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Heated Towel Rail Guide: Sizes, BTU Output and Chrome vs White

Updated 3 min readBy the London Plumbing Supplies counter team

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The short answer

Size a towel rail like a radiator: a typical bathroom needs roughly 500–850 W (1,700–2,900 BTU), more if it's large or poorly insulated. Check the Delta T the output is quoted at — our SCN chrome rails are rated at ΔT60, about 27% higher than the ΔT50 most radiators use. Chrome gives out noticeably less heat than the same rail painted, and a rail covered in towels less again.

How much heat does a bathroom need?

Work it out as you would for any radiator — the room's volume, insulation and outside walls — at a bathroom's 22°C. A 2.5 × 2m bathroom with a 2.4m ceiling needs about 560 W (1,900 BTU); a 3 × 2.5m one about 850 W (2,900 BTU). The radiator size calculator does the sums.

Towel rails give out less than a radiator of the same size, because the bars have less surface than a panel. In a bigger bathroom a single rail often can't heat the room on its own: pair it with a radiator or underfloor heating, or treat the rail as a towel warmer.

ΔT60 or ΔT50: comparing outputs

Outputs are quoted at a temperature difference between the water and the room. Many radiators use ΔT50; many towel rails, including our SCN range, quote ΔT60, which flatters the figure. To compare, multiply a ΔT60 output by about 0.79 to get the ΔT50 equivalent.

For example, the SCN 1200 × 500mm chrome rail is rated at 1,314 BTU at ΔT60 — about 1,040 BTU (305 W) at ΔT50. On a heat pump running at around ΔT30, expect about half the ΔT50 figure.

Live from our shelvesChrome ladder towel rails we stock: height x width, the maker's output at Delta T60, and price inc VAT
Size (H x W)OutputWattsPrice
800 x 300mm608 BTU178 W£68.86
1000 x 300mm831 BTU244 W£75.65
1200 x 300mm966 BTU283 W£97.96
1400 x 300mm1,153 BTU338 W£126.09
800 x 400mm796 BTU233 W£70.80
1000 x 400mm1,034 BTU303 W£81.47
1200 x 400mm1,194 BTU350 W£100.87
1400 x 400mm1,432 BTU420 W£126.09
1600 x 400mm1,592 BTU467 W£141.61
1800 x 400mm1,732 BTU508 W£156.16
800 x 500mm948 BTU278 W£73.71
1000 x 500mm1,237 BTU363 W£81.47
1200 x 500mm1,314 BTU385 W£99.90
1400 x 500mm1,578 BTU462 W£135.79
1600 x 500mm1,752 BTU513 W£152.28
1800 x 500mm1,927 BTU565 W£169.74
800 x 600mm1,010 BTU296 W£81.47
1000 x 600mm1,319 BTU387 W£92.14
1200 x 600mm1,515 BTU444 W£110.57
1400 x 600mm1,824 BTU535 W£144.52
1600 x 600mm2,020 BTU592 W£161.01
1800 x 600mm2,212 BTU648 W£179.44

Chrome or white?

Shiny chrome radiates heat less well than a painted surface, so a chrome rail gives out noticeably less than the same rail in white or anthracite — often quoted at around a fifth less. Makers' figures already allow for the finish, so compare the stated outputs rather than the sizes.

Chrome suits a towel warmer and looks the part; if the rail is the bathroom's only heat, a painted rail or a wider one buys you more output.

Central heating, electric or dual fuel?

Towel rail types
TypeHow it heatsGood to know
Central heatingHot water from the boilerOnly warm when the heating is on
ElectricA sealed electric elementWorks all year; wiring in a bathroom needs a qualified electrician
Dual fuelBoiler water, plus an element on a T-pieceWarm in summer too; fit the kit as its instructions say

Electrical work in a bathroom in England falls under Part P of the Building Regulations, so have an electrician connect any element.

Fitting a towel rail

  1. Measure the pipe centres — the distance between the two pipes — and match the rail. Rails usually connect at the bottom of each leg.
  2. Choose angled, straight or corner valves to suit where the pipes come out of the floor or wall.
  3. Fix to solid walls or noggins: a rail full of water and wet towels is heavy.
  4. Bleed it from the vent at the top once it's filled, and top up the system pressure.

Heated towel rails

Questions

How many BTU do I need for a bathroom towel rail?
Typically 1,700–2,900 BTU (500–850 W) to heat a bathroom on its own, more for a large or poorly insulated room. As a towel warmer alongside a radiator, any size works.
Is a chrome towel rail less efficient?
It gives out less heat than the same rail painted, so you need a bigger chrome rail for the same output. It doesn't waste energy — the heat it doesn't radiate stays in the system.
Can a heated towel rail heat a bathroom?
In a small bathroom, yes, if its output matches the room's heat loss. In bigger rooms, or once it's covered in towels, it usually needs help from a radiator or underfloor heating.
What does ΔT60 mean on a towel rail?
It's the output with the water 60°C hotter than the room. Multiply by about 0.79 for the ΔT50 figure most radiators quote.

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