The best 24kW instantaneous water heaters, compared.
Top pick: GASLAND GS318NG – Tied on 84 with the CAMPLUX listing, and ahead on review count, 947 against 129, for natural gas at 20 mbar. Best value: CAMPLUX GX318LP – The other 4.2-star listing, for LPG at about £239.99. It is not a lower price than the top pick. Updated October 2026.
A 24kW instantaneous water heater heats mains water as it flows, with no stored cylinder, so the litres you get depend on the kilowatts and how cold the mains is. On amazon.co.uk the appliances that claim about 24 kW are gas units, not a 13 A plug-in. At a 30°C winter rise, 24 kW is about 11.5 litres per minute in theory, before losses: one shower, or outlets used in turn, not two unrestricted showers at once. The value label is on the CAMPLUX, the other 4.2-star row, which costs more because it is LPG. A smaller duty is a different page: the [18kW instantaneous water heater](/hub/hot-water/18kw-instantaneous-water-heater). Gas connection, flue and commissioning belong to a Gas Safe registered engineer. None of them is a 13 A plug-in. Supplier notes put UK winter mains near 8–10°C, and lower in parts of Scotland. The 11.5 litre figure is a rule of thumb, not a measured result for these three listings. Whether 24 kW instantaneous is the right type, and which fuel, is set out in the [24kW instantaneous water heater buying guide](/hub/hot-water/24kw-instantaneous-water-heater/sub/24kw-instantaneous-water-heater-buying-guide).
A 24kW instantaneous water heater heats mains water as it flows, with no stored cylinder, so the litres you get depend on the kilowatts and how cold the mains is.
11 products checked · 47 hrs invested · +18,600 readers
Swipe for more
1-2 of 3
Personal buying guide
Question 1 of 2
Which fuel is already there?
The GASLAND GS318NG is the natural-gas unit in this set, listed as methane at 20 mbar with a stated 24 kW and 12 L/min, at about £151.99 and 4.2 from 947 amazon.co.uk reviews on 19 October 2026. A UK mobile-home review describes stable temperature and pressure and a hot shower, with separate flow and temperature controls, and a UK gas engineer who looked at one in an outdoor building called the build sound. The same UK sample includes an exhaust flue that was not in the box, ignition that only fired after the batteries were disconnected and reconnected with water flowing, and a leaking gas valve with no support reply. A reviewer in Italy says it is not a sealed indoor appliance and returned it, and a reviewer in Spain says an official installer would only accept a covered porch, so the bathroom line on the title is a claim rather than a certificate. Many of the first 50 reviews are not from the United Kingdom, and several describe camping or propane use that the GS318NG bullets do not state. Frost protection is described only while the unit is switched on and the water falls below 5°C. In this set it is the top pick when you already have mains natural gas at about 20 mbar and a Gas Safe engineer will specify the flue; it is the wrong appliance on LPG.
Pros
Cons
Best for: You have a natural-gas meter at about 20 mbar and will have a Gas Safe engineer fit a flue that is not listed in the box.
Less suitable: You are on LPG cylinders, or you wanted a certified room-sealed bathroom appliance with the flue included.
Specifications
Common questions
Which gas does the GASLAND GS318NG use?
The listing says methane, natural gas, at 20 mbar, and tells you to check the gas in the house before you buy. It is not described as LPG.
Does the GS318NG include a flue?
The included-items line does not name a flue. A UK review says the exhaust flue was not in the box and was not a part they could find easily.
Does the listing say who should install it?
Yes. It says a licensed professional should install it to local building and plumbing codes. It also states a 220–240 V lead, 150 cm, described as CE-listed.
The CAMPLUX GX318LP is the LPG listing, stated at 28–50 mbar with up to 24 kW and 12 L/min, a 60°C ceiling and a balanced flue of 60/100 mm, at about £239.99 and 4.2 from 129 reviews. Two UK reviews describe a professional install: a holiday let that heated quickly and ran quietly, and a one-bed chalet where the installer also connected a kitchen, a bathroom and three radiators and called the product fine. Most of the 46 texts in the file are from the United States or Canada and talk about off-grid cabins or a 3.18 US gallon-per-minute heater, so they may describe another Camplux model. The specification table says Floor while the bullets describe a compact indoor unit, and the voltage field prints 3 volts with no mains plug. Reviews mention burners that would not light until the flow was raised, shutdowns in the middle of a shower, and a heat exchanger that started leaking within about two years in one household. Class A is printed on the listing without a load profile, so it is not a UK energy-label result you can compare. It suits an apartment, cabin or small home already on LPG in that pressure band, and it is the wrong gas family for a natural-gas meter.
Pros
Cons
Best for: You already have LPG in the 28–50 mbar range and a Gas Safe engineer for the balanced flue.
Less suitable: You have a natural-gas meter, or you need a large sample of UK house installs before you buy.
Specifications
Common questions
Which gas does the CAMPLUX GX318LP use?
The bullets say LPG and a pressure range of 28–50 mbar. Natural gas is not the stated fuel.
What flue does the listing specify?
A balanced flue at 60/100 mm, for coaxial or twin pipe. The box line includes installation kits and a manual. It does not list a separate flue length.
Can it feed a shower and a kitchen tap?
The bullets say up to 24 kW and 12 L/min, and that it can supply two water points at once, naming a shower and kitchen use. They do not state the temperature rise for that flow.
The GEESEN RV05 is listed as an RV water heater at about £219 with 3.8 from 19 reviews, running on liquid propane at 12 V with a remote in the box. The title says 24 kW and 55,000 BTU, the wattage field says 55,000 watts, and the heat-output field says 25,000 BTU, so those lines are not one duty and this comparison does not treat the title as a confirmed 24 kW house heater. The capacity line is 10 L/min. Four of the eleven stored reviews are from the United Kingdom: a van conversion whose owner still wanted an experienced fitter, a replacement for a leaking heater, an RV swap that reported a steady temperature, and a first start that needed about 15 minutes of water flow to clear air before it fired. A Canadian review says the burner ran but the tap stayed cold, and another says the unit failed in under a month and a promised replacement never arrived. A US review says the remote had to be pulled through and was not wireless. Anti-freeze stops when power and gas are off, and the listing tells you to empty the tank. It belongs with a camper propane install, not with a mains-gas multipoint.
Pros
Cons
Best for: You are fitting a 12 V propane heater in a van or motorhome and will reconcile the output lines before you order.
Less suitable: You want a 24 kW natural-gas or LPG multipoint for a house bathroom and kitchen.
Specifications
Common questions
Is the GEESEN RV05 a house water heater?
The item type is RV water heater. The title is a 12 V camper propane unit with a remote. It is not described as a natural-gas multipoint for a house.
What output does the listing actually state?
The title says 24 kW and 55,000 BTU. The wattage field says 55,000 watts and the heat-output field says 25,000 BTU. Those figures are not the same duty.
What power supply does it need?
The listing says 12 V DC. If you use an adapter, it says the adapter must be 12 V and at least 5 A. Anti-freeze stops when power and gas are off.
Scores use the three amazon.co.uk listings kept here, and the star line on each page, read on 19 October 2026. The score is that star rating multiplied by 20 and rounded to a whole number. Nothing else is added or subtracted. This is not a laboratory test. A higher score is a higher star line. It is not a judgement that the heater suits a UK house, a bathroom, or a confirmed 24 kW duty.
Amazon star line
100%The score is the amazon.co.uk star rating multiplied by 20. GASLAND and CAMPLUX are 4.2 × 20 = 84. GEESEN is 3.8 × 20 = 76. Fuel, flue, flow and price are buying filters. They are not added to the score. Review count breaks the tie for the top pick only: 947 against 129. It does not change the 84.
Match the gas you already have, then the winter flow, then a flue a Gas Safe engineer will actually fit. A 12 L/min claim is not a measured winter shower, and an RV propane listing is not a house multipoint.
A 24 kW instantaneous water heater heats mains water as it flows. There is no stored cylinder, so the litres you can draw depend on the kilowatts and on how cold the mains is. In this amazon.co.uk batch the appliances that claim about 24 kW are gas units. None of them is a 13 A plug-in. At a winter rise of about 30°C, 24 kW is about 11.5 litres per minute in theory, before losses. That is one shower, or a bathroom and a kitchen used in turn. It is not two unrestricted showers at once.
At a 30°C rise, 24 kW is about 11.5 litres per minute in theory, before losses. The GASLAND and CAMPLUX listings state 12 L/min and do not state that rise. UK winter mains are often near 8–10°C. The 11.5 figure is a rule of thumb, not two showers at once.
The GASLAND GS318NG is natural gas at 20 mbar. The CAMPLUX GX318LP is LPG at 28–50 mbar. A cylinder and a meter are not interchangeable by turning a knob. The GEESEN RV05 is propane for an RV, not a house natural-gas multipoint.
A UK review of the GASLAND says the exhaust flue was not included. The CAMPLUX listing names a 60/100 mm balanced flue and installation kits, and it does not list a separate flue length. A bathroom gas appliance has to be room-sealed. Sealed on a title is a claim.
Gas family and pressure decide whether a 24kW instantaneous water heater can be connected. Natural gas on the GASLAND GS318NG listing is methane at 20 mbar. The CAMPLUX GX318LP listing is LPG at 28–50 mbar. A cylinder and a natural-gas meter are not interchangeable by turning a knob. The GEESEN RV05 is liquid propane for an RV, and the pressure is not stated, so it is not a third house fuel. Gas connection, the flue and commissioning are Gas Safe work.
Flow at a winter rise matters more than the headline litres. At a rise of about 30°C, 24 kW is about 11.5 litres per minute in theory, before losses. Supplier notes put UK winter mains near 8–10°C, lower in parts of Scotland. That theoretical figure is one shower, or a bathroom and a kitchen used in turn, not two unrestricted showers at once. The GASLAND and CAMPLUX listings state 12 L/min and do not state the temperature rise for that flow, so 12 L/min is not a proven winter shower.
Three typical situations, each with a recommendation from this comparison.
You want hot water without a cylinder, for one bathroom plus a kitchen used separately, and you already have natural gas at about 20 mbar. The GASLAND GS318NG is the top pick for that fuel. A Gas Safe engineer still has to specify a flue that is not listed in the box.
You already have LPG in the 28–50 mbar range. The CAMPLUX GX318LP names that pressure and a balanced flue of 60/100 mm. It is the wrong gas family for a natural-gas meter. Most of the stored reviews are not UK house installs.
You are fitting a 12 V propane heater in a van or motorhome, not a house multipoint. The GEESEN RV05 is the RV listing, with a remote in the box. Reconcile the output lines before you order. Do not treat it as a 24 kW natural-gas heater.
The top pick is the GASLAND GS318NG at about £151.99. It scores 84, tied with the CAMPLUX GX318LP, and the tie breaks on review count: 4.2 from 947 against 4.2 from 129. That is a listing-count rule for a natural-gas, 20 mbar claim, not a British lab verdict. The value label is on the CAMPLUX GX318LP, the other 4.2-star listing, at about £239.99. It costs more because it is LPG, not because it is a cheaper house heater. The lower shelf price is already the top pick. The GEESEN RV05 at about £219.00 has conflicting output fields, so it is not a house-heater value comparison.
GASLAND GS318NG
Tied on 84 with the CAMPLUX listing, and ahead on review count, 947 against 129, for natural gas at 20 mbar.
CAMPLUX GX318LP
The other 4.2-star listing, for LPG at about £239.99. It is not a lower price than the top pick.
Editorial
Peter F. is the editor for DIY & tools at productscompared.co.uk. Comparisons in this category are checked against amazon.co.uk listings, review evidence and public UK sources.
Guides on what to look for, how to use a product, and common mistakes.
Public UK sources named below. amazon.co.uk prices, stars and review counts on these three listings were read on 19 October 2026. Page updated 21 October 2026.
This page contains affiliate links to amazon.co.uk (tag pcuk26-21). If you buy through them, we may earn a commission at no extra cost to you. Prices, stars and review counts are taken from those listings. We did not run a lab test.
