Bungalow, hosted by Roy

Since moving in we have improved the loft insulation, added solar panels (32), replaced the gas boiler with a heat pump and, just recently, added an electric car. Other aspects of the house (eg walls and windows) were either already satisfactory or difficult to improve (floors). Our primary objective all along has been to reduce our CO2 emissions but there have been running cost benefits also and these, I would guess, will be of interest to people generally.

Having both solar panels and a heat pump means that some of the electricity for the heat pump, particularly in the spring and autumn, is self generated and thus very cheap. Having both an electric car and a heat pump means that we can be on a tariff with very cheap nighttime electricity which further reduces the financial cost of operation. Data collection for the latter is in its early stages. Prior to the electric car, our net annual gas and electricity bill was the standing charges (about £350) minus £15. We have yet to see what the situation will be with the electric car included.

The heat pump has worked well. It is extraordinarily quiet outside and very quiet inside   the house. Outside you can only hear the unit if there is no wind, no traffic, no lawn mowers, no dogs and no birds singing. Any of these and the noise made by the heat pump is completely drowned out. Inside, only in the kitchen and loo can any noise be heard at all. In all other rooms you simply cannot hear whether the system is running or not. The kitchen has a fan assisted radiator as there was not room for an ordinary radiator. The noise it makes however is far less than that made by kitchen appliances (microwave, air frier, kettle) and does not interfere with normal conversation. In the loo, it is possible to hear the circulation pump but this is not any sort of a problem.

The heat pump has had not the slightest difficulty maintaining room temperatures in the coldest weather we have had. Initially there was a problem with the radiator system slowly loosing pressure. This was traced to a faulty Schraeder valve and since then there have not been any problems. This problem had, of course, absolutely nothing to do with the system having a heat pump. Boiler systems can and do have exactly this problem.

Last year our heat pump had an overall COP of 3.55. This gives a 38% reduction in CO2 emissions even if all the extra electricity demand it creates came from burning gas. It also makes it marginally cheaper than a gas boiler even without the benefits of also having solar panels and electric car tariffs.