What Is Delta Rating? Understanding BTUs and Radiator Heat Output

During your process of finding the perfect designer radiator for your home, you have probably come across the term Delta Rating. You do not need a comprehensive knowledge of the Greek Alphabet (Delta is the fourth letter) to figure out how it works. In mathematic equations, Delta signifies a change in a figure or amount. Delta T measures the difference between the heat circulating in the radiator and the desired temperature in the room, and allows the BTU to be calculated.

Radiator BTU Comparison

Being able to quickly compare a radiator's BTU output to the BTU needed for your room size will help you choose the perfect radiator for your home that will look great, but more importantly, be powerful enough to generate the heat you need. The delta rating calculates exactly what BTU your radiator will generate at a specific temperature. This is where it gets complicated: different designer radiator brands calculate their BTU at different delta ratings just to add to the confusion!

Whilst the majority of designer radiator and towel rail BTUs are calculated at Delta 50, not all are! This can be misleading as some radiators will appear more powerful than others as the Delta rating is different. Buying a radiator that appears to have an amazing heat output can lead to disappointment and cold rooms if you are not careful. This could be a costly error if you purchase a radiator measured at Delta 60 for a Delta 50 system.

Converting Delta Ratings

The majority of Europe use Delta 50 and the UK converted to Delta 50 in 2013. Delta 50 is based on a much lower expected boiler temperature which is more in-line with modern insulation and boiler performance.

You will want to convert the delta rating of any radiator you are considering buying to Delta 50 to get the most accurate BTU figure possible and avoid purchasing an underpowered radiator. There are several ways to ensure your radiator will perform well, but the most crucial step to take is purchasing a radiator powerful enough to heat your chosen room to begin with.

To do this, it is easy!

To convert Delta 60 to Delta 50: Multiply the BTU at Delta 60 by 0.789 to generate your Delta 50 rating BTU.

Example: 2500 BTU (Delta 60) X 0.789 = 1972 BTU (Delta 50).

As you can see, by measuring the BTU at Delta 50, the figure decreases, providing you with the more accurate BTU reading for UK heating systems.

To convert Delta 70 to Delta 50, the process is similar: Multiple the BTU at Delta 70 by 0.645 to generate your Delta 50 rating BTU.

Example: 2500 BTU (Delta 70) x 0.645 = 1612 BTU (Delta 50).

Before you open the calculator app on your phone, you can breathe a sigh of relief! All radiators on the Designer Radiator Showroom website have their BTUs listed at Delta 50 to give you the most accurate information possible and to help you make the best choice for you and your home. Simply go to the product page of your chosen radiator, use the drop-down menus to select your size and finish and the BTU of your radiator will be displayed in the information table to help you make a well-informed decision.

At the top of every page of our website and on every radiator product page is our handy BTU calculator, an easy way to see how much heat your room will need! We recommend always choosing a radiator that has a higher BTU than the minimum estimate, just to ensure that your new designer radiator or towel rail will give you more than enough warmth.