Are Vertical Radiators Efficient? Heat Output, Placement and Fitting

Yes, vertical radiators are as efficient as horizontal ones. Every watt of heat a radiator takes from the heating water ends up in the room, whichever way up it is fitted, so the shape does not waste energy. What decides whether a vertical radiator works is its rated heat output, which must match what the room needs, and where it goes on the wall. The catch is that many vertical models, especially flat-fronted designer ones, give out less heat than a standard horizontal radiator taking up a similar amount of wall, and swapping one for the other nearly always means moving pipework.

Are Vertical Radiators Less Efficient Than Horizontal Ones?

No. Efficiency is about how much fuel the boiler or heat pump burns, and a radiator cannot change that. The only question for a radiator is how much heat it delivers into the room, and that is set by its size, construction and the temperature of the water.

The idea that vertical radiators are inefficient comes from two real points that get muddled together. The first is output: a slim vertical radiator has less surface area than a wide double-panel radiator, so it can leave a room short of heat. The second is height: a tall radiator puts some of its warmth higher up the wall. In a room with a normal ceiling height that makes little practical difference, because warm air rises from any radiator. In a double-height space or a stairwell it matters more, and the room thermostat position should be considered too.

How Much Heat Does a Vertical Radiator Give Out?

Check the output in watts or BTU on the product listing, not the dimensions. Two radiators of the same height and width can differ widely in output depending on their construction.

• Double-panel vertical radiators with convector fins between the panels give the most heat for their size.
• Single-panel and flat-fronted designer models give noticeably less, because the front is a plain decorative face with no fins behind it.
• Tubular and column-style vertical radiators vary by the number and depth of their tubes.

Manufacturers quote outputs at a standard test condition, usually called Delta T 50, which assumes quite hot water. If your system runs cooler, the real output is lower than the headline figure. Work out what the room needs first, then pick a radiator that meets it. Our guide to radiator sizing and BTU walks through the calculation and the common mistakes. If the room needs more heat than one slim vertical radiator can give, two smaller radiators, or a wider or double-panel vertical, are the usual answers.

Where a Vertical Radiator Works Well, and Where It Does Not

Vertical radiators suit rooms where wall width is short but height is free. They are a poor choice under a draughty window, where a low horizontal radiator does a better job.

• Good fits: narrow alcoves, the wall beside a door, kitchens where the base units take up the low wall space, hallways and landings, and chimney breasts in period terraces.
• Poor fits: under a large window, especially old single-glazed sash windows common in London conversions. A horizontal radiator under the glass warms the cold air falling off the window before it spreads across the floor. Move the heat to a far wall and the room can feel draughty even when the thermostat is satisfied.

With good double glazing, placement is less critical and a vertical radiator on another wall is often fine. Keep furniture and long curtains clear of it either way, because anything in front of a radiator cuts its output.

Swapping a Horizontal Radiator for a Vertical One

This is rarely a straight swap. A horizontal radiator has its valves far apart at the bottom corners, while a vertical radiator is narrow and its connections sit close together, so the pipes almost always need re-routing.

1. Connection type. Vertical radiators come with connections at both bottom corners, at the bottom centre, or both on one end. The pipework has to be brought to whichever positions the new radiator uses, and some models specify which pipe must be the flow.
2. The floor. On a suspended timber floor, which most London terraces and Victorian houses have on the ground and upper floors, new pipe can usually run under the boards. On a solid concrete floor the pipes may have to run along the skirting or be chased into the wall, which adds making-good.
3. The wall. A tall radiator full of water is heavy. Solid brick takes it easily; a stud wall needs timber behind the brackets or suitable fixings.
4. Draining and refilling. Altering pipework usually means draining some or all of the system, then refilling, bleeding, topping up the inhibitor and rebalancing so the other radiators still heat properly.

If you are also moving the radiator to a different wall, the job is really a relocation. Our guide to the cost to move or remove a radiator explains how the pipework drives the price.

Vertical Radiators and Heat Pumps

Vertical radiators can work with a heat pump, but they are harder to size. Heat pumps run the water cooler than a gas boiler, so every radiator gives out much less than its catalogue figure.

A horizontal radiator can often be made longer or swapped for a deeper model to make up the shortfall. A vertical radiator is limited by ceiling height and the width of the wall it was chosen for, so there is less room to grow. If a heat pump is likely in the next few years, choose outputs with that in mind now, or plan for a second radiator in rooms where one slim vertical will not be enough. Our guide on whether your radiators are suitable for a heat pump covers how to check.

What Affects the Cost of Fitting a Vertical Radiator

The radiator itself is only part of the price. The pipework changes needed to reach the new connection positions usually decide whether the job is quick or involved.

• whether the existing pipes can be reused or have to be re-routed, and how far
• the floor type, and whether pipework runs under boards, along the skirting or in the wall
• the wall construction and the fixings needed for the weight
• new valves to suit the radiator's connection spacing
• whether several radiators are being changed in one visit, which means one drain-down and one rebalance instead of several

Designer vertical radiators also range widely in price, so check the output per pound as well as the look. When we fit radiators through our radiator installation and replacement service, we check each room's heat requirement first, and we will tell you if a vertical model will leave a room short or if the window wall would be better served by a horizontal one.