Considering replacing an oil or gas boiler with a heat pump? Good idea but there are a few things you really should know in advance to ensure a successful changeover. Discuss with companies interested in your business – see how they respond.

1. You are almost certainly going to need bigger radiators. It’s not companies quoting for unnecessary work. Heat pumps work best when the radiators can heat the house using water at 30 – 40C. Your boiler probably supplies water at 60C plus. A bigger surface area is needed to transfer the energy at lower water temperatures – so bigger radiators. The plus from larger radiators is that the heat pump will be able to maintain your house at a comfortable temperature at lower cost.

2. You will need space for a hot water cylinder – heat pumps cannot be combi boilers. If you already have a hot water cylinder it may need to be bigger as heat pumps can’t heat your house and hot water at the same time.

3. Still on the subject of hot water you will need a scheme to protect against legionella bacteria – heating the hot water tank to 60C every few days. Some heat pumps can do this or it might be with an electric immersion heater on a timer. Find out what is proposed and what it is likely to cost over a year.

4. Throw away your thermostat – even if it is a ‘smart’ thermostat. Use a wireless room sensor instead – it feeds the actual room temperature to the heat pump allowing for much better control than the on/off you get with a thermostat. Room temperature control will be more comfortable and save you money – win, win.

5. Sort out drainage for the water than will drip from the heat pump. The heat pump extracts heat energy from the air so emits cooler air than it draws in. Cool air can hold less water than warm air so the excess water condenses on the surface of the heat pump and drips out the bottom. Without drainage it’s unsightly at the best of times and dangerous in winter when it freezes.

6. A heat pump will take a couple of hours or more to heat your house from cold. It’s best to leave the heat pump enabled all the time and set a temperature profile (in the heat pump control system) that matches your lifestyle. This doesn’t mean the heat pump will be heating all the time – that will depend on the outside temperature and how well insulated your house is.