Should I Choose a Single or Double Radiator?

When replacing or specifying a radiator, one of the first decisions you will face is whether to go for a single or double configuration. Both have their place, and the right choice depends on the heat output your room requires, the wall space available, and your budget. Here is what each option offers.

What Is the Difference Between Single and Double Radiators?

A single radiator has one panel or one row of tubes. A double radiator has two panels or two rows of tubes set one behind the other. You can identify the configuration by looking at the radiator side-on: the depth of a double radiator will be noticeably greater than a single equivalent of the same height and width.

Panel radiators are also categorised by type, which describes both the number of panels and the number of convector fins:

• Type 11 (single panel, single convector): one panel with one set of fins on the rear
• Type 21 (double panel, single convector): two panels with one set of fins between them
• Type 22 (double panel, double convector): two panels with two sets of fins, delivering the highest output of the three

When shopping for panel radiators, you will often see these type codes used, so it is worth understanding what they mean before comparing radiators.

Single Radiators

Single radiators have less surface area than their double equivalents and therefore produce a lower heat output at any given height and width. Their main advantage is their slim profile: a single panel radiator projects less from the wall, making it a practical choice for rooms where space is at a premium.

They work well in:

• Hallways and landings, where wall depth is often limited
• Downstairs toilets and cloakrooms
• Bathrooms and en-suites, which typically have modest heat loss requirements
• Any smaller room where the required output can be met by a single configuration without needing an oversized radiator

For rooms with low heat loss, a single radiator of the appropriate width and height will often be the most cost-effective solution both to purchase and to run, as there is less material to heat and less water to push through the system.

Double Radiators

A double radiator produces significantly more heat than a single radiator of the same height and width. This has a useful practical implication: you can often replace a single radiator with a smaller double and achieve the same output while taking up less wall space.

Similarly, where a room previously required two single radiators to meet its heat loss requirement, a single well-specified double radiator may be able to do the same job. This reduces the number of radiators on the system, simplifies pipework, and means one fewer unit to maintain.

Double radiators do project further from the wall than singles, which is worth factoring in for narrower spaces. A double tube radiator in particular will have a noticeably greater depth than a single equivalent.

They are most suited to:

• Larger rooms with higher heat loss requirements
• Rooms with poor insulation or large areas of glazing
• Situations where wall width is limited but output requirements are high
• Replacing two single radiators with one unit

Single vs Double: Cost Considerations

Double radiators typically cost more to purchase than comparable single radiators, though the difference varies by style and manufacturer. However, the cost comparison is not always straightforward:

• Replacing two singles with one double may reduce overall purchase cost, installation time, and pipework complexity
• A smaller double achieving the same output as a larger single may be comparable in price
• Running costs depend more on the output required and the efficiency of your system than on single vs double configuration

For larger rooms in particular, it is worth calculating the cost of different configurations. A smaller double radiator achieving the same BTUs as a larger single may work out cheaper overall once installation is factored in.

A Note for Heat Pump Systems

If your home is heated by a heat pump, or if you are planning to install one, the single vs double decision takes on additional importance. Heat pumps operate at lower flow temperatures than traditional gas boilers, which reduces the output of any given radiator compared to its EN442 rating. In practice, this often means that rooms which were previously adequately served by a single radiator may need to be upgraded to a double, or to a larger radiator, to compensate for the lower flow temperature.

If you are specifying radiators for a heat pump system, it is worth calculating the required output at your expected flow temperature (typically 45°C or below) rather than at the standard Delta T50 used in EN442 testing.

How to Choose the Right Option

The most reliable starting point is a heat output calculation for each room. Use our BTU calculator to find the wattage, or BTU figure your room requires, then use that figure to compare single and double options at different dimensions. In many cases, the choice will be straightforward; in others, particularly where wall space is tight or output requirements are high, exploring both configurations will help you find the most practical and cost-effective solution.