Homeowners are unsure whether larger radiators are needed for heat pumps to properly work and questioned whether one can have both radiators and underfloor heating. 

"Is it proposed to replace the radiators with bigger ones, or even install underfloor heating?"

"My understanding is that these don’t work very well on non-new builds and particularly not with traditional radiator systems?"

"Was there any talk of replacing radiators?"

"Bedrooms have smaller radiators, but that doesn’t really bother me; is it a requirement to get the government grant that the radiators need to be appropriately sized?"

Heat pumps tend to operate at lower flow temperatures than gas boilers, so some radiators may need a larger surface area to maintain warmth.

In some cases, double or triple panel radiators can improve heat output without taking up significantly more space. However, homes with high-temperature heat pumps, which operate at around 60 ℃, are less likely to need radiator upgrades. These heat pumps are generally less efficient than low-temperature heat pumps.

While the Boiler Upgrade Scheme and Home Energy Scotland Grant provide £7,500 towards heat pump installation, it does not cover radiator replacements. 

An installer can assess whether existing radiators are suitable or if upgrades are needed.

“is it underfloor heating or radiators?”

"Do you know how it copes with the mixture of underfloor heating and radiators, which might require different water temperatures?"

Heat pumps work well with both radiators and underfloor heating, though underfloor heating is ideal as it operates efficiently at lower temperatures. If a home already has underfloor heating, fewer system changes are needed. However, installation of underfloor heating is usually limited to the ground floor and typically costs between £2,000 and £10,000, depending on the size of your home. A mix of radiators and underfloor heating is possible but requires careful design to manage different water temperatures.