Flats not needing refurbishment.
140 square metres and above.
"A boiler needs replacing" was the condition we originally devised to investigate and solve. Large flats are the most challenging type of property for this scenario. Almost all solutions will require some upfront investment; whether to upgrade the electric power supply to three-phase, or to install infrared panels. Even though it's not always compatible with properties not needing refurbishment, heat pumps must be mentioned as the ideal solution.
Option 0
It is always worth checking whether you can install a heat pump: m a balcony or terrace or roof may be the right place for the external unit. To improve efficiency, heat pump installations may need to be combined with light upgrades of the building, such as replacing or sealing the front door and windows.
Option 1
A combination of heat battery and smart hot water cylinder may still suffice in smaller or better-insulated flats (maximum 150 square metres or up to 12000 kW/year for heating).
Note that heat batteries may require reinforcing the floor or upgrading the power supply.
Option 2
Avoid heat batteries by combining Infrared panels for heating and a smart hot water cylinder.
The infrared panels will be visible and typically installed on the ceiling. The installation entails some construction work: you may want to remove the radiators, and you will need to run cables to the infrared panels. On the other hand, infrared heating usually will not require upgrading the electric power supply to three-phase and does not have space or weight constraints.
Option 3
Combine heat battery + infrared heating + smart hot water cylinder. In this case, you would use the infrared heating panels in rooms that are used seldom or intermittently: bedrooms, for example. Infrared heats very quickly and can be quite smart. Isolating a few areas from the central heating will allow to cover the heating needs with the heat battery alone.
The smart water cylinder will handle the hot water, further relieving the heat battery.
Please note: you may need to upgrade the electric supply to three-phase.
One last thing, not needing refurbishment doesn't mean you can't attempt minimal improvements to the building itself. Replacing or increasing the loft insulation does not require any demolition. In some cases, very smart robots can also insulate under the ground floorboards through the undercroft. Depending on the condition of the heating system and your budget, you have three options.