Gas boiler or heat pump: what to know before you switch

More and more homeowners are asking whether to replace their gas boiler with a heat pump. The decision should rest on your house's data, not on trends. Here we explain how the technologies differ and what we look at when preparing a proposal.

The fundamental difference

A gas boiler produces heat by burning gas: at best almost all the fuel energy becomes heat, but never more than the fuel contains. A heat pump works differently – it does not convert energy into heat, it moves heat from the outdoor air or the ground into the house. Electricity drives the compressor and pumps, while most of the heat comes from the environment. That is why heat pump efficiency is expressed as coefficients (COP, SCOP) well above one. More in SCOP, SEER and COP explained.

Advantages of a heat pump

• No combustion – no chimney, no flue gases, no gas connection to maintain.
• One system for heating and hot water – for example an ECODAN all-in-one unit with integrated cylinder.
• Cooling option – air-to-air systems and some air-to-water solutions can cool in summer.
• Convenient control – wall controller or MELCloud app, schedules, remote monitoring.
• A good match for solar PV – if you have or plan solar panels, the heat pump runs on the same energy.

What must be assessed before switching

• Heating system temperature. Heat pumps work best with low-temperature systems – underfloor heating or adequately sized radiators. If your radiators need very hot water, they may need resizing or a higher-temperature solution.
• Heat demand. The best starting point is your gas consumption in previous seasons, which shows how much heat the house actually uses and allows accurate sizing. See what size heat pump do I need.
• Electrical supply. We check whether the existing connection is sufficient or needs upgrading.
• Space for equipment. The outdoor unit needs a suitable spot for noise, condensate and access; the indoor module needs room in the boiler or plant room.
• Energy prices. Running-cost ratios depend on electricity and gas tariffs, which change. That is why we never promise a fixed savings percentage – we show scenarios using the prices you enter.

A hybrid option

In some homes it makes sense for the heat pump to be the main source while the existing boiler stays as back-up for the coldest days. This allows a gradual transition. Our engineer decides whether it suits your system layout.

How to estimate running costs

The logic is simple: annual heat demand divided by the system's seasonal efficiency gives the energy needed, multiplied by the tariff. For a gas boiler you use its efficiency and the gas price; for a heat pump its seasonal efficiency and the electricity price. Our heating cost calculator lets you enter your own data and shows every assumption. More in heat pump electricity use in winter.

What the switch looks like in practice

The work usually runs in stages: survey and heating system assessment, equipment selection and proposal, preparation of the outdoor unit base and pipework, installation of the indoor module and connection to the existing system, electrical work, then commissioning and fine-tuning. If the gas boiler is removed, gas appliances must be disconnected by specialists authorised to do so. At commissioning we set the heating curve and hot-water mode and show you how to operate the system. We recommend reviewing settings after the first cold spell.

How we help

We handle the whole switch in one place: we assess the house and heating system, select Mitsubishi Electric air-to-water or ground-source equipment, install, commission and fine-tune the system, and service it afterwards. Start with the system finder or send a project request straight away – include your gas consumption from previous seasons and our specialist will prepare a proposal.