Air source heat pumps can be the ideal replacement for an existing gas or oil central heating system but depending on a number of factors, a complete replacement may not always be possible.
Air source heat pumps also deliver heat more slowly over time at a lower temperature compared to a conventional boiler system and so may not be suitable for cases with high domestic hot water demand where water temperatures need to be high.
Many air source heat pump installations can provide the desired heating and hot water temperatures without the need for a boiler or furnace. However, a hybrid heating system consisting of both an air source heat pump and a fossil fuel heating system can often be implemented if required.
Our own air source heat pump fully meets our central heating and hot water demands.
This air source heat pump heating system was installed when the house was built in 2017 and no conventional boiler was also installed.
We discuss in this article more about how you can use an air source heat pump without the need for a boiler (like we do) but also how a hybrid system can be setup where there may also be the requirement for a boiler.
Do You Need A Boiler With An Air Source Heat Pump?
For many installations, an air source heat pump can be used without the need for a boiler or furnace.
In this scenario, an air source heat pump would be used to provide both central heating and domestic hot water.
For an air source heat pump to provide both of the above, it would need to be the air to water heat pump type.
This is in comparison to air to air heat pumps which are used to heat warm air that’s pushed around a home rather than to heat water.
An air to air heat pump cannot provide domestic hot water and so another solution for providing hot water would be required if using an air to air heat pump, such as a boiler or immersion heater.
See our article on using an air source heat pump to provide hot water for more information, including how our air to water heat pumps provides us with domestic hot water.
For an air source heat pump to be used without the need for a boiler (or any other form of heating appliance) the right internal setup will also be required.
For example, our own setup includes an air to water external heat pump unit that sites on the side of our house.
It extracts heat energy from the outside air and delivers it indoors through refrigerant travelling in pipes.
At the other end of the pipes is the hot water heater tank and all other necessary heating apparatus located in our utility room cupboard.
It’s here where the hot water is distributed for use in heating or hot water for taps etc.
As air source heat pumps deliver heat at a slower rate and at lower temperatures compared to a conventional boiler system, the right setup such as large radiators and underfloor heating is required for central heating.
For domestic hot water, a hot water tank will be required, typically with the inclusion of an immersion heater so that water temperatures can be topped up when required.
If you don’t have space for a hot water tank like ours above, then you may need to consider a hybrid system where:
- An air source heat pump provides space heating
- A boiler provides hot water
Reasons why an installer may suggest a hybrid heating system to include both an air source heat pump and boiler can include:
- High hot water demand.
- Insulating an older home wouldn’t be cost-effective.
- A modern and efficient gas boiler is already installed.
- Local electricity energy costs are high.
An air source heat pump can replace the need for a boiler for space heating purposes with the right internal heating setup. Air source heat pumps can also replace a boiler for domestic hot water purposes where a sufficiently sized hot water tank can be installed.
An air source heat pump (ASHP) outdoor unit sits outside your home, drawing in fresh air, which is heated and distributed through ducts to where you require hot water and space heating.
As such, it can be used all year round: during winter, it takes warmth from the ambient air to heat your home; in summer, it takes warmth from within your home to cool it down.
An air source heat pump works by drawing air over evaporator coils. The coils absorb heat from the air and transfer it inside, providing heat for the house using compressor technology. As the liquid travels through the compressor, the pressure rises and the temperature increases, increasing its energy potential.
For an air source heat pump to replace a boiler system entirely you should consider a few factors before deciding if an air source heat pump is the best option for your home.
One downside to air source heat pumps is that they can require more space than traditional boilers.
The outdoor unit must be installed on the floor outside (or potentially mounted on the wall if possible), and the indoor apparatus can take up a lot of space. If you live in a small property, it may not be the best heating option for you.
See our article on air source heat pump space requirements for more information.
Air source heat pump installation can also be more complicated than boiler installation.
You’ll need to hire a professional to install the outdoor and indoor units and connect them to your home’s HVAC system.
If you’re thinking about adding an air source heat pump to your home, it’s important to research the costs of installation.
You may also want to talk to several professional contractors before committing to a company or individual. At this point, you should have a better idea if an air source heat pump is right for your needs and budget.
An air source heat pump installation can be quite costly when completely replacing a conventional central heating system, especially if much of the internal equipment such as pipes and radiators need to be changed.
Air source heat pumps are very efficient appliances and can be more efficient than boilers. Efficiency ratings on paper can be higher for air source heat pumps as they only need electricity for power and transfer heat energy from one source to another rather than converting energy.
When it comes to comparing the efficiency of different types of heating systems, there are several factors to consider: price per unit output, how much heat the system produces, how quickly it heats up water or space, how much maintenance it requires, and greenhouse gas emissions.
An air source heat pump generally costs more to install than a conventional gas-fired boiler. However, if you include the cost of installing a gas line and the boiler itself, the total cost of an air source heat pump may be lower.
An air source heat pump produces over two or more units of heat for every unit of electricity it consumes, while a gas-fired boiler produces about one unit of heat for every unit of natural gas it consumes.
Furnaces and boilers are still less than 100% efficient, however. As air source heat pumps work on the principle of transferring heat energy they can be well over 100% efficient, meaning that more thermal energy is produced than the amount of electrical energy put in.
Our air source heat pump has a COP (coefficient of performance) of over 3, meaning that its very efficient and much more efficient than any boiler installed in our house would be.
Air source heat pumps also excel in other areas. They use a renewable energy source and can typically have a longer life spans compared to boilers.
Air source heat pumps can often be used as standalone heating devices without the need for a boiler.
Air to water heat pumps can be used to provide both space heating and domestic hot water, but for air to air heat pump installation another method for providing hot water will be required.
Where a heat pump can’t provide all of the heated water needs, such as limited space indoors for a tank, a hybrid system could be used where a boiler provides the domestic hot water and the ASHP provides the space heating.
An installer will be able to provide you with the right setup for your home and particular situation.