Heat pumps - information and resources

So why would anyone want a heat pump? Just what makes them such a good bet for nearly everyone? When people ask about them there are nearly always 3 questions at the front of their mind - do they really work, are they really green, and how efficient are they?

So lets address the basic info and myths about heat pumps...

Do they really work?

Where might you go to find this information? Probably the most accurate information readily available can be found in a report written by the Energy Saving Trust about 5 years ago, which looked at around 80 installations. The results were not particularly flattering for the UK Heat pump industry. Many heat pumps were performing below manufacturers predictions - but why?

The take away information from the report was simply that there were a combination of factors leading to poor performance, many of them addressable. Interventions were made on some of the systems and the performance improved, sometimes by quite significant amounts. The report basically highlights how design and customer understanding are two of the most important factors in heat pump performance.

There is no reason why a heat pump cannot perform well as long as the correct design of the system on both the hot (the customer's heating system) and cold (the ground array or evaporator) side of the heat pump. Across Europe there are well over 8million heat pumps installed and this figure is dramatically increasing year on year. However it is worthwhile noting that many manufacturers present the performance in a misleading way, which is less than helpful for the lay person.

Are they really green?

Yes! As long as you install a well designed system then in emissions terms they are greener than natural gas, and nearly every other fuel source once you have taken boiler efficiency into account. Even the heat pump installations from 5 years ago were mostly achieving this.

If you look at the statistics given on the Nottingham Energy Partnership website then you will see in the graph below the following emissions levels are achieved for the various fuel sources... with the exception that the graph below uses the TRUE figure for biomass pellets, which are in fact more harmful to the environment than oil or gas when all the externalities are taken into account.


The heat pump data is represented by a curve as the emissions reduce as the efficiency increases. These figures are actually conservative because the official UK emissions figures for electricity powering the heat pump are artificially high. Using the Carbon tracker page at www.earth.org.uk we can see that the official figure of 518g CO2e per kWH is well above what is being consistently achieved, thanks to increased solar and wind capacity. Figures well below 400 are regularly being reached even through winter, and this increases dramatically as summer conditions prevail - though of course heating demand does drop then as well.​

In this graph, "COP" stands for Co-efficient Of Performance, and is a measure of efficiency - so whilst a boiler performs at a more or less constant efficiency however hard it works (the straight lines in the graph below), a heat pump changes efficiency throughout the year, based on a number of variables. Further down the page this issue is explored in more depth...




How efficient can a heat pump be?

All heat pump manufacturers are obliged to publish the performance levels of their products using a recognised standard - this is referred to normally as a SPF or Seasonal Performance Factor. A COP of 3:1 tells you the heat pump will be capable of putting out 3 units of heat for every 1 unit of electricity used to power the heat pump components in a well controlled laboratory environment - however it does not tell you how it will perform in the situation you are most concerned about - your house or business.


The real life performance can be estimated when a model is created which takes into account the many many factors which affect the installation - such as: radiator or underfloor heating running temperatures, where you are in the country, the average air temperature in your location or if you have a ground source heat pump what the soil quality is like. Suffice to say it is a straightforward but time consuming process to answer that question for each person. However you can make certain assumptions for a quick ball park figure.

You should expect a heat pump to perform in the following ball parks if the system has been designed well. These figures are pretty conservative - it's possible to get even air source heat pumps to achieve close to COP 4 when installed with a well designed central heating system:

Air source heat pump providing only space heating:                            SPF 3.2 - 3.5

Air source providing space heating and domestic hot water              SPF 2.7 - 3.2

Ground source heat pump providing only space heating:                   SPF 3.5 - 4.5

Ground source providing space heating and domestic hot water      SPF 3 - 4

This means you can expect a heat pump to run at significantly lower costs than oil or LPG and it can also give natural gas a good run for it's money as well. When the RHI tariff is taken into account then it adds up into a very simple decision to make if the capital cost is not a problem. The combined benefits of lower running costs and tariff payments mean very quick payback times can be achieved - as low as 4 years is possible. 

For a table showing a comparison of UK domestic  energy costs across the different fuel sources head to this website which is an independent energy agency - you should find the table straightforward to understand - however beware! The figures they use for environmental impact on wood pellets are flawed - burning wood is only good for the environment if it is log or chips. Pellets are actually worse for the environment than oil or gas:

Nottingham Energy Partnership energy cost comparison

If you would like a more detailed appraisal then please use our drop us an email to get in touch... Or you can use the official government RHI calculator to get a basic idea. Please also have a look at our Grants and Tariffs pages for more useful links

What are the running costs?

Running costs will vary based on how efficiently you can get the heat pump to run - the better the heat pump and the lower the output temperature, the lower costs. This graph should give you an idea as to what to expect. The figures are based only on running costs, not tariffs, and the figures used to create the chart assume a 35,000kWH heat demand and came from the Nottingham Energy Partnership cost comparison page. In the key, ASHP and GSHP are Air Source and Ground Source heat pumps, respectively.


Running costs

Who makes the best heat pumps?

There are two basic types of heat pump on the market, inverter driven or standard on-off heat pumps. The inverter driven heat pumps tend to be made by South East Asian companies such as Panasonic, Sanyo and Mitsubishi. Standard heat pumps are often made in Europe, though of course there are many Chinese heat pumps as well, often re-branded and sold as "British" or "European". So which are best?

This can often be confusing to the lay-person. As a rule the very best heat pumps are European and this can be ascertained by looking at independent heat pump tests. There is an independent test centre in Switzerland which publishes league tables which you can find here: www.wpz.ch. Currently the best heat pumps are being made by Austrian, German and other Northern European countries.

Specialist Energy works with Vaillant and Ochsner. Vaillant are a good solid brand with excellent product support - their boilers are rated along with Worcester-Bosch as being the most trusted products in the UK, and they have a team of dedicated heat pump engineers who can deal with breakdowns. Ochsner hold the current record for the best performing heat pump available - they are class leading in every respect, from noise to low temperature performance. 

One of the most important aspects for heat pump longevity is to ensure good design - reducing the number of times the heat pump turns itself on and off - and making sure the compressor is of very high quality. An "average" heat pump will have an expected lifespan similar or better than an average boiler, whilst Ochsner heat pumps could be expected to last over 20.

What are the maintenance requirements?


Maintenance requirements for a heat pump are minimal - it's more likely you will need to maintain the heating system components rather than the heat pump itself. At it's heart is a compressor, much like that found in a fridge. If the system has been designed and installed well then this will have a very long time. One of the heat pumps we use is made by Ochsner. Since Ochsner started operating about 30 years ago, approximately 90% of their heat pumps are still in operation! Cheaper heat pumps or poorly installed ones will not fair so well

Specialist Energy

Hay on Wye, Herefordshire

Tel: 07970 418222


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