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Condensing boiler for a small flat

Updated: October 2026

A one-bathroom flat has a short run of wall, one shower, and a listing that may not say whether the boiler is a combi. A condensing boiler for a small flat, in this set, is a wall-hung card that prints both a fuel family and a hot-water flow. If either line is missing, the card is not a finished specification, however low the price looks. The [condensing boiler comparison](/hub/hot-water/condensing-boiler) is the twelve-row table, with amazon.co.uk prices on 20 October 2026 from £951.54 to £5,437.54. There is no lab test and no UK best-buy ranking. A Gas Safe engineer still confirms mains flow, flue and condensate, and a qualifying purchase can earn a commission at no extra cost to you.

A one-bathroom flat has a short run of wall, one shower, and a listing that may not say whether the boiler is a combi.

Our top picks

Sime Sime Vera HE 30 condensing boiler

Best overall

Sime Sime Vera HE 30 condensing boiler
6.0/10about £980.61
View offer
Beretta Beretta Mynute X 25 C wall boiler

Best value

Beretta Beretta Mynute X 25 C wall boiler
3.6/10about £1,208.84
View offer
Immergas Immergas Victrix 12 kW TT Plus

Rank 3

Immergas Immergas Victrix 12 kW TT Plus
3.1/10about £1,467.17
View offer
On this page
  1. 1.What a one-bathroom flat is asking for
  2. 2.The only printed flow
  3. 3.A combined title with no flow
  4. 4.Rows that fail the flat test
  5. 5.Fazit: wall, fuel and a printed flow

What a one-bathroom flat is asking for

The Energy Saving Trust points to a combi where space is tight and hot-water use is modest: no cylinder, and no loft header tanks. A heat-only boiler is a weak flat fit, because those tanks have to sit higher than the highest tap. Two showers need stored hot water, which this set barely documents. For one bathroom the shortlist is a wall-hung combi shape, not a heating-only boiler and not a floor-standing store. Condensing only means flue-gas heat recovery. The layout words are on the combi or system boiler page. Flows quoted for other brands are not borrowed onto these ASINs. Before the engineer visits, reject a row that is heating only, too heavy for a wall, or silent on flow.

The only printed flow

The Sime Vera HE 30, at £980.61, is the only card that prints a hot-water flow: 13.5 litres per minute, with 30 kW, 85 °C and 3 bar. The title says methane/LPG, the power-source cell says CNG/LPG, and the mount is wall, indoor installation. That is the closest this table comes to a usable tap figure for one bathroom. It is still not a finished order. The card does not say combi, so the flow is not labelled as a combi flow. A 5.1 litre cell is not described as a store, the box list is blank, and there is no star rating. The £980.61 figure is the appliance on 20 October 2026, not fitting.
Sime Sime Vera HE 30 condensing boiler

Testsieger

Sime Sime Vera HE 30 condensing boiler
6.0/10about £980.61
View offer

A combined title with no flow

The Beretta Mynute X 25 C, at £1,208.84, says combined and wall. The item weight is 20 kg, the carton is 70 × 50 × 30 cm, and the box line lists the boiler. It still fails as a finished specification because it prints no hot-water flow and no fuel family. Combined is not the same fact as a printed flow. The Sime card has the flow and lacks the word. The Mynute has the word and lacks the flow. The missing fuel family keeps the Mynute off an order you would place today.

Rows that fail the flat test

Three cards are the wrong object before price. The Immergas Victrix Pro, £2,858.53, says heating only and prints both 55 kW and 50 kW, with no tap flow. The Wolf CGB-2 20, £2,558.25 and 40 kg, refers to a heating circuit and would still need header tanks above the taps. The Vaillant ecoCOMPACT, £5,437.54, is a floor boiler, 140 kg, and it does not go in a kitchen cupboard. The Immergas Victrix 12 kW TT Plus, £1,467.17, is a wall title with 12 kW and no fuel or flow. On the Baxi Victoria, 24/24F is a model name, not a kilowatt output.

Fazit: wall, fuel and a printed flow

If the card is heating only, or it is the 140 kg floor unit, it fails this flat before price. If you need a printed tap figure and a named fuel line on a wall card, the Sime Vera HE 30 is the only row that has both, and it still does not say combi. If you need the word combined, that is the Mynute, with no flow and no fuel family. The 12 kW wall title is not a finished file either. The engineer still confirms the flue, the condensate and the mains.

Common questions

What kind of condensing boiler suits a one-bathroom flat?
Look for a wall-hung boiler that prints a fuel family and a hot-water flow, with no cylinder, which is the Energy Saving Trust starting point when space is tight. Condensing only describes heat recovery. Heat-only boilers need header tanks above the taps. This set’s printed flow and its combined title are not the same card.
Which cards in this set print a hot-water flow?
Only the Sime Vera HE 30 prints one: 13.5 litres per minute, with 30 kW, at £980.61. The title says methane/LPG and the mount is wall, indoor installation. It does not say combi, and the 5.1 litre capacity cell is not described as a store. The other eleven cards leave flow blank, so a kilowatt figure on those rows is not a shower specification.
Is a heating-only 50 kW boiler a small-flat boiler?
No. The Immergas Victrix Pro says heating only and prints both 55 kW and 50 kW, at £2,858.53, with no hot-water flow. A one-bathroom flat needs a wall combi shape and a tap figure, not a large heating-only output. The card does not say which kilowatt figure to use.
Can the floor-standing 140 kg boiler go in a flat cupboard?
The Vaillant ecoCOMPACT is a floor boiler, 77 × 73 × 186 cm and 140 kg, at £5,437.54. That height and weight are not a wall hang and not a cupboard combi. The model string includes 150 without the unit litres, so no store size is stated.
Does 24/24F in a model name mean 24 kW?
On the Baxi Victoria Condens 24/24F, 24/24F is the model name. The card does not print a kilowatt cell, a fuel family, or a hot-water flow. A small-flat question on that listing is asked and not answered. The product dimensions, 28 × 40 × 70 cm, are not a drawing of cupboard clearance. This page does not treat the Victoria as a one-bathroom specification.
Who decides flue position and mains flow?
A Gas Safe registered engineer decides whether the flue, the condensate route and the incoming mains can support the boiler in that flat. You can reject a heating-only card, a 140 kg floor boiler, and any wall card that prints neither fuel nor flow. You cannot sign off the gas work, and a one-bathroom rule of thumb is not the heat-loss calculation the guidance expects.

Related pages

Best condensing boiler

Condensing boiler buying guide

Condensing boiler

Combi vs system boiler: when stored water is the point

How to use a condensing boiler: pressure and a thaw

Sources

Public UK sources named below. amazon.co.uk prices and star lines on these twelve listings were read on 20 October 2026. Page updated 21 October 2026.

  1. Approved Document L Volume 1 (2021, 2023 amendments) (retrieved 20 October 2026)
  2. Boiler Plus policy clarification (retrieved 20 October 2026)
  3. Gas Safe Register boiler appliance guide (retrieved 20 October 2026)
  4. HSE: gas safety for homeowners (retrieved 20 October 2026)
  5. Gas Safety (Installation and Use) Regulations 1998 (retrieved 20 October 2026)
  6. HHIC condensate guide, January 2021 (retrieved 20 October 2026)
  7. Energy Saving Trust: boilers (retrieved 20 October 2026)
  8. Worcester Bosch: frozen condensate (retrieved 20 October 2026)