For more than 30 years, Megaflo has been the name UK installers reach for when a home needs mains-pressure hot water. The Heatrae Sadia Megaflo was the first unvented cylinder to put the expansion space inside the tank, and that simple idea still defines the range today. Now the Megaflo family is getting bigger, simpler and more flexible, which makes it the perfect moment to walk through every Megaflo cylinder type and the job each one is built for.
Whether you're replacing a tired copper cylinder, fitting a new system boiler, going all-electric off the gas grid, adding a heat pump or trying to squeeze more value out of your solar panels, the answer is the same:
The Heatrae Sadia Megaflo unvented cylinder family, available from AIZO Quality Heating.
🔔 What's new in the Megaflo cylinder range for 2026
Baxi, Heatrae Sadia's parent group, has reorganised its hot water cylinder portfolio so that customers get one clear, unified choice under the trusted Megaflo name. Here's what that means in practice:
- Baxi-branded cylinders are moving to Megaflo. The Baxi Direct, Baxi Indirect and Baxi Assure cylinder lines are being retired, with every residential application now covered by a Heatrae Sadia Megaflo equivalent. If you've previously specified a Baxi cylinder, there is a like-for-like Megaflo to replace it.
- New Megaflo Essential range. An entry-level line of Direct, Indirect and Air Source Heat Pump cylinders for budget-conscious projects, featuring 50mm insulation, the enhanced internal expansion system and a 20-year stainless steel tank warranty.
- Megaflo Essential ASHP cylinder. Designed for low-carbon homes and compatible with all heat pumps, including Baxi's own mid-temperature HP40/HP50 and high-temperature HP60 models.
- Upgraded internal expansion on Megaflo Eco. The premium Eco range, with 60mm insulation and a 30-year tank warranty, is getting an enhanced internal expansion mechanism for even better long-term durability, starting with the larger Direct, Indirect and Solar PV Ready models.
The bottom line for homeowners, landlords and installers: fewer brands to choose between, a clear good/better/best ladder, and a Megaflo for practically every hot water scenario.
Why choose a Megaflo unvented cylinder?
An unvented hot water cylinder is fed directly from the cold mains, so you get strong, even pressure at every tap and shower, often across several bathrooms at once, with no loft tank and no noisy pump. Megaflo adds a few things that set it apart:
Internal expansion. Hot water expands as it heats up. Most unvented cylinders need a separate expansion vessel on the wall to cope with this. Megaflo builds the air gap inside the cylinder, which means fewer parts, a tidier install, less to maintain and one less thing to go wrong.
Duplex stainless steel. Megaflo Eco tanks are made from high-grade duplex stainless steel for excellent corrosion resistance, which is why Heatrae Sadia is confident enough to back the inner tank for 30 years.
Fast recovery. High-performance heat exchanger coils mean indirect models reheat quickly from your boiler or heat pump, so the next shower is never far away.
Every heat source covered. Direct (electric immersion), Indirect (boiler or heat pump coil), pre-plumbed, slimline and solar-ready versions mean Megaflo fits gas, electric, heat pump and renewable systems alike.
There's a Megaflo for it: find your cylinder
The easiest way to choose a Megaflo is to start with your home and your heat source. Find the situation that sounds like yours:
Got solar panels exporting power for pennies?
There's a Megaflo for it.
The Megaflo Eco Solar PV Ready comes with a factory-wired Solar iBoost+ controller that diverts surplus solar electricity into the cylinder instead of the grid, turning spare generation into free hot water.
Running a heat-only (regular) boiler?
There's a Megaflo for it.
The Megaflo Eco SystemFit arrives pre-plumbed and pre-wired at the factory with the pump and controls a regular boiler lacks, cutting install time and guaranteeing a neat finish.
Tight airing cupboard or compact flat?
There's a Megaflo for it.
The Megaflo Eco Slimline is just 491mm wide, a full 88mm narrower than the standard Eco, in 100 to 200 litre sizes. Available as Indirect for boiler systems or Direct for all-electric homes.
All-electric or off the gas grid?
There's a Megaflo for it.
Megaflo Direct cylinders, including the Eco Slimline Direct with titanium immersion elements, heat water by electricity alone, ideal on off-peak tariffs. Or pair an indirect Megaflo with an electric boiler such as the Baxi Amptec S.
Switching to an air source heat pump?
There's a Megaflo for it.
The new Megaflo Essential ASHP cylinder is designed around the larger coil and lower flow temperatures heat pumps need, and works with all heat pumps, including the Baxi HP40/50 and HP60.
Landlord, refurb or tight budget?
There's a Megaflo for it.
The new Megaflo Essential Direct and Indirect range gives you genuine Megaflo performance, internal expansion and a 20-year tank warranty at an entry-level price, perfect for rental properties and refurbishment work.
Megaflo cylinder types compared
Here's how the main Megaflo ranges line up. Scroll the table sideways on mobile.
| Megaflo range | Heated by | Sizes | Diameter | Tank warranty | Best for |
|---|---|---|---|---|---|
| Eco Direct | Electric immersion(s) | 70–300 L | 579 mm | 30 years | All-electric homes, off-peak tariffs |
| Eco Indirect | Boiler coil + backup immersion | 70–300 L | 579 mm | 30 years | Gas, oil, LPG or electric system boilers |
| Eco Slimline Indirect | Boiler coil + 3 kW backup | 100–200 L | 491 mm | 30 years | Narrow cupboards and flats with a boiler |
| Eco Slimline Direct | Titanium immersion(s) | 100–200 L | 491 mm | 30 years | Narrow spaces, no boiler |
| Eco SystemFit | Heat-only boiler (pre-plumbed) | 125–300 L | 579 mm | 30 years | Regular boiler upgrades, developers |
| Eco SystemReady | System boiler (pre-plumbed) | 125–300 L | 579 mm | Ask us | Fast system boiler installs |
| Eco Solar PV Ready | Boiler coil + solar-diverted immersions | 210–300 L | 579 mm | 30 years | Homes with solar PV |
| Essential Direct / Indirect | Immersion or boiler coil | 170–300 L | Ask us | 20 years | Budget, rental and refurb projects |
| Essential ASHP | Heat pump coil | 210–300 L | Ask us | 20 years | Air source heat pump systems |
Direct means the cylinder is heated by electric immersion elements only. Indirect means it's heated by a coil connected to your boiler or heat pump, usually with an electric immersion as backup.
Featured Megaflo cylinders and matching Baxi boilers
These are the Megaflo models and Baxi boiler partners we recommend most often. All ship with free express UK mainland delivery on most orders.
Heatrae Sadia Megaflo
Megaflo Eco Solar PV Ready Indirect, 210–300L
Diverts surplus solar PV into the tank via a factory-wired Solar iBoost+ controller, while the internal coil lets your boiler top up on cloudy days. Works with new or existing PV arrays, no roof work needed, and includes secondary return as standard.
From £2,730 inc. VAT
Heatrae Sadia Megaflo
Megaflo Eco SystemFit Indirect, pre-plumbed
Factory pre-plumbed and pre-wired for heat-only (regular) boilers, so installers save hours on site and every job gets the same tidy finish. Coil heat-up in as little as 22 minutes, secondary return on every size.
From £3,200 inc. VAT
Heatrae Sadia Megaflo
Megaflo Eco Slimline Indirect, 100–200L
Just 491mm across, the Slimline Indirect squeezes full Megaflo performance into narrow airing cupboards. A 16.9 kW coil gives full heat-up in 19 to 35 minutes, with a 3 kW immersion as backup.
From £1,170 inc. VAT
Heatrae Sadia Megaflo
Megaflo Eco Slimline Direct, 100–200L
The all-electric Slimline for flats and homes without a boiler. Durable titanium immersion elements (dual 3 kW on 125L and above) cope well in hard water areas and suit off-peak electricity tariffs.
From £1,495 inc. VAT
Baxi
Baxi Amptec S Electric System Boiler, 4–18kW
A compact UK-built electric system boiler with built-in pump, 7L expansion vessel and 9:1 modulation. No flue, no gas, no annual gas safety check. Pair it with any indirect Megaflo for a complete all-electric heating and hot water system.
From £1,190 inc. VAT
Baxi
Baxi 800 System 2 Gas System Boiler, 18/24/30kW
Baxi's premium gas system boiler with a 10-year parts and labour warranty, ErP A-rating, 93% seasonal efficiency and an Adey MagnaClean Micro2 filter in the box. Listed by Baxi as Megaflo Eco compatible, and LPG-convertible without a kit.
From £1,495 inc. VAT
Perfect pairings: Baxi boilers with Megaflo cylinders
A system boiler heats your radiators; the cylinder stores your hot water. Get the pairing right and you'll enjoy powerful showers, fast recovery and simple controls. These are our go-to combinations:
⚡ All-electric, off-gas homes: Baxi Amptec S + Megaflo Indirect
The Amptec S is a system boiler, so it needs an indirect cylinder for hot water. Match it with a Megaflo Eco Slimline Indirect in flats and small homes, or a standard Megaflo Eco Indirect in larger properties. No flue, no gas and a tidy, compact plant cupboard.
☀️ Solar-powered electric: Baxi Amptec S + Megaflo Eco Solar PV Ready
Our favourite low-running-cost pairing. The Amptec S heats the cylinder coil when needed, while the Solar iBoost+ in the Solar PV Ready cylinder uses surplus daytime generation to heat water for free. Add a battery and the Amptec S can run on stored solar energy too.
🔥 Gas system boiler upgrades: Baxi 800 System 2 + Megaflo Eco Indirect
For medium to large family homes with multiple bathrooms, the Baxi 800 System 2 and a Megaflo Eco Indirect (or the Solar PV Ready version if you have panels) deliver mains-pressure hot water to several outlets at once, backed by a 10-year boiler warranty and a 30-year tank warranty.
🔧 Keeping a regular boiler: Megaflo Eco SystemFit
If you're keeping a heat-only (regular) boiler, the SystemFit adds the pump and controls that boiler lacks, all pre-fitted at the factory, so you can move to mains-pressure hot water without swapping the boiler.
What size Megaflo cylinder do I need?
Cylinder size depends on how many people live in the home, how many bathrooms you have and how quickly your heat source can recover. As a general starting point:
100–150 litres: flats and 1–2 bedroom homes with one bathroom. The Slimline range shines here.
170–210 litres: typical 3-bedroom family homes with a bathroom and en-suite.
250–300 litres: larger homes with multiple bathrooms, or heat pump systems where a bigger store makes up for lower flow temperatures.
Heat pump and solar PV systems generally benefit from sizing up, as a larger store captures more free or low-cost energy. Not sure? Send us your property details and we'll recommend the right model.
Need Megaflo for a commercial project?
Beyond the domestic range, we can also supply Megaflo commercial cylinders for schools, offices, hotels, leisure facilities, care homes and multi-unit developments where large volumes of mains-pressure hot water are needed. Commercial cylinders are specified to each project, so pricing is by quote.
Send us your hot water demand, heat source and site details, and our team will come back with a tailored Megaflo commercial quotation.
Megaflo cylinder FAQs
Are Baxi hot water cylinders being discontinued?
Yes. Baxi is retiring its Baxi-branded Direct, Indirect and Assure cylinder lines and consolidating its residential hot water cylinders under the Heatrae Sadia Megaflo brand. Every former Baxi cylinder application now has a Megaflo Eco or Megaflo Essential equivalent. If you already have a Baxi cylinder installed, nothing changes day to day; for replacements and new installs, simply choose the matching Megaflo.
What is the difference between Megaflo Eco and Megaflo Essential?
Megaflo Eco is the premium range, with 60mm of insulation for lower standing heat loss and a 30-year warranty on the stainless steel tank. It also comes in the widest choice of versions: Direct, Indirect, Slimline, SystemFit, SystemReady and Solar PV Ready. Megaflo Essential is the new entry-level range, with 50mm insulation, the same enhanced internal expansion system and a 20-year tank warranty, offered in Direct, Indirect and ASHP versions.
What's the difference between a direct and an indirect Megaflo?
A direct Megaflo is heated only by electric immersion elements, making it ideal for homes without a boiler. An indirect Megaflo has an internal coil connected to a boiler or heat pump, with an immersion heater as backup. If you have a gas, oil, LPG or electric system boiler, an indirect cylinder is usually the more cost-effective choice to run.
Why doesn't a Megaflo need an external expansion vessel?
Megaflo cylinders use an internal expansion system: a pocket of air inside the top of the cylinder absorbs the extra volume as water heats up. That removes the need for a separate potable expansion vessel on the wall, saving space, parts and installation time.
Can I use a Megaflo with a heat pump?
Yes, but you should use a cylinder designed for heat pumps. Heat pumps run at lower flow temperatures, so they need a larger heat exchanger coil to heat water efficiently. The new Megaflo Essential ASHP cylinder is designed for this and is compatible with all heat pumps, including Baxi's HP40, HP50 and HP60 models.
Can the Megaflo Solar PV Ready work with my existing solar panels?
Yes. The Solar iBoost+ controller is factory-wired into the cylinder and works with any new or existing PV array. No roof work is needed, because the connection is made inside the property. Because it's an indirect cylinder, your boiler or heat pump can still heat the water through the coil when solar generation is low.
Who can install a Megaflo unvented cylinder?
All unvented hot water cylinders in the UK must be installed by a G3-qualified competent person under Building Regulations Part G3, with electrical work carried out by a qualified electrician. Annual servicing and a completed Benchmark commissioning checklist help keep the tank warranty valid.
Find the right Megaflo for your home
From slimline flats to solar-powered family homes and commercial projects, there's a Megaflo for it. Shop the range or ask our team for a free, fast quote.