Skip to main content

Peter and Jane, moved into their semi-detached home in Douglas to find they’d inherited a gas boiler that was just one year old. In a bid to be more efficient and lower their carbon footprint, Peter, as an experienced engineer coupled with some extra research, found that by installing a heat pump linked up with their existing system, they could reap the benefits of operating a cheaper hybrid heat pump system for heating their home.   

They had the streamlined and free support of the manufacturer Valiant UK, based in Belper, who are leaders in the heat pump business with their notably quiet systems. An online App was used to configure and specify the system that was the best fit for their home and consisted of a full list of the required components along with Vaillant part numbers and circuit diagrams for both plumbing and electrical circuits; all was sourced by a local Isle of Man supplier. The process was relatively hassle free and the results highly efficient.   

Valiant’s super quiet system and valuable support 

As they had a Valiant gas boiler, they opted for a Valiant aroTherm Plus 7KW heat pump, noting it was one of the quietest and efficient models on the market. It also contains the efficient and environmentally-friendly refrigerant  R290, or propane.  R290 has a Global Warming Potential (GWP) of 3 compared with other heat pump manufacturers refrigerants with GWP’s of up to 2088.   

R290 is the refrigerant gas that circulates inside a heat pump and captures warmth from the outside air, even on cold days down to –20 degrees. Like a fridge in reverse, the device works by compressing the refrigerant into a useable high temperature and pressurised energy source which, in this case, is transferred to a glycol water mix which is piped into the property. 
The BBC reports on R290 refrigerant too, it is up to 34% more efficient, which helps heat pumps supply higher temperatures, and with this technology advancing means they can be suitable in even hard to heat homes. [1]  These higher circulating temperatures also alleviate the need for an additional electric water heater in the system by achieving water circulation temperatures of 75 degrees killing legionella bacteria that can survive up to 60 degrees.  This temperature must be achieved throughout the system for 1 minute to kill the legionella bacteria and can be selected in the software interface for peace of mind.   

To size the right heat pump Peter undertook a room by room heat loss survey using Valiant’s free online software. During this process you can further insulate your home and make improvements to size down the heat pump if needed. 

When arranging the install, it all fell under Permitted Development too as the heat pump did not exceed 42db and observed the property boundary distance requirements.  

The heat pump kit was £6,500 all sourced via CuPlas Callow in addition to the plumbing work at £4,500 which took a week in total. The couple chose to upgrade radiators in two rooms and opted for two Climaventa fan assisted heaters which are up to 4 times more efficient in heat dissipation, 50% smaller than a standard radiator and are completely automatic and smart in operation. 

Smart software and buffer cylinder 

With Vaillant's built-in smart software, the hybrid system (in just 10 minutes) assesses the outdoor temperature and turns on the heat pump. It’s also readily programmed with the Isle of Man’s utility tariffs, and decides which system is cheaper and more efficient to run.  

On the rare occasion when outside temperatures are very cold, the intuitive software opts to supplement the heat pump with the gas boiler kicking in for just 10 minutes to give the system a boost.   This brings the circulating water up to the 55 degrees for the air source heat pump to take over.  This hybrid system ensures that the property benefits from instant heat rather than the delayed effect found in other heat pump systems. 

A 45 litre buffer cylinder which is needed for the hybrid heat pump system is also a clever device.  It is connected to both the gas boiler and the heat pump and also acts as a store of hot water for the system to call upon for either heating or defrosting the heat pump in freezing temperatures to protect itself.  As with all heat pump installations the more water in the system the more efficiently the heat pump runs and reduces cycling; a constant on/off condition that can wear out a heat pump compressor and void warranties. 

Benefit from better tariffs and high efficiency 

In the winter, the couple like to maintain a very cosy 22 degree temperature in their home and utilising the better Cosy Tariff provided by Manx Utilities. They run the heating 2pm – 4pm which then warms their home for the evening, and again from midnight until 6am, which maintains a comfortable heat throughout the morning. 

As well as value tariffs, the heat pump is currently achieving a COP of 4.7. So for 1KW of electricity used it achieves 4.7KW out. This means the heat pump generates 3.7KW worth of heat for free.  As with all heat pumps, the COP does vary according to outdoor temperatures and various parameters.  

Supporting efforts also make a difference 

Wallrock KV600 thermal liner wallpaper was used to decorate their hallway and any other external walls. The thermal wallpaper was easy to apply without the help of a decorator and made an immediate difference.  

Thermal curtains also hang over their front door and all windows. Peter and Jane monitor their energy use on the smart heating control and remotely via the Vaillant App on their phone. 

Cooling on tap 

Thinking of the rising temperatures we may see in the future, the couple also purchase a little additional component plugged into the Vaillant heat pump it will reverse the whole system and provide chilled water to the fan assisted and normal radiators within the house to cool the property in the summer.  This function can be programmed into the smart controller as well. 

The combi gas boiler still provides hot water as normal and should the need arise in the future, when the boiler is removed, the heat pump system can be modified slightly to heat the hot water as well. 



  • Air Source Heat Pumps
  • Hybrid Heat Pump
  • Boiler Ban
  • Fossil fuel heating ban
  • Fossil Fuels
  • Clean heating
  • Home Energy