The Ariston E-Combi ONE 24kW condensing combi boiler is a compact, ErP A-rated gas boiler designed for UK homes with a single bathroom or moderate hot water demand. At the heart of the boiler is Ariston’s patented Xtratech™ stainless steel heat exchanger with 142% wider waterways for superior condensing efficiency and reduced blockage risk. The unique AUTO function continuously optimises boiler output to match real-time heating demand, reducing short-cycling and improving seasonal efficiency. Compact at 735 × 400 × 299 mm and weighing just 29.3 kg, it fits most standard boiler locations. Delivers up to 10.4 L/min of domestic hot water on demand. Supplied with standard horizontal flue kit and LPG conversion kit. Endorsed by the Energy Saving Trust. 2-year warranty, extendable to 5 years on registration.
24kW
Output
10.4 L/min
Hot Water
ErP A
Rated
29.3 kg
Weight
5-yr
Warranty
LPG Kit
Included
⚠ Gas Safe Installation Required: This boiler must be installed by a Gas Safe registered engineer. The installer must commission the boiler and complete the benchmark checklist. Annual service by a Gas Safe engineer is required to maintain the extended warranty.
The heart of the E-Combi ONE is Ariston’s patented Xtratech™ single-coil stainless steel heat exchanger, designed with 142% wider waterways than previous generations. Wider channels reduce pressure drops, lower the risk of blockages from system debris, and provide a larger condensing surface for improved heat transfer. Stainless steel construction resists corrosion across a wide pH range, making the exchanger compatible with most system water conditions. It is easy to remove for cleaning or inspection. Tested and certified by TUV Rheinland.
Xtratech™ single coil142% wider waterwaysTUV Rheinland certified
ErP A Rated — Energy Saving Trust Endorsed
The E-Combi ONE holds an ErP A energy efficiency rating for seasonal space heating and is endorsed by the Energy Saving Trust — one of a small number of gas boilers on the market to achieve both. At 30% load (low-temperature return mode), efficiency reaches approximately 99%, meaning the boiler extracts almost all available energy from the gas during normal heating operation.
ErP A ratedEnergy Saving Trust endorsed~99% efficiency at part load
AUTO Function — Intelligent Load Optimisation
The unique AUTO function monitors and adapts the boiler’s operating parameters to match the actual thermal demand of the building in real time. Rather than cycling to a fixed setpoint, AUTO continuously optimises output between minimum and maximum, reducing short-cycling, lowering average flow temperature and improving seasonal efficiency. It is engaged from the boiler’s built-in controls and requires no additional accessories.
AUTO functionContinuous modulationReduces short-cycling
Natural Gas and LPG Compatible — LPG Conversion Kit Included
The E-Combi ONE is supplied as a natural gas boiler but includes an LPG conversion kit as standard, making it suitable for properties without a mains gas supply. Conversion is a straightforward procedure carried out by a Gas Safe registered engineer. No additional kit purchase is required, saving both cost and procurement time.
Natural gas + LPGLPG kit in the boxGas Safe conversion
Lightweight at 29.3 kg — Colour-Coded Connections for Fast Installation
Weighing just 29.3 kg dry, the E-Combi ONE is straightforward to wall-mount without heavy lifting equipment. Connection pipework uses colour-coded ports to reduce installation errors. All connections are in the same positions as previous Ariston boilers, enabling easy like-for-like retrofit without pipework modification. Minimum servicing clearances are just 5mm on left and right.
29.3 kgColour-coded connectionsEasy retrofit
Built-In Mechanical Clock — Ariston NET Compatible
The E-Combi ONE includes a built-in 24-hour mechanical clock for basic heating and hot water scheduling without any external controls. It is also Ariston NET ready — the boiler can be connected to the Ariston NET wi-fi adapter (sold separately) to enable smartphone app control, remote diagnostics and energy monitoring, all without changing the boiler.
Built-in 24hr clockAriston NET readyApp upgradeable
Horizontal Flue Kit Included — Ready for Standard Installation
This package includes the Ariston Standard Horizontal Flue Kit (3318073), covering a typical straight-through external wall installation. The flue system uses 60/100mm coaxial (balanced flue) connections and is designed to minimise on-site cutting and adjustment. Extension kits are available separately for longer flue runs or non-standard configurations.
Horizontal flue kit included60/100mm coaxialEasy standard fit
The E-Combi ONE carries an IPX5D electrical protection rating, meaning it is protected against water jets from any direction. This allows the boiler to be sited closer to wet areas than a standard IP20 appliance, providing more flexibility for bathroom or kitchen installations in compact properties.
IPX5D ratedSplash-proofFlexible siting
Technical Specifications
Boiler
Model
E-Combi ONE 24kW — Product Code 3301131
Boiler Type
Condensing combi (heating + hot water, mains pressure)
ErP Rating (Heating)
A
Seasonal Efficiency (ηs)
~90%+ seasonal space heating
Heat Output Max (CH)
22 kW
Heat Output Max (DHW)
26 kW
Modulation
Yes — with AUTO function
Heating
Flow Temp Range (High Temp)
35°C – 82°C
Flow Temp Range (Low Temp / UFH)
20°C – 45°C
Domestic Hot Water
DHW Flow Rate (ΔT 35°C)
10.4 L/min
DHW Temp Range
36°C – 60°C
DHW Pressure Min/Max
0.2 / 7 bar
DHW Min Flow Rate
2 L/min
Physical and Electrical
Dimensions (H×W×D)
735 × 400 × 299 mm (approx.)
Dry Weight
29.3 kg
Electrical Supply
230V / 50Hz
Electrical Protection
IPX5D
Flue and Gas
Flue System
Balanced flue (room-sealed), 60/100mm coaxial
Flue Kit
Standard horizontal kit included (3318073)
Gas Types
Natural gas G20 / LPG (conversion kit included)
NOx Emissions
53 mg/kWh
System
Expansion Vessel
8L built-in
Min Ambient Temp
5°C
Servicing Clearances (top/front/bottom)
300 / 450 / 250 mm
Servicing Clearances (left/right)
5 / 5 mm
Included in Package
Boiler
Ariston E-Combi ONE 24kW (3301131)
Flue Kit
Standard horizontal flue kit (3318073)
LPG Conversion Kit
Included as standard
Warranty
Standard Warranty
2 years
Extended Warranty
5 years on registration within 30 days (via Ariston)
Installation Requirement
Gas Safe registered engineer
Manufacturer
Ariston Thermo UK Ltd, Milton Keynes
Frequently Asked Questions
Is the 24kW E-Combi ONE right for my home?
The 24kW model delivers up to 10.4 L/min of domestic hot water at a 35°C temperature rise. It is suitable for smaller to medium homes (1–3 bedrooms, one bathroom) with moderate hot water and heating demand. For larger homes or properties with multiple bathrooms where simultaneous hot water demands are likely, consider the 30kW variant.
Does the boiler include an LPG conversion kit?
Yes. The E-Combi ONE is supplied as a natural gas boiler but the LPG conversion kit is included in the box as standard. Conversion must be carried out by a Gas Safe registered engineer. No additional kit purchase is required.
What is the AUTO function?
The AUTO function is Ariston’s built-in load optimisation feature. It continuously adjusts the boiler’s heat output to match the actual demand of the heating system, rather than cycling between fixed on/off states. This reduces short-cycling, improves seasonal efficiency, and lowers average flow temperature, which keeps the boiler in condensing mode for longer. AUTO is engaged via the boiler controls — no external accessories needed.
Can the boiler be controlled via a smartphone app?
The E-Combi ONE is Ariston NET ready — it can be connected to the Ariston NET wi-fi adapter (sold separately) to enable remote control via the Ariston NET app (iOS and Android). The adapter plugs into the boiler without any modification. Without the adapter, the built-in 24-hour mechanical clock provides basic time programming.
What are the warranty terms?
The Ariston E-Combi ONE comes with a standard 2-year manufacturer warranty. This can typically be extended to 5 years by registering on the Ariston website within 30 days of installation. A Gas Safe registered engineer must carry out the installation. Annual service by a Gas Safe engineer is recommended to maintain the warranty.
Related Products
Ariston E-Combi ONE 30kW with Horizontal Flue
Higher-output combi for larger homes and multiple bathrooms
BTU & WATT Calculator
Room Dimensions
Room Type
Living Room
Bedroom
Kitchen
Bathroom
Conservatory
Hallway
Glazing Type
Single Glazed
Double Glazed
Triple Glazed
External Walls
0 Wall
1 Wall
2 Walls
3 Walls
4 Walls
Insulation Level
Poor
Average
Good (New Build)
Required Heating
0
Watts
0
BTUs
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