Guide: What Size Heat Pump Does My Home Need [And More]?If you’re considering a heat pump instead of another conventional HVAC system for your Treasure Valley home, there are plenty of options to choose from. But, you need to know what size model you’ll need.

Any home’s heating and cooling system needs to be in the Goldilocks zone: Not too big, not too small, but just right.

Most people realize that an HVAC system that’s too small won’t make your home warm or cool enough. It will also break down early from excessive strain.

But the opposite is also true: If you go too big, your heat pump won’t function properly.

That means hot and cold spots in the house. And a shorter service life because of extra wear and tear.

So, how do you know what size model to choose? Since a heat pump will last much longer than a conventional furnace and central air, it’s important to make the right choice. Especially since these units provide benefits that gas and traditional electric heaters can’t.

Ultimately, you need a professional to give you an accurate recommendation because quite a few factors are involved.

But the good news is that you can get a rough estimate before we come out to your home. That way, you’re ahead of the game when it’s time to pick your system!

In this article, we’ll walk through everything you need to know about sizing and choosing your new heat pump. If you have any questions about your Boise Metro or Valley County home, call or email us here at Snowflake Air.

How To Measure Cooling And Heating Capacity

When it comes to HVAC equipment, the two measurements for heating and cooling capabilities are:

  • BTUs
  • Tonnage

We’ll briefly go into what they mean and how you can estimate your home’s needs. But, we need to stress that these formulas are only part of the equation.

A professional, more accurate load calculation factors in your home’s layout, insulation, windows, and more.

Capacity For Heat Pumps Vs. Conventional Furnaces

Traditional gas furnaces and central air systems use BTUs for heat and tonnage for the AC. Heat pumps are different in that you’ll only get a tonnage rating.

We’re only measuring how much heat, or thermal energy, your heat pump transfers from one place to another. That’s as opposed to gas or electric furnaces, which generate heat.

But, the two terms are related, as you’ll see below.


BTU stands for “British Thermal Unit.” It measures how much energy your system must produce to heat one pound of water by one degree.

That seems impractical when we’re talking about keeping your home warm. But, it’s used as a standard measuring unit to quantify how much heat your system can transfer into your home.

Estimating BTUs

You can estimate how many BTUs your heat pump needs to produce by multiplying the square footage of your home by 30 for newer homes and 35 for older homes (Newer homes generally have better insulation and retain heat better).


Where BTUs measure how much power you need to heat a pound of water, tonnage measures the amount of heat you need to melt a one-ton block of ice.

In practical terms, a system needs one tonnage of cooling to remove 12,000 BTUs worth of heat from your house every hour.

Estimating Tonnage

You can get a rough estimate of the tonnage your home needs by measuring one ton of cooling for every 600 square feet.

Now, let’s see how this applies to some common home sizes here in Boise Metro and up in Valley County.

What Size Heat Pump Do I Need For A 2,000-Square Foot Home In Boise, ID?

If You've Needed Frequent Repairs, It's Time For A ReplacementIf your heat pump is your primary heating source, a 2,000-square-foot home in Boise, ID needs a five-ton system. Or three tons for cooling and supplementing another heating system. But, you need a professional load calculation to be certain.

The difference comes in when you convert tonnage to BTUs:

2,000 square feet multiplied by 30 = 60,000 BTUs for heating. Divide that by 12,000 (one ton of cooling for every 12,000 BTUs), and you’re at 5 tons.

But it’s one ton of cooling for every 12,000 BTUs. So 2,000 divided by six is 333.

That’s why it’s important to work with an HVAC contractor who understands if you’re planning to use the system in the winter on its own. Or if your heat pump is more for air conditioning and “tops off” your existing heater.

What Size Heat Pump Do I Need For A 4,000-Square Foot Home In Boise, ID?

A 4,000 square foot Boise home needs a six-ton heat pump for cooling and some heat. Or a ten-ton system if it’s also your primary heat source. But, you need a professional load calculation to factor in your layout, insulation, and more.

The formulas work the same as with a 2,000-square foot home.

How Much Does It Cost To Install A Heat Pump?

The average ducted heat pump cost in Valley County or Boise Metro is around $7,000, including the unit, labor, ductwork adjustments, and more. High-end systems can be $18,000. Mini splits start around $3,000 per room and often average $18,000 for an entire home.

Of course, those are some big ranges. This is mainly because ducted units and ductless systems use very different setups. But, their energy efficiency makes them elibile for various rebates, including the Inflation Reduction Act, which kicks in early 2023. 

Read More: Rebates and Financing Options For Treasure Valley Heat Pump and Mini Split Installations


Ducted Heat Pump

A three-ton ducted heat pump runs between $4,000 and $6,500 to install. A five-ton system costs between $5,000 and $9,000. Within the price range for each size, you can then choose your efficiency.

The higher the efficiency, the higher the upfront cost. But, the lower your electric bill every month. Lower efficiency works the other way: Lower cost to install, but higher bills each month.

Mini Split

A mini split is much more customizable — hence the wider price range. To start, you can install one indoor unit to treat a single problem room for around $3,000.

Or, add more to treat more of — or your entire — home. Most homes require three to five air handlers. Once again, price varies on efficiency and tonnage. Most top out at $17,000.

A heat pump supports up to eight air handlers. So, the price does not double with each additional indoor unit.

Read Real Case Studies Of Heat Pump And Mini Split Installations In Boise Metro and Valley County

Heat Pump Installation In Cascade, ID And Boise Metro

Snowflake Air is known throughout Boise Metro and up through Valley County for excellent, professional heat pump installations in Cascade, ID and other towns that are done right the first time. We’re certified for Mitsubishi, Carrier, Daikin, and all other major heat pump brands. Call today or click below for your free consultation!