How to Buy a Radiator: A Step-by-Step Guide

Buying a radiator involves more than picking one that looks right. The room it is going into, the heat it needs to produce, the system it will connect to, and the finish that suits your decor all need to be considered before you place an order. Get it right, and you will have a radiator that performs well, looks great, and lasts for years. Get it wrong, and you could end up with something that struggles to heat the room or simply does not fit.

To make the process as straightforward as possible, we have broken it down into six steps.

Step 1: Work Out Your Heat Output Requirements

Before you look at styles or sizes, you need to know how much heat your room actually requires. This is measured in BTUs (British Thermal Units) or Watts, and it is determined by a number of factors including the size of the room, how well it is insulated, the number of windows, and whether it is a ground floor or upper floor space.

Buying a radiator with insufficient output means the room will never reach a comfortable temperature, no matter how long the heating runs. Buying one that is significantly oversized is wasteful and can make the room uncomfortably warm.

Our BTU Calculator gives you a quick starting point, but we always recommend confirming the required output with your heating installer before purchasing. They will be able to account for your specific system and any factors unique to your property.

Step 2: Choose Your Design

Once you know your heat output requirements, you can start thinking about style. At Radiators Direct, we carry a wide range of radiators and towel rails to suit every type of home and interior.

If you are looking for something classic, our cast iron radiators and traditional steel radiators are a popular choice, particularly in period properties or rooms with a heritage feel. For more contemporary spaces, our designer radiators offer striking modern profiles that work as a feature in their own right. If efficiency is a priority, aluminium radiators heat up quickly and cool down fast, making them well suited to modern heating systems and homes that value responsiveness.

Beyond radiators, our heated towel rail range covers everything from simple ladder rails to more decorative traditional styles, available in hydronic, electric, and dual fuel configurations.

Take your time at this stage. The design you choose will be a fixture in your home for a long time, so it is worth exploring the options properly.

Step 3: Select a Size That Meets Your Heat Output Requirements

With a design in mind, you can narrow down to a specific size. Each product page on our site includes full output data for every size variant, shown in both BTUs and Watts at Delta T 50°C, which is the industry standard measurement for radiator output.

Use your required BTU figure from Step 1 to find a size that meets or slightly exceeds your needs. If you are unsure how to interpret the figures, our Delta T Conversion tool can help you adjust outputs for systems running at different temperatures, which is increasingly relevant for heat pump installations and lower temperature heating systems.

It is also worth thinking practically at this stage. Consider the available wall space, the position of existing pipework, and whether you need a horizontal or vertical orientation to make the most of the room layout.

Step 4: Choose Your Finish or Colour

This is where you can really make the radiator your own. We offer an extensive range of RAL colours and special finishes, giving you the flexibility to match your existing decor or introduce a bold accent colour that turns the radiator into a focal point.

All available colours and finishes are shown on each product page, and you can view the full range on our Colours and Finishes page. We strongly recommend ordering either a Colour Chip Sample or Colour Sample Box before committing to a finish, particularly for painted cast iron radiators where the tactile quality of the surface can be difficult to judge from a screen alone.

It is also worth noting that due to the nature of powder coat and painted finishes, colours can vary slightly between batches, so if you are ordering multiple radiators in the same colour, it is best to order them together where possible.

Step 5: Select Your Valves

Valves are often an afterthought, but they play an important role in both the performance and the appearance of a finished radiator installation. We offer a full range of thermostatic (TRV) and manual radiator valves in styles designed to complement our radiator ranges.

For living rooms and bedrooms, we recommend thermostatic valves in all cases. TRVs allow each radiator to be controlled independently, so rooms are only heated to the temperature you set rather than relying on the boiler thermostat alone. This can make a meaningful difference to both comfort and energy bills.

When selecting your valves, make sure to factor in their dimensions when calculating the overall width of the installed radiator, particularly if you are working to tight pipe centres or fitting into an alcove.

Step 6: Add to Basket and Place Your Order

With everything confirmed, placing your order is straightforward. Browse to your chosen product, select the size, colour, and any additional options, and add it to your basket. You can add valves and accessories at the same time to keep everything in one order.

When you are ready, head to your shopping cart and proceed through checkout to confirm your payment and delivery details.

If you are unsure about anything before placing your order, whether that is confirming a size, checking delivery times, or simply talking through your options, our customer services team is on hand to help. You can call us on 01342 305555 or email info@radiatorsdirect.co.uk, and we are always happy to advise on technical questions such as heat output, valve compatibility, or pipe centres before you commit to a purchase.

Additional Information Worth Knowing

Product Standards

All radiators sold by Radiators Direct are produced and measured in accordance with European standard EN442. Radiators are supplied with BOE (Bottom Opposite End) connections as standard unless otherwise stated.

Inhibitor and System Protection

When commissioning any radiator, including aluminium models, on an indirect or closed system, we recommend using a suitably mixed metal inhibitor in the correct quantities to protect against scale and corrosion. Consult your installer for advice on the right product and dosage for your system.

Electric and Dual Fuel Towel Rails

Some of our towel rails can be adapted to operate as dual-fuel models with the addition of an electric element and a T-piece. If you intend to use a towel rail as dual-fuel, it is important to inform your installer in advance so that the pipe centres can be adjusted accordingly. Suitable elements and T-pieces are available in our accessories range. Dual fuel compatibility is noted in the product overview section of each applicable product.

Pipe Centres

We take care to ensure all pipe centre measurements are accurate, but manufacturing tolerances mean that some variation is possible. For this reason, we strongly recommend that you do not alter or adjust any pipework until your radiator or towel rail has been delivered and you can measure directly from the product. Radiators Direct will not accept responsibility for claims arising from incorrect pipe centre assumptions made before delivery. Learn more about pipe centres and how they are measured.

Heating Systems

All radiators and towel rails on our website are suitable for indirect or closed systems complying with BS5449 Section 1 for forced circulation hot water systems. Systems running at low pressure (under 1 bar) or using microbore pipework may experience flow or heating issues if not accounted for in the system design.

If you have any radiators or towel rails connected to a direct heating system, these should be made from stainless steel (or brass) to prevent rusting and contamination of the hot water supply.

Powder Coat and Painted Cast Iron Finishes

Powder coat colours can vary by plus or minus 5 -10% from sample chips, and between radiators ordered in the same colour but at different times. All painted cast iron radiators are checked and tested before despatch. Cast iron radiators have a characteristically textured surface with small natural imperfections from the casting process, which will be visible through the paint finish.