Short answer
A 1,200 sq ft space needs roughly 24,000 BTU (2 tons) of cooling and about a 50,000 BTU furnace in a temperate, average-insulation home. Size up for hot climates, poor insulation, high ceilings, or lots of sun.
Cooling needed
24,000 BTU
Tonnage
2 ton
Furnace (heating)
50,000 BTU
Unit type
Single-zone mini-split
For cooling, 1,200 sq ft at roughly 20 BTU per square foot works out to about 24,000 BTU (2 ton) in a temperate, average-insulation home. For heating, a furnace is sized by climate zone — around 50,000 BTU in a temperate climate, and more in a cold one (50–60 BTU/sq-ft up north).
These are whole-space estimates. Poor insulation, high ceilings, lots of glass, or an extreme climate all raise both numbers — run your home through the calculator to adjust them.
| Factor | Effect on the load |
|---|---|
| Floor area | ~20 BTU per sq ft cooling baseline (ENERGY STAR, 8-ft ceiling) |
| Climate zone | -15% (cold) to +25% (hot) on the cooling load |
| Insulation | Poor +15%, average no change, good -10% |
| Ceiling height | Scales with height ÷ 8 ft — a 10-ft ceiling adds ~25% |
| Sun exposure | Shaded -10% to sunny +10% |
| Occupancy & use | +600 BTU per person over two; +4,000 BTU for a kitchen |
| Climate zone | Cooling BTU | Unit size | Typical unit |
|---|---|---|---|
| Hot (e.g. Phoenix, Miami) | 30,000 BTU | 30,000 BTU · 2.5 ton | Multi-zone mini-split |
| Warm (e.g. Dallas, Atlanta) | 26,400 BTU | 30,000 BTU · 2.5 ton | Multi-zone mini-split |
| Temperate (e.g. St. Louis) | 24,000 BTU | 24,000 BTU · 2 ton | Single-zone mini-split |
| Cool (e.g. Chicago, Boston) | 21,600 BTU | 24,000 BTU · 2 ton | Single-zone mini-split |
| Cold (e.g. Minneapolis) | 20,400 BTU | 24,000 BTU · 2 ton | Single-zone mini-split |
Temperate (highlighted) is the baseline for the figures above; set your exact climate, insulation, and sun in the calculator.
Real, widely available units in the 12,000 – 24,000 BTU class. Independent picks — we're not affiliated with any manufacturer or retailer and earn nothing from these links. Always match the unit's BTU to the size above.
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12k / 18k / 24k BTU
Ductless mini-split · heat pump · Cools + heats · strong all-rounder
A consistent independent favorite — efficient inverter heat pump that both cools in summer and heats in winter, at a mid-market price.
Find on AmazonBest value
12k / 18k / 24k BTU
Ductless mini-split · DIY · Pre-charged quick-connect · warranty holds on self-install
The only mainstream line with true pre-charged quick-connect line sets, so a homeowner can install it without a vacuum pump — and keep the full warranty.
Find on AmazonBudget pick
12k / 18k / 24k BTU
Ductless mini-split · Lowest entry price in the class
The budget way into a ductless heat pump. Field-charging and a licensed install get you the longer warranty.
Find on AmazonMini-splits mount permanently and need a small wall penetration; DIY kits are homeowner-installable, others want an HVAC tech.
About 24,000 BTU (2 tons) of cooling for 1,200 sq ft in a temperate, average-insulation home — more in a hot climate or with poor insulation.
Roughly a 50,000 BTU furnace in a temperate climate. Cold climates need 50–60 BTU/sq-ft, so the same home can need a larger furnace further north.
2 tons (24,000 BTU), since one ton equals 12,000 BTU. Confirm with a Manual J load calculation before a professional install.