UKRadiators - Free delivery on all ordersFree delivery on all orders
UKRadiators - Limitless, free returnsLimitless, free returns
UKRadiators - Radiators from £19Radiators from £19
UKRadiators - Buy now, pay later with KlarnaBuy now, pay later with Klarna

What is a Delta Heat Output?

Advice Centre
Welcome to our Advice Centre, where you’ll find inspiration, practical tips and now-how guides for the best and most economical ways to heat your home.
What is a Delta Heat Output?

With a variety of heating systems and radiators out there, its important that you purchase the right product for your home. This quick guide explains what a Delta heat output is and which Delta may apply to you, so that you can make sure you are purchasing the correct size/type of radiator for each room in your home.

What is a Delta Heat Output?

This is the Heat Output of the radiator under different operating conditions, or Boiler Temperatures as they are otherwise known.

Radiators are constructed from metal and heated by hot water. and as you would expect the hotter you make the water, the hotter the metal will get and subsequently the higher the heat output the radiator will have, which is why a Radiator has multiple Delta Ratings to represent how it will work, with higher delta numbers meaning a higher boiler temperature is in place (It is not good to have a higher boiler temperature, as it will cost more to run, damage the environment and have a shorter life).

So the heat output you will get from the radiator is ultimately determined by the temperature that your boiler heats to.

Modern boilers and Heat Pumps run at lower temperatures by design, which means they are cheaper to run and have less impact on the environment, but require slightly bigger radiators to produce the heat required for your room.

We currently provide 3 delta ratings (Δ30/Δ40/Δ50) for all of our central heating/gas and dual fuel radiators. The delta rating you need to look at when purchasing our radiators depends on the type and age of boiler you have.
The below will help you to know which delta you should be browsing by:

  • Delta 50 = Non-Condensing Boilers installed before April 2005 with a standard configuration, with a flow temperature of around 75-85 degrees (you might have this).
  • Delta 40 = Condensing boiler.
  • Delta 30 = (Recommended) Condensing Boiler configuration and A+ Rated Heat Pumps, with a flow temperature of around 55 degrees (you should have this).

Column RadiatorIf you are unsure of what you have, and to future proof your purchase, purchase your radiator based on the Delta 30 heat output as you can manage the room temperature using Thermostatic Radiator Valves in rooms that are not the reference room (reference room is the one with the main boiler thermostat) which will stop the room and radiator from producing too much heat on a higher boiler temperature, but should allow your radiator purchase to be used on newer lower temperature systems when replacing in the future.

How do I compare Heat Outputs with different suppliers?

All suppliers of radiators as part of BS EN 442 and the Construction Products Regulations (law) must show on their products and catalogues (including website catalogues) the Delta 30 and the Delta 50 heat outputs.

These are the values that should be compared between different suppliers and websites to see what heat output you will get for your boiler type.

If you go to purchase a radiator from a supplier where these two values are not visibly clear and marked as Delta 30 and Delta 50, then those radiator listings do not comply with BS EN 442, and you should not purchase the radiator from that website/supplier.

Simple steps to purchase a radiator:

1. You need to know the heat requirements of the room in BTU or Watts.
2. Purchase a radiator where the Delta 30 value is higher than the heat requirement of the room to ensure it will work suitably on the current system and future systems
3. If the radiator is going in a room where the main boiler thermostat is not present, purchase a Thermostatic Radiator Valve
Main Boiler Thermostat - Little box on the wall to control the temperature, this will only be in one room of your house.

Now that you know these simple steps you can see our full range of radiators and heated towel rails.