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Heat pump it pump it...

June 18, 2017

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 in people's homes. 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 system is designed to work with a well sized central heating system - this essentially means making sure the radiators are large enough and the pipe work is sized correctly. 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 they are attached to a well designed heating system then in emissions terms they are greener than natural gas, and nearly every other fuel source. Even the heat pump installations from 5 years ago were mostly achieving this. The only thing they cannot beat in emissions terms are log boilers burning locally felled wood - but these are unfortunately a disaster in pollution terms - see my other blog post on burning wood

If you look at the statistics in the graph below the following emissions levels are achieved for the various fuel sources... this graph uses figures for pollution from wood pellets which represents their true environmental impact when felling, processing and transporting the pellets has been accounted for. The lines for the fossil fuel systems are all straight because their efficiency is basically set at around 95% and this doesn't change whatever time of year it is - whereas the heat pump figure varies dramatically because if you install a system badly, or measure performance in the winter the performance will be poor (a low SPF), whereas when you install the system well and connect it to a good central heating system it will perform very well indeed (and give a high SPF).


SPF standards for Seasonal Performance Factor, and represent an AVERAGE performance figure for the WHOLE year. A heat pump with an SPF of 4 will create 4 units of heat for every 1 unit of electricity used to drive it. So as long as you can achieve an SPF of greater then SPF 2.3 (the bottom axis), you are winning in emissions terms versus natural gas, which is the best performing fossil fuel...


The SPF 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 time consuming process to answer that question for each installation. However you can make certain assumptions for a quick ball park figure.




Another factor which makes heat pumps even more sensible is that our national grid is becoming greener all the time - so the electricity used to drive the heat pump is becoming less polluting as well. The official figures have not yet caught up with the reality we are seeing on the ground. On a summers day the emissions for heat pumps are sometime less than a quarter of what we see here.

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 heat distribution 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 knock natural gas into a cocked hat 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. 

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 below 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 large 4 bedroom house.




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: 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 heating 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 - in fact around 90% of their heat pumps installed since 1985 are still operating.


So there you have it -heat pumps really are the most sensible choice when it comes to new builds, and even for older properties, as long as you are willing to ensure your heating system is able to work well with the heat pump.

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