Skip to content
Square footage is the fastest way to get a rough heat pump size range for a home — and the least precise. This chart gives you a starting range for an air-to-water heat pump by square footage, using the same coverage tiers published on each APOLLO model's product page. Your actual load also depends on climate, insulation, ceiling height, and how you distribute heat (radiant floor, fan coil, or baseboard/radiator) — use the heat pump size calculator for a number tailored to your home.
Two APOLLO series are shown side by side: the standard series (radiant floors, fan coils, air handlers, water up to about 131°F) and the MAX series (baseboards, cast-iron radiators, water up to about 170°F). The right column for your home depends on your heat emitter type, not your square footage.
Heat pump size chart by square footage
Find your home's approximate square footage on the left, then read across to the standard or MAX column that matches your heat emitter type. Rows above 4,000 sq ft in the MAX column have no published model yet — those projects need a direct conversation with MBTEK.
| Square footage | Typical standard-series fit | Typical MAX-series fit |
|---|---|---|
| Up to 500 ft² | APOLLO 3.5 Ton ( 42,000 BTU) | APOLLO MAX 3 Ton ( 36,000 BTU) |
| 750 ft² | APOLLO 3.5 Ton ( 42,000 BTU) | APOLLO MAX 3 Ton ( 36,000 BTU) |
| 1,000 ft² | APOLLO 3.5 Ton ( 42,000 BTU) | APOLLO MAX 3 Ton ( 36,000 BTU) |
| 1,250 ft² | APOLLO 3.5 Ton ( 42,000 BTU) | APOLLO MAX 3 Ton ( 36,000 BTU) |
| 1,500 ft² | APOLLO 3.5 Ton ( 42,000 BTU) | APOLLO MAX 3 Ton ( 36,000 BTU) |
| 1,750 ft² | APOLLO 3.5 Ton ( 42,000 BTU) | APOLLO MAX 3 Ton ( 36,000 BTU) |
| 2,000 ft² | APOLLO 3.5 Ton ( 42,000 BTU) | APOLLO MAX 3 Ton ( 36,000 BTU) |
| 2,250 ft² | APOLLO 3.5 Ton ( 42,000 BTU) | APOLLO MAX 4 Ton ( 48,000 BTU) |
| 2,500 ft² | APOLLO 3.5 Ton ( 42,000 BTU) | APOLLO MAX 4 Ton ( 48,000 BTU) |
| 2,750 ft² | APOLLO 5 Ton ( 60,000 BTU) | APOLLO MAX 4 Ton ( 48,000 BTU) |
| 3,000 ft² | APOLLO 5 Ton ( 60,000 BTU) | APOLLO MAX 4 Ton ( 48,000 BTU) |
| 3,500 ft² | APOLLO 5 Ton ( 60,000 BTU) | APOLLO MAX 5 Ton ( 60,000 BTU) |
| 4,000 ft² | APOLLO 5 Ton ( 60,000 BTU) | APOLLO MAX 5 Ton ( 60,000 BTU) |
| 4,500 ft² | APOLLO 6 Ton ( 72,000 BTU) | Contact MBTEK — above published MAX range, may need two MAX units |
| 5,000 ft² | APOLLO 6 Ton ( 72,000 BTU) | Contact MBTEK — above published MAX range, may need two MAX units |
| 5,500 ft² | APOLLO 6 Ton ( 72,000 BTU) | Contact MBTEK — above published MAX range, may need two MAX units |
| 6,000 ft² | APOLLO 6 Ton ( 72,000 BTU) | Contact MBTEK — above published MAX range, may need two MAX units |
Chart assumes moderate climate and average insulation. Rows are matched using each model's published coverage ceiling — the smallest model that covers your square footage. Homes near a row boundary (e.g. 2,400 or 2,600 sq ft) should use the calculator instead of rounding.
What changes your actual number
Square footage alone leaves out several factors that shift real heating load up or down within the same chart row:
- Climate: a mild climate can need roughly half the BTU/h of a very cold climate for the same square footage.
- Insulation and air leakage: newer, well-insulated homes need less capacity than older homes with the same footprint.
- Ceiling height: rooms taller than 8 ft add volume to heat, increasing the load beyond what floor area alone suggests.
- Heat emitter type: radiant floors, fan coils, and air handlers pair with the standard series; baseboards and cast-iron radiators typically need the MAX series for higher supply-water temperature, not necessarily more capacity.
- Heating and cooling together: a system also handling cooling and domestic hot water may need to be sized differently than heating-only.
For the underlying formula, see our BTU calculator guide. For a number that already accounts for all of the factors above, use the heat pump size calculator.
Standard vs MAX: which column applies to you
The chart above shows both series because the choice isn't about square footage — it's about how heat reaches each room:
- Standard APOLLO is the default for radiant floors, fan coils, and air handlers, delivering water up to about 131°F.
- APOLLO MAX is for baseboards and older cast-iron radiators, delivering water up to about 170°F at the same capacity tiers.
Your BTU/h load doesn't change between the two series for the same home — only which product line can deliver the water temperature your distribution system needs. See both series side by side in the APOLLO collection.
Buying checklist
Before choosing a size from this chart alone, confirm:
- Which heat emitter type your home uses — radiant floor, fan coil, air handler, baseboard, or radiator.
- Your climate and insulation level — both shift the real load within the same square-footage range.
- Whether the system also needs to handle cooling or domestic hot water.
- Whether your home is near a chart row boundary — use the calculator instead of rounding up or down.
- Whether the estimate has been confirmed with a full load calculation before final equipment purchase.
Frequently asked questions
What size heat pump do I need for 1,000 sq ft?
For a 1,000 sq ft home in a moderate climate with average insulation, the APOLLO 3.5 Ton (42K BTU) standard model is a typical fit for radiant floor or fan coil distribution. Homes with baseboard or radiator heating typically fit the APOLLO MAX 3 Ton (36K BTU) instead.
What size heat pump do I need for 1,200 sq ft?
A 1,200 sq ft home falls in the same range as 1,000 sq ft on this chart: the APOLLO 3.5 Ton (42K BTU) standard model, or the APOLLO MAX 3 Ton (36K BTU) for baseboard or radiator distribution.
What size heat pump do I need for 1,500 sq ft?
1,500 sq ft still fits under the APOLLO 3.5 Ton (42K BTU) standard model's published coverage, or the APOLLO MAX 3 Ton (36K BTU) for baseboard or radiator systems. Confirm with the calculator if your home has a cold climate or older insulation.
What size heat pump do I need for 1,800 sq ft?
1,800 sq ft is close to the top of the APOLLO 3.5 Ton (42K BTU) standard model's typical range. The APOLLO MAX 3 Ton (36K BTU) covers the same footprint for baseboard or radiator heating. If your climate is cold or your insulation is older, check the exact number with the heat pump size calculator.
What size heat pump do I need for 2,000 sq ft?
2,000 sq ft is right at the ceiling of both the APOLLO 3.5 Ton (42K BTU) standard model and the APOLLO MAX 3 Ton (36K BTU). Homes at this size with a cold climate, taller ceilings, or older insulation may need the next size up — the calculator accounts for those factors directly.
What if my exact square footage isn't listed in the chart?
Round up to the next row for a conservative estimate, or use the heat pump size calculator to enter your exact square footage along with climate, insulation, and ceiling height.
Can I size a heat pump from square footage alone?
Square footage gives a useful starting range, but DOE guidance and industry best practice both point to a full heating and cooling load calculation before final equipment selection — rule-of-thumb sizing by square footage alone can lead to an oversized or undersized system. Use this chart and the calculator for planning, then confirm with MBTEK or a Manual J-style load calculation before purchase.
What if my home is bigger than 6,000 sq ft?
Our largest single unit is the APOLLO 6 Ton (standard) or APOLLO MAX 5 Ton. Very large homes typically use two units running in parallel — for example, two APOLLO 6 Ton or two APOLLO MAX 5 Ton — rather than one oversized system. The right combination depends on your home's zoning and layout, so contact MBTEK or use System Builder for a multi-unit design.
Conclusion: use this chart as a starting range
The table above gives a fast, typical-home answer for most square footages between 500 and 6,000 sq ft, split by APOLLO's standard and MAX series. It assumes a moderate climate and average insulation — the same assumptions built into most square-footage rules of thumb.
For a number that reflects your actual climate, insulation, ceiling height, and heat emitter type, use the heat pump size calculator, or work through the full project with System Builder.
