What size AC does my home need?
A desert-tuned tonnage estimate in under a minute — then the honest part: why the real answer is a Manual J calculation, and how to get one free.
What size AC does my Arizona home need?
A desert-tuned tonnage estimate from your home's real characteristics — no email required.
Your result
Estimated 4–5 tons (50,000–57,000 BTU/h) for Arizona's cooling load.
This is honest rule-of-thumb guidance, tuned for desert heat gain — the real answer is a Manual J load calculation, which accounts for orientation, ductwork, and infiltration. Oversizing is as costly as undersizing: short-cycling wears equipment out and leaves monsoon humidity in the air.
Estimate only. Two same-size homes a street apart can need different equipment — we confirm with a free in-home Manual J before quoting any system.
How AC sizing really works in Arizona
Air conditioner capacity is measured in tons — one ton moves 12,000 BTU of heat per hour. National rules of thumb say one ton per 500–600 square feet, but those numbers were written for milder climates. In the Greater Phoenix area, with 110°+ design temperatures, long west-facing sun exposure, and attics that hit 140°F, the realistic band is closer to one ton per 350–450 square feet — which is what this calculator uses.
Your home's envelope moves the answer as much as its size. Pre-1990 insulation, vaulted ceilings, heavy afternoon sun, and walls of glass each add real load; shade, upgraded attic insulation, and modern low-E windows subtract it. That's why two same-size homes a street apart in Queen Creek can genuinely need different equipment.
The honest caveat: no online calculator — ours included — can see your duct locations, air infiltration, or window orientation. The industry-standard answer is a Manual J load calculation, done room by room in your home. We perform that sizing evaluation free with every replacement quote, and we'd rather you use this tool to sanity-check any contractor's proposal (including ours) than to buy a system from a slider.
Beware the "bigger is safer" pitch. An oversized system short-cycles: it hits the thermostat number fast, shuts off before it dehumidifies, and repeats — wearing itself out while leaving monsoon-season air clammy. Right-sizing is the whole game.
Sizing questions we hear every week
- How many square feet does one ton of AC cool in Arizona?
- In the Phoenix-metro desert, one ton of cooling typically covers roughly 350–450 square feet — noticeably less than the 500–600 sq ft rules of thumb used in milder climates. Our 110°+ design temperatures, intense solar gain, and 140°F attics all push the load up. Envelope quality moves the number more than any other factor.
- Is a bigger AC always better?
- No — oversizing is one of the most common and costly sizing mistakes in Arizona. An oversized system cools the air fast, then shuts off before it has run long enough to wring out humidity, which matters most during monsoon season. It also short-cycles, which wears components out faster and costs more to run. Right-sized beats oversized every time.
- What is a Manual J load calculation?
- Manual J is the industry-standard room-by-room load calculation. It accounts for your home's orientation, window types, insulation values, duct location, and air infiltration — the things no online calculator can see. Any contractor quoting a new system without one is guessing. Paragon Service Pros performs the sizing evaluation free with any replacement quote.
- Do two-story homes need bigger systems?
- Usually somewhat, but the more common problem in Greater Phoenix two-stories is distribution, not raw size — hot upstairs bedrooms with a correctly sized system point to duct design or zoning. That's why our in-home evaluation looks at airflow, not just tonnage.
Skip the guesswork — get a real Manual J, free.
Every Paragon replacement quote starts with a proper in-home load calculation, written options at good-better-best pricing, and zero pressure. Same-day appointments across the Greater Phoenix area.