Renewable Heat Pump Cylinders

McDonald Engineers has been at the forefront of developing hot water cylinders designed to harness renewable energy since the early 1970s. Working initially with solar energy, we have continued to remain one step ahead by anticipating the developments of the energy market and have focused on optimising the heat transfer process for maximum efficiency. 

As the first company to launch a dedicated Heat Pump Cylinder and the first to offer a combined Cylinder and Buffer, Tank on Tank unit for heat pump installations, McDonald Engineers have developed a range of cylinders suitable for use with all forms of Renewable Energy.

Potential Sources

  • Solar Power -  harnessing the sun’s energy using solar thermal panels, can provide up to 70% of your annual hot water requirements. Solar PV can be linked to low rated immersion heaters in cylinders
  • Air Source Heat Pumps - utilise the outside air as their energy source and can extract heating energy from temperatures as low as -25°C
  • Ground Source (Or Geothermal) Heat Pumps - extract heat from the earth or water all year round,via heat collectors buried beneath the surface 
  • Biomass / Solid Fuel - Heat produced from stoves, ovens and boilers burning wood, solid fuel and biomass products, can be used to provide heating and hot water
  • Wind & Hydro Power - The use of small domestic wind turbines or small hydroelectricity systems from running water such as rivers, can produce electricity to power lights or heat your water

Using Dual And Multiple Fuel Sources 

In some applications multiple technologies are used. We offer a multi-fuel system on a number of our cylinders to draw the energy from every available source, thereby delivering the most cost effective hot water solution.

Thanks to copper’s flexibility and unrivalled thermal transfer properties, we can incorporate a number of high efficiency coils into a cylinder. This added to the numerous cylinder options we have, the flexibility of positioning coils and connections, allows us to maximise potential gains.

Our Range Of Cylinders Suitable For Use With All Forms Of Renewable Energy

  • Unvented POWERflowThe pinnacle of unvented cylinders with fabulous performance and reliability. Built to deliver superior mains pressure simultaneously for showers, sinks and wash hand basins. Now available as ECOflow, the first dedicated heat pump cylinder providing an off the shelf solution as well as a completely bespoke manufacturing service.
  • Thermal Store THERMflow - One of the most flexible thermal stores on the market today. Providing instant, mains pressure hot water but with a vented store. Perfect for multiple fuel sources including solid fuel. Ideal for Passive & Eco Homes. No annual service required. Mains pressure with Solid fuel.
  • Electric Wet Boiler ELECTRAflow - A combined electric boiler and storage cylinder, providing a wet central heating solution. This can be combined with a solid fuel boiler and the hot water supplemented with solar. Available in Vented, Unvented and Thermal Store models.
  • Rectangular Copper Tanks CUBEflow The CUBEflow range of copper hot water tanks are available as either a traditional Combination tank, providing gravity hot water, or as a Thermal Store unit, delivering mains pressure hot water.The CUBEflow’s flexible design, means savings of up to 27% in space required for the same capacity, compared to an equivalent cylinder. Wide range of options available.
  • Commercial Calorifiers / Buffer Vessels For large scale projects, which require very large capacities. Our full range of Calorifiers and Buffer Vessels are suitable for commercial, large domestic, biomass and marine applications. They are available to suit multiple fuel systems
  • Stainless Steel Unvented STEELflow STEELflow is manufactured from premium grade duplex stainless steel, to our uncompromising efficiency and quality standards. STEELflow offers a range of high performance Indirect, Direct and Solar cylinders for those on a budget.

Looking to find out which products can be used with which source energy? Check out our ready reckoner.

Heat Pump Cylinder Ready Reckoner



As well as holding an extensive stock of our standard products ready for immediate despatch, our advanced manufacturing process enables us to cope with any order level, from one-off bespoke cylinders to large production runs of custom designed units.

Custom Designed Heat Pump Cylinders For Contracts And One-Off ProjectsRenewable Energy Pre Plumbed Cylinder

Although we carry an extensive range of standard products, a large part of our operation is manufacturing custom designed cylinders, to facilitate large contracts or for one off projects.

  • Custom heat pump cylinders for large production contracts
  • One-off heat pump cylinders 
  • Any height
  • Wide range of diameters
  • Up to 100mm Lagging - improving SAP ratings
  • Additional connections to allow multiple fuels or under floor heating
  • Pre-plumbed features such as pumps, zone valves,  solar differential controllers
  • Special positioning of connections, to make the installation quicker, easier and cheaper

Whatever your heat pump cylinder requirements, our highly experienced technical sales team are on hand to provide expert advice and ensure you get the renewable energy cylinder exactly the way you need it, using the fuel source you desire - to discuss your options just contact us on 01592 611123 or contact us online.

Why not download our renewable energy brochure or to find out more about our Solar Cylinders click here

McDonald Engineers: Renewable energy heat pump cylinders manufactured for distribution across the UK and Ireland.