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G3 qualified engineer commissioning a Mixergy smart hot water cylinder in a London property
Mixergy Approved Installer — G3 Qualified

Mixergy Smart Cylinder London

App-controlled, heat-pump ready, PV diverter compatible smart hot water cylinders installed across London. G3 qualified engineers, full Octopus Agile / Cosy tariff pairing, Building Regulations Part G3 notification included. From £3,295 supply & fit.

Cut your hot water electricity bill by 40–70% with half-hour smart-tariff charging. Free survey, fixed-price written quote, single-day install on like-for-like swaps.

0207 046 1363WhatsApp 07456 975436Book online
G3 Qualified engineers
25yr Tank warranty
Octopus Tariff partner
UK Built in Oxford
MCS Heat-pump ready
Quick Answer

A Mixergy is a smart, app-controlled unvented hot water cylinder built in Oxford. It heats from the top down so you get a usable hot shower from a 30% charge, integrates natively with Octopus Agile and Cosy smart tariffs, works with PV diverters and is heat-pump ready out of the box. Fully fitted in London from £3,295 by a G3 qualified engineer, with Building Regulations Part G3 notification, Benchmark commissioning and a 25-year tank warranty included.

What is a Mixergy smart cylinder?

A Mixergy is an unvented hot water cylinder with software on top. Mechanically it is a duplex stainless steel pressure vessel with the same four-layer safety architecture as a Megaflo, Gledhill or Telford — working thermostat, non-self-resetting energy cut-out, expansion device and T&P relief valve discharging to a safe visible location. The difference is what sits on top of that.

Conventional unvented cylinders heat the whole tank evenly from a coil or immersion. You either have a full tank of hot water or you wait 30–40 minutes for the heat source to bring it up. The Mixergy uses a controllable stratification element that heats from the top down — the cylinder knows exactly what percentage of the tank is hot, and you can set the charge to anywhere between 30% and 100% from the app. A 30% charge in a 180L cylinder is enough for one full power shower and is ready in around 12 minutes on cheap-rate electricity.

The on-board PCB connects to your home Wi-Fi and pulls half-hour pricing data from your electricity supplier. Pair it with Octopus Agile or Cosy and the cylinder automatically charges during the cheapest half-hours of the day — typically 5p–8p/kWh overnight versus 27p/kWh on a flat-rate tariff. Add a PV diverter (MyEnergi Eddi / Solar iBoost+) and surplus solar charges the tank before being exported to grid at 5p. The result is a cylinder that delivers more usable hot water at 30–70% lower running cost than a same-size Megaflo.

Mixergy features at a glance

Eight features that distinguish a Mixergy from any conventional unvented cylinder. Every one is enabled at our standard install — no extra modules, no third-party controllers.

Mixergy smart cylinder app showing charge level and tariff schedule

  • Top-down heating

    Mixergy heats from the top down using a controllable immersion stratifier — you get a hot shower from as little as 30 litres of charge instead of waiting for a full tank.

  • App-controlled charge level

    Set the tank to 30%, 60% or 100% from your phone. Schedule charges around your shower times. Override on the way home from work.

  • Smart tariff integration

    Native integration with Octopus Agile, Cosy and Go tariffs. The cylinder automatically charges during cheap half-hour slots — typical London household saves £180–£320 per year.

  • PV diverter ready

    Works out of the box with MyEnergi Eddi, Solar iBoost+ and Marlec Solar iBoost. Solar surplus charges the tank before exporting to grid.

  • Heat pump ready

    Pre-installed coil port, large-surface heat exchanger and HP-friendly stratification profile. MCS-compliant for retrofit air-source heat pump installs.

  • Carbon dashboard

    App tracks kWh used, cost per charge and CO₂ saved. Useful for landlords reporting on EPC C / MEES improvements and for SAP / EPC uplift evidence.

  • Real-time leak detection

    Pressure sensor inside the cylinder flags abnormal drops within minutes — you get a phone alert before water reaches the ceiling below.

  • Holiday & frost modes

    One-tap holiday mode drops the tank to 35°C standby; frost protection auto-engages below 5°C for second-home and rental cylinders.

Mixergy vs Megaflo, Telford, Gledhill, Kingspan

The Mixergy sits at the premium end of the unvented market. Like-for-like against the most popular UK indirect cylinders at 210L:

CylinderCapacitySmart featuresWarrantyFitted (London)Notes
Mixergy X Indirect 210L210LNative app + tariff API25 yr tank / 2 yr parts£3,795UK-made (Oxford). Heat-pump and PV ready out of the box.
Heatrae Sadia Megaflo Eco SolarFlo 210L210LSolar coil only (no app)25 yr tank / 2 yr parts£2,150Best-in-class brand support, but no smart controls and no tariff integration.
Telford Tempest Smart 210L210LTelford Connect app25 yr tank / 2 yr parts£2,650Slim app feature set, no tariff scheduling on the Agile half-hour level.
Gledhill StainlessLite Plus Solar 210L210LSolar coil + manual programmer25 yr tank / 2 yr parts£2,295Strong recovery rate, manual programmer only, no app or smart-tariff brain.
Kingspan Albion Ultrasteel Aerocyl 210L210LHeat-pump optimised — no app25 yr tank / 2 yr parts£2,495Heat-pump ready but no smart scheduling. Pair with a third-party controller.

Mixergy carries a £1,000–£1,500 premium over a conventional Megaflo. Payback comes from the smart tariff scheduling — typical London 3-bed household saves £300–£450/year on hot water, payback 4–6 years.

Mixergy install cost London — 2026 pricing

Every Mixergy quote is a fixed figure given in writing after the on-site survey. No call-out fee, no parking add-ons, no surprise extras on the day. All prices include VAT.

JobWhat's includedFitted (inc. VAT)
Mixergy X Electric 150L — supply & fitMixergy 150L direct electric smart cylinder, full G3 inlet group, app pairing, Wi-Fi commissioning, Building Regs G3 notification, benchmark logbook.£3,295
Mixergy X Electric 180L — supply & fitMixergy 180L direct electric, G3 group, app pairing, smart-tariff setup (Octopus Agile / Cosy), commissioning, certificate.£3,495
Mixergy X Indirect 210L (boiler-fed)Mixergy 210L indirect for combi / system boiler, primary coil tie-in, G3 group, app commissioning, full notification.£3,795
Mixergy X Indirect 250L (4–5 bed home)Mixergy 250L indirect, expansion vessel, discharge re-route if required, app + tariff pairing, commissioning, certificate.£3,995
Mixergy + PV diverter integrationMyEnergi Eddi / Solar iBoost+ paired with Mixergy cylinder, immersion routed through diverter, solar surplus charging configured.+£395
Mixergy + heat pump pre-wire (HP-ready)Pre-installed heat-pump coil port, wiring centre for future ASHP tie-in, MCS-compliant flow / return labelled, app set for HP profile.+£295
Vented → Mixergy unvented conversionStrip out vented cylinder + loft tank, full repipe, new G3 group, discharge to outside, Mixergy 180–210L, building control notified.£3,895–£4,495
Mixergy annual service (smart cylinder)G3 12-point checklist + firmware update, app diagnostic pull, vessel pre-charge, T&P witnessed lift, certificate refreshed.£165

* Prices include VAT and Building Regulations G3 notification. Full price list on the pricing page. Conventional unvented prices on the unvented cylinders page.

Get a fixed-price Mixergy quote

Call 0207 046 1363

What size Mixergy do I need?

Mixergy sizing is more forgiving than conventional cylinders because the top-down stratification gives you usable hot water from a partial charge. As a rule of thumb you can drop one size step versus a like-for-like Megaflo, but the survey is what locks the figure.

Studio / 1-bed flat, 1 occupant

Mixergy 120L direct electric

Single shower, no bath. Top-down stratification means a 120L Mixergy delivers the same usable hot water as a 150L conventional tank.

2-bed flat, 2 occupants, 1 bathroom

Mixergy 150L direct or indirect

Two morning showers covered easily. Schedule charge to 70% overnight on cheap-rate tariff.

3-bed terrace, 3–4 people, 1 bath + ensuite

Mixergy 180L indirect

Full family use, school-run shower stacking, dishwasher / washing machine hot fill if specified.

4-bed semi, 2 bathrooms

Mixergy 210L indirect

Two simultaneous showers possible. Schedule 100% charge for evenings + 60% top-up midday.

5+ bed home, 3 bathrooms or freestanding bath

Mixergy 250L indirect

Large bath fills (180L+) plus multiple morning showers. Consider secondary circulation for distant ensuites.

HMO / serviced apartment, 4–6 tenants

Mixergy 250L indirect + tariff scheduling

Predictable charge cycles + tenant-facing app share. Cuts landlord energy spend versus always-on storage.

Mixergy install process — 5 steps

1

Free phone consultation + smart-tariff review

10 min

Call 0207 046 1363 or WhatsApp 07456 975436. We confirm property size, existing system (vented / unvented / combi), current electricity tariff and whether you have PV or are planning a heat pump.

2

On-site survey — power, pipework, Wi-Fi

30–45 min, free

G3 engineer attends, checks mains inlet pressure (must be ≥1.5 bar dynamic), discharge route, consumer-unit spare-way, Wi-Fi signal at the cylinder location and confirms the right Mixergy model and size in writing.

3

Order, schedule, fixed-price quote

Within 24 hr

Cylinder ordered direct from Mixergy (Oxford-built). Install day booked. Fixed-price quote in writing — no parts mark-up, no surprise extras.

4

Install day — strip out, fit, commission

6–10 hours

Old cylinder isolated and removed, G3 inlet group fitted, discharge piped to outside per Approved Doc G, Mixergy cylinder set on plinth, electrical and primary connections made, system filled, vented and pressure-tested.

5

App pairing, tariff setup, Benchmark handover

45 min same visit

Mixergy app paired to your home Wi-Fi, account created in your name, smart tariff connected (Octopus / Cosy), charge schedule configured to your usage pattern. Benchmark logbook signed off, Building Regs G3 certificate posted within 28 days.

G3 compliance & Benchmark commissioning

Smart electronics do not change the law. A Mixergy is an unvented hot water vessel over 15 litres, so every install is a controlled service under Building Regulations Part G3. The same paperwork trail applies as a Megaflo: G3-qualified engineer, four-layer safety architecture, Benchmark logbook signed at commissioning, Building Control notified within 30 days via the Competent Persons Scheme.

G3

Approved Document G3 — Hot water supply and systems

A Mixergy is still an unvented hot water vessel over 15 litres, which makes it a controlled service under Building Regulations Part G. Installation, commissioning and modification must be carried out by a G3 qualified engineer (BPEC HWSS / LCL Awards / C&G 6189) and notified to building control directly or through a competent person scheme.

Benchmark

HHIC Benchmark commissioning scheme

Every Mixergy ships with a Benchmark logbook that must be filled out and signed by the installing engineer at commissioning. We complete every field — pre-charge pressure, T&P lift confirmation, app pairing reference, and the customer signature — and email a PDF copy on the day. Required to validate the 25-year tank warranty.

BS EN 12897

Unvented closed water heater product standard

Governs cylinder construction, the four-layer safety architecture (working thermostat, energy cut-out, expansion device, T&P relief valve) and the labelling on every UK unvented cylinder. The Mixergy is BS EN 12897 certified and WRAS-approved.

MCS

Microgeneration Certification Scheme — heat pump compatibility

When a Mixergy is paired with an air-source heat pump now or in future, the cylinder coil and stratification profile meet MCS sizing rules. Required for BUS grant eligibility (£7,500 off heat pump install) — the cylinder choice cannot block the grant.

BS 7671

18th Edition Wiring Regulations

The Mixergy immersion and control board are electrical loads governed by BS 7671 — RCD protection on a dedicated 16A circuit, isolator switch within 2 m, bonding to the cold and hot water pipework. Every install includes the electrical safety check and notification where applicable.

GDPR / DPA 2018

App data + customer account

The Mixergy app stores hot water usage, charge cost and CO₂ data tied to the customer account. We register the customer as the data owner — never our own engineer email — so you keep full control of your usage data and can transfer the cylinder to a new owner if you move.

PV diverter integration with Mixergy smart hot water cylinder

Real London Mixergy installs

Six anonymised installs from the last twelve months across London. Each shows the property, the install scope, the smart-tariff outcome and the final figure.

Victorian terrace, Camden — Mixergy 210L paired with Octopus Agile

Replaced a tired 1998 vented copper cylinder with a Mixergy X Indirect 210L. Strip-out of loft tank, full repipe in 22 mm copper, new G3 group, discharge to outside above the gully. App paired to Octopus Agile — first month showed average charge cost of £0.062/kWh against a flat-rate baseline of £0.27. Customer's hot water spend fell from £42 to £14 per month. Total invoice: £3,895 inc. VAT, including Building Regs notification.

1930s semi, Wandsworth — Mixergy + PV diverter on a 4kW solar array

Existing 3.8 kWp PV array exporting most surplus to grid at flat 5p/kWh. Fitted MyEnergi Eddi diverter to a new Mixergy X Direct 180L. Surplus solar now charges the tank from 11:00–15:00 in summer; app shows free hot water on every sunny day from April to September. ROI on the diverter + smart cylinder upgrade: 4.5 years against the customer's previous electric immersion bill. Cost: £3,890 inc. VAT.

New-build townhouse, Wandsworth — heat-pump ready Mixergy 250L

Customer planning an ASHP install in 2027. Fitted Mixergy X Indirect 250L now with the heat-pump coil port pre-wired and labelled. Currently fed by a gas system boiler. When the heat pump goes in, the engineer connects the existing labelled port and reprograms the app — no cylinder change needed. Future-proof spend, BUS grant pathway preserved. Cost: £4,090 inc. VAT.

Listed mansion flat, Kensington — vented to Mixergy conversion

Two-bath flat with a tired 1970s vented cylinder in the airing cupboard and a header tank in the loft. Stripped out both, fitted a Mixergy 210L indirect, ran new mains in 22 mm copper to the new inlet group, discharge piped through the external wall above the gully. Listed-building consent not required (internal pipework only). Cost: £4,295 inc. VAT, two-day install.

5-bed family home, Hampstead — Mixergy 250L for shower-stacking

Family of six, three bathrooms, hot water shortfall every school morning. Replaced 180L Megaflo with Mixergy 250L Indirect. App scheduled to charge to 100% by 06:30 and top up to 70% at 16:00. End of cold-shower complaints. Customer adopted Octopus Go (5p overnight) for the cylinder cost saving. Cost: £4,095 inc. VAT.

HMO conversion, Tower Hamlets — Mixergy for tenant billing fairness

5-bed shared house with rotating tenants. Landlord wanted hot water cost transparency. Fitted Mixergy 210L Indirect with the app set to landlord master + read-only tenant view. Monthly kWh / £ data exported to the tenancy bills. Removes disputes over hot water usage. Cost: £3,895 inc. VAT.

Book your Mixergy survey

Free on-site survey across all London boroughs. Fixed-price written quote within 24 hours. Single-day install on like-for-like swaps. G3 qualified, Mixergy installer-trained, Building Regulations Part G3 notification included.

Call 0207 046 1363WhatsApp 07456 975436Book online

Mixergy installs across London

Mixergy work carried out across every London borough. Heaviest demand currently from Camden, Islington, Wandsworth, Hackney, Kensington & Chelsea, Richmond and Hammersmith & Fulham — properties with PV, smart-tariff customers and heat-pump retrofit plans.

CamdenWestminsterIslingtonHackneyTower HamletsSouthwarkLambethWandsworthHammersmith & FulhamKensington & ChelseaHaringeyRichmond upon Thames

Mixergy FAQ — London installs

What makes a Mixergy different from a regular unvented cylinder?
Three things. First, the Mixergy uses a controllable top-down heating element instead of heating the whole tank — you get a hot shower from a 30% charge that takes 12 minutes instead of waiting 40 minutes for a full Megaflo to recover. Second, the cylinder is software-controlled and Wi-Fi connected: you pick the charge level from your phone, schedule charges around cheap-rate tariff windows, and see usage in kWh and pounds. Third, it ships with native integrations for Octopus Agile, Cosy, MyEnergi Eddi PV diverters and most UK air-source heat pumps — no third-party controller required.
How much does a Mixergy install cost in London?
Fully fitted by a G3 qualified engineer in London: from £3,295 for a 150L direct electric, £3,495 for a 180L, £3,795 for a 210L indirect (boiler-fed) and £3,995 for a 250L. PV diverter integration adds about £395, heat-pump pre-wire adds £295, and a vented-to-Mixergy conversion runs £3,895–£4,495 depending on size and discharge route. Every price includes the cylinder, all G3 safety devices, app commissioning, smart-tariff pairing, the Benchmark logbook and Building Regulations Part G3 notification.
Will a Mixergy save me money on my electricity bill?
Yes — provided you switch to a time-of-use tariff. Typical London households on Octopus Agile or Cosy see hot water electricity costs fall by 40–70%. Real example: a 3-bedroom Camden household using 6 kWh per day for hot water paid £1.62 per day on flat-rate (27p/kWh) but only £0.45 per day after the Mixergy shifted charging to the 5p–8p overnight half-hours. Annual saving roughly £400. Payback on the cylinder upgrade against a like-for-like Megaflo replacement is 4–6 years.
Do I still need a G3 qualified engineer for a Mixergy?
Yes. A Mixergy is still an unvented hot water storage vessel over 15 litres, so Building Regulations Part G3 applies in full. The engineer must hold a current G3 ticket (BPEC HWSS, LCL Awards or City & Guilds 6035), the work must be notified to building control, and the four-layer safety architecture — working thermostat, energy cut-out, expansion device, T&P relief valve — must be installed and tested. The smart electronics are an addition to G3 compliance, not a replacement. Our engineers are all G3 qualified and Mixergy installer-trained.
Can a Mixergy work with my existing gas boiler?
Yes — the Mixergy X Indirect models have a primary coil that connects to any standard system or heat-only boiler in the same way as a Megaflo or Tempest. The boiler heats the tank through the coil; the Mixergy app controls when and to what level. The smart immersion element gives you a second cheap-rate route via the tariff API, so on a cheap overnight slot the cylinder can charge electrically instead of running the gas boiler. Most London customers use both, swapping automatically based on which is cheaper per kWh.
Is the Mixergy heat-pump ready?
Yes. The Mixergy X Indirect has a large-surface heat-pump-friendly coil and the stratification profile is optimised for the lower flow temperatures (50–55°C) that an air-source heat pump produces. If you are not ready to install a heat pump now but plan to within five years, we recommend fitting the Mixergy now with the heat-pump coil port labelled. When the heat pump goes in, the tie-in is a single morning's work — no need to replace the cylinder. The Mixergy is MCS-compliant for BUS-grant heat-pump installs.
How does the Mixergy work with solar PV panels?
Pair the cylinder with a MyEnergi Eddi, Solar iBoost+ or Marlec Solar iBoost diverter on your existing PV system. When the solar array is generating more than the house is using, instead of exporting at 5p/kWh the surplus is routed to the Mixergy immersion. Free hot water on every sunny day. The Mixergy app reports kWh charged from solar versus grid, so you see your free hot water count in real time. Diverter integration costs £395 on top of the cylinder install.
What happens if my Wi-Fi drops out?
The cylinder keeps working on its last-known schedule. The Mixergy has a local control PCB and a fall-back schedule stored on-cylinder — even if the internet is down for a week, the cylinder still heats on the schedule it last received. You lose the half-hour smart-tariff optimisation while offline, but you do not lose hot water. The app reconnects automatically when Wi-Fi returns and resumes optimisation from the next half-hour slot.
How long does the install take?
A like-for-like swap from an existing unvented cylinder (Megaflo, Gledhill, Tempest) is a 6–8 hour single-day job. A vented-to-Mixergy conversion takes 1.5–2 days because the cold-water mains, expansion control and discharge pipework are all new. Heat-pump or PV diverter integration adds 2–3 hours at the same visit. We give a firm time on the survey and very rarely run over — Mixergy installs are a planned job, not an emergency callout.
Will my hot water flow rate be better than my current cylinder?
Flow rate is determined by your mains inlet pressure and the cylinder PRV setting, not the brand. If you have 3.0 bar dynamic at the inlet, a Mixergy delivers the same 18–22 L/min as a Megaflo of equivalent size. What changes is recovery — the Mixergy can deliver a full hot shower from a 30% charge in 12 minutes (versus 35–40 minutes to fully reheat a Megaflo from cold), so practical hot water availability is significantly higher even on a smaller tank size.
What warranty comes with the Mixergy?
25 years on the duplex stainless steel tank, 2 years on parts (PCB, immersion, expansion vessel, T&P valve) and 12 months on our installation workmanship. The tank warranty requires an annual G3 service — we book those in your calendar and the app reminds you automatically. The 2-year parts warranty extends to 5 years if the cylinder is on our PPM service contract, because Mixergy give registered installer customers the longer cover.
Can I keep my existing cylinder cupboard?
Almost always yes. The Mixergy 150L–250L footprint is within a few centimetres of a standard Megaflo of the same size. Heights for like-for-like indirect cylinders run 1,210 mm (150L) up to 1,800 mm (250L). The survey takes measurements before the cylinder is ordered, so there are no nasty surprises. The only common change is a small extension to the spare-way circuit at the consumer unit if the existing immersion supply is not on its own RCD.
Do you provide the Building Regulations certificate?
Yes — every install includes Building Regulations Part G3 notification via our Competent Persons Scheme (BESCA / WaterSafe). You receive the Benchmark logbook on the day of install, and the Building Regs Compliance Certificate is posted to you direct from the scheme within 28 days. Keep both with your property paperwork — they are required for re-sale, re-mortgage, building insurance claims and any future installer touching the cylinder.
What if I move house? Can I take the Mixergy with me?
Technically yes, but most customers leave the cylinder with the house. The smart cylinder is a measurable asset on a home sale — it appears on EPC reports as a high-efficiency system and supports a higher SAP rating. If you do move, the app account transfers to the new owner with a simple email change. Removing and refitting a Mixergy at a new property is a £950–£1,250 G3 labour job, so it rarely makes sense versus leaving it in place and fitting a new one.
Is the Mixergy made in the UK?
Yes. Mixergy cylinders are designed and built in Oxford. Parts supply, replacement vessels and PCB swaps are stocked in the UK with next-day delivery to London. This matters for warranty turnaround — if a control board fails, we typically have a replacement in hand within 24–48 hours, versus 5–10 days for some imported smart cylinders.

Question not answered? Call 0207 046 1363 and speak to a Mixergy installer-trained G3 engineer directly.

Service area

Mixergy Installs — All London Boroughs

G3 qualified, Mixergy installer-trained engineers based in central London with cover across all 32 London boroughs and the City. Free surveys booked within 3–5 working days, installs scheduled within 2 weeks.

Ready for a smart hot water cylinder?

Mixergy installs from £3,295 fitted across London. G3 qualified, Mixergy installer-trained, Octopus Agile and Cosy tariff pairing on the day. Free survey, fixed-price written quote, Building Regulations Part G3 notification included. £5M public liability, fully insured.

0207 046 1363WhatsApp 07456 975436Book online

London 247 Home Services Ltd · Company No. 17120057 · £5M public liability · G3 qualified · Mixergy installer-trained

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