Heat Pump Sizing

By | May 24, 2015

The best possible way of ensuring that your Heat Pump is sized correctly is by working with a qualified and experienced HVAC (heating, ventilation & air conditioning) contractor. They have the experience to make sure your eat pump is big enough and will be properly installed and set up to be as reliable and energy efficient as possible.

One of the biggest problems that consumers (unknowingly) face is that their homes are fitted with heat pumps that are seriously oversized, a problem which costs them much more than they should be paying and in turn generates a bigger income for someone who wanted to make a quick buck by selling them an oversized unit.

Sizing is probably the single most important factor when you’re considering getting a heat pump installed. A full heat load analysis should be conducted before your contractor decides on a size of heat pump as this will significantly affect the efficiency of your heat pump. 

When a contractor starts to determine your required size of heat pump, he starts by determining your required cooling capacity.

Here is an explanation of how a heat pump is sized:

The first step in determining the size of heat pump your home would need is to determine the required cooling capacity, just like they would for any air conditioning system.

A rough guide to help you determine which size you would need looks something like this:

Supplemental Heating Element Kw by climate and tonnage

Very warm winter climates (Average low winter temperatures of 35 degrees and up)

1.5 – 3.0 tons Heat Pump – Use a 5 Kw
3.5 – 5.0 tons Heat Pump – Use a 10Kw

Mild winter climates (Average low winter temperatures of 25 degrees and up)

1.5 – 2.0 tons Heat Pump – Use a 5 Kw
2.5 – 5.0 tons Heat Pump – Use a 10Kw

Colder winter climates (Average low winter temperatures of 0 degrees and up)

1.5 – 2.5 tons Heat Pump – Use a 10 Kw
2.5 – 3.5 tons Heat Pump – Use a 15 Kw
4.0 – 5.0 tons Heat Pump – Use a 20 Kw

Coldest winter climates (Average low winter temperatures of -10 degrees and up)

Heat pumps are not recommended for these climates unless no other choice exists
1.5 – 2.0 tons Heat Pump – Use a 10 Kw
2.5 – 3.0 tons Heat Pump – Use a 15 Kw
3.0 – 5.0 tons Heat Pump – Use a 20 Kw

Heat pumps come in a wide variety of sizes. They start at 1.5 tons and move up in half ton increments up to 5 tons. Residential homes use sizes anywhere from 2 to 5 tons when it comes to capacity abilities of Heat Pumps.

1 Ton = 12,000 BTUs (British Thermal Units)

The best way to calculate the heat loss in your house is by getting a professional HVAC contractor to do it for you. It will cost anywhere between $300 and $1000 to have this done, but it’s a surefire way of ensuring that the house has been properly analyzed and measured up to determine the size of heat pump required.

If you really feel the need to do this yourself, doing a manual calculation by hand is seriously complicated and could take hours. Head on over to www.loadcalc.net for a free and super straight forward way of calculating it and comparing it to what your contractor came up with.

Most manufacturers of Heat Pumps make their products available in several different sizes ranging from 1.5 to 5 tons of capacity. This measurement was originally referred to as the amount of ice needed to cool the equivalent amount of air. Your typical residential home uses (again under normal circumstances) a 3 ton Heat Pump to efficiently heat up the house.

Like we mentioned before, figuring out the required size of a heat pump is something that a professional HVAC contractor should do, but you can easily figure out a rough estimate of what size you’ll need. 400 square feet of living space would need a 1 ton heat pump to be warmed up effectively, so if you have a 1,600 square foot house, you would probably need a 4 ton system to efficiently heat up the home. That is based on older homes though and some of the newer houses that have double-paned windows and extra insulation would easily be able to get away with a smaller system.