What size AC for Ontario, OR? 3.5 tons for 2,000 sq ft

What size AC a 2,000 sq ft house in Ontario needs

3.5 tons central AC or heat pump, about 36,500 BTU/hr of load

The 20 BTU per square foot chart would put in 3.5 tons, about 15% more than this climate needs. An oversized unit cools the air fast, shuts off before it pulls moisture out, and leaves the house cold and clammy.

If a contractor quotes you more than 3.5 tons for an average 2,000 sq ft house here, ask to see the Manual J load calculation behind it before you sign. That works out to one ton per 657 square feet in this climate. For a single room, size by the room: 18.3 BTU/hr per square foot.

The climate it is sized for

Climate from NOAA's 1991 to 2020 normals at Ontario (1.7 mi away). Jul is the hottest month, averaging a high of 95.1°F and a low of 61.5°F, with about 61 days a year at 90°F or more. That gives a design temperature of 101°F against 75°F inside.

What it costs to run

About 1,436 kWh a year at SEER2 14.3, or roughly $222 at Oregon's average residential rate of 15.46¢ per kWh. Cooling runs 5 months of the year here.

What drives the load in Ontario

Of the 36,500 BTU/hr, 18,720 comes through walls, roof and windows on a 101°F afternoon (51%), 13,000 is sun on the house (36%), 2,120 is four people and their appliances, and 2,700 is moisture the coil has to wring out of Ontario's summer air (7%).

Heat through the shell is the biggest share here, so insulation and air sealing cut the size you need more than shading would. Sensible heat totals 33,840 BTU/hr before the moisture allowance.

Other house sizes in Ontario

Single rooms with a window or mini-split unit: a 150 sq ft bedroom needs about 2,700 BTU/hr; a 350 sq ft living room needs about 6,400 BTU/hr; a 600 sq ft open plan kitchen and family room needs about 11,000 BTU/hr.

Month by month in Ontario

Jul alone uses 38% of the year's cooling energy. The unit runs the equivalent of 562 hours a year at full output.

Ontario against nearby cities

Of 57 Oregon cities here, Ontario has the highest cooling load. The range runs from North Bend at 15,700 BTU/hr to Ontario at 36,500.

Where Ontario's weather numbers come from

The nearest NOAA station with full 1991 to 2020 normals is Ontario, 1.7 miles from the center of Ontario at 2,188 ft above sea level. That is close enough that the station's summers are Ontario's summers.

No other city in this set uses Ontario, so this sizing is Ontario's alone.

The sun over Ontario in late July

At 44.03°N, the noon sun on 21 July stands 66.4° above the horizon over Ontario and the day runs 14 h 49 min from sunrise to sunset. A lower noon sun puts more of the day's heat on east and west walls than on the roof, which is why shading west glass pays off here. Long days mean the house keeps gaining heat into the evening, well after the outdoor peak.

11,957 people live in Ontario, the 44th largest of the 57 Oregon cities sized on this site. Coordinates used: 44.0253, -116.9774.

Ontario AC sizing questions