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Shopping for a water heater can feel like learning a new language: tankless, multipoint, immersion timers — where do you even start? Whether you’re replacing an old unit under the sink or fitting out a small flat, knowing the options makes a big difference. This guide walks through popular models like Zip, Hyco, Stiebel Eltron, and Ariston, explains what the specs mean in plain terms, and helps you pick the right system based on capacity, power (in BTU/hr), and point-of-use needs — all using familiar imperial units so you can visualise the real-world impact.
Your water heater is the unsung hero of the home: it keeps showers hot, dishes clean, and laundry effective. Choosing the wrong size or type can mean cold showers, wasted energy, or frequent repairs. Think of it like picking the right engine for a car — too small and you'll struggle uphill; too big and you waste fuel. We’ll break down the leading options, from instant boiling taps to small under-sink tanks, and explain who each one suits best.
Instant or tankless heaters provide hot water on demand and save space, while tanked heaters store hot water for immediate use but take up more room. Tankless units are great for point-of-use applications like a single bathroom or kitchen sink. Tanked models make more sense if several outlets need hot water at once. Below, we profile real models so you can see concrete examples of both styles.
The Zip ES3 is designed as a compact under-sink instant heater. While its product name mentions 2.8 kW, that equates to roughly 9,554 BTU/hr of heating power, which is ideal for a single tap or small prep sink. If you need reliable warm water for handwashing or a single kitchen sink, this is a sensible, low-draw option.
About 9,554 BTU/hr output — small footprint and quick to install under a sink. Perfect where only one outlet is needed and low flow is expected.
Small flats, garden rooms, or utility sinks where space is tight and demand is modest.
Hyco’s IN60T steps up the power. Converting 6 kW into imperial units gives about 20,472 BTU/hr, which supports higher flow rates and can handle short simultaneous use across two small outlets. It’s a good middle-ground between tiny point-of-use heaters and full household systems.
Approximately 20,472 BTU/hr — suitable for a small kitchen and bathroom combo or faster recovery if you’re frequently using hot water.
Small households or flats where two nearby outlets might be used alternately, such as a kitchen sink and adjacent washbasin.
The Zip ES6 is known for rapid heating in commercial-style or busy household kitchens. Its 5.5 kW rating translates to around 18,766 BTU/hr, delivering near-instant hot water to a single outlet while handling higher flow than lower-power point-of-use models.
About 18,766 BTU/hr — designed for countertop or under-counter installs where frequent use is expected, including small commercial setups.
Home cooks, coffee stations, or small break rooms where fast, consistent hot water is a must.
This model includes a small hot tank designed for on-demand boiling water. The listed capacity is 7.5 liters, which is roughly 2.0 gallons — enough for repeated quick top-ups of hot water, tea stations, and small catering needs without waiting for a full kettle.
About 2.0 gallons of boiled water stored at any time for instant use; ideal for boiling and hot-drink prep rather than showering or washing dishes.
Office tea points, coffee bars, or home kitchens where you want true boiling water instantly without using a kettle every time.
Stiebel Eltron’s DEM series are popular mini-instant heaters. If you see a 3 designation, that typically points to around 3 kW of rated power — roughly 10,236 BTU/hr. These units are efficient, quiet, and excellent for single taps or point-of-use heating where you want to avoid running a large tank heater.
Approximately 10,236 BTU/hr for the 3-unit, giving fast warm water at low to moderate flow rates — a tidy solution for tight spaces.
Under-sink kitchen installations, en-suite washbasins, or as a booster in low-flow setups.
This Ariston model lists 15 liters of capacity, which converts to roughly 4.0 gallons. A small tank like this is ideal for point-of-use applications where you want a ready store of hot water without a full-size cylinder taking up space.
About 4.0 gallons of stored hot water — provides multiple hand washes or several dishwash cycles back-to-back in a compact form factor.
Under-sink installation in kitchens or bathrooms where demand is intermittent but you still want a buffer of hot water on hand.
The Hyco HW30A is an automatic unit with a rating around 3 kW, roughly 10,236 BTU/hr. The “auto” aspect suggests built-in controls for temperature or priority heating, taking some of the guesswork out of installation and use.
About 10,236 BTU/hr with automatic control features — handy if you want minimal fiddling and a consistent temperature output.
Busy households or landlords fitting rentals where ease-of-use and predictable performance are priorities.
These Hyco SF series models are tailored to point-of-use needs. The SF10k12’s 1.2 kW rating converts to about 4,094 BTU/hr and the “10” may imply a small capacity near 2.6 gallons, while the SF15SS at 2 kW is around 6,824 BTU/hr. Together, they cover a spectrum from tiny warm-up duties to slightly larger hand-washing or prep sink demands.
SF10k12: roughly 4,094 BTU/hr and a small on-board capacity around 2.6 gallons; SF15SS: about 6,824 BTU/hr for slightly higher flow.
Microwave kitchens, cloakrooms, and workshop sinks where hot water is needed but only in small volumes.
This Hyco multipoint model has a 1 kW rating — around 3,412 BTU/hr — paired with a 30 liter capacity, which is roughly 7.9 gallons. As an unvented multipoint heater it can feed several low-demand outlets within a short run, giving a stored buffer while working off modest power.
About 3,412 BTU/hr and 7.9 gallons of stored water — good for supplying cold-to-warm flows across a small apartment or flat with multiple low-flow outlets.
Small homes or flats where a few taps are used intermittently and installing a full central cylinder isn’t practical.
The Stiebel Eltron SNU compact unit offers about 1.3 gallons of on-site hot water, perfect for a single basin or as a booster for low-flow faucets. It’s like having a miniature kettle that keeps a small amount of warm water ready at all times.
Approximately 1.3 gallons capacity — space-saving and simple to fit beneath a sink where you need a quick hit of hot water.
Small washrooms, utility rooms, or anywhere that needs a tiny, constant supply of warm water without wiring or plumbing fuss.
Don’t overlook control gear. A mechanical immersion timer like the Selectric LGA lets you schedule when a tank heats, saving energy by only heating during peak use times. Think of it like setting the hot water to wake up with you, not run all night.
Mechanical timers are simple to set and compatible with most immersion heaters, letting you control tank heating cycles on a daily schedule.
Households with predictable routines who want to reduce energy use without investing in smart thermostats.
Start by listing what you want to run at the same time: shower, dishwasher, and one sink? Then consider flow rates. Instant units are measured in BTU/hr and flow (gallons per minute), while tanks are measured in gallons of stored hot water. For a single sink, a tiny instant unit or a 1–4 gallon tank will do. For a shower plus sink, step up to models offering 10,000 BTU/hr or more or a stored tank of around 4 gallons or higher depending on frequency.
Tankless units often use less energy because they heat only when needed, but if you have high simultaneous demand a larger tanked system may be more efficient in practice. Look at wattage or BTU/hr and compare to your electricity rates. Small tanks are cheap to run if you use hot water intermittently and have a timer to avoid warming water when you don’t need it.
Under-sink point-of-use systems are quick to install and save on wasted hot water in long pipe runs. Keep the heater close to the tap you’ll use most to reduce heat loss. For multipoint or larger tanks, check clearance for maintenance and ensure safety valves and expansion allowances are in place. If you’re not confident with wiring or pressurised systems, hire a qualified technician — it’s like calling a surgeon for a complex operation; you don’t want surprises afterward.
Choosing a unit purely on size or price is a common error. Oversized units waste energy and can cost more up-front; undersized units disappoint at peak use. Also, don’t forget to count how many fixtures might run simultaneously and whether you’ll need a true boiling point for drinks (a Zip Hydroboil-style unit) or just warm water for washing.
For a studio flat or single sink, consider the Stiebel Eltron SNU or Zip ES3 for compact, reliable performance. For a busy kitchen or small cafe, Zip ES6 or Zip Hydroboil Plus gives the speed and convenience you need. For small homes with multiple low-flow outlets, Hyco Powerflow with its roughly 7.9-gallon tank is a practical middle ground. And if you want a simple energy-saving add-on, a Selectric mechanical timer can trim wasted heating hours.
Think in terms of how you use water, not just product specs. A heater should fit your routine like a good pair of shoes — comfortable, reliable, and fit for the tasks you do every day. Measure available space, check electrical supply compatibility, and consider future needs like extra fixtures or increased household size before deciding.
Conclusion: Choosing the right water heater boils down to matching capacity, power, and placement to your real-life habits. The models covered here — from compact Stiebel Eltron and Zip instant units to Hyco multipoint tanks and Ariston small storage heaters — offer a spectrum of solutions for point-of-use and small household needs. Use the BTU/hr and gallon conversions provided to compare real-world performance, and don’t shy away from getting a pro to confirm sizing and installation for pressurised or unvented systems.
| Water Heaters | Price | |
|---|---|---|
| Ariston 3100310 Water Heater 2 Kw 15 Litre | £ 152,40 | |
| Ariston 3100718 Water Heater 10 Litre | £ 156,- |
