Air source heat pumps (ASHPs) use electrical energy to help transfer the heat stored naturally within the outside air into a home for use as heating, and also domestic hot water if required.
However, as outside air temperatures get colder the amount of heat energy available lowers, and so air source heat pumps need to work harder in colder temperatures to heat a home to the same temperatures. Are air source heat pumps reliable in such situations?
Air source heat pumps can be a very reliable way to heat and cool a home, even when temperatures are very low as modern units can typically still extract heat from outside air up to around -4°F (-20°). Heat pumps can also typically last a long period of time before needing to be replaced.
We’ve been relying on our own air source heat pump to provide central heating and domestic hot water to our home for over 5 years now and have never had any problems with a lack of heating or hot water, or with the unit itself.
We discuss throughout this article more about how air source heat pumps can be reliable, both in terms of consistently being able to generate heat for a home as well as reliability in terms of maintenance and servicing.
Unlike traditional heating systems such as oil and gas that transfer energy from energy source to another, air source heat pumps move heat readily available in the outside air for use in a home.
Since ASHPs extract heat from another air source, they’re sensitive to the temperature of the outside air that they’re pulling heat in from. Temperate climates with steady temperatures can be more beneficial when using air source heat pumps.
While they’ve become viable in places that experience freezing temperatures, households that regularly endure weather at or below 10 to 25°F (-12 to -4°C) can experience reliability issues if they relied solely on an air source heat pump.
Hence, many opt to go for a hybrid system with their original gas boiler or oil system as a backup for particularly cold winter days. See our article on hybrid heat pump systems for more information.
Similarly, an air source heat pump’s efficiency can falter when trying to air condition in much hotter climates.
The SEER and HSPF ratings (seasonal efficiency ratings for cooling and heating respectively) come quite in handy for both hot and cold climate households. SEER ratings, which indicate how well the system cools, matter most in hot climates, whereas HSPF matters most in cold climates.
We live in a relatively moderate climate (the UK) where temperatures experienced throughout the year are never too extreme.
As a result, our air source heat pump has always worked reliably whatever the weather. The coldest temperatures we experience is typically just below 0°C and our ASHP still works effectively in this weather because there still plenty of heat energy stored within outside air even at these low temperatures.
As mentioned earlier, if you live in a climate where temperatures can reach minimum operating temperatures for an air source heat pump of around -20/25°C then you’ll an air source heat pump to become increasingly less reliable.
Our heat pump can work down to around -20°C.
As we use our air source heat pump for both central heating and domestic hot water, the outside unit is paired with a water heater storage tank located inside our home, which itself has a built-in immersion heater as a backup feature that can help to raise water temperatures when needed (such as in very cold temperatures during times of high water demand).
While air source heat pumps are specifically designed for efficiency, incorrect installation or usage can help to reduce their reliability.
Whether it’s the placement of the outdoor unit or the amount of refrigerant, we as consumers hold a lot of sway over the success of our heating pumps.
There are several things we can do to maximize their efficiency:
Air source heat pumps should be placed in a sheltered location out of the way of direct sunlight and high winds, but still located in an area that won’t hinder airflow.
For example, our air source heat pump is installed down the side of our house and meets these installation guidelines.
Correct placement of an ASHP will help to keep it reliability extracting heat as much as possible through ensuring adequate airflow through the unit isn’t restricted.
SEER, or Seasonal Energy Efficiency Ratio, ratings max out at 27.5, and you want a system that rates as at least a 15. For HSPF, or Heating Seasonal Performance Factor, aim for an 8.5 minimum out of the 12.5 maximum.
In terms of efficiency, it never hurts to go higher.
Our ASHP is rated using the COP (coefficient of performance) rating factor and the COP for our heat pump is shown below.
It’s a pretty efficient model that can produce at least over three times the units of heat energy for every one unit of electrical energy consumed, making it an efficient source of heat for our home under the right climate conditions.
See our article explaining air source heat pump COP for more information.
Before installing an air source heat pump, ensure that the rest of your home is as energy efficient as possible. This includes:
- Insulating walls
- Insulating the attic
- Sealing ducts
- Pre-programming thermostats (which alone can save you up to 10 percent on your energy bill)
By maximizing the efficiency of your entire home, you’ll help to minimize the size and cost of the system you’ll be installing.
Your efforts will also further reduce the energy required by your air source pump heater to begin with, since the home itself will maintain warm and cool temperatures more steadily.
As air source heat pumps extract and release heat into your home more slowly over time, they typically need a longer of period of time to work (such as leaving the heating on for longer).
An air source heat pump may not work very reliably in a poorly insulated home that where heat is escaping just as quickly as it’s being released.
Air Source Heat Pumps Are Up to 3.5 Times More Efficient
Gas heaters are 90 percent efficient (0.9 kWh heat energy released per 1 kWh consumed), and electric heaters are one-to-one. Air source heat pumps can be up to between 300 and 350 percent efficient. That is, under ideal conditions, an air source heat pump can release up to 3.5 kWh of heat energy per 1 kWh consumed.
Air source heat pumps can also double as an air conditioning system that can cool your home twice as efficiently as traditional air conditioners. Air source heat pumps derive much of their efficiency from their minimal ductwork and the fact that they transfer heat rather than generate it.
See our article on air source heat pump efficiency for more information.
Air Source Heat Pumps More Cost-Effective Over Time
Air source heat pumps usually cost more upfront, at between $2,000 to $8,000 (£1,500 to £6,000) per single-source unit (read: per room or area of your home), of which you may need between 3 and 5 for the average home.
However, air source heat pumps can also save you thousands of kilowatt-hours of electricity per year—and, consequently, hundreds of dollars (or pounds).
Based on Northeast and Mid-Atlantic region data, those with oil displacement systems can save around $300 per year (£225) on electricity bills by switching to air source heat pumps.
Furthermore, those with electric resistance heaters can save nearly $460 annually (£345), and those with oil systems can conserve almost a thousand dollars (£715) per year. And these pumps can last 15 to 20 years with proper maintenance, potentially saving you thousands.
You also have the option to install only one pump or multiple, targeting your heating and cooling to the areas or rooms that need it most. And you don’t need to run every heat pump all the time since you can run them separately from one another, meaning you can save money on heating or cooling only frequently used rooms versus heating all rooms at all times.
Most Reliable Air Source Pump Heater Brands
If you’re seriously considering an air source pump heater, you probably want to know which brands are the most durable and satisfactory for customers.
Based on consumer report data, the following are the most reliable brands for air source heat pumps:
- Carrier and Bryant
All seven of these brands scored quite highly on consumers’ lists of the most reliable.
Air source heat pumps can work very reliably down to their minimum operating temperatures, but how reliably they work can also depend on a number of other factors such as house insulation and the effectiveness of the central heating system inside a home.
Air source heat pumps are exceptionally reliable for energy-efficient homes in temperate climates. They’re also dependable for households in more extreme environments so long as the systems are maintained and precautions are taken to protect their efficiency from external conditions.
While the upfront cost is higher than that of a traditional heating system, the long-term financial savings can certainly tempt even the most frugal homeowners. And in an ever more eco-conscious world, the environmental benefits speak for themselves.