Megaflo Alternatives: Gledhill Platinum and OSO Compared
Yes, and two stand out. If you want what makes a Megaflo a Megaflo, internal expansion with no separate vessel on the wall, the Gledhill Platinum does the same job for about half the price. If you want comparable performance in a more compact, pre-plumbed package, look at OSO. Both are the cylinders we recommend most often when customers ask us for a Megaflo alternative.
Why people look for a Megaflo alternative
Megaflo is so well known that many plumbers use the name for any unvented cylinder, the way people say "Hoover" for a vacuum cleaner. Heatrae Sadia's Megaflo cylinders made internal expansion popular: the expansion space sits inside the cylinder, so there is no separate expansion vessel to fit, find room for or maintain. Other makers now offer the same idea, and some do it for a lot less money.
Gledhill Platinum: the closest match for less
The Gledhill Platinum is the alternative we point most customers towards. Like a Megaflo, it has internal expansion, so there is no external vessel to plumb in, which saves wall space and installation time.
Duplex stainless steel, the same type of material Megaflo uses.
Direct models (120 to 210 litres) come with two 3kW immersion heaters, so one can run on cheaper off-peak electricity and the other as a boost.
Indirect models (120 to 300 litres) use a corrugated heating coil that Gledhill designed for faster recovery from your boiler.
A temperature and pressure relief valve comes fitted as standard.
Where it saves money is the finish: it is less pre-plumbed than a Megaflo or an OSO, so your installer does a little more of the pipework. For most domestic jobs that is a small trade for a cylinder that costs around half as much. Gledhill cylinders carry a £33 delivery charge, and they are still far cheaper once that is added.
OSO: comparable performance, built for tight spaces
OSO Hotwater is a Norwegian maker with a strong reputation in the UK. Its cylinders compete with Megaflo on quality and performance, at a slightly lower price.
Super Xpress VIP (direct, 120 to 300 litres) and Super Coil (indirect, 120 to 250 litres) arrive pre-plumbed, with the expansion vessel fitted at the factory. OSO says this saves up to 70% of the installation labour. The 300 litre Super Xpress is the exception: it comes with a separate expansion vessel.
The Super Xpress VIP uses vacuum insulation panels to cut heat loss.
OSO says its cylinders are the shortest on the market and produce around 20% more usable hot water than others of the same size, so you may be able to choose a smaller model. Up to 210 litres, they can sit in the footprint of a washing machine using an extra frame.
Gledhill vs Megaflo vs OSO at 210 litres
Prices are ex VAT at the time of writing (October 2026) and may change.
You want internal expansion for the lowest price: Gledhill Platinum.
You want a compact, pre-plumbed cylinder that is quick to fit: OSO.
You are replacing a Megaflo like for like, or want the most widely stocked spares: stay with Megaflo.
Whichever you choose, an unvented cylinder must be fitted by a G3 qualified installer under Building Regulations Part G. If you would like a hand comparing sizes or models for your job, call our water heating team on 01934 253600.
