So, was it worth it? Martin concludes the story of his family’s decisions and experience of switching to an air source heat pump.
Find the journey so far here and here.
It has been about four weeks since we had our heat pump switched on and since then we have had a houseful of people in the house over Christmas and we have experienced some cold weather. So I think it a good time to let you know how it has performed.
The heat pump is designed to provide all our hot water needs as well as run the central heating. The management of the system is very different from our previous gas system in that it is switched on at all times. With the old system in the winter we would generally put the water and central heating on twice a day and top it up when necessary. Now we have continuous hot water and we can control the house temperature using an app on our phones. This means we can control the house temperature in blocks of time of our design.
The system is much less responsive compared to a gas system. This is because the temperature of the radiators is about 50 degrees compared to about 70 degrees in our old gas system. With cooler radiators the rate at which the house changes temperature is quite a lot slower and so we tend to keep the house at between 15 (at night) and 17 degrees. We have noticed that we are getting a more even temperature in the house. We have also noticed that with the cold weather the heat pump is working much harder and increasing the temperature of the radiators slightly allowing the house to reach the set temperature. During cold weather the heat pump becomes less efficient as it takes heat from cold air. However, we have been told that averaged over the year the pump should have a seasonal coefficient of performance (SCOP) of 3.59 – that means for every 1kWh of electricity used to power the pump 3.59kWh of heat will be produced.
The sound level of the pump varies according to how hard it is working. When working at its maximum, we can hear the pump – it is outside our kitchen window. The noise is well within tolerable limits and not much louder compared to a gas boiler. It is worth noting that from Spring to Autumn the pump will be operating for short periods of time and at well below maximum effort.
Any snags? The hot water system is now pressurised and as the system was switched on a hot water pipe to a basin sprung a leak. This was easily fixed but it is worth noting that old pipework could be susceptible to leaks if it is pressurised. We have also found that we will need to replace a couple more radiators for larger ones in rooms where we feel that a higher temperature is needed. The cost of running the system is a bit more expensive (about 10%) compared to our old gas boiler but the advantage is having the house continually at a comfortable temperature.
Are we pleased with the heat pump? Yes we are. Just looking at the machine as it takes heat from the air and pumps it into our house is awesome! We are also confident that if we have problems, the company that fitted it will deal with it. Please do talk to Christine or me if you have any questions. You are very welcome to pop round to have a look at the system.