The EHS Flex Heat Only Electric Boiler is a range-rateable electric boiler that can be configured anywhere from 2kW up to a full 12kW output, letting a single unit be specified across a wide range of property sizes instead of stocking multiple fixed-output models. Designed to work alongside a separate hot water cylinder (vented or unvented), it is built for homes without mains gas, off-grid properties, and retrofits where a flue-free, low-maintenance heat source is needed. The boiler is pre-wired with an integrated pump and internal expansion vessel, and produces zero carbon monoxide or combustion emissions at the point of use.
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12kW
Heat Output
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2–12kW
Range-Rateable
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100%
Efficient at Point of Use
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No Flue
Required
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Heat Only
Regular Boiler
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5 Years
Manufacturer Guarantee
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🔴 Electrical Installation: This boiler must be installed and commissioned by a qualified heating engineer and a qualified electrician in accordance with current BS7671 IEE Wiring Regulations and Building Regulations. The unit must never be opened for servicing or wiring access without first isolating the electrical supply.
🟡 Automatic Bypass Valve Required: An Automatic Bypass Valve (ABV) is not built into this unit and must be fitted as part of the heating circuit, opening as soon as the first radiator valve or actuator closes. This is a mandatory installation requirement, not an optional extra.
🟢 Built for Off-Gas and Solar-Ready Homes: With no flue, no annual gas safety certification, and full compatibility with solar PV systems and off-peak electricity tariffs, this boiler suits properties transitioning away from gas as well as new-build off-gas heating strategies.
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Range-Rated Output
Because a single unit modulates from 2kW to 12kW, installers spec one boiler across a range of heat-loss calculations rather than stocking multiple fixed-output models — reducing oversizing and the energy waste that comes with it.
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Integrated Pump & Expansion Vessel
The circulating pump and expansion vessel are built into the casing, cutting down on the ancillary parts and pipework an installer needs to source and fit on site.
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No Flue, No Combustion
With no burner or flue, there's no carbon monoxide risk and no annual gas safety inspection to schedule — simplifying both the installation location and the ongoing compliance burden for the homeowner.
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Pre-Wired Electronics
Internal wiring is completed at the factory, reducing the electrician's time on site to making the final mains and control connections rather than building up the control circuit from scratch.
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Works With Existing Cylinders
As a heat-only unit, it's designed to pair with a separate vented or unvented cylinder already on-site, making it a straightforward swap for a gas regular boiler without redesigning the hot water side of the system.
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Tariff and Solar Flexibility
Because output is electric and modulating, the boiler can be timed around off-peak tariff windows or paired with solar PV generation to shift running costs to cheaper or self-generated electricity.
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| General |
| Boiler Type |
Heat Only (Regular) Electric Boiler |
| Fuel Type |
Electric |
| Heat Output |
12kW (range-rateable 2–12kW) |
| Flow Temperature Range |
20°C – 80°C |
| Colour |
White |
| System & Compatibility |
| Hot Water Cylinder Compatibility |
Vented and unvented cylinders |
| Pump |
Integrated |
| Expansion Vessel |
Internal, 5 litres |
| Flue |
Not required |
| Automatic Bypass Valve |
Required on installation — not included |
| Solar PV / Off-Peak Tariff Compatible |
Yes |
| Compliance & Identification |
| Wiring Standard |
BS7671 IEE Wiring Regulations |
| Manufacturer Guarantee |
5 years |
| MPN |
ALS1-1PHO-12F |
| EAN |
5065008142300 |
What's the difference between this and an electric combi boiler?
This is a heat-only (regular) boiler — it provides central heating but relies on a separate hot water cylinder for domestic hot water, rather than heating water on demand like a combi.
Do I need a hot water cylinder to use this boiler?
Yes. It is designed to work alongside a separate vented or unvented cylinder already installed, or specified as part of the wider heating system.
Does this boiler need a flue?
No. As a fully electric boiler with no combustion process, no flue is required, which gives more flexibility over where it can be sited.
Can the output be set below 12kW?
Yes. The boiler is range-rateable from 2kW up to its full 12kW output, so it can be configured on installation to match the specific heat loss of the property.
Does it need annual servicing like a gas boiler?
There's no requirement for an annual gas safety certificate since there's no gas supply or flue involved, though routine checks by a qualified electrician are still good practice for any fixed electrical appliance.
Can this boiler be paired with solar PV or an off-peak electricity tariff?
Yes. The boiler's electric, modulating output is compatible with solar PV systems and can be scheduled around off-peak tariff windows to help reduce running costs.
