Sizing Your System
What size HVAC do I need?
Get a quick ballpark with the estimator below, then see why the real size for your Des Moines home comes from a load calculation — not a guess.
HVAC size is measured in tons (cooling) and BTUs (heating). A rough starting point is one ton per ~600 square feet, so an 1,800 sq ft Des Moines home lands near 3 tons. But that’s only a sanity check — the right size comes from a Manual J load calculation that accounts for your insulation, windows, ductwork, and Iowa’s temperature swings. And remember: bigger is not better. Try the estimator below, then confirm the real number on site.
AC Sizing Estimator
What size air conditioner do I need?
A common starting point is one ton of cooling per ~600 square feet (about 20 BTU per square foot), so a 1,800 sq ft Des Moines home lands near 3 tons. Ceiling height, insulation, sun exposure, and how many people live there move that up or down. Use the estimate below as a sanity-check range — never as a final size.
3.0–3.5 tons
About 36,600 BTU/hr of cooling (roughly 3.1 tons before rounding to the nearest half-ton unit).
Basis: ~20 BTU/sq ft, adjusted for ceiling height, insulation, occupants, and sun. A bigger range means more of your inputs push the load toward the edges — an on-site measurement narrows it.
Common misconception
“Bigger is better — just oversize it to be safe.” An oversized AC short-cycles: it blasts cold air, hits the thermostat fast, and shuts off before it pulls humidity out. In an Iowa summer that leaves your home cold but clammy, and the constant on-off wears the equipment out faster. Right-sized beats oversized.
What a Manual J load calculation looks at
The estimator above is a quick range. A proper load calculation goes further and measures:
- Square footage and ceiling height of each conditioned room
- Insulation quality and how well the home is air-sealed
- Window count, size, and which direction they face
- Local Iowa design temperatures for deep cold and humid heat
- Ductwork condition, leakage, and layout
- Number of occupants and major heat-producing appliances
Signs your current system is the wrong size
- Short-cycling: the system turns on and off in quick bursts
- The house feels cold but clammy in summer (humidity isn't removed)
- Some rooms never reach the thermostat setting
- Energy bills climbed after a recent system swap
Iowa local truth
“Just match the size of my old unit.” That old unit may have been wrong-sized from day one — and if you’ve added insulation, replaced windows, or finished a basement since then, the load has changed. Iowa’s deep-cold winters and humid summers punish a mismatched system, so the right move is a fresh measurement, not a copy of the old nameplate.
Get the exact size for your home
All Seasons HVAC performs an on-site load calculation before recommending a system size for your Des Moines home — so you get comfort and efficiency, not an oversized guess.
Common questions
What size HVAC do I need for my Des Moines home?
A rough starting point is one ton of cooling per ~600 square feet, so an 1,800 sq ft home lands near 3 tons. But that's only a sanity check. The right size comes from a Manual J load calculation that accounts for insulation, windows, ductwork, and Iowa's temperature extremes. Use the estimator on this page for a ballpark, then confirm on site.
Is a bigger HVAC system better?
No. An oversized system short-cycles — it blasts the house to temperature and shuts off before it pulls humidity out, leaving you cold and clammy in an Iowa summer. The constant on-off also wears equipment out faster. Right-sized beats oversized every time.
Should I just match the size of my old unit?
Not automatically. Your old unit may have been wrong-sized to begin with, and changes like added insulation, new windows, or a room addition shift the load. The accurate answer is a fresh load calculation, not a copy of the nameplate on the old equipment.
Keep exploring
See more in the Learning Center.