Say you're cross-shopping two homes priced at $550,000. One sits in Upper St Clair. The other is in Peters Township, a few miles south across the Washington County line. You pull up the listing sheets, scroll to the assessed value line, and something looks broken. The Upper St Clair home shows an assessed value around $110,000. The Peters Township home shows something closer to $530,000. Same price, same buyer, wildly different numbers on paper.
Nothing is broken. You've just crossed into a county that assesses property on a completely different logic than the one you're leaving, and if you use that assessed value as a shortcut for comparing tax burden or home value, you'll draw the wrong conclusion in a predictable direction.
The Assessed Value Line Is Telling You Two Different Stories
Pennsylvania doesn't require counties to reassess property on any regular schedule, and most don't. Allegheny County, home to Upper St Clair, Mt Lebanon, Collier Township, and South Fayette, still bases its assessments on 2012 property values. Home prices across the region have climbed substantially since then, but the assessed values on file at the county haven't moved to match. To account for that gap, the state's Tax Equalization Board publishes a Common Level Ratio every year, a single number that tells you roughly what fraction of true market value a county's assessments actually represent. In May, the board certified Allegheny County's ratio at 49.3 percent, according to the Allegheny Institute for Public Policy, which tracks the figure annually. In plain terms, a typical assessed value in Allegheny County reflects about half of what the property would actually sell for today.
Washington County runs on a different model. Rather than freezing values to an old base year and letting a statewide ratio quietly erode over a decade, Washington County sets its predetermined assessment ratio at 100 percent, a figure confirmed on the Washington County assessment office's own site. The intent is that an assessed value should track market value one for one, not sit at half of it. That's the entire reason the numbers on those two listing sheets look so far apart. You're not looking at two homes with different tax pictures. You're looking at two counties measuring the same concept with two different rulers.
| Allegheny County (Mt Lebanon, Upper St Clair, Collier Township, South Fayette) | Washington County (Peters Township) | |
|---|---|---|
| Assessment approach | Frozen to a 2012 base year | Predetermined ratio set at 100 percent |
| 2025 Common Level Ratio | 49.3 percent | Designed to sit near market value |
| What the assessed figure tells you | Roughly half of true market value | Intended to equal market value |
The Pennsylvania Department of Revenue publishes the current ratio table every summer, and the factor tied to this year's Allegheny figure applies to real estate transactions recorded between July 2026 and June 2027.
What To Actually Compare Instead
None of this means Peters Township taxes more heavily than Allegheny County suburbs, and it doesn't mean the reverse either. The assessed value alone tells you nothing about what you'll actually owe until you multiply it by the local millage rate, and that rate is set independently by the county, the municipality, and the school district in each case. A buyer who sees a higher raw assessed value in Peters Township and assumes a heavier tax load is comparing an apple to an entirely different fruit.
The number that actually matters is the current annual tax bill, not the assessed value that produced it. When you're weighing two homes on either side of the county line, ask for the seller's most recent tax bill directly, or have your agent pull it from public records. That figure already accounts for each county's ratio and each district's millage, so it's the only number that translates cleanly between Allegheny and Washington counties.
This matters just as much once you're under contract. Mortgage lenders build your escrow estimate off the property's current tax bill, and an appraiser or loan officer unfamiliar with the Allegheny-to-Washington ratio gap can misjudge how a home's assessed value relates to its sale price, particularly on new construction where no tax history exists yet. If you're financing a purchase in Peters Township after years in an Allegheny County suburb, flag this early with your lender so the escrow projection reflects Washington County's actual millage rather than an assumption carried over from your last home.
Peters Township Also Isn't One Market
Once you've cleared the county-line confusion, there's a second layer worth understanding before you start comparing listings inside Peters Township itself. The township splits into two distinct halves that behave like separate small markets, McMurray and Venetia, and a single township-wide median glosses over real differences in what your money buys in each.
McMurray is the commercial and convenience side of the township, built around a denser mix of homes with smaller lots and closer proximity to Donaldson's Crossroads, the retail node at Route 19 and Valley Brook Road. It's also home to Valleybrook Country Club and Lindenwood Golf Course, and to Peterswood Park, which sits roughly in the middle of the township and serves both sides.
Venetia, by contrast, is where the open land and the new construction have concentrated. Builders like Benjamin Marcus Homes have developed communities such as Tuscany II on larger, more scenic lots, and the area has easier access to Mingo Creek Park, with its walking trails, dog park, and equestrian area, along with the 1781 Club, a newer golf club with a clubhouse and simulator bays. Homes in the Brush Run and Valley Brook sections have routinely closed above $750,000 in the early months of 2026, while listings in Venetia and parts of McMurray have started closer to $385,000 over the same stretch. That's a spread wide enough that treating "Peters Township" as one price tier will steer a buyer's expectations in the wrong direction before they've toured a single house.
Even The Subdivision Name Can Mislead You
There's a smaller version of the same lesson buried in the township's street signs. A subdivision marketed as McMurray Highlands is actually located in Venetia's zip code, not McMurray's. If a buyer is scanning listings by neighborhood name and assuming it maps cleanly to the side of the township they think they're choosing, that assumption can be wrong.
The pattern running through all of this, the county line, the township split, the subdivision name, is the same one. Labels are a starting point, not a verified fact. Whether it's an assessed value, a township boundary, or the name on a development sign, the number or word on the page is only useful once you've confirmed what it actually represents on the ground.
Frequently Asked Questions
Will a higher assessed value mean I pay more in property taxes in Peters Township? Not by itself. Your actual bill comes from multiplying the assessed value by the combined county, municipal, and school district millage rate. Compare tax bills directly rather than assessed values when you're weighing homes across a county line.
Does the Allegheny-Washington ratio gap affect my mortgage escrow? It can, particularly if your lender's estimate is built off an assumption carried over from a previous Allegheny County purchase. Ask your loan officer to confirm the escrow projection is based on Peters Township's actual current tax bill and Washington County's millage, not a ratio pulled from your last home.
Is Washington County likely to change its assessment approach soon? Common Level Ratios are recalculated statewide every year by the state's Tax Equalization Board, and any county can see its ratio shift as sales data comes in. There's no indication of a countywide reassessment change on the horizon in Washington County, but buyers should always confirm current figures with the county assessment office rather than relying on last year's numbers.
Numbers that look identical across a county line rarely mean the same thing, and a subdivision name doesn't always tell you which park or golf course you'll end up closest to. If you're weighing a move into Peters Township, or trying to figure out what a listing's assessed value actually implies about your future tax bill, The Burgh Luxury can walk through the real numbers with you street by street. Let's Connect.
