The Ariston Velis Tech Wi-Fi 45 Litre is an unvented, wall-hung electric storage water heater combining Ariston's unique twin-tank design with full Wi-Fi connectivity via the Aqua Ariston Net app. The 45L nominal capacity translates to an impressive V40 of 70 litres of usable hot water — up to 16% more than a conventional single-tank unit of the same size — thanks to the twin-tank's reduced thermal stratification. At just 27 cm deep, it is one of the slimmest water heaters available and is rated for a shower-ready reheat in under 30 minutes. Fitted with a 3 kW dual Incoloy enamelled heating element, it is designed for domestic use in studios, loft rooms, and en-suite cylinder replacement installations. The unit is supplied with a full unvented installation kit and carries a 5-year warranty.
45L / V40 70L
Nominal / usable
60 min
Shower-ready (ΔT=50°C)
⚠ Qualified Installation Required (Unvented) — This is an unvented hot water storage appliance. Installation must be carried out by a competent person holding a current Part G (Schedule 2) qualification in unvented hot water storage systems — such as G3 or equivalent — in accordance with Building Regulations Approved Document G. Installation must be notified to the local authority building control or an approved inspector. The supplied unvented kit (expansion vessel, tundish, and pressure reducing valve) must be fitted as part of the installation.
ℹ Supplied with Unvented Kit — Each unit is supplied with a 12-litre expansion vessel, tundish, and pressure reducing valve (KIWA certified) as required for UK unvented installations. All Ariston electric water heaters in this range are UKCA marked.
Features & Benefits
✔ Twin Tank — Up to 16% More Hot Water
Ariston's twin-tank design separates cold inflow and hot storage, reducing thermal stratification. This means more of the stored water stays at delivery temperature — resulting in up to 16% more usable hot water than a single-tank 45L unit. V40 = 70 litres.
✔ Wi-Fi Control via Aqua Ariston Net
Control and monitor the unit from anywhere via the Aqua Ariston Net app (iOS and Android). Set the water temperature, activate modes remotely, schedule weekly hot water patterns, receive shower-ready notifications, and monitor consumption. Saves up to 25% on energy bills with smart programming.
✔ Eco Evo — Learns Your Habits
The Eco Evo function monitors usage patterns and automatically adapts the heating schedule to deliver hot water when needed — without heating water unnecessarily. Saves up to 14% on electricity bills compared to operating at constant temperature.
✔ Boost Function for Urgent Demand
The Boost function heats water to maximum temperature as rapidly as possible for unexpected demand — useful when guests arrive or hot water has been depleted. Accessible from the app or the soft-touch HMI display.
✔ Titanium-Coated Twin Tank
The stainless steel twin-tank structure is coated with Ariston's titanium enamel for enhanced corrosion resistance and longevity. The electronic anode provides active tank protection without requiring periodic physical anode replacement.
✔ ABS Safety System + Anti-Legionella
Active protection includes Anti-Overheating, Anti-Freezing, and Dry Heating Self-Diagnosis. Once a month, the unit automatically raises tank temperature to 65°C to eliminate Legionella bacteria risk — a requirement under ACOP L8 for domestic hot water systems.
✔ Ultra-Slim 27 cm Depth
At 275 mm deep × 405 mm wide × 797 mm tall, the Velis Tech Wi-Fi is one of the most compact unvented cylinders available — designed for airing cupboards, loft spaces, and wall-mounted installations where a traditional cylinder will not fit.
✔ Soft-Touch HMI Display
The on-unit LED soft-touch display shows current water temperature, hot water availability at 40°C/50°C/60°C/70°C, heating status indicator, and Wi-Fi connection status. Error codes are displayed on screen and sent to the app for remote diagnosis.
Technical Specifications
| Brand / Model |
Ariston Velis Tech Wi-Fi 45L |
| Part Number (inc. unvented kit) |
4018072 |
| Nominal Capacity |
45 litres |
| V40 (usable hot water at 40°C) |
70 litres |
| Heating Element |
Dual 3 kW Incoloy enamelled (draws max. 3 kW at any one time) |
| Reheat Time (ΔT = 50°C) |
60 min |
| Standing Heat Loss @ 65°C |
0.96 kWh/24h |
| Max Working Temperature |
65°C |
| ErP Energy Rating |
B |
| ErP Tapping Profile |
M |
| IP Protection |
IPX4 |
| Wi-Fi / App |
Yes — Aqua Ariston Net (iOS & Android) |
| Display |
LED soft-touch HMI |
| Tank Protection |
Electronic anode + titanium enamel coating |
| Anti-Legionella |
Automatic monthly 65°C cycle |
| Installation |
Vertical wall-hung (unvented — G3 qualification required) |
| Dimensions (H × W × D) |
797 × 405 × 275 mm |
| Weight (empty / full) |
25 kg / 70 kg |
| Voltage / Frequency |
230–240 V / 50–60 Hz |
| Unvented Kit Included |
Yes — 12L expansion vessel, tundish, pressure reducing valve (KIWA) |
| Certification |
UKCA |
| Warranty |
5 years |
Frequently Asked Questions
What does V40 mean and why is it higher than the tank size?
V40 is the volume of hot water at 40°C that can be drawn from the unit in a test sequence defined by the ErP regulation — it accounts for mixing the stored hot water (stored at up to 65°C) with cold water to reach 40°C. Because the Velis Tech Wi-Fi's twin-tank design minimises stratification, a greater proportion of the stored water stays at full temperature, giving a V40 of 70 litres from a 45-litre nominal tank. V40 is the ErP test metric for usable hot water at 40°C mixed delivery — higher than nominal capacity because stored hot water is mixed with cold at the tap.
What qualification does the installer need?
Unvented hot water storage systems require installation by a person holding a current Part G (G3) qualification or equivalent — this covers design, installation, commissioning, and handover of unvented systems. The work must be notified to Building Control. The installer is responsible for correctly fitting the supplied 12L expansion vessel, pressure reducing valve, tundish, and temperature/pressure relief valve in accordance with the installation manual and BS 7074.
Can I control the pre-heat schedule to save electricity?
Yes — this is one of the strongest features of the Wi-Fi model. Using the Aqua Ariston Net app you can set a weekly heating schedule so the unit heats water only before the times you need it. The Eco Evo function further refines this by learning from actual usage patterns. Turning off constant heating and using scheduled or Eco Evo mode can save up to 25% on electricity consumption compared to running at a fixed setpoint continuously.
What is the difference between the Velis Tech Wi-Fi and the Velis Pro?
The key differences are: the Velis Tech Wi-Fi has a 3 kW element (faster reheat — shower-ready in 60 min) and built-in Wi-Fi for app control. The Velis Pro has a 1.5 kW element (slower reheat — around 50–60 minutes for 45L) with no Wi-Fi — it uses an on-unit display only. The Velis Pro is rated for leisure installations (mobile homes, glamping, cabins) where 13A circuit limitations apply. For domestic mains-connected installations with a 16A+ circuit, the Velis Tech Wi-Fi is the recommended choice.
