A heat pump can heat any building that a gas boiler can heat - it just needs to be sized correctly and the system designed correctly. Here is an example of a Grade 2 Listed building built originally in 1805 heated by an Air Source Heat Pump.

Because heat pumps are so efficient at harvesting energy from the ambient environment, a house will be cheaper to heat using a heat pump than with a gas boiler, even given the unfair disparity between electricity and gas unit prices, as illustrated here.

It is important that the effective surface area of radiators is sufficient to deliver the energy needed, at the lower flow temperature used by heat pumps, but that can be done with double panel or triple panel radiators. Underfloor heating can enable a lower flow temperature (eg. 35°C) but radiators can easily deliver the same heat with a slightly higher flow temperature. In the example of a 1805 house given above (Myth 1) only a third of the radiators needed up-sizing from double to triple panel when moving from gas boiler to heat pump.

A living space is typically heated to 21°C, and a large enough radiator warmed to 40°C will have no problem heating the room. New building regulations say that the flow temperature must not exceed 55°C, so the old practice of having radiators heated to 70°C or more is unnecessary, wasteful and unsafe. With a heat pump the system tends to stay on for longer to compensate for slower rate of heating the house up, and in many cases they are kept on overnight but set back a few degrees at night. This turns out to be cost effective and maintains comfort, instead of the wild swings often experienced with gas boilers.

Where radiators need to be increased in size (and this is by no means always required), they often do not need to be larger in length or height; just fattened a bit in going from double-panel to triple-panel. This can be achieved without any need for changing pipework.

The modern building regulations state that hot water from the tap should not exceed 48°C, and a heat pump has no problem achieving this. It is actually unsafe to stick with the very hot temperatures often existing with gas boiler systems. With heat pump and unvented hot water tank, showers are at mains pressure and an unexpected advantage for many when switching to a heat pump.

A Ground Source Heat Pump (GSHP) will be more efficient than an Air Source Heat Pump (ASHP) in the depths of winters, but over the whole year the advantage is only marginal and unlikely to justify the much greater costs (about double) of a ground sourced system. In any case, mostly don’t have the area of ground needed (and if one goes for bore holes the costs are likely to be 3 times as much, which significant risks due to water tables, etc.). The great majority of individual householder systems will be ASHPs, but there is a big role for Water Source Heat Pumps (WSHP) than can be used for District Heating (Stroud District Council’s offices in Ebley are heated using a WSHP).

This may have been the case 20 years ago, but manufacturers have worked to eliminate this (mainly by having larger fans that therefore can run slower and quietly). When the birds are singing, you will barely notice a heat pump even from a few feet away. They are no noisier than a microwave. Also, when installer follow MCS* standards, they will consider locating the heat pump to avoid any potential issues with neighbours for example. As we learned from a talk on heat pumps, people always asks about noise when they consider an Air Source Heat Pump, but never raise it again after it is installed.