Is Your Cylinder Heat Pump Ready?
Heat pumps run at lower temperatures than boilers. That changes everything about your hot water cylinder. Here is what needs to be different, and what I do on the plumbing side to get it right.
If you are thinking about a heat pump, or your MCS installer has already surveyed and told you the cylinder needs changing, this post explains why. It is not a sales pitch. A heat pump runs differently from a boiler, and the cylinder that worked fine with your old system genuinely will not do the same job at lower temperatures.
I am Will Gaze, a G3-qualified plumber with 22 years of experience, covering Andover (SP10/SP11), Marlborough (SN8), and Hungerford (RG17). I install heat pump-ready cylinders. I do not install the heat pumps themselves because that requires MCS certification, which I do not hold. The MCS installer fits the heat pump; I fit the cylinder and plumbing. The two of us work together to make sure the system connects properly.
What This Guide Covers
- - Why boiler cylinders struggle with heat pumps
- - What makes a cylinder heat pump ready
- - Coil area, insulation, and sizing
- - Brands I fit: Heat Geek, Vaillant, Viessmann
- - How the BUS grant works with cylinders
- - Costs and what to expect
The Temperature Problem: Why Your Existing Cylinder Struggles
A gas or oil boiler heats water to 60-80°C and pushes it through your cylinder coil at those temperatures. A heat pump typically delivers water at 35-45°C. That is not a small difference. It changes what the cylinder needs to do.
With a Boiler (60-80°C)
Your boiler sends very hot water through the cylinder coil. Because the temperature difference between the coil and the stored water is large, heat transfers quickly even through a small coil. A coil surface area of 1.5-2m² is enough.
The cylinder heats up fast, the boiler shuts off, and everything works. This is how most cylinders in UK homes are designed.
With a Heat Pump (35-45°C)
A heat pump sends much cooler water through the same coil. The temperature difference between the coil and the stored water is smaller, so heat transfers slowly. That 1.5m² coil cannot move enough energy into the cylinder.
The result: the heat pump runs for hours trying to heat the water, uses far more electricity than it should, and may never reach the temperature you want. Your running costs go up, and hot water runs out faster.
The short version
A heat pump is not broken if your hot water is lukewarm. The problem is almost always the cylinder. Fitting a proper heat pump-ready cylinder is the single biggest thing you can do to make the system work as it should.
What Makes a Cylinder Heat Pump Ready
Three things change when a cylinder is designed for heat pump use. Every one of them matters, and a cylinder that gets only one right will still underperform.
Larger Coil Area
Standard boiler cylinders have coils of 1.5-2m². A heat pump cylinder needs 4.5-6m² of coil surface area. That larger coil compensates for the lower flow temperature by giving the heat more surface to transfer through.
The Heat Geek Super, for example, has a 6.0m² coil. Some cylinders use twin coils where the bottom coil connects to the heat pump and the top one to an immersion heater or boiler as backup.
Better Insulation
Because the stored water temperature is lower, heat loss matters more. Losing 5°C from a 70°C cylinder is manageable. Losing 5°C from a 45°C cylinder means tepid showers.
Heat pump cylinders use thicker, higher-grade insulation to keep standing losses low. The best ones lose less than 1-2 kWh per day, even in an unheated cupboard.
Larger Capacity
A boiler can reheat a cylinder quickly. A heat pump cannot. If you run the tank down, it takes longer to recover. So you need a bigger tank to start with.
As a rule of thumb, a household that managed with a 150L boiler cylinder usually needs 200-250L with a heat pump. A family of four or five often needs 250-300L.
Quick comparison
| Feature | Standard Boiler Cylinder | Heat Pump-Ready Cylinder |
|---|---|---|
| Coil area | 1.5-2m² | 4.5-6m² |
| Typical capacity | 120-180L | 200-300L |
| Flow temperature | 60-80°C | 35-45°C |
| Insulation | Standard foam | High-density, thicker |
| Reheat time | 20-40 minutes | 1-3 hours (at 40°C flow) |
Heat Pump Cylinders I Fit
These are the brands I supply and install. Each one is designed specifically for heat pump systems and comes with the manufacturer's own warranty on top of my 12-month workmanship guarantee.
Heat Geek Super
The largest coil on the market at 6.0m², designed from the ground up for heat pump efficiency. Available in 170L, 210L, and 250L. The coil design means the heat pump runs shorter cycles, which reduces electricity use.
Coil: 6.0m² | 170-250L
Vaillant uniSTOR
Well-established cylinder with a 5.2m² coil. Pairs well with Vaillant heat pumps but works with any brand. Good availability and a strong manufacturer warranty.
Coil: 5.2m² | 200-500L
Viessmann Vitocell
German-engineered cylinder with excellent insulation. The Vitocell 100-W and 300-V models are designed for heat pump use with coils from 4.7m². Viessmann offers some of the longest manufacturer warranties in the market.
Coil: from 4.7m² | 200-500L
Grant & Telford
Grant cylinders pair with their Aerona heat pumps, while Telford offer a broad range of heat pump-compatible cylinders at competitive prices. Both are widely used by MCS installers in this area.
Various specs | UK manufactured
A note on brand choice: your MCS installer may have a preferred cylinder that works best with the heat pump they are fitting. I am happy to fit the brand they recommend, or to discuss alternatives if you want a second opinion on the cylinder side. The important thing is getting the coil area, capacity, and insulation right for your household.
Who Does What: The Cylinder and the Heat Pump
This is important because I get asked regularly. A heat pump installation involves two distinct pieces of work, and they are done by different people.
What Rosebourne Does (The Cylinder)
- ✓Survey your existing hot water setup and advise on the right cylinder
- ✓Remove the old cylinder and any associated pipework
- ✓Install the new heat pump-ready cylinder with all safety components
- ✓Connect the pipework ready for the heat pump installer
- ✓Commission the hot water system and notify Building Control (G3)
What the MCS Installer Does (The Heat Pump)
- ✓Design the heat pump system and apply for the BUS grant
- ✓Install the heat pump unit (outdoor and indoor components)
- ✓Connect the heat pump to the cylinder and heating system
- ✓Commission the full system, set up controls
- ✓Issue the MCS certificate and handle the BUS grant paperwork
In practice, I coordinate with the MCS installer so the cylinder is ready when they need to connect the heat pump. Sometimes I fit the cylinder first and they connect later; sometimes we are on site at the same time. Either way, there is one point of contact for each side of the work.
The Boiler Upgrade Scheme (BUS) Grant
The government's BUS grant offers £7,500 towards an air source heat pump installation. Here is how it works alongside the cylinder.
Key Points
- - £7,500 grant for air source heat pump installations
- - Applied for by the MCS-certified installer, not the homeowner
- - Your property must have an EPC (valid or expired is fine)
- - You must be replacing a fossil fuel heating system
- - The grant covers the heat pump system, which may include the cylinder
- - Extended to March 2028 (check gov.uk for current status)
Cylinder and the Grant
Whether the cylinder falls inside or outside the grant depends on how your MCS installer structures the quote. Some include the cylinder in the heat pump package, in which case the grant contributes towards the total. Others quote the heat pump separately and the homeowner arranges the cylinder.
Either way, the cylinder is essential for the system to work. I provide a separate fixed-price quote for the cylinder installation, and your MCS installer handles the grant application for the heat pump.
I do not apply for or administer the BUS grant. That is the MCS installer's responsibility. If you want to know whether you qualify, or how the grant is allocated, ask your heat pump installer or check gov.uk/apply-boiler-upgrade-scheme.
What the Cylinder Side Costs
These are the costs for the cylinder installation only. The heat pump itself is a separate project quoted by your MCS installer.
| Item | Typical Range |
|---|---|
| Heat pump-ready cylinder unit | £1,200-£2,500 |
| Safety components (expansion vessel, valves, tundish) | £150-£350 |
| Labour (cylinder installation) | From £800 + VAT |
| Additional pipework (if required) | £200-£500 |
| Total cylinder installation | £2,000-£4,000 + VAT |
All prices exclude VAT. Based on standard installations in the Andover, Marlborough, and Hungerford area. Complex installations with significant pipework changes will cost more. I provide a fixed written quote after a free survey.
What affects the price
Cylinder brand and size
A 170L Heat Geek costs less than a 300L Viessmann Vitocell. Pick the size that matches your household.
Existing pipework
If the old cylinder is in the same location and the pipes line up, it is quicker. Moving it or running new pipes adds time.
Access
A cylinder on a ground floor with a wide door is easier to deliver and install than one up a narrow staircase.
Vented to unvented conversion
If your old cylinder was vented (gravity-fed), converting to an unvented heat pump cylinder involves additional safety components.
Frequently Asked Questions
Common questions from homeowners in Andover, Marlborough, and Hungerford about heat pump cylinders and how the installation works.
Can I keep my existing cylinder when I get a heat pump?
It depends on the cylinder. If your existing cylinder has a coil surface area of at least 3m², good insulation, and enough capacity for your household at lower flow temperatures, it may work. However, most standard boiler cylinders have coils of 1.5-2m², which is too small for efficient heat transfer from a heat pump. Your MCS installer will assess this during the heat pump survey, and I can advise on the cylinder side.
Who installs the heat pump and who installs the cylinder?
The heat pump itself must be installed by an MCS-certified installer. Rosebourne Plumbing is not MCS registered and does not install heat pumps. What I do is the cylinder and plumbing side: removing the old cylinder, fitting the new heat pump-ready one, connecting the pipework, and commissioning the hot water system. I hold G3 certification for unvented cylinders. The MCS installer and I coordinate so that everything connects properly.
Does the BUS grant cover the cylinder as well as the heat pump?
The £7,500 Boiler Upgrade Scheme grant is applied to the overall heat pump installation. Whether the cylinder is included depends on how the MCS installer quotes the project. In some cases the cylinder is part of their package; in others, the homeowner arranges the cylinder separately. Either way, a heat pump-ready cylinder is essential for the system to work efficiently. Ask your MCS installer how the grant is applied to your specific project.
How much does a heat pump-ready cylinder cost to install?
The cylinder unit itself typically costs between £1,200 and £2,500, depending on brand, capacity, and specification. Labour for the cylinder installation starts from £800 + VAT. The total installed cost for the cylinder side of the work is usually £2,000-£4,000 excluding VAT. This is the plumbing and hot water storage side only, not the heat pump itself.
What brands of heat pump cylinder does Rosebourne Plumbing fit?
I fit Heat Geek Super, Vaillant uniSTOR, Viessmann Vitocell, Grant Aerona cylinders, and Telford heat pump cylinders. The right choice depends on your heat pump model, household size, available space, and budget. I am happy to discuss options during a free survey, and your MCS installer may also have a preference based on the heat pump they are fitting.
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