Life with a heat pump in a Victorian house

Published on 30 May 2024 in , ,

Heatpump at the back of our house
Our Midea heatpump, sitting under the kitchen window.

It feels like you can’t go a week without seeing an article about Heat Pumps in the press. Many positive. Some negative.

Heat pumps are touted as the future of household heating. A key solution as the world seeks to reduce carbon emissions, and wean itself off fossil fuels. Fully electric and highly efficient. 

Other articles will firmly tell you they’re completely unsuitable for British housing stock without costly upgrades. And yet there’s an article about a castle in Cumbria that uses a heat pump for heating

Looking at the plethora of articles in the press, I noticed something. They were rarely written by someone who actually had one. One in their very normal home. Although given only about 1% of households in the UK actually have one, this shouldn’t surprise.

But as it happens, in April 2023 we had one installed in our house. Over a year on, I thought I’d share our experiences.

First though, let’s talk about our house.

Our house

Let’s not beat around the bush here. You’re guaranteed to find articles saying stuff about how houses aren’t suitable for a heat pump unless they meet certain requirements.

And at one time this was true. But as one heat pump installer told me, the technology has moved on in a big way. It’s improving every year. And that’s why a recent research project found this:

There is no property type or architectural era that is unsuitable for a heat pump – the Government-funded Electrification of Heat project has demonstrated.

Electrification of Heat project

From Victorian mid-terraces to pre-WWII semis and a 1960s block of flats – the project has proven that heat pumps can be successfully installed in homes from every style and era.

With that in mind, let me tell you my house. It’s a real house that has a very real heat pump.

Our abode is a Victorian semi-detached property built  in 1884. It has four bedrooms, high ceilings, and is spread over four floors.

Lowest floor is the (unheated) cellar. Ground floor contains the kitchen, dining room and living room. A small single floor extension was built at time unknown in order to make the kitchen bigger. The first floor contains two bedrooms, an en-suite and the main bathroom.

The top floor is a converted attic. When built it would have been a single room, most likely assigned as quarters for a servant. At some point it was split into two rooms set into the roof. As such the rooms have sloped ceilings. Most of the light comes from Velux windows. Unlike the rest of the house, the interior walls on this floor are plasterboard. Other internal walls are all brick.

There’s a small (essentially unusable) loft above that. The loft is insulated at least 20cm deep min. We believe the sloped roof in the top floor rooms is also well insulated but we’ve never had the plasterboard off to check. Unusually for a house built in 1884, there appear to be cavities in the walls. There is no cavity wall insulation. All wall windows are double glazed, and all installed in the last 10 years. The Velux windows in the roof were installed in 2022.

Room heating is done by radiators. Before the heat pump, they were fed by a pretty normal gas combi-boiler.

The house is pretty good at staying cooler in the summer and not too cold in the winter. The top floor is the exception. As often happens, the ex-attic rooms get hotter than the rest of the house in the summer. And they’re harder to heat in the winter.  But they’re not terrible or anything.

Wall insulation.

It’s worth a little detour here to talk wall insulation.  Firstly, wall insulation is great if your property is suitable and it’s installed properly.  Our previous house had wall insulation.  My parents house has wall insulation.  It works.  It saves money.  It saves energy.  It’s great!  If your house was built from the 1930s onwards, it’s likely to be suitable.  If in doubt, find a few companies.  Preferably ones who also offer insulation removal services too.  They’ll know when it works and when it doesn’t.

Our house is older, and older houses don’t tend to have cavities. But ours does, so I spoke to two experienced insulation companies.  And the result was the same thing.  For OUR house, it was a no. 

There were multiple reasons.  One was that – due to the age of the house – the cavities were likely to have a lot of crap and rubbish in them.  This would make getting the insulation in difficult, leading to gaps in the insulation.  These gaps would likely create damp patches.

Another massive reason was that we have a cellar.  And damp gets in the cellar.  We were told that the damp from the cellar would be soaked up by the insulation “like a sponge”.  And would cause damp problems. 

We don’t currently have any damp problems in our house.  And I certainly didn’t want to introduce any.  We ruled cavity wall insulation out.  This did cause some extra work and complexities.  Nothing that couldn’t be solved in the end though.

Why a heat pump?

We looked at getting a heat pump for two reasons.  One is that we wanted to be more environmentally friendly, and heating is basically the biggest carbon impact an individual household has.  Another was that our gas combi-boiler was getting a bit old, and would have needed replacing in a few years time.  Finally we were looking at re-doing our kitchen.  Most likely the boiler would have needed replacing AFTER the kitchen had been done.  If we’d looked at heat pumps at that point, we could have caused damage and disruption to our shiny new kitchen. 

Of course, heat pumps aren’t the only solution.  We could have had a biomass boiler.  But that’s still burning fuel.  Or an electric one.  But they are very expensive to run.  For a while hydrogen got spoken about a lot.  But in a domestic setting it’s completely unproven.  No domestic trial has even been run, yet alone been successful.  In contrast heat pumps are a proven technology.  They’ve been around for decades. 60% of houses in Norway have heat pumps.  43% in Sweden.

I confess, I was still doubtful.  Scandinavian houses tend to be very well insulated.  But then I read about that castle in Cumbria being heated by heat pumps…. Well frankly if a castle can, surely a Victorian semi will be fine? Talking to some installation companies, they agreed.

Our Heat Pump System.

The water cylinder and lots of pipes.
The water cylinder tucked away in a corner of our cellar.

Before I talk about our system, a very quick introduction to the technology.  There are two sorts of heat pumps.  First are ground source which take heat from the ground.  Ground source heat pumps either need very deep boreholes, or pipes being laid across a huge land area.  Heat from the ground is used to heat the water.  One installer I spoke to told me that they’re better for new builds or if you have a big field. 

For most people retrofitting a retrofitting a house, an air source pump is likely to be your best bet.  These take in air, and convert it into hot water.  Our heat pump can take in air even when it’s minus 20 outside, and convert it into water that’s up to 65°C.  This sounds bonkers, but it’s true. The Guardian has a lovely piece on the science that makes this happen.

Heat pumps come in different sizes, depending on the property needs. As with any new heating system, an installer will look at your property and work out what’s best.  Handily for this blog post, our installer scoped out two systems for our house.  One was assuming we would have cavity wall insulation installed.  The other was that we didn’t.

Had our walls been insulated, they recommended a Midea 12kW pump.  But without insulated walls, they recommended an Midea 18kW pump.  More powerful and more expensive (although the additional expense was roughly the same as the price of what installing wall insulation would have been.)

It’s coupled with a whopping 250 litre hot water tank in our cellar.  Heat pumps are usually coupled with water cylinders as (I am told) they can’t always heat water up fast enough for the rate people use water.  So instead you have a tank of water ready to go that the heat pump keeps topped up.  Whilst the tank can operate as a traditional immersion heater, it’s far cheaper and efficient for the heat pump to heat the water instead.  The tank is very well insulated so the stored water is slow to lose heat.  When water gets used and the tank needs topping up, the heat pump turns on to provide it.  Our hot water is set to a nice 45°C.  Slightly lower than the 55°C or so that a gas combi boiler would be set to, but more than hot enough for showering, pot washing etc.  

Incidentally, you may be aware that water tanks and cylinders can be a breeding ground for Legionnaire’s disease if the water isn’t kept hot enough.  Legionella bacteria grow and thrive in water temperatures that are between 20 – 45°C.  And they’re killed at temperatures of 60°C and above.  Traditional hot water cylinders store water above 60°C for this reason.  Our heat pump system is obviously storing water at a lower temperature. Because of this, it runs a weekly Legionnaires disease prevention programme where it heats the tank water up to the right temperature to kill off any bacteria. So no need to worry about that low temperature problem.

Radiators.

One of the biggest difference with heat pumps is that your radiators won’t necessarily feel as hot to touch.  With a gas boiler your radiator will be filled with water that’s 60-75°C in temperature.  Whilst a heat pump can output hotter water, they usually use water temperatures of 35-50°C.  Lower temperatures means lower running costs, saving you money.  It also means it takes a little longer to heat up your house.

This leads to one of the common things you’ll see in articles about heat pumps.  That because of the lower temperatures, you will need to replace all your radiators. 

Actually, for many houses this is no longer true.  If you’ve got loft and wall insulation and your current radiators are appropriately sized, your existing radiators will likely be fine.

But as I said, we don’t have wall insulation.  We were recommended to have nine of our twelve radiators replaced to ensure our house would be warm enough.  Our new radiators have a larger area and so will work well at a lower water temperature.   Most of the new radiators aren’t that much bigger than you’d normally expect, although a couple of them have three panels on them so are quite chunky. 

Thermostat.

Now we get to an interesting point, because in doing my research I didn’t pay much attention to an important part of the system.  The thermostat.  Well a thermostat is a thermostat, isn’t it? It turns the heating on and off when it needs to.  Modern one probably has a smartphone app.  But other than that, there’s nothing particularly exciting.  Yes?

Well it turns out that thermostats can be quite interesting. 

Our system was installed by a company called Evergreen Energy[1].  They installed a thermostat called Homely[2].  Homely’s a dedicated heat pump thermostat, and has a smart mode. 

Let’s say you want the heating on at 6pm and off at 11pm, and you want the temperature to be 21°C.  With a traditional thermostat the heating comes on at 6pm, heats the house to 21°C, and keeps it there until 11pm when the heating is turned off.

With Homely’s smart mode, you tell the thermostat that you want the house to be heated to 21°C at 6pm until 11pm.  To do that, the heating comes on earlier.  And it heats the house in the most efficient way.  So the heating may come on at – say 4pm but at a lower temperature.  Whereas your gas combi-boiler will always output water for your radiators, Homely can control the temperature of the heat pump’s water.  Lower temperatures equals lower costs.  Heating your house slowly with 35°C water is cheaper than heating the house to the same temperature quickly using 55°C water.  So if it thinks it can get away with a lower water temperature, it will.  Homely also apparently takes notice of the weather, and learns how your house heats and cools, so it can do everything in the most efficient way. 

The heat pump experience.

Heat pump surrounded by snow.
Our heat pump, happily running on a snowy day in January.

So all that said, how has the experience been? 

We had our system installed in April 2023. It’s now been running over a year. Since that time, the weather has varied – as you’d expect. It’s been warm and sunny, and cold and snowy. In January 2024 it was snowing outside and the temperatures fell to -6°C. But even at that point, the house was cosy and warm. There’s a big myth that heat pumps don’t work in freezing temperatures, despite them being really common in snowy countries like Norway and Switzerland. And it really is a myth.

The heating’s now off for the summer, but during winter the house was warmer than it was before. Because heat pumps run more efficiently at lower temperatures, it’s more efficient to maintain the temperature in the house, rather than let the house get cold and then heat it up again. That means the heating is on much of the time. It’s on at times the gas heating was never on. Such as overnight. Because it’s on all the time, it often runs at a lower temperature. Homely picks the right temperature based, and it’s not uncommon for us to find the temperature of the radiators set to be 35°C. And the lower the water temperature, the lower the bills.

There’s also been a big health impact. I have asthma. It’s well controlled and generally fine. But on cold winter nights have always triggered it, waking me up and needing to use my inhaler. Not this last winter. Despite several very cold nights (as I said, it went down to -6°C here) I haven’t needed my inhaler once overnight. We didn’t even put the thick winter duvet on our bed at all.

Operationally the heat pump is pretty quiet.  It tends to get a little noisier when working hardest, such as when there’s snow outside, but it’s still quieter than our gas boiler.

What a lot of people want to know though is the costs. Well heat pumps are at least three times as efficient as a gas boiler. For every 1 unit of energy you put into a heat pump, you’ll get about 3 units back out in heat. For a modern gas boiler, that’s about 0.8. Even taking into consideration the costs of electricity vs gas, running costs of a good system should be cheaper.

Pipes coming out of a water cylinder.
A pointless picture of some pipes coming out of our water cylinder. (Look, pictures of heat pumps aren’t that exciting.)

Alas I can’t tell you for sure that it definitely has been though. It’s difficult to do full on year-on-year comparisons due to weather differences, price changes, and so on. And they wouldn’t be comparing like for like either. Due to the energy crisis, in winter 2022/23 I was being incredibly frugal with our heating costs in order to keep the gas bill lower. In 2023/24, we had the heat on a lot more. But either way I’m sure our monthly costs are definitely down, even factoring in drops in energy prices have dropped a little. And we could easily save more money by turning down the thermostat settings if we wanted. Personally I think I’d rather take the warmer home. And as for our gas costs, now we’re only using it for cooking, they are now about £2 a month for the gas itself. We pay more for for the standard charge (currently about £7!) than the gas.

And the downsides?  Well I’d love to say it’s all perfect and there aren’t any.  But there is definitely a big one.  The heat pump and tank both take up far more space than our old combi.  A gas combi-boiler is incredibly compact and space efficient.  Ours was about the size of an under-counter fridge.  In contrast the water tank is the size of a large fridge-freezer, and the heat hump takes up a similar amount of space to a large chest freezer.  As it happened, we have a lot of cellar space so it didn’t really matter.  Although in many houses the water tank will fit in the spot where the gas boiler was, or in a garage.

From the point of view of our house, the heat pump isn’t in a very discrete location.  It’s quite obvious in our garden.  Ideal world we would have had somewhere down the side of the house out of the way that we could have put it where no one would have noticed it.  But down the side of our house is our driveway, and putting the pump there would have reduced our parking space from 2 to 1 cars.  So a place in the garden it was. 

Incidentally I thoroughly recommend asking an installer how big the unit will be, purely so you can visualise it before it arrives.  I burst out laughing when I saw ours arrive on the first day of installation.  I’d done a huge amount of research into heat pumps, but not once had I asked how big the thing would be!  Such an obvious question and I’d never asked it!

Overall though, we’ve no concerns or regrets.  Heat pumps are different.  But they do work and they work very well.  We’re glad we made the move.  From an environmental point, we’ve made a massive move to decarbonise our home.  And we’ve future-proofed and started our tranisition away from fossil fuels. And all this in a Victorian house with no wall insulation.

And if it works for us, then there’s a very good chance it will work for you.

Footnotes

  1. When we had our system installed, Evergreen Energy were an independent company. They’ve since been taken over by a bigger company, SMS plc. How much that has changed things, I can’t tell you.
  2. At the time Homely was owned by Evergreen Energy, but wasn’t part of the sale to SMS.