Disadvantages of ASHP

In recent years, air-source heat pumps have become a popular choice for heating homes and providing hot water. While ASHPs offer a number of benefits, there are also some disadvantages that consumers should consider before making a purchase.

In this article, I will explore seven of the most significant disadvantages of air source heat pumps.

Air Source Heat Pumps: Disadvantages

1. Air source heat pumps can be expensive to install and maintain

Perhaps the number one disadvantage is that air source heat pumps can be expensive to install (usually between £8,000 and £18,000), and the cost of the installation may not be worth it in the long run.

The pump itself may be expensive, and the installation process can be complicated and costly.

The cost of an air source installation varies but is typically around £1000 per kW of capacity, so a pump with a capacity of 6 kW would cost around £6000 to install.

For those living in England and Wales, there is the Boiler Upgrade Scheme that pays (for the first 90k eligible applicants) £5,000 towards an air source heat pump installation cost, making it more affordable.

Air source heat pumps require more maintenance than other heating options. For example, the coils and filters on air source heat pumps need to be cleaned regularly to ensure that the unit is running at peak efficiency.

If the filters are not clean, the unit will have to work harder to heat your home, which will increase your energy costs.

Furthermore, given that the EPC is not compatible with heat pump goals, it may be more cost-effective and less disruptive to install a gas boiler rather than a heat pump to improve this rating.

Furthermore, when considering home improvements to increase the Energy Efficiency Certification scheme (EPC) rating, heat pumps are not an obvious choice given that installing a gas boiler is less expensive and less disruptive.

2. Lower heat supply than a conventional boiler

In a gas boiler central heating system, water is circulated through radiators operating at a higher temperature than those of most ASHP systems.

Underfloor heating system

Compared to oil and gas boilers, air-source heat pumps do not provide the same level of heat output. This type of heating system is better suited to homes with larger surface area radiators and an underfloor heating system.

To deliver heat equivalent to that of a conventional heating system you will need larger heat emitting surfaces that are optimised for low flow temperatures.

3. Air source heat pumps can be noisy and disruptive

Air source heat pumps can be noisy and disruptive when they are running, making them unpopular in residential areas.

The pump itself is usually located outside the building, and the noise it emits can be intrusive. In addition, the unit’s condensers emit cool air that may be a cold and drafty annoyance to residents if they are being blasted with it.

Companies are continually working on improvements in this area with quieter and more efficient pumps, but for now, air source heat pumps remain one of the noisier central heating options.

4. Air source heat pumps still require electricity

Air source heat pumps consume electricity in order to operate, so unless you generate and store electricity using another method of renewable energy such as solar PV combined with a battery, going completely off-grid will not be possible.

5. Only suitable for well-insulated and draught-proof homes

To realise the full advantages of an air source heat pump, your home must be well-insulated and draught-proof. While this is true for any space heating technology, air-source heat pumps are particularly sensitive to drafts and leaks.

Loft insulation

If your home’s insulation is poor, and heat can easily escapes from your home through windows, doors, or walls, you will find that air source heat pumps are not an energy-efficient option. You will need more energy to keep the space warm.

Home temp loss after 5 hrs - a comparison across EU homes.

Tado°, a home climate management firm, conducted a study that found that British houses lose heat far more swiftly than European neighbours, even when outside temperatures are taken into account.

According to the study, conducted between December 2019 and January 2020 across 80k homes, a UK house will lose on average 3°C of heat, after five hours. This is with a starting indoor temperature of 20°C and an outdoor temperature of 0°C.

In comparison to homes in some Western European countries such as Norway and Germany, UK homes lose heat up to three times as fast.

Almost 38% of homes in the UK were built before 1946, compared to 24% for Germany and Sweden.

With the above in mind, I would always recommend investing in home fabric insulation upgrades before any other form of heating system investment in order to make sure they are effective and you’re not wasting money.

6. Air source heat pumps are not suitable for all climates

ASHP in the snow

Air source heat pumps are not suitable for all climates. Yes, they can work at temperatures as low as -25°C and are found in many European countries with cold climates, but they start to lose efficiency below 0°C and are less efficient than other forms of heating such as using a gas or oil boiler.

A ground source heat pump, with pipes, buried deep under the ground providing a more stable temperature, might be a better low carbon heating alternative.

While heat pumps can be reversed in the summer to provide cooling, They don’t work very well when it’s really hot outside. In fact, air conditioners are often used to supplement air source heat pumps in the summertime.

7. Air source heat pump units can be bulky and take up a lot of space

Air source heat pumps can be bulky. This can be a disadvantage if you are trying to install it in a small area or if you don’t have much storage space.

There are two types of air-source heat pumps: monobloc and split systems.

A monobloc system has all the components in a single outdoor unit, with pipes carrying water to the central heating system and a hot water cylinder inside your home (assuming you have one). These systems don’t take up as much space in your home

A split system separates air source heating systems components between indoor and outdoor units and is typically more efficient than monobloc systems.

The external unit in domestic air source heat pumps is typically no larger than a washing machine and can be located anywhere where there’s a decent flow of fresh air (or ambient airflow) and a bit of breathing room.

The unit can be fitted to a wall or placed on the ground and it must have suitable clearance around it to allow a good flow of air.


FAQ:

What is an air source heat pump and how does it work?

An air-source heat pump is a heating system that extracts heat from the ambient air outside your home and uses it to warm up the air inside your home.

An air-source heat pump utilises electricity to power a compressor and fans which transfer heat energy from the external air into the building but the heat energy delivered to your home is more than the electrical energy used to power the system.

If well designed, you could expect the heat pump system to deliver three times as much heat energy as is used in electrical energy to drive the system.

What are some of the benefits of using an air source heat pump for heating your home?

Air source heat pumps provide a number of benefits over traditional fuel-based heating systems.

  • They can be much more efficient than traditional heating systems, meaning that you may save money on your energy bills.
  • Air-source heat pumps are much less reliant on fossil fuels, making them a low carbon heating system.
  • Heat pumps have the added benefit of providing cooling in summer, making them a versatile option for year-round climate control.
  • They are relatively easy to install compared to other types of heating systems. Heat pumps do not require a lot of expensive or difficult-to-install infrastructure making them a great option for a heating system upgrade.
  • Air-source heat pumps are generally very reliable. These systems have been around for decades, and they have a proven track record of reliability.
  • They are generally cheaper to run than oil boilers and can be cheaper than running gas boilers, especially in the current climate of increased gas costs.

How to choose the best air source heat pump for your needs?

When it comes to choosing the best air source heat pump for your needs, there are a few factors you’ll want to take into consideration.

  • Air source heat pumps are generally more expensive than traditional heating systems, so you’ll need to make sure that you can afford the initial investment.
  • Air source heat pumps need to be installed by a qualified technician, so you’ll need to make sure that you’re comfortable with the installation process.
  • Reliability is another key factor to consider. Air source heat pumps are generally very reliable, but it’s always best to check with manufacturers and reviews to make sure that you’re getting a reliable product.
  • Finally, you’ll need to consider the possible need for home adaptations. Air source heat pumps generally don’t require any special adaptations, but it’s always best to check with your installer to make sure that your home (e.g. radiators) is compatible with an air source heat pump.

What are the costs of air source heat pumps?

The cost of an air source heat pump will vary depending on the size and type of system you need, as well as the climate in which you live. In general, however, air-source heat pumps are cost-effective, with some systems paying for themselves in just a few years.

Installation of an air source heat pump is usually straightforward, and while they can often be installed by an experienced DIYer we would recommend hiring a professional installer, especially if you are installing a larger system, or if your home is not well-suited to an air source heat pump.

The cost to install is typically higher than a conventional heating system with costs anywhere between £8 – £20k, typically coming in around £12k.

From April 2022 to March 2025, the government’s Boiler Upgrade Scheme will reduce the cost of air source heat pumps by £5,000.

Further savings will be realised after Rishi Sunak’s Spring Statement announced on the 23rd March 2022:

What are some of the advantages of an air source heating system?

  • Environmentally friendly – Air source heat pumps are very eco-friendly and leave a far smaller carbon footprint than traditional gas or LPG boilers allowing you to do your bit for the environment. As well as being more energy-efficient than traditional heating systems they can also be used to cool your home.
  • Cheaper than other green heating systems – compared to other eco-friendly heating systems, such as a ground source heat pump, air source heating systems are much cheaper to buy.
  • Low running costs – An air source heat pump costs much less to run than a gas boiler so your energy bills should be lower. They have low maintenance costs and can be expected to provide safe, reliable and emission-free heating for many years
  • Easy Installation – An air source heat pump can be much simpler to install than other environmentally-friendly heating systems. This means less disruption and lower installation costs too.
  • Eligible for Incentives – Renewable Heat Incentive ends March 31 2022 replaced by TBC.

Simply, air-source heat pumps (ASHPs) are a type of renewable energy technology that can be used for space heating and cooling, as well as water heating. ASHPs work by extracting heat from the air outside and transferring it inside, or vice versa.

What is output size?

Output size represents how powerful a pump is, and how much energy is produced.

How is output measured?

The amount of energy required to operate an air source heat pump and the output of a pump is measured in kW.

Most air-source heat pumps are between 4kW and up to 15 kW in output.

The output required for a house is generally determined by the size of your home and how energy efficient it is.

Everything being equal, a larger home will require a heat pump with a greater output.

With the right-sized system, you should be able to get most or all of your hot water needs all year round from an air source heat pump.

When it comes to heat pumps, bigger is not always better. An incorrectly sized system will not be efficient and may increase operating costs or not be able to produce sufficient hot water for your home.

What size air source heat pump do I need?

MCS-accredited heat pump installers can precisely calculate the ideal size for your home and will recommend a size that is most appropriate.

The following will give you an indication of the range of sizes you might be dealing with:

Property TypeEstimated ASHP Output
1-bed flat/apartment3kW
2-bed house/flat3kW to 5kW
3-bed house – poor insulation7kW to 9kW
4-bed house – good insulation9kW to 12kW
4-bed house – poor insulation12kW to 16kW
5-bed house – good insulation12kW to 16kW
Typical heat pump output requirements

All figures are estimated and should be used as a rough guide. Your requirements will be dependent on several factors including the energy efficiency of the property, the type of heat delivery system, and seasonal weather temperatures.

Can I install an air source heat pump in an existing home?

It isn’t always easy to switch to an air source heat pump in an existing home, doing so may require certain adjustments to be performed such as new pipework and radiators.

A gas boiler will typically operate at high flow temperatures of approximately 70°C, however, air heat pumps operate at lower temperatures and are better suited to properties with underfloor heating and good levels of insulation and draft exclusion.

Do heat pumps work well in cold climates?

As can be seen in How heat pump sales are starting to take off around the world – Carbon Brief the highest penetration of heat pumps across Europe is in countries with the coldest climates.

The four European countries with the largest share of heat pumps are:

  • Norway – 60% of households
  • Sweden – 43% of households
  • Finland – 41% of households
  • Estonia – 34% of households

The four countries above are countries that face some of the coldest winters in Europe.

Are air source heat pumps cheap to run?

It’s a common enough fact, that an air-source heat pump generates much higher levels of heating power than the electricity they consume. However, you would need a well-insulated house and a particularly efficient heat pump to be cheaper to operate than a conventional gas boiler – even with today’s gas prices.

Running costs of conventional heating systems (Gas + Electricity)

The 2022 data from the UK Department for Business, Energy & Industrial Strategy (BEIS), has the average electricity prices as high as £0.28 per kWh, and £0.07 per kWh for gas. This is based on the latest energy price caps (April 2022).

Average price cap unit rate for Gas and Electricity from October 2021 through to September 2022

According to Ofgem, the average household uses 12,000kWh of gas and 3,100 kWh of electricity annually.

Ofgem
BEIS Standard White Logo

Note: The Ofgem standard energy consumption rates used (12,000 kWh for gas and 3,100kWh for electricity) are lower than the BEIS standard energy consumption rates used to calculate annual bills (13,600kWh for gas and 3,600kWh for electricity).

The average household energy bill equates to £840 for gas and £868 for electricity totalling £1,708 per year!

Running costs of an air source heat pump

For every 1 kWh of electricity, a typical air source heat pump can produce 3kWh of heat. So, installing an air source heat pump over a modern gas boiler to produce domestic hot water and generate heat, could see the annual energy consumption drop (as well as lower overall carbon emissions).

All things being equal, the 12,000 kWh of gas to provide heating and produce hot water, would be replaced with 4,000 kWh of electricity with an air source heat pump.

Priced at £0.28 a unit, this will cost around £1,120 per year.

Assuming the 2,900 kWh of electricity consumed by households when using gas to produce heat and hot water remains, the total electricity bill when using an air source heat pump would be ~£1,932 (£1,120 + £812).

So, an air source heat pump isn’t cheaper to run?

Even if you are one of the lucky 90,000 households eligible for the UK Boiler Upgrade Scheme, you will be unlikely to recoup the costs of buying and installing an air source heat pump (and this is without factoring in costs of new underfloor heating, and possible replacement of existing radiators if required) anytime soon.

That doesn’t mean to say that there are no advantages to an air source heat pump and that you shouldn’t consider getting one.

They are a low carbon alternative and we all need to be doing our bit to reduce carbon footprints – and it’s not like we install heating systems purely to save money!

On the positive, the technology is constantly improving with several manufacturers now with models of heat pump systems with every 1kWh of electricity used to power the heat pump providing up to 4kWh of heat.

This means that a heat pump’s efficiency can reach around 400% – this far exceeds that of either gas or oil boilers that tend to run from 80% to 92%.

Conclusion

Air source heat pumps, while becoming more popular in recent years as people become more environmentally conscious, do have their disadvantages. Some of these include the noise they emit, the need for electricity to run them, and the fact that they are not suitable for all climates. Additionally, they can be bulky and take up a lot of space.

While air-source heat pumps are not the perfect heating solution for everyone, they can be a great option for those living in well-insulated homes with a moderate climate. Thanks for reading!

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