Heat pumps - anyone with experience?

Hi, anyone with experience of using an air source heat pump as a replacement for a gas boiler powered heating system?

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My father-in-law has one. I was keen to get one until he did and I found out how noisy it was. It’s ridiculous. It’s outside the sitting room and I can hear it the entire time I am in there. A low rumbling noise. Much more noticeable than a gas boiler, but I guess in a larger house or with it further away then it would be ok. I only notice it in that one room.

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Hello just turned my heat pump / air conditioner on never really used it to heat my home I am testing it at the moment it is belting the heat out and is well able to cope with my large living area set at 22 Celsius. However it is very mild at the moment so its easy for the unit to cope I will monitor it and will blog again later

From the all the information I have been able to gather regarding heat pumps, my conclusion is that they are not really a viable alternative to a gas boiler, with a conventional radiator system, especially in an older house. Heat pumps are not able to achieve the temperatures required for a normal radiator system. They work well with underfloor systems, as they run at much lower temps and require loads of insulation but a modern gas boiler is also fairly efficient in the same situation.
It is supposedly possible to run a radiator system using multiple heat pumps and installing a new system with huge radiators but the cost is astronomical and will take many years to pay for itself if at all. Plus your neighbours will probably hate you for all the noise!
If you are building a new house with a concrete floor, then great, but to replace a boiler with a radiator system, not cost effective. I read recently, that it would cost, on average £16000 per house to insulate an older property to the standard required to be viable for a heat pump system.


Having retro fitted air source into many types of property from new homes to cob walled thatched cottages have found them to be efficient at heating premises and supplying hot water when suitably surveyed and controlled.
Re noise some have toothed blades to lessen but never found an annoyance and if concerned position away from property.

hi been using my air conditioner as a heat pump to heat a large area down stairs to include living room, kitchen, hall landing and stairs so a fair sized area the system cost £300.00 10 years ago and works a treat, Over the last week or so it has used around 10 kilowatts of energy per day on average so around £1.60p . Currently belting the heat out in to every corner of the house. The heat output is rated at around 3.5 kilowatts for heating and cooling its currently cheaper for me to use the system than to use my normal mode of heating have a look on ebay at through the wall air conditioners/ with heat pump to get an idea of price and consider taking the plunge I have never regretted the decision i made all those years ago

While not disputing the fact that your air conditioner / heat pump unit will heat a certain area. It is effectively a wall mounted electric fan heater. It is not a direct replacement for a boiler running a radiator system that the op was enquiring about.
If someone can offer a reasonably priced heat pump that can genuinely replace a gas boiler to run a conventional radiator system then it will be worth looking at. From all the information I have read, single heat pumps can’t generate the temperatures necessary to run a radiator system.


Hi we were looking at the possibility of an air source heat pump for our newly extended four bed bungalow. As a previous poster said firstly it’s ok if you can have all underfloor heating and are well insulated (great for our extensions) but not when you need rads. We saw systems at Build It Live etc and really to make a big difference you need to go the whole hog ie solar, heat recovery and air pump, which obviously costs a huge amount.
The units are noisy and use electricity to run which you can offset with solar. They have a relatively low heat output which is fine on a full spec, well insulated new build but not anything older.
The final nail for us was when we had a guy round to look and bearing in mind he was a salesman for air source systems he said he wouldn’t want it in his house.

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I have had heat pump system in my villa since 2010. Totally love it. I’m in Turkey so winters from November to March. Switch on in November and it’s on 24/7 till its not required by end March. The main unit is fitted externally with pump etc in cupboard under stairs. Very quiet system and economical. We have huge open plan 4 bedroom villa with 3 bathrooms and it heats the whole place with large radiators in every room. Best thing we ever did. Just had latest bill which includes ALL electrical use including laundry, cooking and TVS etc. Equivalent of £60 for this month. This is highest bill so far.

I have had an air source heat pump fitted at the end of October supplying both central heating and hot water. In reply to the previous comments:- Yes, the system does run at a lower temperature than a gas boiler system & some rads do have to be up-rated. In my case they were either 2 panel to 3 or just a bit taller. Yes, it is true that the system is a bit noisy - not deafening, and mostly from the pipework.As for cost, it’ll take 12 months to get a real handle on it - it’s a bit heavy at the moment, but am expecting a big reduction in spring/summer. Hope this helps.

Are there any websites with brands and specs? Who are the Valient of the heat pump world?

Also any website explaining the science would be helpful. You don’t get “free heat energy from the environment” any more than your kitchen gets free heat energy from your freezer.

To use your freezer analogy. Imagine your neighbours freezer was in their kitchen, but the radiator on the back is in your kitchen. When your neighbours run their freezer, it moves heat out of the freezer compartment and puts that heat in your kitchen. You could class that as getting free heat energy in your kitchen.

Now consider that your kitchen is your entire house, and your neighbours kitchen is the whole outside environment. You pay to run your heat pump and it moves heat from outside to inside. The nifty trick is the efficiency. If the heat pump were 100% efficient, it would take 1kWh of electricity to move 1kWh of heat energy from outside to inside. This would be no better than directly converting the electric to heat using a fan heater. But they’re better than that. It takes 1kWh of electric to move several kWh of energy from outside to inside, they are more than 100% efficient. That’s not to say they’re creating free energy out of nowhere, they’re just moving free energy from outside where there’s so much of it that no one notices if you take some and put it in your house.

What happens when it’s cold outside? Well, remember that temperature is more correctly measured on the Kelvin scale. Going from 25C, or 298.15K, down to 0C still gives you 273.15K. Although it feels cold to a human, the actual reduction in available energy is not as much as it first appears. It’s rather more complicated than this and heat pumps do become significantly less efficient as the temperature drops near or below 0C. This is why ground-source heat pumps are better, if you have the necessary room, since the temperature a few metres underground is typically more stable year round.


As Hooloovoo says, it’s not “Free Energy” you are pumping calories into your house, lowering the temperature outside by an infinitesimal amount/ Your fridge/freezer does this, it pumps heat out into the kitchen from the water it is freezing. See Coefficient of Performance - an overview | ScienceDirect Topics
for an explanation of this.
The upshot of this is that you can pump heat in the same way that you pump water from a low point to a high one - if you arrange for the waste heat from your electric motor to be used you get an even better result. My system is by Mitsubishi, I really can’t help on comparisons - best bet might be to look for complaints about heat pumps as a guide as to what to avoid!

I live in a 3 bedroom 1960s housing Association house, with cavity wall insulation and live in an off gas area, in 2015 my housing Association decided to install Mitsubishi Air Source heat pumps in my scheme, since then I have found them extremely efficient, with in the coldest weather only spending around £35.00 a week on electricity for the whole house, with all rooms being lovely and warm, my house I may add is all electric, prior to the air source installation I had storage heating, and when one heater was switched on it cost me £70.00 a week, since air source installation the temperature during the day is set at 20°, and the thermostat drops to 15° at 11.00 at night, although in reality the living room where I have the thermostat has never dropped low enough for it to kick in during the night, my recommendation from experience is to have the thermostat in the room you use the most, situated at about coffee table height and out of direct sunlight, also it must be a minimum of 1.5 meters away from any direct heat source.
To finaly conclude, I would highly recommend the Mitsubishi units to anyone. P.s. my outside fan is located beside my back door, and can not be heard in any part of the house.


Thanks for the info everyone!

Wow, thanks for all your opinions! I must admit to being pleasantly surprised that so many of you took the time to respond. My feeling, from all your advice, is that perhaps a heat pump is not the best replacement for a fairly modern gas boiler (although it isn’t a combi boiler).

I’ll keep looking!

I have one on a 3 bed 1960s detached house for heating and hot water. My house is all electric and my electric bill was just over £1000 this year which is way is less than I was paying but I was on LPG. It cost about 8K to put in as I did some of the pipework my self (you will need 28mm primaries from the heat pump and bigger rads ). The good bit is the RHI is just short of 1K a year for 7 years so the subsidies almost pay for the whole thing let alone the savings on your bill.

It isn’t easy to answer the initial question without the response becoming quite long and involved.

The point is that we, as a nation, will have to address the issue of replacing gas boilers with something else and, in many cases the something else will be heat pumps of one form or another.

I have posted on this subject when I was with bulb previously.

We live in an 1859 stone built farmhouse in Aberdeenshire and have improved it since we moved here in July 2000. When we moved in the heating was supplied by a single burner oil fired Stanley range in the kitchen which was replaced by an LPG condensing boiler based system the following year and a GSHP in December 2016.

It hasn’t been a cheap process but we have taken advantage of every interest free loan or FIT or RHI payment going to get to where we are now.

A gas powered combi boiler is a wonderful thing - we recently had to replace the old gas boiler in the flat in Aberdeen but it comes at a price to the environment and this is where we all need to learn to change the way we do things. It isn’t possible for somebody to have a bath and then somebody take a shower immediately afterwards in a house powered by a GSHP/ ASHP.

GSHP/ ASHP are best suited to UFH systems but can work with radiators - we have UFH in the kitchen and dining room now but everywhere else is still fitted with radiators. We had to replace a significant number of the radiators with larger double panels ones or, in most cases, with triple panel versions.

The system works at the end of the day. My wife isn’t impressed with the temperature or volume of the bath water though - she likes it hot and full but that is what I mean about adjusting our expectations.

We have spent significant amounts of our own money to get to where we are.

People can find money to do the things they want to do such as take holidays or buy a new car or whatever, how keen are those same people to spend money on improving the insulation of their home?

We can’t all wait for somebody else to do something, we can all do something ourselves. It’s a mind set thing.




There are bad heat pumps and fantastic heat pumps. There are bad installers and fantastic installers. I have been installing, advising and supplying heat pumps for 14 years and have seen the whole spectrum. Its the same for any equipment you have installed in your house.

Use an MCS certified heat pump and installer but check out their pedigree, get at least 3 quotes. First, go to the MCS web site for information.

Heat pumps work. Good ones are quiet. They will give you between 3 and 4 times as much heat as the electric you put in. New ones will run at the temperature you need.

Its for the good of the environment therefore for all of us. Zero carbon electric,zero carbon heat.


On the bath/shower comments, this is something I was thinking about recently when discussing the potentials for wet solar in a large shared house.

Does anyone know whether such a thing exists that can take incoming warm water, and electrically heat it up to a thermostatically controlled temperature? If the incoming water is hot enough, no electricity would be used to bump up the temperature. If it’s not (your tank is running empty/daily inputs have not been enough to get it up to temperature) then it uses electric heating to get it up to temperature.

If you feed warm water into an electric shower then what you get out of the other end is very hot water as they’re all (as far as I know) simply a fixed power electric element (or sometimes two with a high and low setting).
The fine temperature control in an electric shower is simply adding more cold water. If your incoming water is hotter then you end up with a higher flow rate as more cold water is added, rather than using less energy to heat up the water to the desired temperature.