How our first heat pump winter went

So many people have reached out to ask how we’ve gotten on with our heat pump through the winter.

We even got a week of snow which I wasn’t expecting to see for at least another year so that was a happy surprise.

Whenever I talk about my heat pump people always say “ah, but they don’t work once it gets below zero degrees right?”.

I’d like to debunk that “it doesn’t work when it’s cold” thought with my experience of our first really cold winter.

Getting used to weather compensation

Our heat pump is configured to work with the footprint and heat loss of our home. So everyone’s home with a heat pump is uniquely different and that’s what makes gauging how well they’ll work in your home that much harder.

A proper installation process includes a heat loss survey, an assessment of what heat pump and radiator upgrades you’ll need and an approximate idea of how much it’ll cost to run.

Have to say our install and cost estimate was pretty much spot on.

However the biggest change for us was getting used to the idea of weather compensation – where the flow temperature of the heat pump relates directly to the temperature it actually is outside. The warmer it is outside, the less the unit has to work to get your home up to temperature.

In order to keep the system as efficient as possible, we also had to get used to having the heating on 24/7. Having the heating on at a lower temperature at night in particular took some getting used to. It’s not something I did before. We currently have our house aiming for 20 degrees in the day and 16 degrees at night.

As someone who is more mindful of the environment with each passing year, being more mindful of the weather around me is a good thing. I found myself being more mindful of daily temperatures and forecasts as it got colder. It actually helped me settle into winter a bit better (it’s my least favourite time of year).

Using the cold heat pump air to dry clothes on a clothes horse.

Isn’t it cold inside?

I am usually cold and I was worried about whether or not the heat pump would heat me and my home sufficiently. I didn’t need to worry. I am always toasty. In fact with weather compensation I think the heat pump is doing better at heating my home than my previous gas system. Possibly because of the improved efficiency, but also due to the care that went into sizing this system.

Lastly, it’s been great not to use gas, especially with the knock-on effect on the war in Ukraine. It’s also been a great relief of climate anxiety to not watch the daily fumes escape our house from the vent. Gas remains in our house (for hob cooking) but I will be very glad to shut this off very soon.

We are settled into heat pump usage and I am very happy with my investment.

Turning the heating on 💸

We switched on in mid-October. A little earlier than we needed to but we were keen to check everything was working OK and as I get up at 6 am each morning (chronic pain is a great alarm clock). I was starting to notice it was getting very cold, and my pain was getting worse.

Getting used to the ambient heating is strange, I put on checked all the radiators and our house is cosy at a 20 degrees average temperature. Only thing that really felt different is the cooler radiators.

Again, I can completely dispel the idea that life with with heat pumps is cold. I’ve been plenty toasty and it’s actually made me a bit hot on a couple of occasions. Really impressive heat.

As a result our house averages 20 degrees on all three floors. The ground floor is normally 18 degrees and our bedroom is 19, the middle floor (where the thermostat is) is usually about 20 degrees or higher. We just leave the heat pump to it and it just works.

Our cats like it too.

Both of our cats sits next to the radiator.

Costs are so subjective, because it depends on your home and your tariff and your circumstances but I can say that he harder the system has to work the more energy used, but so far it averages between 3-8kWh a day to keep us warm in October. Between 10-20kWh in November.

In really cold weather (like the snow we had) we were using about 30-35 kWh per day.

Your mileage will vary though obviously, more information about our home is in this post.

Our house uses more energy heat up until about lunchtime and then it settles and the cost slows into the evening as it maintains heat.

What’s is really like when it’s snowing though?

I’d describe at as toasty – but slightly more expensive. Our heat pump has a estimated COP of 3.67 (above zero degrees), I think that drops to nearer 2.0 when it’s really cold. The whole system has to work harder. Prior to the snow it was working out at about the same as our gas system (not including price rises) with cold weather and snow it was slightly dearer.

Plus the system itself was working a lot harder. The unit outside was marginally more noisy. I doubt anyone will have noticed, (it’s pretty quiet) but the contents of our cupboard where the pipes, inverter and other equipment was was noticeably louder. A gentle hum permeates the floor that the cupboard is on.

It’s rather like having a boiler in your house to be perfectly honest. I work next to the cupboard all day. The radiators really got hot when it was snowing though that felt a bit more like gas central heating system.

As for the snow on the unit itself outside. Well it was a complete surprise when I awoke to snow as it felt no different in the house. The heat pump worked happily outside. I took a picture of it covered in snow, and cleared the top and sides of it a little, but it’s legs and it’s defrosting worked perfectly. Our lowest temperature outside was -6.

A side view of our heat pump in snow.

Insulation is of course important but becomes even more important at colder temperatures. I really started to notice the impact of heat loss in the snow and it’s something I’ll have to improve. However with our roof and cavity walls done all that is really left is the exterior walls of the original victorian house which will require expensive external insulation. We do also have two windows to replace and that’s about all that’s left that we can really improve.

Overall on price (not including the overall increases to prices) it’s about ~10% more expensive to run – but only on really cold days (sub zero degrees). Every other time it works out about the same (maybe a pinch more) but I have some more ideas on this topic. If you have a well-insulated home you could definitely save more money, it’s such a impressive piece of kit.

Future things to look at

  • Homely by evergreen energy – this device which is installed next to your heat pump internal control helps manage the weather compensation, learns about your houses heat lost and reduces the need to have the heat pump on 24/7. When paired with a smart tariff we could potentially save quite a bit.
  • Smart tariff – We’re working on getting enough usage data (minus gas) to switch to Octopus Energy.
  • Heat pump tariff – Also exploring this offering from Octopus Energy.
  • Insulation – there’s some cheap and easy insulation we can still do, plus I’ll get a survey on some external insulation.

In conclusion then, really happy with our heat pump, works exactly as described it would and our home is always warm and comfortable.


Our first few months with a heat pump

It’s time for an update on my heat pump before what is likely to be a very expensive winter for everyone in the UK starts.

Here’s what we think of the heat pump now that it’s been outside our home for a few months.

Heat pump and hot water

I’ve been very impressed with our heat pump throughout the summer for our hot water. We had good water pressure before but our shower is much improved now. There are two reasons for this. Firstly a pump was put in to improve the pressure from the unit up into our old boiler cupboard as the system is no longer gravity fed. Secondly we have much better temperature control of our water now.

Our old boiler either gave out scolding hot water, or it’s ice cold equivalent. We still have the mixer taps on our shower, but we can now control the top temperature of our hot water far more easily and the hot water takes less time to come out of the tap too.

Heat pumps can heat your water to whatever temperature you like, but we’ve set it a bit lower than the default, with the immersion tank set to heat up the water once a week at 3am every Monday for one hour to get it to 55 degrees (and kill any Legionella and other bacteria in our system).

We basically have the water at the temperature we need and have largely eliminated the need to cool down the water too much. Not something we could have considered with a gas system.

For the first time since I’ve moved into my house I can set my own water temperature, not burn myself and waste less water waiting for it to warm up.


We put the heating one for one full day back in June to to check all the radiators worked. Although we later realised that the heat pump and thermostat had actually been coming on about 3 times a day in May/June based on the settings that the installer left us with. I turned the thermostat off and the heat pump has not been active since (save for our hot water).

We also had a bit of a scare one day after adjusting the system pressure when no water came out of our upstairs tap. We quickly realised this was due to a big pipe leak in the area and the effect on our system was a complete coincidence.

What it sounds like

The unit outside sounds like a very gentle fan when it’s warming our hot water. It will definitely be louder when it’s colder and working harder. We have heard it going full pace as part of its commissioning and it was fine to be honest. We can’t really hear it from indoors and we won’t be outside for long when it’s really cold.

The pumps, pipes and inverters inside the old boiler cupboard sound rather like our old boiler did only quieter, I work next to this all day and it’s fine. A new thing is that the heating system can be heard through the radiators ever so quietly. I’ll report on this more once we’re using it every day.

We no longer need to have a carbon monoxide monitor in the room where I work, so that’s nice.

Energy usage

We’re averaging about 10-12kWh for our daily total electricity usage at the moment (lighting, appliances and hot water) and of that in the summer 1kWh/day for heat pump usage alone (we know this because it has its own meter). On our current tariff, our total usage costs about £2.50 a day (with no heating). We work from home every day so this checks out.

Obviously this is going to cost a lot more over the winter.

Post install paperwork and compliance checks

We had a couple of additional checks from the Boiler Upgrade Scheme (BUS) where we had to sign some digital documents and provide proof of address and identity. This presumably to prevent fraud.

Ofgem selected us for a desk audit which basically means providing them with more paperwork, photographs serial numbers etc, about 20 documents in total. This is presumably to make sure something has been installed, done adequately and been completed. There was an optional step for them to visit our property, but we were not selected for this and our documents were sufficient.

The Microgeneration Certification Scheme (MCS) also called us separately to double check our contact details and to make sure we were happy with both the installer used and the installation work done.

Questions from others

Does the heat pump cool your house too?

No, most heat pumps that do this are air-to-air heat pumps. These are common in places where central heating are done by units high up on walls that put out air that can be heated or chilled. Most UK domestic heating is water based, so most of our heat pumps are air-to-water or ground-to-water so that existing piping and underfloor heating/radiators can be reused. So in short they can be used to cool your home if they’re the right type of heat pump, but these aren’t as common in the UK.

Does the heat pump output cold air in the summer to cool you down?

Our heatpump has been very inactive when it’s warm, only really coming on to top up our hot water, and when it’s warm this rarely needs to happen. So usually there is no cooling breeze in the garden – but I experienced this happening once on the last day of the UK 40 degree heatwave and it was lovely.

I need to find a way to automate our system so I get an alert when it switches on, so if one of us wants to cool down in the summer we can do this. I am looking at some solutions for this including Home Assistant.

Should the heat pump be put in the sun or shade?

So it can benefit from extra warmth? It will work with the ambient temperature it’s in. This wasn’t a factor mentioned in installation. The most important factors were a) having enough space around and in front of the unit b) us being happy with the location.

What about installation, and your research process?

I wrote about this in another post, check out my heat pump tag.

Next update will be either during, or post this coming expensive winter. Please let me know if you have any other questions.


How our heat pump installation went

Following on from my last blog post about how we researched our heat pump. We’ve just finished having the unit, new equipment, electrics and plumbing done. Our home has been upgraded with a heat pump.

It’s exciting to finally have one in our garden after months of researching it. There’s lots of information online about how heat pumps work but not quite so much on how the install goes and what’s involved in that step by step. So here’s a breakdown to everything that happened and what to expect.

How it went

This is just my experience of installation, your home and therefore your setup and experience may be entirely different, but I really wanted to provide a bit more detail around what actually happened on each of the days.

We worked from home for the duration of the project. There was loud drilling and sawing for short periods of time on each day. Mostly because new pipes and power lines were drilled from the external house wall into our boiler cupboard area and near the fusebox.

The workmen worked quickly, put protective sheets down on our carpets, took off their shoes and made sure our indoor cats didn’t escape!

We had a really positive experience with the installation overall.

What to expect

  • We were advised there would be 5 days for work, but it ended up taking 6 (as the electrician wasn’t available to wrap up the project until the following week)
  • We were without hot water for around 3 days. This was while the old water storage tank was removed and the new tank (with immersion heater) was installed
  • We had about a half day without cold water while our old water storage tanks in the attic were removed and new water storage and expanders were installed
  • We were without heating for the duration of the project (for about a month beforehand due to boiler breaking) but if this wasn’t the case, we would have been without heating for 8 days, basically from the moment the installation started (with everything disconnected) to the moment the electrician commissioned the heatpump
  • There was no power in our home for about 2 hours in total on the final day while the heat pump was made live with the fuse box and other electrical work in the old boiler cupboard was done.

How to prepare for heat pump installation

We weren’t given any instructions for what to do to prepare our house, so this is what I’d suggest to do before your installer arrives.

  • Inform your neighbours ahead of time about the noise and roughly when you’ll complete, especially if you have any party walls
  • Completely empty your boiler cupboard, removing all shelving and any other objects, so only the plumbed units and electrical controls are in there with no other clutter
  • Clear the room around where your new tanks and plumbing will be (in our case the boiler cupboard), the installers had a lot of equipment and they’ll need somewhere to leave their equipment each night
  • Make clear space around where your current water storage is, or make your attic accessible as best you can as they’ll need space to work and remove these if applicable
  • Make space in the garden for all the equipment, pipes and boxes that need to be delivered and obviously, clear where the heat pump needs to go.

Day 1

Old boiler and tank is removed, showing the empty cupboard where they both were
Felt good to get rid of that old boiler and tank, also here’s the empty cupboard where they lived.
  • Delivery of items for install (including 200 litre water cylinder, 8kW Midea heat pump, 5x radiators, 1x towel radiator among many other things)
  • Removal of immersion heater, old boiler, and two old water storage tanks
  • Prepping the cupboard for the cylinder (new, stronger floor needed)
  • Placement of cylinder in cupboard
  • Removal of old pipes
  • Loss and restoration of cold water
  • Loss of hot water
  • Recycling of old tanks and boiler

Day 2

  • Removal of old radiators
  • Hanging new (larger) radiators
  • Plumbing in cylinder, adding extra stop valves
  • Installing most of the items in the old boiler cupboard
  • Putting the heat pump unit in place
  • Deciding on plumbing and wiring routes for heat pump
  • Recycling of old radiators

Day 3

You can see the water tank, expanders (white for cold water, red for hot water) the diverter at the top and the black magnetic filter on the right.
  • Hanging last radiator
  • Soldering all the new radiator connections
  • Drilling three holes into the external wall for the heat pump connections
  • Placing and soldering pipe route from outside of house into old boiler cupboard
  • Restoration of hot water (from new immersion heater)

Day 4

It’s important to have some space around all sides of the heat pump, this shows it quite well.
  • Moving our outdoor tap
  • Putting feet on the pump to give it clearance on our drain
  • Unboxing pump and placing it in our garden
  • Finishing external pipework and connecting to heat pump
  • System pressurised and air removed by bleeding radiators

Day 5 (half day)

Ready for the electrician to start.
  • Filling in old flue hole
  • Clearing rooms of tools and mess
  • Adding lagging (foam wrapping) to internal and external pipes
  • Registering our new water tank

Day 6 (half day)

  • Electrician visit – drilled holes for power wires to heat pump
  • Connected heat pump to home, from line to fuse box
  • Added an outside isolator switch
  • Added meter to calculate electricity usage just for heat pump
  • Wired in internal controls for heat pump and immersion heater
  • Installed Midea heat pump internal control and Honeywell wireless thermostat and receiver
  • Loss of about power for about two hours total on and off (with warning)
  • Commissioning of system and showing us how to use our three control panels (heat pump, thermostat, immersion heater)
  • Handover of manuals etc.

Wrapping up

So all in all it was a really positive experience and I am looking forward to how our system does in its first year. I’ll be collecting lots of data as I go to compare how the heat pump does to our old gas boiler.

Next time: initial impressions from our first few weeks with a heat pump and what it feels and sounds like inside and outside the house. Plus some starting impressions of how it’s managing heating our water and home.


How to find out more about getting a heat pump

We’re getting an air source heat pump installed at the moment. It’s something that we’ve been thinking about doing for about a year now but when our ancient boiler finally died this spring we decided to make the leap to heating our home in a cleaner way.

The main thing that put me off doing it sooner was the vast amount of unknowns about what heating with a heat pump would actually mean in practice. So I want to use this as an opportunity to learn as I go and crucially pass on what I’ve learnt to others who are heat pump curious.

I want to know all the little things that matters day to day, like what it looks and sounds like, how you service it, and what the controls are like and how long it takes to get used to the different way of heating your home.

My information is UK-centric, but those of you outside of the UK may still get some benefit.

I’m not going to talk about how heat pumps work because there’s plenty of other advice about this online.

Aren’t heat pumps expensive?

Well, yes they are. Ours is going to cost about £12,000, but at time of install we get £5,000 up front in subsidies from the UK Government for not choosing another gas boiler. This is organised through our installer.

To look at it another way though. I work from home now, as I have a fully remote job I never go to an office. So the largest part of my carbon footprint is now heating my home. Previously my rail season ticket was about £3,300 a year (not including price increases), so two years of not travelling by train has paid for our heat pump.

What an indictment on the state of the British rail network…

Ground source heat pumps cost more, and need a big garden or space around the property to dig down into which we do not have. So I can only share my experience with an air to water heat pump.

What are the benefits?

I’m doing this to reduce my carbon footprint. The upgrade we’re going for makes more economic sense for someone not on mains gas.

We’ve been advised that our monthly energy costs should be comparable to our old gas boiler. Electricity usage is more expensive than gas in the UK, but the heat pump generates up to 3 times the energy for the amount of energy used to create it. So it should work out about the same, or slightly less than what we pay now. I used to work for two green energy companies and doing the maths, this checks out. It will be more expensive than quoted, but this is because the energy prices are going up so much generally.

Given the economics of the world too, I’m primarily also doing this to reduce my gas usage. It will reduce the local pollution in our area. Plus more electricity and a greener grid is key to energy independence.

Energy prices are only going to go up from here on in as prices in the UK are tied to the energy price cap which is due to go up this autumn, so it’s going to be harder for me to measure the financial benefits in the short term, but I’ll collect all the data I can.

Some stats about our home (pre heat pump)

How well a heat pump works is based on your home and things like its physical footprint, how big it is, the number of rooms you have and how much heat loss you have.

  • Victorian semi-detached property with a small modern extension
  • 3 bedrooms
  • Energy rating D (with potential to be B)
  • Powered by green energy supplier
  • 6 radiators in the house
  • Done all the easy insulation we can do, we have some insulated floors and split bedroom/attic roof insulation that needs upgrading
  • No underfloor heating
  • 75 square meters of floor space over three floors
  • Our house has rising damp (which is common for something built around 1891). It’s been treated, but something we have to balance when improving insulation more
  • We have a wood burner as backup heating, although this is used sparingly due to local pollution
  • Our average electricity usage in a year is 2,861 kWh and our gas is 12,409 kWh
  • Normally have our heating on from end of September to March, we don’t have our heating on overnight and have our thermostat at 19 degrees when we do.

What are the steps for getting started?

  • Find an MCS accredited installer – this is important for making sure that the correct steps are followed for both assessing the suitability of your home and handling the commissioning and eligibility for the boiler upgrade scheme (which gives you £5,000 towards a heat pump, paid directly to your installer)
  • Get a suitability assessment booked in, this is where representatives from your installer visit your home, measure your rooms and your radiators and look as your current plumbing and heating and complete a form that will form the basis for your quote. From this they’ll work out what capacity heat pump your home needs, and what if anything (such as radiators) need upgrading. They’ll need details from you like where your energy meters are, where your fuse box is, where your boiler is currently sited, where your cold water tanks are etc
  • They’ll also measure the space where you intend to place your heat pump. For air source you need more space than you think – over a meter wide and two meters clear space in front. There can’t be anything blocking the air flow. We had a small wall that had to be removed for example. They’ll let you know about the feasible spots for your heat pump unit, and where your water tank should go – normally in the location where your boiler was
  • You’ll also need a new Energy Performance Certificate (EPC) created. You may already have one if your home has any other green tech installed, or if it’s been put on the market in the past two years. Otherwise you’ll need a separate, independent assessor to come to your home to assess how your home is currently heated, what insulation you have, and what your likely heat loss is. An EPC is a requirement for proof of eligibility for the boiler upgrade scheme
  • Both of these checks take about an hour each, and are organised through your chosen installer. It’ll cost about £150-£200 although many installers seem to deduct this from the overall bill if you do decide to go ahead
  • Get a few different quotes and compare their advice and prices, ask lots of questions. It’s a lot of money to spend on something that’s still quite a new idea for a lot of people
  • Once you have a quote, you should an an estimation of your energy costs/usage, and your expected stats, including your Coefficient of Performance (COP) and Seasonal Performance Factor (SPF). Basically how efficiently your system could work in your home at its best and at different times of the year
  • Visit a heat pump – if you’ve not actually seen one, they’re rather like an outside air conditioning unit that works in reverse. I didn’t know anyone else with one, but it would be good to get an idea of their size and what they sound like. I didn’t have this option sadly.

What are some of the pitfalls?

  • Don’t you need underfloor heating? Some homes might, but our small little victorian semi should be toasty enough with upgraded radiators
  • Don’t you need to be fully insulated? Yes, but you should really be with gas as well and many homes are not. This is something we’ll have to improve more as we go
  • It may take more time – depends on ow busy your installer is but in theory we could have gone from about a month from initial enquiry to install
  • Prices for running a heat pump are going up but then the costs for heating are going up across the board. I’m hoping this will make our home more resilient to this in the longer term
  • They people say don’t heat as well, this may be subjective, it uses slower ambient heat, either way I will be a good test subject because I run cold and really prefer warmer weather
  • Refrigerant is needed for heating to work, but arguably has less impact and no air pollution fumes when compared to something like gas or oil
  • Heat pumps are more hands on than gas, requiring you to monitor how it’s working, optimise and improve things as you go. I find this sort of thing fascinating, but others may not
  • There are fewer people to service and help when things go wrong but this is something that should improve over time.

Heat pumps require some behaviour change

Heat pumps use ambient heat, which means setting the temperature for it to come on and leaving it on (even overnight) rather than boosting up the heating as and when you need it. The carbon cost is a lot lower than having the heating on and off as with gas, but that is going to take some getting used to. I’m so used to turning something off when it’s not needed, but that’s simply going to make the heat pump less efficient at what it does.

Some people say heat pumps don’t heat as well, but they heat your home different to something like oil and gas, you can’t boost the temperature up really quickly, and that leads people to say they’re not as warm, when it simply works differently, and takes some adjustment.

They make some noise outside so it’s worth having a chat to your neighbours about it, but this should only be an issue in the winter when it’s working harder. It’ll be quieter than the road at the back of our house at up to 35 decibels. I am looking forward to hearing this in the real world.

Our planned system

  • Midea 8kw air source heat pump using R32 refrigerant
  • 200L water cylinder (with immersion heater)
  • All but one of our radiators are being upgraded, one is being reused in one of our smaller rooms
  • Old boiler will be taken away and recycled, as will some of the old piping, and supply to boiler will be capped off (as we still have a gas hob to cook on)
  • Coefficient of Performance (COP) estimated at 3.67 (average)
  • Electricity usage total estimated at 4,605 kWh (heating and hot water)
  • Installation will take about 5 days

What could I improve in the future?

This heat pump itself will last about 20 years, and I expect the costs will come down over time, a new unit will be much cheaper by the time we need one again, and the pipework, electrics and radiators will already be upgraded for this purpose by our initial install.

Heat pumps don’t improve your rating on your EPC rating as far as I can tell which seems a bit of an oversight, but clearly they do improve the energy impact of your home, so I hope this will be addressed.

There are no heat pump tariffs in the UK at the moment. Seems to me that we should be charging people less for electricity and more for gas due to its lower carbon cost. Some suppliers are trialing heat pump specific tariffs in the UK, and there are smart tariffs (which charge you less when there’s less strain on the grid). Reducing the unit rates for electricity or having cheaper rates to use in the summer would encourage more people to make the leap.

Retrofitting insulation – our EPC advises that we could improve our energy rating by at least one letter by looking at this. it’s on the list, but is potentially more expensive than the heat pump and more intrusive in terms of the work needed (scaffolding etc) and changes the outside appearance of our house. We have few cavity walls in our home, so this or internal insulation are our only options I believe.

We might consider putting some solar panels on the roof, but we don’t have a lot of feasible roof space that would make this viable, however it’s more of an appealing prospect with a heat pump (we’d use it primarily to heat water).

We will remove our gas hob in the future, as we’ll only be paying the standing charge for gas to cook with (we have an electric oven).

Next time

What happens during installation, and more pictures.