The best Thermoflow tankless water heaters, compared.
Top pick: SIVUATEK 14 kW Best value: Mulcort 3 kW LF-001 – Clearest low-cost proposition for a single hand-wash basin, at about £46.99, if you accept a restricted flow. Updated 17.10.2026.
A tankless water heater heats mains water as it flows, so the outlet temperature depends on the kilowatts, the flow and how cold the inlet is. On amazon.co.uk this search returns electric point-of-use units, hard-wired 11–14 kW units and heaters. None of the eleven listings is a Thermoflow. Separate them by stated watts, a 13 A plug or a dedicated breaker, and the flow the listing prints. A 3 kW unit can warm a basin. A shower or a one-bed flat needs about 10–12 kW and a matching circuit. At 230 V a 13 A plug is about 3 kW, so a pictured plug on a 6 kW heater is not a normal socket. Is a different job: a van, a garden or a site with no spare electrical capacity, fitted by a Gas Safe registered engineer. Kilowatts, flow and outlets are set out in the [Thermoflow tankless water heater buying guide](/hub/hot-water/thermoflow-tankless-water-heater/sub/thermoflow-tankless-water-heater-buying-guide).
A tankless water heater heats mains water as it flows, so the outlet temperature depends on the kilowatts, the flow and how cold the inlet is.
38 products checked · 64 hrs invested · +22,800 readers
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Personal buying guide
Question 1 of 2
What are you trying to heat?
The SIVUATEK 14 kW has the highest stated electric output in this set and claims up to 3.3 gallons per minute for one or two points. That makes it more plausible on paper for a shower than the 3–6 kW sink units. Its 4.5-star line from 88 ratings is also the highest shown, but every written review in the extract is marked United States. The listing asks for a 60 A breaker, and no UK plug or UK installation evidence is provided. At £329.51 it is not an inexpensive experiment once circuit work is included. Consider it only after checking UK suitability, documentation and spare electrical capacity; the star line alone does not make it the top pick for a British home.
Pros
Cons
Best for: A professionally designed high-current installation after UK compatibility and documentation are confirmed.
Less suitable: A socket-fed retrofit or anyone treating US reviews as proof of UK shower performance.
Specifications
Common questions
What breaker does the listing ask for?
One 60 A circuit breaker, at 240 V and 14 kW.
Can it go under a sink?
The listing question is unanswered. The bullet gives the size as 15.87 × 11.14 × 2.87 inches.
Are the written reviews from the UK?
No. All 48 reviews in the extract are marked United States. The star line is 4.5 from 88.
The Stiebel Eltron DCE-X 10/12 is the most credible option here for a flat, utility sink or carefully specified shower because its listing states 12 kW and 5 litres per minute. Its degree-by-degree control and two memory keys are more useful in daily use than a vague maximum-temperature claim. The UK review evidence is stronger than for the other high-output electric units, and several buyers report satisfactory use in flats or at basins. Shower feedback is not unanimous, however: some reviewers find the flow adequate while others say it is too restricted. It also needs a substantial hard-wired electrical supply rather than a normal 13 A socket, so the installation can cost more than the heater itself. At £412.86 it is the most expensive electric listing in the comparison, but it is our top pick because the specifications and UK evidence are clearer than those of the cheaper alternatives.
Pros
Cons
Best for: A flat, utility sink or modest shower where an electrician confirms the required dedicated supply.
Less suitable: A home limited to a 13 A socket, or anyone expecting high shower flow without checking winter inlet temperature.
Specifications
Common questions
What output and flow does the listing state?
12 kW, 240 V, 5 litres per minute, and a maximum of 55°C. Maximum pressure is 10 bar.
Does the listing include a 13 A plug?
No. The power source is an electric cable prepared for the power connection.
What do UK reviews say about a shower?
Some UK reviews report a shower in a flat. Others say the flow is not enough. The listing itself names showers.
The CAMPLUX BW528B is the clearest LPG option here for an outdoor shower, off-grid cabin or campsite rather than an indoor sink. It uses butane or propane and two D-cell batteries, so it does not depend on a high-current mains circuit. The listing claims 40 kW and up to 20 litres per minute, but that is an outdoor product specification rather than a measured UK household result. UK reviewers describe it as well built and useful off grid or in a camper, while one reports disappointing customer service. The 4.4-star line is based on only 19 reviews, and a permanent gas or flue arrangement still requires the appropriate professional assessment. At £379.99 it is expensive, but its intended job is more coherent than the less documented RV gas listings.
Pros
Cons
Best for: An outdoor shower, campsite, cabin or suitable leisure setup using the specified LPG supply.
Less suitable: Indoor under-sink use, a normal mains-water-heater swap or an unassessed fixed gas installation.
Specifications
Common questions
Does this heater need mains electricity?
The listing says no. It uses two D-cell batteries and butane or propane.
Where does the listing say to put it?
Outdoors: caravan, campsite, poolside, cabin, or barn. The style line says outdoor installation.
What do UK reviews say?
Well built, useful off grid and in a camper. One review says customer service let them down.
The WINTEMP 11 kW sits between the small basin units and the more expensive high-output heaters, with a listing claim of 2.6 gallons per minute. Its temperature lock and LED display suit a fixed point-of-use installation, and £176.47 is substantially below the Stiebel price. The listing asks for a 50 A double-pole breaker and specifies 8 AWG cable, however, so a UK electrician must design the supply rather than copying the US-oriented cable wording. Its 4.4-star line looks encouraging but covers only 13 ratings. More importantly, all six written reviews in the extract are marked United States, so they are not UK proof of shower performance or installation compatibility. This is a specification-led option to investigate, not a confident recommendation based on British use.
Pros
Cons
Best for: A point-of-use project where a UK electrician can validate the unit and design the 240 V supply.
Less suitable: Buyers relying on UK shower reviews or an existing 13 A socket.
Specifications
Common questions
What breaker does the listing ask for?
One 50 A double-pole breaker, with a stated maximum of 46 A and 8 AWG cable.
What flow is printed?
2.6 gallons per minute. The extract does not convert that to litres.
Are the written reviews from the UK?
No. The six reviews in the extract are marked United States. The star line is 4.4 from 13.
The GEESEN RV05 is aimed at camper and conversion-van hot water, using propane for heat and 12 V for its controls. Its stated 10 L/min flow and remote are more relevant to a van shower than the small electric basin units. UK comments include a satisfactory shower and conversion-van use, although the review base is only 19 ratings. The listing weakens confidence by printing several conflicting output figures: 24 kW, 55,000 BTU, 25,000 BTU and 55,000 W all appear. A fixed LPG system in a leisure vehicle is not a casual DIY connection, and the applicable installation and flue work need competent assessment. The £219 price is competitive among the gas rows, but verify the exact model plate and documentation before choosing it.
Pros
Cons
Best for: A campervan hot-water project where the exact specification and fixed LPG installation are professionally verified.
Less suitable: A domestic kitchen, a simple portable setup or anyone relying on the printed output figures without confirmation.
Specifications
Common questions
Why do the power figures disagree?
The title says 24 kW and 55,000 BTU. The heat-output field says 25,000 BTU. The wattage field says 55,000 W. All are kept as printed.
What do UK reviews say?
A conversion van, a decent shower, and a request to use a qualified gas engineer. One buyer found air in the system on first use.
Does it use mains electricity?
No. The listing says liquid propane and 12 V DC.
The Mulcort LF-001 is best treated as a hand-wash heater for a garage, workshop or occasional basin. UK reviewers repeatedly say that hotter water requires a trickle, while normal dishwashing flow often needs help from a kettle. That matches the limits of a 3 kW element rather than the broader kitchen wording in the title. At £46.99 it is inexpensive, and its LCD gives useful feedback as the outlet temperature changes with flow. The 3.5-star average from 23 reviews is modest, and the listing provides only generic safety wording rather than a detailed electrical specification. It is our best-value pick for a narrow, realistic job, not a budget route to a shower or full kitchen supply.
Pros
Cons
Best for: A garage, workshop or occasional hand-wash basin where modest flow is acceptable.
Less suitable: Normal dishwashing flow, showers or more than one outlet.
Specifications
Common questions
How much power does the title state?
3,000 W at 220 V, with a maximum of 122°F and a stated 43.2 gallons per hour.
What do UK reviews say it is for?
A vanity or a garage hand-wash. Several say dishes need a kettle, because hot water means a trickle.
Does the listing name a shower?
No. The title says a sink and a kitchen.
The Briwellna 5.5 kW is intended for one tap, and its stated 40°C maximum makes that limit unusually clear. At a low flow it may provide useful hand-washing water, but it is not a convincing shower option and is marginal for washing dishes in cold weather. The listing calls for a dedicated 25 A double-pole breaker, so its £108.99 shelf price does not make it a plug-in appliance. Its 177-review count is the largest in this set, yet the 3.4-star average and repeated reports of a trickle, leaks, blown fuses and failed displays weaken the case. A few buyers do use it successfully at one sink, which keeps it from being dismissed outright. Choose it only when a modest single-faucet job and professional wiring are already part of the plan.
Pros
Cons
Best for: One hand-wash basin where low flow is acceptable and a suitable dedicated circuit is available.
Less suitable: Showers, simultaneous outlets or buyers expecting simple plug-in installation.
Specifications
Common questions
What maximum temperature does the listing print?
40°C. That is the specification figure, not a shower setting.
What supply does the bullet ask for?
A dedicated 25 A double-pole breaker for 5,500 W, and water pressure of 0.04–0.8 MPa.
What do UK reviews repeat?
A trickle before the water is hot, units that stop or lose the display, leaks, and blown fuses. A few reviews use it at one sink.
The Delousiber 6 kW promises useful heat from a small £46.99 box, but its power connection is the central problem. The listing says a 6,000 W heater generally needs a dedicated circuit and fuses of at least 40 A, while UK reviewers report receiving a 13 A-style plug. At 230 V, 6 kW is far beyond the normal 13 A socket range, so the fitted connector must not be treated as evidence that the unit is safe to plug in. The 3.1-star line from 20 reviews is also the weakest rated result in this comparison. Reports include leaks, blown fuses and units failing within days or months, although one buyer reports useful heat after six weeks. We would skip this model unless a qualified electrician can first resolve the rating, wiring and product-compliance questions.
Pros
Cons
Best for: No routine household recommendation; only consider it after independent electrical and product checks.
Less suitable: Plugging into a normal UK socket, showers or unattended daily use.
Specifications
Common questions
What supply does the listing warn about?
The first bullet says this rating generally needs a dedicated circuit, cable of 2.5 or 4 mm², and fuses of at least 40 A.
What do UK reviews say about the plug?
Reviewers say a 13 A-style plug is fitted, one of them with a 20 A fuse, on a 6,000 W heater.
What failures show up in the 12 UK reviews?
Leaks on two units, blown fuses, and heaters that stopped within days or a couple of months. One buyer reports about 50°C after six weeks.
The Mulcort 3 kW with remote is designed around one basin, with an under-sink format, G1/2 connection and a claimed UK plug. Its remote and 28–55°C setting range are convenient when the unit sits inside a cupboard. Those temperature figures are settings, not evidence that it will deliver 55°C at a normal tap flow, and the listing gives no flow rate. A 3 kW appliance is close to the practical limit of a 13 A supply, so the socket and circuit still need checking before use. There is no customer-review line in the extract, leaving reliability and real winter performance unknown. At £57.99 it is a plausible hand-wash candidate, but the reviewed LF-001 gives more evidence at a slightly lower price.
Pros
Cons
Best for: One wash basin where remote control matters and the existing circuit is confirmed suitable.
Less suitable: Showers, dishwashing at normal flow or buyers who want proven reliability.
Specifications
Common questions
Does the listing claim a UK plug?
Yes. The bullet says a UK plug and tells you to check that the socket and circuit suit a 3,000 W appliance.
What temperature range is printed?
28–55°C. The outlet still depends on inlet temperature and flow.
Is a shower head included?
The bullet says a shower head, a flexible hose, and a wall bracket are included. No shower flow is stated.
The COAKUE 65,000 BTU is an RV appliance rather than an alternative to an electric heater under a UK kitchen sink. It combines propane combustion with a 12 V supply and fits a stated 15 × 15 inch RV door, so the intended installation is unusually specific. The listing claims up to 3.9 gallons per minute and a 50°C maximum, which could suit washing in a compatible leisure vehicle. There is no customer-review line in the extract, however, and no UK gas approval is printed in the collected data. Its NPT connections and US-style dimensions also require careful compatibility checks. At £285.99, it only makes sense when your vehicle, gas system and qualified installer all match the product.
Pros
Cons
Best for: A compatible leisure vehicle project assessed and installed for the applicable UK LPG requirements.
Less suitable: A house, flat, kitchen cupboard or buyer seeking established UK review evidence.
Specifications
Common questions
What fuel and voltage does the listing state?
Liquid propane, plus 12 V DC. It is not a 230 V mains heater.
What flow and door size are printed?
Maximum 3.9 gallons per minute, and a 15 × 15 inch door.
Is there a review line?
No customer-reviews line is in the extract.
The laloohome Ewh-6000t is a compact, low-cost heater whose own listing does not agree on the basic output. The title says 6,000 W while the technical table says 5,500 W, and two different sets of dimensions are also printed. Its 30–55°C control range sounds flexible, but no stated flow means you cannot tell what temperature it can hold at an ordinary tap. The listing names a dedicated circuit and fuses of at least 40 A, which rules out treating the £44.99 unit as a normal socket appliance. There is no customer-review line in the extract, so there is no UK experience to balance those inconsistencies. The price is attractive, but the unresolved specifications make this a higher-risk choice than a documented basin heater.
Pros
Cons
Best for: A buyer prepared to verify the nameplate, manual and electrical requirements before purchase.
Less suitable: Anyone seeking a proven UK sink or shower heater with dependable published specifications.
Specifications
Common questions
Why are two wattages printed?
The title and bullet say 6,000 W. The technical table says 5,500 W. Both are left as printed.
What circuit does the bullet name?
220 V, cable of 2.5 or 4 mm², and fuses of at least 40 A, on a dedicated circuit.
Is there a review line?
No customer-reviews line is in the extract.
Eleven amazon.co.uk listings are scored as a comparison aid, not a laboratory test. The score does not certify electrical, plumbing or gas compliance. None of the kept ASINs is a Thermoflow. Suitability for the stated job, UK review evidence, specification clarity, value, and safety or support signals carry the weights below. Deductions sit outside those weights: no review line, US-only written reviews, conflicting specifications, a connector that conflicts with the load, and repeated reports of leaks, blown fuses or early failure.
Suitability for the stated job
30%Output, stated flow, temperature control, and whether the unit is credibly matched to a basin, a shower, an RV or outdoor use.
UK evidence
25%The amazon.co.uk star line, the review count, and whether the written reviews are UK experience. US-only written reviews are marked down.
Specification clarity
20%Wattage, dimensions, supply and connection information that agrees with itself. Conflicting output or size lines score lower.
Value
15%Shelf price against the realistic job and the likely installation burden, not against the cheapest headline alone.
Safety and support signals
10%Clearly stated protections, warranty or support evidence, and the absence of an unresolved connector or supply conflict.
These eleven amazon.co.uk listings are electric point-of-use heaters, hard-wired 11–14 kW heaters and LPG units. Shelf prices in the extracts run from about £44.99 to about £412.86. None of the ASINs is a Thermoflow. Read the stated watts, the connector and the printed flow before you compare a price. A star line from the United States is not UK shower proof.
A tankless water heater heats mains water as it flows. Outlet temperature depends on the kilowatts, the flow and how cold the inlet is. It does not store a cylinder of hot water, and it does not remove legionella risk. HSE guidance on 60°C stored water and 50°C at the outlet describes stored systems. A tankless heater is outside that claim. On amazon.co.uk this search mixes three jobs.
None of the eleven kept ASINs is a Thermoflow. A title that ranks for the query is not proof of that brand, and this page does not test a Thermoflow model. Read the brand line on the listing before you compare a price.
At 230 V a 13 A BS 1363 plug is about 3 kW. A 6 kW nameplate is about 26 A. UK reviews of the Delousiber say a 13 A-style plug is fitted to a 6,000 W heater. A pictured plug is not evidence that a normal socket is suitable.
Inlet water is colder in January, so flow has to fall if you want the same outlet temperature. WINTEMP and SIVUATEK written reviews in the extracts are marked United States. They are not UK proof of shower performance or of a UK installation.
Name the outlet first: one basin, one sink, a shower or a van. Do not buy a shower from a 3 kW title. A 3 kW unit can warm a basin. A shower or a one-bed flat needs about 10–12 kW and a circuit to match. The Stiebel listing states 12 kW and 5 litres per minute. WINTEMP states 11 kW and asks for a 50 A breaker. SIVUATEK states 14 kW and asks for 60 A. Briwellna prints a 40°C maximum for one faucet. Match power to flow. A rule of thumb is that about 70 watts raise 1 litre per minute by 1°C.
Match the connector to the watts. At 230 V a 13 A BS 1363 plug is about 3 kW. A 6 kW nameplate is about 26 A. UK reviews of the Delousiber say a 13 A-style plug is fitted to a 6,000 W heater, while the listing asks for fuses of at least 40 A. The Mulcort with remote claims a UK plug and says to check the circuit for 3,000 W. The Stiebel supply is a cable, not a 13 A plug. WINTEMP names a 50 A breaker and 8 AWG cable, which an electrician has to design to BS 7671 rather than copy.
Three typical situations, each with a recommendation from this comparison.
You can pay for a dedicated circuit and you want a basin or a carefully specified shower in a flat without gas. The Stiebel Eltron DCE-X 10/12 states 12 kW and 5 litres per minute, at about £412.86, with 4.4 from 116 reviews. Shower feedback is mixed, and the heater is hard-wired.
You want one hand-wash and you can live with a trickle when the water needs to be hotter. The Mulcort 3 kW LF-001 is about £46.99, with 3.5 from 23 reviews. UK reviewers describe that restricted flow. It is not a shower and not a normal dishwashing supply.
You are fitting a van, a garden shower or an off-grid site, and a Gas Safe engineer will handle the LPG. The CAMPLUX BW528B states 40 kW and up to 20 litres per minute, at about £379.99, with 4.4 from 19 reviews. It is an outdoor heater and it does not use mains.
The Stiebel Eltron DCE-X 10/12 is the top pick because it states 12 kW and 5 litres per minute and has the strongest UK review evidence in this set, at about £412.86 with 4.4 from 116 reviews. Shower flow is mixed, and the installation needs a substantial dedicated supply. The Mulcort 3 kW LF-001 is the best value when the job is one hand-wash basin: about £46.99, with UK reviews that describe a warm trickle. None of the eleven listings is a Thermoflow. A 6 kW unit with a 13 A-style plug is not a socket appliance, and US-only written reviews are not UK shower proof.
Mulcort 3 kW LF-001
Clearest low-cost proposition for a single hand-wash basin, at about £46.99, if you accept a restricted flow.
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 used with the amazon.co.uk listings; last checked on 16 October 2026. Prices are the extract shelf figures, not a live check.
This page contains affiliate links to amazon.co.uk. A qualifying purchase can earn a commission at no extra cost to you. Prices and review counts are the shelf figures in the listings used for this comparison. This is not a laboratory test of flow, electrical safety or gas compliance.
