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Electric or gas tankless water heater for the UK

Updated: 17.10.2026

Your consumer unit may have no spare capacity, or the hot-water job may be in a campervan, garden or off-grid cabin. Choosing an electric or gas tankless water heater is less about which fuel sounds cheaper and more about which installation you actually have. The [Thermoflow tankless water heater comparison](/hub/hot-water/thermoflow-tankless-water-heater) includes socket-class basin heaters, 40–60 A electric units and three propane or LPG listings. None is a Thermoflow product. LPG belongs to a suitable RV, outdoor or off-grid brief, with a clear boundary between a portable appliance and regulated fixed gas work. A qualifying purchase can earn a commission at no extra cost to you.

Your consumer unit may have no spare capacity, or the hot-water job may be in a campervan, garden or off-grid cabin.

Our top picks

Stiebel Eltron Stiebel Eltron DCE-X 10/12

Best overall

Stiebel Eltron Stiebel Eltron DCE-X 10/12
9.4/10about £412.86
View offer
CAMPLUX CAMPLUX BW528B

Alternative

CAMPLUX CAMPLUX BW528B
8.4/10about £379.99
View offer
Mulcort Mulcort 3 kW LF-001

Preis-Tipp

Mulcort Mulcort 3 kW LF-001
7.6/10about £46.99
View offer
On this page
  1. 1.Two fuels for two different jobs
  2. 2.When electric is still the right fuel
  3. 3.When the LPG listings fit the job
  4. 4.Portable cylinder or fixed connection
  5. 5.The conditional recommendation

Two fuels for two different jobs

Electric instantaneous heaters turn mains electricity into heat at the tap, with no combustion or flue. The constraint is current: a 13 A socket is roughly the 3 kW class, while a shower-capable listing may ask for 40 A, 50 A or 60 A. A bigger electric box does not help if the property cannot support that circuit. Gas heaters take more heat from propane and add fuel storage, combustion air and exhaust. GEESEN and COAKUE are RV units with 12 V controls. CAMPLUX is for outdoor use and battery ignition. A gas title is not permission to put that appliance indoors. Propane is a poor way to dodge the wiring cost of a kitchen appliance.

When electric is still the right fuel

For one basin, electric is the coherent option. The Mulcort LF-001 at £46.99 is a 3 kW hand-wash candidate, and UK reviews say hotter water needs a low flow. The remote model at £57.99 claims a UK plug and has no review line. Neither is a shower heater. For a flat or modest shower, the Stiebel Eltron DCE-X states 12 kW and 5 litres per minute at £412.86, with the strongest relevant UK review evidence in the high-output rows. Reviewers still disagree about shower flow. WINTEMP 11 kW at £176.47 asks for 50 A. SIVUATEK 14 kW at £329.51 asks for 60 A. Their written reviews in the extracts are from the United States. A lone 13 A socket means a basin heater. The instantaneous water heater buying guide sets out the output bands.
Stiebel Eltron Stiebel Eltron DCE-X 10/12

Testsieger

Stiebel Eltron Stiebel Eltron DCE-X 10/12
9.4/10about £412.86
View offer

When the LPG listings fit the job

The GEESEN RV05 is the least expensive gas row at £219, on propane and 12 V, with a stated 10 litres per minute and a remote. UK comments mention a conversion van and a satisfactory shower. The listing also prints conflicting power figures, including 24 kW and 55,000 BTU. Verify the data plate first. The CAMPLUX BW528B at £379.99 uses butane or propane and two D-cell batteries, not mains. It claims 40 kW and up to 20 litres per minute. UK comments describe off-grid and camper use. That claim is not a domestic multipoint heater, and these rows do not replace an electric unit under a kitchen sink.

Portable cylinder or fixed connection

A heater plumbed into a campervan, on gas pipework or a flue, is a different project from a freestanding outdoor unit used as designed. Gas work within scope must be done by a Gas Safe registered engineer qualified for the appliance and LPG. Do not fit the pipe or flue and ask for a signature afterwards. The UK tankless water heater installation guide covers the order of work without providing DIY gas-connection instructions. For a product-level shortlist, use the best tankless water heater listings by job.

The conditional recommendation

Choose electric indoors when the outlet is known and the property can support the circuit. At 3 kW, accept a modest basin flow. At 10–14 kW, budget for a hard-wired supply. Choose LPG only for an RV, garden or off-grid site that matches the product, with a Gas Safe engineer from the design stage if the connection or flue is fixed.

Common questions

Should I choose propane if the consumer unit is full?
Only when the actual job is suitable for an outdoor, RV or off-grid gas appliance. A full consumer unit may rule out a 50–60 A electric heater, but propane introduces location, flue and gas-safety requirements. For one indoor basin, a correctly supported 3 kW electric heater may remain the simpler option.
Can a camping gas heater go under the kitchen sink?
No. The gas listings in this set are described for RV or outdoor use, not a kitchen cupboard. Combustion needs appropriate air and exhaust arrangements, and an outdoor appliance must remain outdoors. Use a product explicitly designed and professionally assessed for the intended indoor installation.
Is a portable cylinder the same as fixed LPG in a van?
No. A portable appliance incorporating its own supply can sit outside parts of the fixed-vehicle standard, while gas pipework and a flue installed into a habitation vehicle form a different system. The complete setup determines the rules, so ask a qualified LPG professional before purchasing or modifying equipment.
Will an 11 kW or 14 kW heater run from a 13 A socket?
No. The WINTEMP 11 kW listing asks for a 50 A double-pole breaker, and the SIVUATEK 14 kW asks for 60 A. Both need a professionally designed dedicated supply. A normal UK 13 A socket belongs around the 3 kW appliance class, subject to the exact instructions.
Can I fit the gas pipe and have an engineer approve it later?
Do not use that approach for regulated gas work. A Gas Safe registered engineer qualified for LPG and the appliance should be involved before installation and must control work within scope. Retrospective sign-off does not make unregistered gas or flue work acceptable.
Are the gas listings made by Thermoflow?
No. The gas products retained here are branded GEESEN, COAKUE and CAMPLUX. Thermoflow is the searched category phrase, not the manufacturer of these ASINs. Use each product’s own manual, data plate and UK suitability evidence.

Related pages

Gas water heater comparison

Thermoflow tankless water heater

Best tankless water heater UK by basin, flat or van

Instantaneous water heater buying guide for UK homes

How to install a tankless water heater in a UK home

Under-sink water heater for one basin, not a shower

Sources

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.

  1. Approved Document G (2024 amendments) (retrieved 16 October 2026)
  2. Approved Document G FAQ (retrieved 16 October 2026)
  3. GOV.UK, use a competent person scheme (retrieved 16 October 2026)
  4. IET Part P FAQ (retrieved 16 October 2026)
  5. Gas Safety (Installation and Use) Regulations 1998, regulation 30 (retrieved 16 October 2026)
  6. HSE on the Gas Safe Register (retrieved 16 October 2026)
  7. HSE legionella, hot and cold water (retrieved 16 October 2026)
  8. Water Supply (Water Fittings) Regulations 1999, Schedule 2 (retrieved 16 October 2026)