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Stiebel Eltron instant vs storage water heater

Updated: 17.10.2026

For one new basin or kitchen sink, the cheapest heater may not be the smallest case. This Stiebel Eltron instant vs storage water heater page separates the DCE range from the SNU 10 Plus (GB), which stores 10 litres and needs a special open tap. Choose the SNU for one compatible undersink outlet and a modest electrical load. Choose a DCE for an appropriate mains-pressure tap or shower when an electrician approves the high-current circuit. The [main Stiebel Eltron comparison](/hub/hot-water/stiebel-eltron-water-heater) lists all four products. Peter F. checked the UK listings and the maker’s data, not a lab. A qualifying purchase can earn a commission at no extra cost to you.

For one new basin or kitchen sink, the cheapest heater may not be the smallest case.

Our top picks

Stiebel Eltron Stiebel Eltron SNU 10 Plus (GB)

Best overall

Stiebel Eltron Stiebel Eltron SNU 10 Plus (GB)
10.0/10about £160.68
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Stiebel Eltron Stiebel Eltron DCE-X 10/12 Premium

Rank 2

Stiebel Eltron Stiebel Eltron DCE-X 10/12 Premium
8.8/10about £412.86
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Stiebel Eltron Stiebel Eltron DCE-S 10/12 Plus

Preis-Tipp

Stiebel Eltron Stiebel Eltron DCE-S 10/12 Plus
7.6/10about £327.61
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On this page
  1. 1.Two families, not two sizes of the same heater
  2. 2.The SNU only works with an open tap
  3. 3.What you connect and what you wait for
  4. 4.Which family should serve one basin?

Two families, not two sizes of the same heater

A DCE is a sealed instantaneous heater. About 0.277 litre inside is not a usable store. Water heats as it passes, and heating stops when the tap closes. It does not run out after 10 litres, but flow is limited by kilowatts and the temperature rise. The SNU stores 10 litres. Its 2 kW element heats that water in advance, so you get a short draw, then a wait. Technical data gives roughly 19 litres mixed to 40 °C from a full hot store, depending on stored and incoming temperatures. A DCE is about 372 × 217 × 109 mm and 2.5 kg, over or under a suitable outlet. The SNU is about 506 × 290 × 282 mm and 4.2 kg on the listing, and it must stand vertically under the sink. Check the tap, the cupboard and the circuit before you compare £160.68 with £327.61 to £412.86.

The SNU only works with an open tap

The SNU 10 Plus (GB) is non-pressurised, for one draw-off through a compatible three-pipe open tap. Cold mains displaces the hot water. “Open vented” does not mean a loft-tank trickle. The open outlet is the expansion route, and a normal mixer closes it when shut. Follow the SNU manual rather than a note about standard taps on other models. The researched Amazon product did not include a tap. A bundle with a WST-W tap is a different package, so price the correct fitting separately. Fill the store before power: open the cold supply and run the hot side until the water is free of air. If you must keep a normal mains-pressure mixer, a DCE is the relevant family here, once the water and the circuit fit. Those checks are in the buying guide.
Stiebel Eltron Stiebel Eltron SNU 10 Plus (GB)

Testsieger

Stiebel Eltron Stiebel Eltron SNU 10 Plus (GB)
10.0/10about £160.68
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What you connect and what you wait for

The SNU is 2 kW at 230 V, on about a 10 A supply. Standing loss in the technical data is about 0.31 kWh per 24 hours at 65 °C. That is a test figure, not a promised bill saving. A DCE needs permanent high-current wiring, not a BS 1363 plug. Published protection is 30/40 A for the 6/8 band and 50/60 A for the 10/12. At 230 V the steps are about 6.6/8.7 kW and 11.0/13.1 kW. An electrician must confirm the consumer unit, cable and connected load before you order. The SNU then empties and you wait on a 2 kW reheat. A shower starts with the 10/12 band, still subject to the flow calculation in the shower guide.

Which family should serve one basin?

Choose the SNU 10 Plus for one undersink basin or kitchen sink when you can fit the open tap and a modest load matters more than continuous hot water. It suits handwashing or intermittent use. It is not a mains-pressure shower and must not take a standard mixer. Choose a DCE for a suitable pressure tap, for hot water as long as the modest flow continues, or for one correctly sized shower. The DCE-X 6/8 fits the basin end. The 10/12 models need more current and only make sense when the outlet needs that output. No unvented store is in this set. Do not treat the open-vented SNU as an unvented cylinder. If neither the special tap nor the DCE circuit is acceptable, look further. Stars do not settle it. The SNU’s 5.0 is one rating, and the DCE-X 10/12 reviews still split on showers.

Common questions

Should I buy a DCE or an SNU for one sink?
Choose the SNU for one undersink outlet if you can use its open-vented tap and accept a finite 10 litre store. Choose a DCE if you need a compatible mains-pressure tap and an electrician approves the dedicated circuit. The DCE-X 6/8 is the proportionate instantaneous starting point for a basin.
Why can the SNU not use my normal mixer?
The SNU is non-pressurised and uses its open tap as the expansion route. A normal mixer closes the outlet when shut, removing that route and pressurising a store designed for zero permissible pressure. Use the matching three-pipe tap rather than adapting the appliance.
Does open vented mean weak water pressure?
Not in the sense of a loft-tank trickle. Mains cold water enters and displaces hot water from the SNU. The system must still use its specified non-pressurised tap, and its finite hot-water volume and plumbing differ from a mains-pressure DCE.
How much usable hot water does the SNU provide?
It stores 10 litres, and the technical sheet gives approximately 19 litres mixed to 40 °C under its test conditions. The actual mixed volume depends on stored temperature and incoming cold water. Once that useful hot volume is used, the 2 kW element needs time to reheat it.
Which heater is smaller beneath a basin?
The DCE is much shallower, at roughly 372 × 217 × 109 mm and 2.5 kg. The SNU is about 506 × 290 × 282 mm, and the listing gives 4.2 kg. The DCE’s compact case comes with a much more demanding electrical circuit.
Does the SNU’s single 5.0 rating settle the choice?
No. One rating without written feedback cannot establish performance or reliability, and it cannot make an open-vented store suitable for a pressure tap or a shower. Installation type, stored volume, circuit and outlet must decide the family before ratings are considered.

Related pages

Best Stiebel Eltron water heater

Stiebel Eltron water heater

Stiebel Eltron water heater buying guide for UK use

Stiebel Eltron water heater for one shower in the UK

How to use a Stiebel Eltron water heater day to day

Sources

Manufacturer pages, UK public sources and the amazon.co.uk listings in this comparison, retrieved on 17 October 2026.

  1. Stiebel Eltron DCE-X 10/12 Premium (retrieved 17 October 2026)
  2. Stiebel Eltron DCE-X instruction and installation manual (retrieved 17 October 2026)
  3. Stiebel Eltron DCE-S 10/12 Plus (retrieved 17 October 2026)
  4. Stiebel Eltron SNU 10 Plus (GB) technical data (retrieved 17 October 2026)
  5. Water Supply (Water Fittings) Regulations 1999, Schedule 2 (retrieved 17 October 2026)
  6. Approved Document G (England) (retrieved 17 October 2026)
  7. HSE: hot and cold water systems (retrieved 17 October 2026)
  8. IET: Part P in England and Wales (retrieved 17 October 2026)