Radiator Installation SW9

Types of radiators

Single panel radiators are the most common and suit rooms with moderate heat demand. Double panel radiators output more heat in the same wall space — ideal for larger rooms or rooms with poor insulation. Column radiators (cast-iron style or steel) suit period properties or rooms where aesthetics matter. Heated towel rails serve bathrooms and en-suites, connecting directly to the central heating circuit.

Output calculation: BTUs and watts

Radiator output is measured in BTUs or watts. To calculate required output, multiply the room volume (length x width x height in metres) by 153 to get BTUs. Divide by 3.412 to convert to watts. We carry out this calculation before ordering any radiator to ensure the replacement meets the room heat load.

Replacing a radiator without draining the system

For a direct swap-out on a system fitted with TRV and lockshield valves, we isolate the individual radiator by closing both valves fully. This drains only that section — the rest of the system stays full and pressurised. No system power flush required for a standard like-for-like replacement.

New radiator with new pipework vs swap-out

A direct swap-out (same position, same pipe centres) costs £150 to £250. Installing a new radiator in a new location — requiring new pipework run from the nearest flow and return — costs £300 to £500 depending on pipe run length and whether floorboards need to be lifted.

Balancing the system after a change

After adding or replacing a radiator, the central heating system must be balanced. This means adjusting the lockshield valves on each radiator so that heat is distributed evenly throughout the property. Without balancing, some radiators will be too hot and others too cold.

TRVs and smart TRVs

Standard thermostatic radiator valves (TRVs) cost £15 to £30 and allow per-room temperature control. Smart TRVs — from Tado, Hive, or Drayton Wiser — cost £50 to £80 each but allow per-room scheduling from a smartphone. They integrate with most existing central heating systems without requiring a new boiler.