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First decide what “hot water only” means in your home: hot water while the radiators are off, or tap water with no need for boiler-powered space heating at all. For the first, a combi or a boiler-and-cylinder system may suit. For the second, a hot-water cylinder with an immersion heater may be the more direct solution. A heat-only electric boiler does not heat tap water by itself.
Which hot-water setup do you need?
In UK product terminology, “hot water only” can describe an operating mode or an entire system requirement. Turning off central heating in summer while retaining domestic hot water is different from needing an appliance solely to heat taps and showers. Identify which applies before comparing boilers.
| Configuration | How it provides tap hot water | Best suited to | Main trade-off |
|---|---|---|---|
| Electric combi boiler | Heats water instantaneously on demand. | Homes with limited space and moderate hot-water demand. | Flow depends on the particular model and temperature rise; simultaneous outlets need careful assessment. |
| Electric system boiler with a cylinder | The boiler heats water stored in a separate cylinder. | Homes where stored hot water or greater draw-off is useful and there is room for a cylinder. | Needs a correctly sized cylinder and system design. |
| Heat-only electric boiler with a separate hot-water source | The boiler heats the central-heating circuit only; a cylinder may use an immersion heater or another source for tap water. | Existing systems that already handle hot water separately. | The boiler alone does not meet domestic hot-water demand. |
| Electric boiler with integrated storage cylinder | Stores hot water in a cylinder combined with the boiler package. | Homes where a combined appliance fits the space and demand. | Check the exact model’s capacity, footprint and operating modes. |
| Cylinder with immersion heater, without relying on boiler hot water | An immersion element heats stored tap water. | Hot-water-only needs independent of boiler-powered space heating. | Requires a suitable cylinder, compatible element, controls and electrical supply. |
How to choose between instantaneous and stored hot water
Choose a combi when space is tight and demand is modest
A combi heats tap water as it is drawn, so it avoids a separate hot-water cylinder. Its practical limit is the model’s flow at the required temperature rise. Do not assume that a stated litres-per-minute figure will apply equally at every temperature rise or support several outlets running together.
ECA’s published-product comparison lists an Arceus 15 kW combi at 8 L/min with a 26.9°C rise, a Trianco Aztec Mini 12 kW at 5 L/min with a 35°C rise, and a Strom 14.4 kW model at 7 L/min with a 30°C rise. These are figures reported by ECA from product information, not independent laboratory results, and the differing temperature rises mean they are not directly comparable. See ECA’s electric boiler comparison.
#1 Best Overall
- No Plastic Contact with Your Water——With no plastic inside, water never touches plastic, ensuring a pure taste and safer drinking experience
- Faster Than a Stovetop Kettle——Heats 0.5L (2 Cups) water in under 3 minutes for less wait time
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- Safe & Easy to Use——Worry-free auto shut-off and boil-dry safety feature
- Auto Shut-Off Safety——Automatically shuts off within 30 seconds after the water reaches a boil
Choose a cylinder-based system when storage suits the household
A cylinder stores heated water for draw-off. That can be useful where demand is greater or outlets may be used at the same time, but performance depends on cylinder capacity and how the complete system is designed. A system boiler heats water in an external cylinder; a separate immersion heater can also heat cylinder water without relying on the boiler.
Baxi describes its Electromax as an electric boiler and hot-water storage cylinder supplied pre-plumbed with a factory-fitted circulating pump. A secondary guide reports a 180-litre cylinder and hot-water-only, boost and heating-only modes for Electromax; verify capacity and controls against current manufacturer information for the exact model before specifying it. Sources: Baxi electric boilers and Combi Boiler Prices’ Electromax guide.
Rank #2
- Fast Boiling: Experience rapid boiling with this 1500W electric kettle. Get hot water in just 3 minutes, perfect for making tea, coffee, and other hot beverages efficiently.
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- LED Indicator Lights: Blue LED lights illuminate during heating, providing clear visibility and assurance of the water warming process in this electric tea kettle, and turn off when water is boiled.
- Sleek & Stylish Design: Elevate your kitchen's aesthetic with this borosilicate glass water kettle, complemented by stainless steel accents and blue LED lights for a modern, sophisticated look.
Choose an immersion cylinder if the boiler need not make hot water
If the requirement is tap water and no boiler-powered space heating, a cylinder with an immersion heater may be a better match than buying an electric boiler for that job. The cylinder still needs to be sized for demand, and its element, controls and electrical connection must be compatible. ECA describes immersion-heated cylinders as a common separate arrangement in its guide to boiler types: Combi, system or heat-only: which electric boiler is right for your home?
Why “heat-only” does not mean hot-water-only
A heat-only boiler is designed to heat the central-heating circuit, not tap water. ECA Boilers UK explains: “A heat-only boiler — sometimes called an open vent boiler or regular boiler — does exactly what it says: it heats your central heating circuit and nothing else.” Domestic hot water must be provided separately, commonly by a cylinder and heat source. A system boiler, by contrast, heats water stored in an external cylinder; a combi heats domestic water on demand. The exact product configuration matters: ECA’s comparison describes Arceus variants as combi, system and heat-only, and notes that the Viessmann Vitotron 100 uses a separate cylinder for stored hot water. These are product descriptions, not a recommendation for every property. Source: ECA’s comparison.
Rank #3
- Premium Stainless Steel - 304 food-grade stainless steel inner pot and brushed stainless steel housing. BPA-free food grade materials, removable nylon filter for easy cleaning, easy-to-view water window
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- Precise & Safe - With the professional thermostat controlling system, this kettle can automatically shut-off when the water is boiling. Additionally, it has boil-dry protection
- Friendly Design - Cool touch handle with a simple release button and pop up lid to protect you from accidental burns. 360° swivel base is connected with UL standard power cord for safe usage and convenient storage
- Easy Clean - Use white vinegar, baking soda, water, cleaning bottle brush and microfiber cloth to clean your kettle and keep it looking new.
Check the electrical supply before selecting a model
Electric boiler output, phase and the property’s available electrical capacity can constrain the options. The boiler’s rating alone does not establish that an existing supply, fuse, breaker or cable is suitable. Strom’s brochure advises checking supply availability, current draw, breaker and cable sizing, and notes that combis generally have lower flow rates than cylinder-based arrangements. Have a qualified installer assess the system and an appropriately qualified electrical professional assess the connection. Source: Strom Boiler Brochure 2023.
One vendor-specific example illustrates why figures must not be generalized: the Electric Combi Boilers Company’s 2025 brochure describes a 12 kW single-phase model as usable as a combi or hot-water-only boiler and states a main-fuse requirement above 80 A. This is that company’s stated requirement for the described product, not a general sizing rule. Confirm the exact model and electrical suitability for the property. Source: Electric Combi Boilers Company 2025 brochure.
Rank #4
- FAST BOILING: Chefman kettles boil water fast. Boil your water for as little as 3 minutes for tea, hot chocolate, pour-over coffee, and other hot beverages.
- VARIABLE HEAT SETTINGS: Custom temperature control includes seven presets with boiling temps ranging from 160-212°F for the perfect cup.
- TRI-COLOR LED LIGHTS: Easily see when your glass teapot with infuser is in standby mode (white lights), heating mode (red lights), and in keep warm/steep mode (green lights).
- STEEP LOOSE LEAF TEA: With the included removable tea infuser, you can steep a whole pot in our hot water kettle to serve multiple people efficiently.
- CORDLESS CONVENIENCE: Our cord-free portable kettle for heating water allows you to serve guests in another room while leaving the base plugged in.
Questions to settle with the installer
- Is the requirement hot water while central heating is off, or tap water with no boiler space-heating role?
- How many outlets are likely to run at once, and what flow and temperature do they need?
- Would instantaneous heating meet that demand, or does a stored-water cylinder make more sense?
- Is there room and access for a separate cylinder or integrated storage appliance?
- Can the available electrical supply support the selected model, including its phase and protection requirements?
- What are the exact model’s current specifications, cylinder compatibility, warranty, availability and total installed cost?
Current prices, regional availability, installation compliance and tariff-dependent running costs are not established by the product comparisons cited here. Ask for a property-specific design and quote rather than inferring costs or suitability from a boiler’s kW rating.
Quick Recap
Best Value
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Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
