Summary
A typical Greater Rochester home needs about 1 ton of cooling per 600-700 square feet of conditioned space, but that’s a starting point, not the answer. The real number depends on insulation, windows, ceiling height, sun exposure, ductwork condition, and the home’s air-tightness. Most Rochester homes need somewhere between 2 and 4 tons. The biggest mistake we see is oversizing – and it costs you in humidity, comfort, and lifespan. Here’s how proper sizing actually works.
Quick reference (rule of thumb only)
| Home size (conditioned sq ft) | Rule-of-thumb tonnage | What we usually find |
|---|---|---|
| 900-1,200 sq ft | 1.5-2 tons | Older Brighton / East Rochester capes often need closer to 2 tons |
| 1,200-1,800 sq ft | 2-3 tons | Most Pittsford and Fairport ranches sit here |
| 1,800-2,400 sq ft | 3-3.5 tons | Typical Victor / Farmington 1990s-2000s build |
| 2,400-3,200 sq ft | 3.5-4 tons | Larger Pittsford / Penfield / Canandaigua homes |
| 3,200+ sq ft | 4-5 tons or zoned | Often better with two systems or zoning |
This table will be wrong for your specific home roughly 30% of the time. That’s why we do a real load calculation, not a square-foot guess.
Why the square-foot rule fails (and why it costs you)
The rule-of-thumb chart above is what most contractors quote on the phone. It’s also why a lot of Rochester homeowners end up with oversized AC units. Here’s what changes the actual answer:
- Window count and orientation – a Pittsford colonial with 14 west-facing windows needs more cooling than the same square footage with 6 north-facing
- Insulation – a 1920s Park Avenue home with original plaster walls needs more cooling than a 2005 Victor build with R-19 walls
- Ceiling height – 9-foot or vaulted ceilings add 15-25% to the load
- Ductwork condition – leaky ducts in unconditioned attic or crawlspace can lose 20-30% of cooling before it reaches the rooms
- Number of occupants – each person adds about 400 BTU of internal heat gain
- Air-tightness – a tight home holds the cool air; a leaky one fights it
The right answer comes from a Manual J load calculation, the residential load standard from ACCA. We do this on every install.
Pro Tip
If a contractor quotes you a tonnage by phone or after a 5-minute walkthrough, get a second opinion. We’ve seen homes in Pittsford, Fairport, and Henrietta where the previous installer bumped the tonnage up “just in case” – and the homeowner spent the next 12 summers fighting humidity and short-cycling. Right-sized beats oversized every time.
Why bigger is NOT better for AC sizing
This is the part most people get wrong. An oversized AC sounds like it should cool faster – and it does cool the temperature down faster. But it doesn’t run long enough to remove humidity. Result: a 72-degree house that feels muggy, sticky, and uncomfortable.
What an oversized AC does in a Rochester summer:
- Short-cycles – turns on, blasts cold air for 6 minutes, shuts off, repeat. Each cycle is the highest-stress moment for the compressor
- Doesn’t dehumidify – dehumidification happens during longer run times. Short cycles skip this
- Uneven cooling – rooms farther from the air handler don’t get the time they need to come down
- Wears out faster – a compressor rated for 12-15 years can fail in 8-10 with constant short cycling
- Higher utility bills – the start-up surge is the most energy-intensive moment of any cycle
A right-sized AC runs longer, removes humidity properly, and costs less to operate. Counterintuitive, but it’s the single biggest “lesson learned” we hear from Rochester homeowners on their second install.
“We initially asked for quotes from a very large contractor in Rochester with those famous red trucks, and a very reputable contractor based out of East Rochester. Both ‘salesmen’ insisted that the furnace needed to be upgraded off the bat, and that our desired ductwork layout was unattainable. Then I called Dalton. Darren (the owner) showed up a day after first contact and personally quoted the job. He was genuinely interested in coming up with a solution that satisfied the client’s goals. We hired Dalton, their crew showed up on time, and the price was right. Two years later the system is still running strong.”
May 2020 · Architecture firm · Forced-air retrofit on 1920s colonial
What Manual J actually checks
A real load calculation considers about 30 inputs. The big ones for Greater Rochester homes:
- Square footage of every conditioned room
- Window area, type (single / double / low-E), and direction
- Wall, ceiling, and floor insulation R-values
- Air infiltration (blower-door tested when possible)
- Climate data for our specific zip code
- Occupancy count
- Internal heat gain (kitchen, electronics)
- Ductwork location (conditioned vs. unconditioned space) and condition
For a typical Pittsford / Victor / Fairport home, the calculation takes us 30-45 minutes during the proposal visit. Output: actual BTU heat gain in summer and BTU heat loss in winter. From those, we size the AC.
What new central air costs in Rochester (sizing-related)
| System size | Typical install cost (Greater Rochester) |
|---|---|
| 2-ton AC | $5,000-$7,000 |
| 2.5-ton AC | $5,500-$7,500 |
| 3-ton AC | $6,000-$8,500 |
| 3.5-ton AC | $6,500-$9,000 |
| 4-ton AC | $7,500-$10,000 |
| 5-ton AC | $8,500-$12,000 |
Higher SEER2 ratings (16+, 18+) push these higher but qualify for more rebates. We pull the current RG&E, NYSEG, and federal tax credit numbers for your address as part of every AC installation proposal.
Want a Real Load Calc, Not a Phone Guess?
Free in-home AC proposal. We do the Manual J load calc, walk you through the windows, ductwork, and insulation, and quote the right size system. Honest, no pressure.
Family-owned in Victor, NY since 1989.
Frequently Asked Questions
What size AC for a 2,000 sq ft Rochester home?
Usually 3 to 3.5 tons, but it depends on insulation, windows, and ductwork. A 2,000 sq ft 1920s Pittsford colonial often needs more than a 2,000 sq ft 2005 Victor build. Manual J load calc gives the real answer.
Is bigger always better for AC?
No. Oversized AC short-cycles, fails to dehumidify, wears out faster, and costs more to run. Right-sized is the goal.
How many BTUs in a ton of cooling?
12,000 BTU per hour. So a 3-ton AC removes 36,000 BTU per hour at design conditions.
Should I match the AC tonnage to my old unit?
Not always. If your old AC was oversized, repeating the mistake locks in another 12-15 years of bad performance. Get a fresh load calc – the answer might be smaller, not larger.
Does SEER rating affect sizing?
No. SEER measures efficiency. Tonnage measures capacity. They’re independent. A 3-ton 14 SEER and a 3-ton 18 SEER both remove the same amount of heat per hour – one just uses less electricity.
Can a 2.5-ton AC handle a 1,800 sq ft Rochester home?
Often yes. With reasonable insulation and a tight envelope, 2.5 tons cools 1,600-2,000 sq ft well in our climate. Older homes or homes with lots of west-facing glass may need 3 tons.
Family-owned in Victor, NY since 1989. Serving Monroe, Ontario, and Wayne counties. Built on Trust. Powered by Principle. The DALTON Team Is On Hand to Help.