1930
Italian Heritage
27 cm
Slimmest Twin Tank
G3 Kit
Included as Standard
5 Yr
Warranty (Pro / Tech)
Ariston has been a fixture in British plant rooms and bathroom cupboards for decades, and the brand is now the UK's number-one selling electric water heater of 30 litres or less. The current line-up at Quality Heating stretches from a 6 litre point-of-use Andris Lux right up to a 100 litre Pro1 Eco — covering kitchens, en-suites, glamping pods, mobile homes, flats, loft conversions and small commercial premises with a single coherent range.
This guide focuses on the two newest twin-tank ranges — Velis Pro and Velis Tech Wi-Fi — separates the Wi-Fi from the non-Wi-Fi models, gives the cylindrical Pro1 Eco series a section of its own, and treats the small-format Andris Lux family as a distinct category. Every twin-tank and Pro1 Eco model from Ariston ships with a G3-compliant unvented kit in the box, which we explain in detail further down.
Ariston Electric Water Heater Comparison Chart
The four sub-ranges sold at Quality Heating answer four different installation problems. The table below distils the trade-offs: tank shape, element power, control type, suitable applications and circuit requirement.
| Range | Capacity | Element | Tank Design | Control | Best For |
|---|---|---|---|---|---|
| Velis Pro Newer | 45 L / 80 L | 1.5 kW (13 A) | Twin tank, 27 cm slim | On-unit LED | Mobile homes, glamping, cabins, leisure |
| Velis Tech Wi-Fi Newer Wi-Fi | 45 L / 80 L | 3 kW (16 A) | Twin tank, 27 cm slim | Aqua Ariston Net app + LED | Flats, small homes, smart-home users |
| Pro1 Eco | 50 L / 80 L / 100 L | 3 kW (16 A) | Single cylinder + WaterPlus | Electronic + digital display | 1–3 bed homes, loft conversions, small commercial |
| Andris Lux | 6 L / 10 L / 15 L / 30 L | 2 kW or 3 kW | Compact single tank | Mechanical dial | Point-of-use sinks, basins, holiday lets |
All four ranges are unvented and supplied with a factory-fitted T&P relief valve. The Velis Pro / Tech and Pro1 Eco ranges are supplied with a full G3-compliant unvented kit; Andris Lux models ≥ 10 L are paired with the Ariston Kit A.
Newer Range — Focus
Velis Pro & Velis Tech Wi-Fi: The Twin-Tank Generation
The Velis Pro and Velis Tech Wi-Fi sit at the top of Ariston's domestic electric line-up. Both share the same flat, ultra-slim twin-tank chassis at 27 cm depth — the slimmest UK-certified unvented electric water heater on the market — and the same Italian-designed soft-touch interface. The difference between them is a deliberate split for two very different installation contexts: power and connectivity.
Velis Pro 80L wall-mounted — only 27 cm depth allows installation in shallow alcoves and recesses
The double-tank explained
The headline feature on every Velis Pro and Velis Tech is the twin tank — but the engineering reason it exists isn't always obvious. Standard cylinders suffer from thermal stratification: when cold water enters at the bottom, it mixes with the stored hot water above and drops the deliverable temperature. By splitting storage into two interconnected tanks placed in series, Ariston isolates the cold inflow from the hot outflow, so a much higher proportion of the stored volume is available at delivery temperature. The result is a real-world V40 (litres at 40°C) that is up to 16% higher than a single-tank cylinder of the same nominal capacity.
Always at delivery temperature
The "front" tank holds water already heated to the set temperature. Hot water leaves to the tap from this tank, so what comes out is not diluted by the colder mains water entering the system.
Receives the cold inflow
Cold mains water enters the "back" tank first and is pre-heated there before transferring to Tank 1. Each tank has its own element, so reheat is faster and the unit only ever draws one tank's worth of power at a time.
Cutaway: two interconnected tanks, two heating elements, one combined slim chassis
Both ranges use a titanium-enamelled inner tank and the ABS Safety System (anti-overheating, anti-freezing and dry-heating self-diagnosis), plus an automatic monthly anti-Legionella cycle that raises the tank to 65°C as required under ACOP L8 for domestic hot water systems.
Wi-Fi vs Non-Wi-Fi: Picking the Right Velis
The two newer Velis ranges are deliberately separated by power draw and control method. This isn't a marketing gimmick — it changes which circuit you can wire it into and which homes it suits.
Velis Pro — 1.5 kW, no Wi-Fi
Maximum draw of 1.5 kW means it runs on a standard 13 A circuit. Designed for mobile homes, glamping pods, cabins, holiday lets and outbuildings where a dedicated 16 A radial isn't available. On-unit LED display only — no app, no smart scheduling.
Velis Tech Wi-Fi — 3 kW, app control
Draws up to 3 kW (16 A dedicated circuit) and is shower-ready in under 30 minutes. Built-in Wi-Fi pairs with the Aqua Ariston Net app for remote on/off, weekly scheduling and energy monitoring — Ariston quotes savings of up to 25% versus a constant-temperature setup.
Same chassis, same warranty
Both use the same 27 cm twin tank, ErP B/M rating, and ship with a 5-year warranty. Both are supplied with the same KIWA-certified unvented kit (12L expansion vessel, tundish, PRV).
Price parity
At Quality Heating both ranges are priced equivalently — the choice is genuinely about circuit and control preference, not budget. £535 for the 45 L, £570 for the 80 L (Velis Pro 80 L confirmed; Tech 80 L Wi-Fi at the same tier).
Eco Evo: the smart function on every Velis
Every Velis variant — Pro and Tech alike — runs Ariston's Eco Evo learning algorithm. Over the first weeks of use, the unit observes when and how much hot water you actually consume. After that learning period, it pre-heats only the volume you need, only when you need it, rather than holding a full tank at temperature 24/7. Ariston quotes savings of up to 14% on energy bills from Eco Evo alone, rising to 25% on the Wi-Fi model when combined with weekly app scheduling.
For homes on Octopus Go, Cosy or Economy 7, the Wi-Fi version is the natural pick: schedule heating for the off-peak window and let the slim twin tank deliver hot showers all day on cheap electricity.
Ariston · Velis Pro
Velis Pro 80L — 1.5kW Twin Tank
Newer 80 L twin-tank running on a 13 A circuit. V40 of 115 L from a flat 27 cm chassis. Ideal for mobile homes, cabins, glamping pods and any installation without a dedicated 16 A radial. Includes G3-compliant unvented kit. 5-year warranty.
£570.00 Inc. VAT
Ariston · Velis Tech Wi-Fi
Velis Tech Wi-Fi 80L — 3kW Twin Tank
Same slim 27 cm twin-tank chassis with a 3 kW dual element and built-in Wi-Fi. Shower-ready in under 30 minutes; full control via the Aqua Ariston Net app for weekly scheduling and up to 25% energy savings. Ideal for flats and smart-home setups.
£570.00 Inc. VAT
Ariston · Velis Pro
Velis Pro 45L — 1.5kW Twin Tank
Compact 45 L sibling to the 80 L Pro — same twin-tank engineering scaled down for a single bathroom or off-grid hot-water point. 13 A circuit, shower-ready in 50 minutes. Perfect for compact glamping accommodation and shepherd huts.
£535.00 Inc. VAT
Ariston · Velis Tech Wi-Fi
Velis Tech Wi-Fi 45L — 3kW Twin Tank
Smaller-capacity Wi-Fi option for studio flats, en-suites or small homes with a single bathroom. 3 kW dual element, twin-tank, full Aqua Ariston Net app integration. Shower-ready in under 30 minutes — fastest reheat in its size class.
£535.00 Inc. VAT
Ariston Pro1 Eco: The Classic Cylinder, Modernised
If the Velis Pro and Tech are the slim minimalists of the range, the Pro1 Eco is the dependable workhorse — a more conventional cylindrical wall-mounted unit available in 50, 80 and 100 litres. It uses a different technology to the twin tank: WaterPlus, which restructures the inlet flow to minimise mixing of cold-mains water with stored hot, achieving the same 16% V40 uplift without splitting the tank in two. The form factor is 470 mm in diameter, which makes it the right pick when wall depth isn't constrained and you'd prefer a familiar cylindrical body.
The Pro1 Eco range — 50L, 80L and 100L with the supplied G3-compliant unvented kit
The 80 L Pro1 Eco heats from cold in approximately 97 minutes with its 3 kW element and delivers a V40 of 92 L. It carries Ariston's Titanshield tank-protection system (titanium-reinforced enamel plus a magnesium sacrificial anode) and the same Eco Evo learning function as the Velis range. A neat addition unique to the Pro1 Eco is T-MAX, an instant boost button that drives the cylinder to its maximum 65°C as fast as possible when an unexpected guest stays the night.
WaterPlus tech
Minimises cold-water mixing for up to 16% more usable hot water — achieves the same V40 uplift as a twin tank in a single-cylinder layout.
Eco Evo + CoreTech
Learns daily usage and reduces electricity consumption by up to 14% versus constant-temperature operation. Configured via the on-unit display.
T-MAX boost
Single-press boost to 65°C for unexpected demand — house guests, large baths, or recovery after a power cut. No need to reset the schedule.
Titanshield + Mg anode
Titanium-reinforced enamel resists corrosion and scale; a magnesium sacrificial anode adds a second layer of tank protection inspected at annual service.
Ariston · Pro1 Eco
Pro1 Eco 80L — 3kW Cylinder
The most popular Pro1 Eco. 80 L nominal / 92 L V40, 3 kW element, Titanshield tank, Eco Evo, T-MAX boost and electronic display. Sized for 1–2 bedroom flats, loft conversions and light commercial. G3-compliant unvented kit included. 5-year warranty.
£495.00 Inc. VAT
Ariston · Pro1 Eco
Pro1 Eco 100L — 3kW Cylinder
The largest cylindrical Ariston in the line-up — 100 L nominal capacity for 2–3 bedroom homes, family bathrooms, or small commercial premises with sustained hot-water demand. Same WaterPlus, Eco Evo and Titanshield as the 80 L; same G3 unvented kit included.
£525.00 Inc. VAT
Every Ariston Includes the G3 Unvented Kit
An unvented water heater operates at mains pressure, which makes it brilliant at delivering strong showers from a single appliance — but also means it needs discharge protection to handle the pressure rise that occurs when water is heated. Under Building Regulations Approved Document G (Schedule 2, "G3"), every unvented hot water vessel installation in the UK must be carried out by a competent person holding a current G3 certificate, and must be notified to Building Control or an approved inspector.
The cost-saving insight here is that Ariston includes the entire G3 unvented kit in the box — you don't have to source the parts separately. Across the Velis Pro, Velis Tech Wi-Fi and Pro1 Eco ranges, that kit consists of:
12 L expansion vessel
A potable, KIWA-certified expansion vessel sized for the heater's capacity — absorbs the volume increase when stored water is heated so pressure cannot rise above safe limits.
Pressure reducing valve (PRV)
Steps incoming mains pressure down to the appliance's working range (typically 3.5 bar) so that any pressure spike on the mains supply cannot reach the cylinder.
Tundish
A visible air-break between the temperature/pressure relief valve and the discharge pipe — required so any release of hot water from the safety valve is immediately visible.
Factory-fitted T&P valve
The temperature and pressure relief valve is pre-fitted on the appliance — opens automatically if either the stored water exceeds 90°C or the pressure exceeds the rated maximum.
For the smaller Andris Lux range (10–30 L), the equivalent kit is the Ariston Kit A — a 2 L expansion vessel with a 15 mm non-return valve — supplied with the 30 L Andris Lux as standard, and available as an inexpensive add-on for 10 L and 15 L installs. Below 15 L stored hot water, G3 notification is generally not required, but the expansion vessel is still recommended to absorb thermal expansion in the system.
Ariston Andris Lux: Compact Point-of-Use Water Heaters
The Andris Lux family is a different proposition entirely. Where the Velis and Pro1 Eco are wall-mounted unvented cylinders sized to feed a whole bathroom or flat, the Andris Lux is a compact point-of-use unit mounted directly above or below a single sink, basin or worktop. With dimensions starting at 315 mm wide × 250 mm deep, they fit inside kitchen cabinets, under butler sinks, or on the wall behind cloakroom basins. They're available in 6, 10, 15 and 30 litre capacities, in 2 kW or 3 kW versions, and in both oversink and undersink configurations — the difference being where the inlet and outlet connections are placed and which way up the unit is hung.
Andris Lux 15L undersink — fits inside a standard kitchen base unit
Why the Andris Lux dominates its category
Ariston are the largest supplier to the UK market of electric water heaters of 30 litres or less, and the Andris Lux is the reason. Three things set it apart from generic small-format heaters:
ErP A energy rating
Up to "A" rated for energy performance — best in the small-format category. Means lower standby losses and substantially less wasted electricity when the unit is left on between uses.
Titanium-enamelled tank
The same Titanshield enamel coating used on the larger Pro1 Eco — exceptional durability and corrosion resistance for a unit at this price point. Combined with a copper element on the standard Lux range.
12-minute reheat
Fast reheat times from only 12 minutes — particularly important for point-of-use applications where you don't want to wait for warm water at a kitchen handwash or guest cloakroom.
3-year warranty (Lux) / 4-year (Lux Eco)
Standard Andris Lux carries a 3-year warranty; the upgraded Andris Lux Eco — which adds the ECO EVO learning function — extends to 4 years. Anti-Legionella cycle on both.
Watch: Ariston Andris Lux product overview
Ariston UK's official product overview video walks through the Andris Lux's physical design, mounting orientation and the difference between undersink and oversink configurations. Tap to play:
▶ Ariston UK — Andris Lux Product Overview (official)
Oversink vs undersink — which to pick
Undersink models hang inside the kitchen cabinet, with the inlet and outlet on the top — the unit sits below the worktop, out of sight, feeding a normal mixer tap above. Best for kitchens, utility rooms and any sink that has a base unit beneath it. Oversink models hang on the wall above the basin, with the inlet and outlet at the bottom — the unit is fitted with a hot-only spouted tap pre-attached. Best for butler sinks, pedestal basins, garage handwashes or outbuilding sinks where there's no usable cabinet below.
Ariston · Andris Lux
Andris Lux 15L Undersink — 3kW
The most popular undersink Andris. 15 L stored at 3 kW handles kitchen washing-up demand and a small en-suite handwash without the flow limitations of an instantaneous unit. Compact 360 × 294 mm footprint sits inside a standard 600 mm cabinet.
£175.00 Inc. VAT
Ariston · Andris Lux
Andris Lux 30L Oversink — 3kW
The largest in the Andris Lux range — 30 L of stored hot water for kitchens with sustained demand or as a light shower backup in a utility/annexe. Supplied with Kit A, B or C as required to match the specific plumbing configuration on site.
£395.00 Inc. VAT
Applications: Where Each Range Fits Best
The four Ariston ranges cover almost every domestic and light-commercial hot-water scenario. Pairing the right one to the application is mostly a question of capacity, circuit, and form factor:
Pro1 Eco
1–3 bed flats & small homes
Velis Tech Wi-Fi
Smart-home flats, BTR apartments
Velis Pro
Mobile homes & glamping
Andris Lux
Sinks, basins & cloakrooms
Suitable households at a glance
Sizing electric storage water heaters is mostly about peak demand rather than total daily use. As a rule of thumb for the Ariston ranges available at Quality Heating:
| Household / Use Case | Recommended Ariston | Capacity |
|---|---|---|
| 1 person · studio flat · 1 shower a day | Velis Tech Wi-Fi 45 L or Pro1 Eco 50 L | 45–50 L |
| 1–2 people · 1-bed flat · 1 bathroom | Velis Tech Wi-Fi 80 L or Pro1 Eco 80 L | 80 L |
| 2–3 people · 2-bed flat or small house | Pro1 Eco 100 L | 100 L |
| Mobile home · glamping pod · cabin | Velis Pro 45 L or 80 L | 45–80 L |
| Kitchen handwash · cloakroom · garage sink | Andris Lux 6 or 10 L | 6–10 L |
| Kitchen with sustained demand (washing up, cleaning) | Andris Lux 15 L | 15 L |
| Annexe · outbuilding · light shower backup | Andris Lux 30 L | 30 L |
Installation: What to Expect
Velis Pro 80L installed in a domestic airing cupboard — vertical wall-mount, 27 cm depth
Specify the right model and confirm circuit
Confirm capacity for the household (table above), then check the available electrical circuit. Velis Pro and all Andris Lux models run on a standard 13 A circuit. Velis Tech Wi-Fi and Pro1 Eco require a dedicated 16 A radial — get this confirmed by the electrician before purchase.
Engage a G3-qualified installer
All Velis Pro / Tech and Pro1 Eco units are unvented hot water storage appliances. Installation must be carried out by a competent person holding a current Part G (Schedule 2) qualification — typically G3, ACS or equivalent — and the installation must be notified to Building Control. Andris Lux installations of 15 L or less are generally exempt from G3 notification.
Mount and connect the unvented kit
Wall-mount the heater vertically in a frost-free location. Fit the supplied PRV on the cold inlet, the expansion vessel after the PRV, and the tundish on the T&P discharge — running the discharge pipe to a safe, visible drain via a metal tundish that's accessible for inspection. Use ½" BSP male connections at top (hot) and bottom (cold).
Commission and configure
Fill the cylinder via cold supply, bleed air through the hot outlet, energise the circuit, and set the working temperature on the LED display (typically 60–65°C). On Velis Tech Wi-Fi, pair the unit to the Aqua Ariston Net app and set up your weekly schedule — particularly worthwhile if you're on Octopus Go, Cosy or Economy 7.
Notify Building Control & record warranty
Your G3 installer issues a Building Regulations compliance certificate via their Competent Persons Scheme (BPEC, CIPHE etc.). Register the appliance with Ariston UK to activate the 5-year warranty (3-year on Andris Lux, 4-year on Andris Lux Eco). Schedule the first annual service for 12 months after install.
Frequently Asked Questions
What's the practical difference between Velis Pro and Velis Tech Wi-Fi?
Both share the same 27 cm twin-tank chassis, ErP B/M rating, ABS Safety system and 5-year warranty. The Velis Pro draws a maximum of 1.5 kW (13 A circuit, no app) and is built for leisure / off-grid use. The Velis Tech Wi-Fi draws 3 kW (16 A circuit) for faster reheat — under 30 minutes — and adds Wi-Fi for app control and weekly scheduling. Pick on circuit availability and whether you want app integration.
Do all Ariston water heaters include the unvented kit?
Yes — every Velis Pro, Velis Tech Wi-Fi and Pro1 Eco at Quality Heating ships with a complete G3-compliant unvented kit (12 L expansion vessel, KIWA-certified PRV, tundish), and the T&P relief valve is factory-fitted. The 30 L Andris Lux ships with the smaller Kit A; 10 L and 15 L Andris Lux can be paired with Kit A as an inexpensive add-on.
Why does the twin tank matter — isn't it just marketing?
No. Splitting storage into two interconnected tanks reduces thermal stratification — the cold mains inflow doesn't dilute the stored hot water. The measurable result is V40 (litres at 40°C delivery) up to 16% higher than a single-tank cylinder of the same nominal capacity. Each tank also has its own element, so reheat is faster and the unit only ever draws one tank's worth of power at a time.
Can I install a Velis or Pro1 Eco myself?
No — these are unvented hot water storage appliances and must be installed by someone holding a current Part G (Schedule 2 / G3) qualification, with the installation notified to Building Control under Approved Document G. The Andris Lux units of 15 L or less can typically be installed by a competent plumber outside the G3 regime, but always check the manufacturer's installation manual and local building regulations before proceeding.
What does V40 mean and why is it higher than the tank capacity?
V40 is the ErP test metric for usable hot water at 40°C mixed delivery — the temperature at which most showers and taps actually run. It's higher than nominal capacity because stored hot water (typically 65°C) is mixed with cold at the tap. For the Velis Pro 80 L, V40 is 115 L; for the Pro1 Eco 80 L it's 92 L. The difference is the technology — twin tank versus WaterPlus.
Are Ariston water heaters compatible with Octopus Go, Cosy or Economy 7?
Yes — any Ariston with the Eco Evo function will benefit from off-peak scheduling, but the Velis Tech Wi-Fi is the natural fit because it lets you schedule via the Aqua Ariston Net app. Set heating to coincide with your cheap-rate window (typically 12:30–05:30 on Octopus Go) and the slim twin tank then carries the household through the day on cheap electricity.
Need help choosing the right Ariston for your project?
Our team can match the right model to your circuit, your space and your hot-water demand — domestic, BTR, leisure or commercial.