Foley AC Replacement Sizing in 2026: 3-Ton vs 4-Ton vs 5-Ton, Backward from the Bill

Picture two August 2025 power bills in a 1,950 sq ft Foley home: one with a 4-ton AC, one with a 3-ton variable-speed. The variable-speed bill is meaningfully lower — often $40-$60/month — and over 96 months that's a substantial chunk of the install delta. The 3-ton variable-speed costs more upfront than the builder-grade 4-ton, but on 8-year total cost of ownership the math frequently flips. The Foley sizing math runs backward from the bill, and most contractors won't show you that page.

This post walks through three Foley sizing scenarios — 3-ton, 4-ton, and 5-ton replacements — with the framework for comparing them on 8-year total cost of ownership rather than headline install price. The point is to show why the cheaper install is sometimes the more expensive house, and why the more expensive install is sometimes the cheaper house, depending on what's behind the equipment. For written quotes on your specific home, call 251-383-HVAC.

How to read a sizing decision in reverse

Most homeowners get this conversation handed to them forwards: contractor walks the house, eyeballs the existing equipment, says "you've got a 4-ton, we'll put in a 4-ton." That's how Foley ended up with a generation of oversized equipment in Glenlakes, Cypress Gates, and Cottages on the Greene — every spec builder in the early 2000s used the same lazy rule of thumb and every replacement contractor since has matched what was already there.

Run it backward instead. Start from the August power bill. A Foley home with a properly sized variable-speed system and decent ductwork should run a peak summer bill in the $260-$310 range for 1,800-2,000 sq ft. If your bill is $340-$400, something in the equipment-plus-envelope chain is wrong, and replacing the equipment with the same size you've always had is going to give you the same bill you've always had.

The four things that move that number:

• Equipment efficiency rating (SEER2 in 2026; was SEER through 2022)
• Equipment staging (single-speed vs two-stage vs variable-speed)
• Equipment sizing relative to actual load (Manual J calculation, not square-footage rule of thumb)
• Duct system condition and insulation

A 4-ton single-speed system installed correctly through good ductwork can outperform a 3-ton variable-speed installed badly through leaky ductwork. The equipment label only tells part of the story. The duct side gets covered in the Foley pre-summer punch list approach and the builder-grade vs premium comparison — same logic applies to Foley.

Scenario one: 1,950 sq ft Foley single-story, 3-ton vs 4-ton

This is the most common Foley scenario. Single-story home in Glenlakes or Cottages on the Greene, built 2008-2018, currently running a 4-ton single-speed system that's 11-14 years old.

Manual J calculation result: roughly 30,800 BTU/hr cooling load at 95-degree outdoor / 78-degree indoor design conditions. That's 2.6 tons. Round up: 3 tons.

The original 4-ton install was oversized by roughly 30%. Common in this neighborhood profile.

The replacement menu for this scenario:

• 4-ton single-stage R-454B at 14.3 SEER2 (matches what's there — cheapest install, highest operating cost)
• 3-ton single-stage R-454B at 14.3 SEER2 (right-sized, basic equipment)
• 3-ton two-stage R-454B at 16.0 SEER2 (right-sized, mid-tier)
• 3-ton variable-speed R-454B at 18.5 SEER2 (right-sized, premium)

The 8-year cost-of-ownership comparison usually lands the 3-ton variable-speed and the 3-ton single-stage close to each other, with the over-sized 4-ton single-stage costing the most on total ownership despite the cheapest install price. The cheapest install is the most expensive house. The 3-ton single-stage and the 3-ton two-stage land in similar territory — your choice on those depends on humidity preference and how long you plan to stay.

Scenario two: 2,650 sq ft two-story Foley, 4-ton vs 5-ton

Different profile. Two-story home in Greystone Village or Hidden Lakes, 2,500-2,800 sq ft, built 2012-2020, running a 5-ton single-speed.

Manual J calculation result: roughly 41,200 BTU/hr cooling load. That's 3.4 tons — call it a strong 4-ton with proper ductwork balancing between floors, or a 4-ton with a small mini-split for the bonus room over the garage that always runs hot.

The original 5-ton install was oversized by roughly 25%. Common when the builder used a single piece of equipment to serve two floors with marginal duct sizing.

The replacement menu for this scenario:

• 5-ton single-stage R-454B (matches what's there)
• 4-ton single-stage R-454B (right-sized, no zoning)
• 4-ton two-stage with zoning damper system
• 4-ton variable-speed with zoning

The zoning piece is what makes the math actually work for two-story Foley homes. A single-speed 4-ton serving both floors with no zoning will do a worse job than the oversized 5-ton it replaces — you'll get the right total tonnage but wrong distribution. With zoning between upstairs and downstairs, the variable-speed 4-ton can match output to which floor is calling, which is the actual problem the 5-ton was trying to solve with brute force.

Closer race on 8-year total cost than the single-story scenario. The variable-speed zoned setup often lands close to just replacing what's there with a 5-ton single-speed on total ownership — but the comfort difference is night and day. Two-story homes in Foley benefit more from zoning than from raw tonnage.

Scenario three: smaller Foley home, 3-ton vs 2.5-ton

Less common but worth covering. Smaller home in older Walker Grove-era Foley, 1,400-1,600 sq ft, currently running a 3-ton.

Manual J result: roughly 22,400 BTU/hr. That's 1.9 tons — call it 2 tons or 2.5 tons depending on duct condition and shading.

The replacement menu for this scenario:

• 3-ton single-stage (matches what's there)
• 2.5-ton single-stage (right-sized)
• 2-ton variable-speed mini-split with existing furnace/air handler staying
• 2.5-ton two-stage central

Operating differences are smaller in absolute dollars on this profile because the load itself is smaller, but the proportional savings are similar. The right answer depends heavily on the duct condition. If the original 1970s ducts are still in the house, a mini-split conversion sometimes pencils out cheaper than running a full central replacement through compromised distribution. The mini-split decision in the Alabama homeowners guide covers this trade-off in detail.

What this means for a Foley homeowner shopping a quote

If you're holding a contractor's quote for a 4-ton replacement and you live in a 1,800-2,100 sq ft single-story Foley home, ask the contractor for the Manual J calculation. Not the rule-of-thumb number. The Manual J. If they didn't run one, they don't know whether 4-ton is right — they're matching what's there.

A Manual J site visit takes 45-60 minutes. It comes standard with every ACExperts replacement consultation at no charge. The output is a 4-page report with the actual cooling load number and a recommended equipment range. From there the variable-speed-vs-single-stage decision becomes a budget conversation, not a guessing conversation. Run the ROI calculator for your specific scenario and you'll see the same pattern these three examples show: the cheapest install is rarely the cheapest house.

Downsizing blindly is just as wrong as oversizing. A 2.5-ton in a house that genuinely needs 3.5-ton produces its own set of problems. Manual J is the answer either direction.

A note on R-454B pricing in 2026

All the install prices above assume R-454B equipment, which is the default for new Foley installations as of January 2026. R-410A new installs are no longer available from major manufacturers. The supply-and-pricing dynamics on the refrigerant side are covered in the R-410A vs R-454B refrigerant leak post — short version: new equipment on R-454B carries roughly the same install price as equivalent R-410A would have, and the long-term service economics favor R-454B because the refrigerant supply will be stable.

How to actually run this for your house

Three numbers are enough to run the same exercise for your specific Foley home:

1. Square footage of conditioned space (excluding garage and unfinished basement)
2. Year built
3. Last August's power bill

That's enough to estimate where you sit on the curve. A 30-minute conversation at the kitchen table plus a Manual J site visit gives you the actual numbers in writing — equipment options, sizing, install cost, and projected 8-year operating cost on each. Free estimate, no pressure either direction. Foley, Silverhill, Loxley, and Bay Minette are all on the same routing schedule. Diagnostic calls are $79 if you also want a current-equipment evaluation; replacement estimates by themselves are free.

The math runs backward when you let it. Start from the bill, work back to the equipment. Most Foley homes were sized forward, and most Foley homes are paying for it.