The Truth About Air Source Heat Pumps

If you have a new build, or nearly new house that is insulated well and built to code 4 standard and the ASHP was fitted from new with underfloor heating and a water cylinder, it will work ok. The problems arise with retro fitting to older properties. The Government, Energy Companies in particular and housing associations will offer an attractive grant, usually 5k to 7.5k towards the costs, telling you it will be the best thing you ever did. In reality you will have spent many thousands of pounds and be left with a system that does not work as designed, which will cost you a small fortune in electric to get it to produce any heat. We have taken out a high number of ASHP and replaced them with boilers due to running costs. Energy companies are in it for the money only. 

Problem number two, your existing steel radiators will struggle to get to temperature, and your rooms will not get warm enough without cranking up the design temperature to 70 degrees which will cost you hundreds per month in electric. ASHP work best with underfloor heating, upstairs and downstairs. This is easy in a new build, not so much as a retro fit. It can work with underfloor heating downstairs and aluminium radiators upstairs. The aluminium radiators give out 50% more heat output than steel ones for the size and are a more efficient conductor. You would have to double the size of the steel radiators which still would not get hot enough, or replace with aluminium ones, onto the correct sized pipework.  

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Finally, lets not forget the hot water issues. All ASHP work along side an unvented hot water cylinder or thermal store. There ae several issues with this, the ASHP system is designed to work at 50 degrees. This is not really hot enough for domestic hot water. Legionella also needs to be considered in any storage cylinder. The water temperature needs to be raised to 65 degrees twice per week to keep Legionella killed off. So the water needs boosting by immersion heater twice a week miniimum for legionella control, and usually needs boosting anyway because an ASHP running at design temperature wont be enough. 

You can not fit an ASHP onto existing heating pipework in most houses. Most existing systems in most houses will have 22mm branching off to 15mm pipes to each radiator, at best, some will be 15mm throughout, some are entirely micro bore 10mm or even 8mm pipes. Because ASHP work at lower temperatures, 50 degrees, those existing pipes can be too small, increasing flow velocity, noise and pressure loss, requiring bigger pumps and too much stress on the system, too large and your wasting money and risking sluggish performance. Pipe sizing is crucial and it will not be correct on most existing systems and usually requires replacing completely which is very costly and time consuming. Which leads to problem number two.......

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Problem number three is insulation. Most existing houses over ten years old will in all probability not be insulated enough for ASHP to work properly. You need roof insulation, proper cavity wall insulation, stud wall insulation, modern double glazing, doors etc. It also nneds to be air tight like code 4. Without this insulation the heat will disappear and you will be running the system on max temperature which will cost hundreds of pounds per month in electric. You can already see how the cost of retro fitting ASHP properly is not achievable or affordable by most homeowners. We as a company will not retrofit any ASHP into an older property, as it just does not work, it never will work, and the customer, one example of one we removed recently, was paying over £600 per month in electric, and still could not heat the house. Fitted by a very popular energy company.​​​​​​​​

So, when you take into account all the things needed to allow an ASHP to operate as it should, unless you live in a new build, you will need to spend a serious amount of money to get it to work, you will never recoup that money from an ASHP even by adding solar. Gas and Oil boilers for existing properties are far more efficient and use far less energy than a retro fitted ASHP. 

Do not believe the energy companies, they make money from the government for selling ASHP wether they work or not, they will not care if your electric bill triples and your struggling to have a shower. This includes all the popular big energy companies. Beat the Boiler Ban and fit a new boiler while you can.