Fourteen hundred square feet is a three-bedroom ranch, a large apartment, a main floor plus a sunroom, or a split-level with the upper and main floors counted together. The cooling load is 28,000 BTU/hr, 2.33 tons, and the calculator rounds up to 30,000 BTU, which is the 2.5-ton system most homes this size get.
Two tons fits only the shaded, well-insulated version of this house (22,700). Average conditions (28,000), four people (29,200) and shade alone (25,200) are 2.5 tons. Anything that adds load, a sunny exposure (30,800), poor insulation (32,200), a kitchen (32,000), a 10 ft ceiling (35,000) or sunny plus poor (35,400), is 3 tons (36,000 BTU). A hot climate with sun and poor insulation (39,000) is the one row that calls for 3.5 tons, and the calculator, which does not carry a 42,000 BTU class, shows it as 48,000. Do not read that as a recommendation for 4 tons.
Split-levels are the classic 1,400 sq ft comfort complaint. The system is sized right on paper, but the upper bedrooms sit above the main floor and under the roof, and they run five to eight degrees warmer in July. The fix is not a bigger condenser, which would short-cycle on the main floor. It is either a zoning damper system on the ductwork, or a separate 9,000 or 12,000 BTU mini-split for the upper level, with the central system sized for the main floor alone.
Ductless for the whole 1,400 sq ft means a 36,000 BTU outdoor unit with four heads, typically 18,000 in the open living and kitchen area and 6,000 to 9,000 in three bedrooms. That connected total will exceed the outdoor unit's rating and that is fine; manufacturers allow 130 percent or so because not every room peaks at once.
Heating 1,400 sq ft with average insulation runs 42,000 BTU/hr in a hot climate, 56,000 in a moderate one (16.4 kW) and 77,000 in a cold one (22.6 kW). That is a 60,000 BTU furnace in most of the country and an 80,000 in the north; a poorly insulated house in a cold climate (92,400) needs 100,000. A 3-ton cold-climate heat pump covers a 1,400 sq ft home with backup strips for design-day cold.
Example: a 1,400 sq ft ranch with a kitchen, four people, average sun and insulation, moderate climate. 1,400 × 20 = 28,000, plus 1,200 for the extra people and 4,000 for the kitchen, is 33,200 BTU/hr, so 3 tons. The same house shaded and well insulated is 22,700 + 5,200 = 27,900, which fits a 2.5-ton system. The shade trees and the attic insulation are worth half a ton.
Cooling BTU for 1,400 sq ft by sun exposure and insulation
Two occupants, 8 ft ceiling, moderate climate. Each cell shows BTU/hr needed and the unit size to buy.
| Sun exposure | Poor insulation | Average insulation | Good insulation |
|---|---|---|---|
| Heavily shaded | 29,000buy 30,000 BTU | 25,200buy 30,000 BTU | 22,700buy 24,000 BTU |
| Average | 32,200buy 36,000 BTU | 28,000buy 30,000 BTU | 25,200buy 30,000 BTU |
| Very sunny | 35,400buy 36,000 BTU | 30,800buy 36,000 BTU | 27,700buy 30,000 BTU |
Common adjustments for a 1,400 sq ft room
| Scenario | Cooling BTU/hr | Unit to buy |
|---|---|---|
| Average (baseline) | 28,000 | 30,000 BTU |
| 4 people instead of 2 | 29,200 | 30,000 BTU |
| 10 ft ceiling | 35,000 | 36,000 BTU |
| Kitchen in the space | 32,000 | 36,000 BTU |
| Hot climate, very sunny | 33,900 | 36,000 BTU |
Heating BTU for 1,400 sq ft by climate and insulation
| Climate | Poor insulation | Average insulation | Good insulation |
|---|---|---|---|
| hot | 50,40014.8 kW | 42,00012.3 kW | 35,70010.5 kW |
| moderate | 67,20019.7 kW | 56,00016.4 kW | 47,60014.0 kW |
| cold | 92,40027.1 kW | 77,00022.6 kW | 65,50019.2 kW |
1,400 sq ft sizing questions
What size air conditioner do I need for a 1,400 sq ft room?
About 28,000 BTU/hr in average conditions (2.3 tons), so a 30,000 BTU unit. The table above covers sunnier and worse-insulated rooms.
Do I need 2.5 or 3 tons for 1,400 sq ft?
Average conditions come to 28,000 BTU/hr, so 2.5 tons (30,000 BTU) with a little margin. Add a kitchen, a sunny exposure or poor insulation and the load is 30,800 to 32,200 BTU/hr, which is 3 tons. Only a hot, sunny, poorly insulated house (39,000) needs 3.5 tons.
Why is the upstairs of my 1,400 sq ft split-level so hot?
The upper bedrooms sit under the roof and above the warm main floor, so they carry more of the load than their square footage suggests. A bigger central unit will short-cycle downstairs. Zoning dampers or a separate 9,000 to 12,000 BTU mini-split upstairs fix it.
What size furnace for 1,400 sq ft?
About 56,000 BTU/hr in a moderate climate with average insulation and 77,000 in a cold one: a 60,000 BTU furnace for most of the country, 80,000 in the north, and 100,000 for a poorly insulated northern house.