one type will mislead roughly half the people reading it.
On a detached house the roof is normally broad enough that your consumption, not your geometry, sets the system size. The right conversation is about which plane, how much shade, and the age of the covering, and the right quote is one modelled against twelve months of your own kilowatt hour totals.
On a rowhome the plane is narrow, often shallow, and bounded by party walls. Area binds before irradiance does, so the useful question is how many panels fit well once setbacks, vents and existing equipment are allowed for. Ask for a layout drawing rather than a capacity figure: a quote expressed only in kilowatts tells you nothing about whether those panels fit your actual roof, and two quotes that differ in size usually differ in what they assumed about it.
Attached property also brings shared structure into play. Fixings, penetrations and future roof access affect the buildings either side, and coverings on a row are often replaced as a block rather than unit by unit. Establish what agreements exist before a design is drawn. Buildings of 20 or more units are 9.5 percent and 5 to 9 unit buildings 7.5 percent, where the roof belongs to an owner and the route is a written proposal rather than a quote.
Full retail during the year, a lower rate for what is left
Pennsylvania's PUC sets net metering at the full retail rate, and excess generation is credited kilowatt hour for kilowatt hour against your usage each billing period. That is a strong arrangement, better than the supply-only crediting new customers face in Illinois and better than avoided-cost approaches elsewhere.
The part that decides system size comes once a year. The utility reconciles any remaining banked credit at the regulated Price to Compare rate rather than at full retail. So a kilowatt hour you generate and use, directly or via a credit consumed during the year, is worth full retail. A kilowatt hour still sitting in the bank at reconciliation is worth less.
The rule that follows is simple and it is the most useful thing on this page: build to what you actually consume across a year. Generation absorbed by your own usage keeps its full value; generation accumulating into a year-end balance does not. Ask your installer to model against twelve months of your own kilowatt hour totals and to say explicitly what they assume happens at reconciliation.
Ask PPL Electric Utilities when in the year reconciliation falls. Whether the settlement lands before or after winter has drawn down your summer surplus changes what a given size is worth to you, and it is a question with a specific answer.
Alternative Energy Credits are a market price, not a rate
Beyond net metering, solar owners can register systems for Pennsylvania's Alternative Energy Credit market, and quotes often mention it. It is a genuine second stream of value, separate from bill savings.
The qualification matters more than the opportunity. AEC prices are set by supply and demand on an open market and fluctuate, so they should not be treated as a reliable income stream. A payback calculation with a fixed annual AEC figure baked in is presenting a market price as though it were a tariff.
Ask any installer who includes AECs what price they assumed, where that price came from, and to show the payback with the AEC line removed. If the project only clears with an assumed AEC price, the decision you are being asked to make is a market bet rather than an equipment purchase, and it is fair to want that separated out before you sign.
Output, and the credit that no longer applies
Plan on roughly 1,259 kilowatt hours a year for every kilowatt installed on a well oriented, unshaded array. That is a screening figure derived from irradiance data rather than a measurement from Bethlehem roofs, so treat it as a ceiling. On an attached property, expect usable area to bind before irradiance does.
Orientation erodes it first and cannot be bought back with better equipment: a south-facing plane produces the most, east and west planes give up output, and a north plane rarely repays the hardware. Shading erodes it most, because it takes production out of the middle of the day, so ask for an assessment across the whole year rather than the hour of the site visit.
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 Bethlehem now cannot claim it. Several widely used sources have not been updated and still carry the old text, so a quote showing it may be out of date rather than dishonest, but the payback it produces is wrong.
Ask for the arithmetic rebuilt from what remains: retail-rate credits during the year, whatever the annual reconciliation leaves, the electricity you stop buying, and any AEC value shown as its own line. If you take a lease or power purchase agreement rather than buying, the provider may claim the business version of the credit under Section 48E and reflect part of it in the rate offered, which is a question for the provider and a tax advisor.