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Vertical or horizontal hot water cylinder: which shell fits

Updated: 21 October 2026

You are standing in a low cupboard, a loft, or a tall alcove, and the listing title says vertical or horizontal as if the word settled the job. It does not. Measure the ceiling and the access first. Choose the horizontal TESY in this set only when a vertical shell will not fit, and treat usable hot water and the wattage as unsettled. Peter F. used the amazon.co.uk cards in our [80 litre hot water cylinder comparison](/hub/hot-water/80-litre-hot-water-cylinder) and trade notes on stratification, with listings read on 20 October 2026. There was no draw-off test. A qualifying purchase can earn a commission at no extra cost to you.

You are standing in a low cupboard, a loft, or a tall alcove, and the listing title says vertical or horizontal as if the word settled the job. It does not. Measure the ceiling and the access first.

Our top picks

TESY TESY 80 litre BiLight vertical

Best overall

TESY TESY 80 litre BiLight vertical
8.8/10about £234.99
View offer
Eldom Eldom Spectra 80 litre

Best value

Eldom Eldom Spectra 80 litre
8.6/10about £189.00
View offer
TESY TESY BiLight 80 litre horizontal

Rank 3

TESY TESY BiLight 80 litre horizontal
0.0/10about £229.99
View offer
On this page
  1. 1.Choose from the ceiling, not from the title
  2. 2.Why the same 80 litres can draw differently
  3. 3.The TESY pair, and the Eldom dimensions
  4. 4.Orientation does not change the installer

Choose from the ceiling, not from the title

Measure height and access before you trust the title. Horizontal suits a loft or a low ceiling. Vertical is the usual footprint when the wall is tall. The horizontal TESY, B0D2DSL2ZG, prints 86 × 47 cm at about £229.99. The plain vertical TESY prints 44 × 50 cm, short for an 80 litre vertical tank, so check the data plate before you assume a 90 cm height. The Wi-Fi TESY prints 44 × 90 cm and a depth bullet of 455 m, which is a unit error. The Thermex prints only a depth of 460 mm. Do not lay a vertical unit on its side. Flexiheat says a horizontal store is a specified product, not a vertical cylinder turned over.

Why the same 80 litres can draw differently

Hot water in a vertical store sits above cooler water. A horizontal shell spreads that layer, so it mixes sooner. Trade pages treat that as less usable hot water and often specify a size up. The horizontal card’s up to 3 people and 24 minutes are seller sentences, not a draw-off test. A retailer V40 of 111 litres is a declared figure for that retail row, not a test of B0D2DSL2ZG. A horizontal 80 litre store is the weaker draw, and it may still be the only shell that fits. Showers against a bath stay on the one bathroom page.
TESY TESY 80 litre BiLight vertical

Testsieger

TESY TESY 80 litre BiLight vertical
8.8/10about £234.99
View offer

The TESY pair, and the Eldom dimensions

The horizontal Amazon card is model GCH 80 44 20 B12 TSR at 3,000 W. Modern Heat’s horizontal BiLight table lists 2,000 W and a heat-up of 2 hours 8 minutes. Do not merge those wattages. The Wi-Fi card, part 306344, clashes 2 kW with 220 watts. The plain vertical card’s 1,500 kW field is not an element. The Eldom title says vertical and the dimensions are 82.5 cm wide by 45.7 cm high, close to the horizontal TESY’s 86 × 47 cm. You cannot mount the Eldom either way from the title. Mark the wall for the printed dimensions, then check the plate.

Orientation does not change the installer

A horizontal 80 litre store is still an unvented store over 15 litres. In England and Wales that work is notifiable unless a competent-person installer self-certifies, under Approved Document G. Scotland and Northern Ireland use their own standards. The loft floor is a question for that installer. Eighty kilograms of water plus the shell is not a load you confirm by rocking the tank. The tundish and a new circuit do not become optional because the shell is 47 cm high. The horizontal card still omits the valve. If you are unsure this is an electric store rather than a boiler cylinder, use the buying guide. Orientation chooses the shell. It does not choose the person.

Common questions

What height do I need for the vertical TESY cards?
The Wi-Fi TESY prints 44 × 90 cm, so you need that height plus clearance for the pipework and the valve, not a bare 90 cm of wall with the tundish jammed against the ceiling. The plain TESY prints 44 × 50 cm, which is short enough to flag as suspicious for 80 litres. Measure the unit that arrives. Do not lay either vertical card on its side if the 90 cm shell does not fit.
Can I mount the Eldom either way?
The title says vertical and the dimensions say 82.5 cm wide by 45.7 cm high. Those two statements cannot both describe the same mounting plan. Mark the wall for 82.5 cm across and 45.7 cm up, then check the data plate. Do not rotate it to suit the cupboard because the title and the table disagree. A landscape shell and a vertical shell are different products.
Is 3,000 W on the horizontal Amazon card the element?
It is the figure printed on B0D2DSL2ZG, at 220 V, class C. A UK retailer table for a horizontal BiLight 80 prints 2,000 W and a heat-up of 2 hours 8 minutes. Both cannot be the element of one model. Use 3,000 W only as the Amazon claim until the plate confirms it. Three kilowatts at 230 volts is about 13 A, so if the plate does say 3 kW, expect a wired circuit rather than a casual 13 A plug.
Is a loft floor strong enough?
The cards do not say. Empty weights here run from 22 kg on the horizontal TESY to a printed 85 kg on the Wi-Fi card, and the water is about 80 kg on top. A loft boarding that holds boxes may not be the support an unvented store needs, including the brackets and the filled pipework. Ask the installer to judge the structure. Do not rest the tank on ceiling plaster.
Does horizontal change who may install it?
No. Both orientations in this set are unvented electric stores over 15 litres. The competent-person route, or a building notice, still applies in England and Wales. A lower shell does not remove the tundish, the two safety devices, or Part P if you are adding a circuit. The installation page is the stop list. This page only chooses the shape.

Related pages

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Is 80 litres enough for a shower in one UK bathroom

Sources

Public UK sources named below. amazon.co.uk prices, stars and review counts on these five listings were taken from the listing files read on 20 October 2026. Page updated 21 October 2026.

  1. Approved Document G (2024 amendments) (retrieved 20 October 2026)
  2. Approved Document P (2013) (retrieved 20 October 2026)
  3. HSE hot and cold water (retrieved 20 October 2026)
  4. HSE cylinder checks (retrieved 20 October 2026)
  5. Retained Regulation 812/2013 (retrieved 20 October 2026)
  6. GOV.UK energy labelling of products (retrieved 20 October 2026)
  7. Hot Water Association sizing (retrieved 20 October 2026)
  8. TESY BiLight 80 datasheet (retrieved 20 October 2026)