We had a Vaillant 7KW heat pump installed in June 2024, along with a new hot water tank. We took the opportunity to bring the hot tank into the insulated part of the house and shortened most of the pipe runs. Every heat pump installation and house is different, so heat pump happiness is a personal and subjective experience.
Our family’s experience
Our first experience of heat pump happiness was that the heat pump was much quieter than we feared. I walked into the garden when the installation engineer was running the heat pump flat-out and didn’t even realise the fan was running. After all the scare stories about noise, this was a delightful surprise.
Our next experience of heat pump happiness was the readily available hot water. Our old hot water cylinder was too small for the house and cooled down quickly, so a second shower in the morning could be cold. The bigger tank, storing more water at a lower temperature and with shorter pipe runs, means we always get hot water from the hot tap. Bliss! And it’s cheaper than gas. In summer, we were getting between four and five units of water heating for each unit of electricity we put in.
It’s a warm and welcome change to come into the house on a cold day and feel the whole house being at a comfortable temperature. The pump controls work out the correct running temperature depending on the outside temperature.
For the bill-payer, heat pump happiness is running the heat pump in the first chilly weather in September and seeing that for each unit of electricity used for heating, we generate nearly six units of heat (according to the app, at any rate). So not only are we no longer polluting the atmosphere by burning gas – we are also saving money. And that’s before we factor in heat pump tariffs (which everyone can get once they have a heat pump) and our solar panels and battery.
Maybe the best bit of heat pump happiness was working carefully with the installers to make sure we could put our 25-year-old Ikea kitchen back together again after the installation with the pipe runs hidden behind the kitchen units.
Heat pump happiness is… well, you get the idea. It’s a big change in thinking about heating, but we’re very happy – particularly since our gas boiler broke down ten days before the installation and we didn’t have to pay to get it repaired!
There are three things you need to know to achieve heat pump happiness.
A gas boiler is a hare, a heat pump is a tortoise
If you have a gas boiler, you probably set it to come on when you want the house to be warm, running at high power sending hot water round the radiators for a short time. When the heating’s on, you expect your radiators to be hot. That’s fine, particularly if you’re out most of the day and only need the house to be warm in the morning and evening. But it’s not the most efficient way to heat a house.
Heat pumps work differently. Instead of using electricity to heat the house directly, they work like a refrigerator. You probably know that the heat exchanger on the back of your fridge gets warm, while the inside of the fridge gets cold. Heat pumps cool down the outdoors and warm up your home. For each unit of electricity it uses, a heat pump produces several units of heat. Ours claims it’s giving us around five units of heat for heating just now, and four for hot water for each unit of electricity used.
Heat pumps are most efficient when working at much lower temperatures than a gas boiler. Instead of heating the house in quick bursts (like a hare) they run slowly and steadily for a long time (like a tortoise). Often the radiators are scarcely warm to the touch. They put in the same amount of heat but over a longer time. The house stays at a comfortable temperature all the time, and your bills are way down.
The other thing that makes a heat pump happy at low temperatures is bigger radiators or underfloor heating. That way, the temperature can be lower for the same amount of heat. If you can’t cope with the disruption just now, you could decide to see how you get on, and if necessary, upgrade your radiators later. On the plus side, you can do it when it suits you. The downside is that you miss out on another heat pump happiness factor. A heat pump installation is free of VAT, including any radiator changes or new underfloor heating. If you upgrade your radiators later, you’ll pay VAT on them.
The biggest heat pump happiness factor of all is that you can get grants of £7.5k from Home Energy Scotland towards a heat pump installation if you live in town, or £9k if you’re in the country. The application process is rather time-consuming and difficult (a bit tortoise-like), though Home Energy Scotland will help you work through it. With the grant, the heat pump installation won’t cost you much more than installing a new gas boiler. Don’t accept the kind offer of a heat pump salesperson to help you submit the grant application after you’ve paid a deposit – they have a strong vested interest in you buying from them rather than somebody else.

Insulation is very important
Contrary to popular belief, you can use a heat pump in an old building. You need the heat pump system designed for your building, using the best estimate of its actual heat loss on a cold winter’s day.
Your house loses heat in two ways: draughts, and conduction through the walls, floor and roof. Home Energy Scotland won’t normally give you a grant for a heat pump unless you already have wall and loft insulation, though they do offer grants for these as well. Also eliminate as many draughts as you can, though make sure that you don’t create a condensation problem. Old Scottish houses were designed to be draughty, to avoid the build-up of moist air, and ensure plenty of oxygen for the coal fires. A really draught-proof house needs deliberate ventilation; the best kind is what’s called a ‘mechanical ventilation and heat recovery’ (MVHR) system.
Also vital is the insulation of the critical parts of the heat pump system. If the pipes connecting the inside and outside units are not really well insulated, a lot of the money you’ve spent on your heat pump – and will spend on electricity – will be spent heating areas of your house you don’t live in and parts of your outside walls. Heat pump happiness depends on getting a contractor who will do a brilliant job of insulating all the pipework in the system. And use good quality material that is suitable for the environment – it might need to be UV and mouse-proof, for example!

A competent and caring contractor is extremely important
Getting a competent contractor is a big heat pump happiness factor. Because electricity costs three or four times as much as gas – if you’re paying a standard variable tariff, you need the heat pump to be three or four times as efficient as a gas boiler to break even on running costs. Happily, a well-designed heat pump installation is perfectly capable of doing that. This is not a DIY job!
We spent two years talking to heat pump suppliers before finding three we’d have been happy to go with, one of which we chose. You don’t want to do that. Here are our thoughts, they might help.
There is no perfect recipe. A sole trader may be an expert, give you excellent advice and conscientiously install and maintain an excellent system (I know one I can recommend!).
A large company such as a utility company should be able to achieve levels of price, consistency and quality that small companies can’t match – but equally, they may hire the cheapest subcontractors, not give them time or budget to do a proper job and refuse to quote if your house doesn’t suit their cookie-cutter operating model.
Unless I knew an expert and they lived close to me (the one I know doesn’t) I would only feel comfortable with a smallish fairly local company that has been in the business for some time, is clearly going to stay around, doesn’t subcontract but uses and trains its own staff for installations, and offers service contracts. Also look for very high ratings on Trustpilot, and good personal recommendations if you can get them from recent and not-so-recent clients. You want a company that sticks to a few well-known and reputable brands of heat pumps with a strong market presence in the UK so you can be confident of being able to get spares in ten years’ time.
Most importantly, choose a company with the necessary certification (usually the Micro-generation Certification Scheme (MCS), though there are now others). This is essential to allow you to get installation grants and then access to special heat pump tariffs from your electricity supplier.
MCS is paperwork-heavy and doesn’t necessarily mean that the company is good at installations. It does mean the company is required to base their proposal on a fairly detailed heat loss assessment of your home, which is really important. Look at other factors as well. Check them on Company’s House to make sure the directors are committed to the one company and don’t have lots of other directorships in existing and folded companies. Heat Geek trained or certified is the gold standard for competence, but there are other good companies out there as well. Have a conversation about weather compensation and how to set the flow temperature. If they seem to know less than you do after watching a couple of heat geek videos that’s a bad sign.
Refuse to give unreasonable deposits. If you pay a deposit, you’re an unsecured creditor and are unlikely to get the money back if the company goes bust. A reputable company will take an initial deposit on a credit card, to give Section 75 protection, and not ask for more than 20% on signing the contract. After a bad experience buying solar panels, I will never give a 50% deposit again! The best companies won’t take any money until the goods are on your premises. The very best ones will guarantee a year-round efficiency figure, but I don’t know of any doing that yet.
They should also explain how the system works and set it up for you. Because every home is different, even the best companies may not do a brilliant job of this. To learn more, check out the Heat Geek website and YouTube channel.
Final thoughts
Heat Pump Happiness doesn’t need as much knowledge and research as it did when we started. There are good companies and good products out there, and attractive tariffs. Heat pumps are clean and quiet, offer a more comfortable home, and have the potential to save money as well. Our family is certainly glad of the improvements.