Heat Pump Without Hot Water Cylinder: UK Guide 2026
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Quick Answer: Can a Heat Pump Work Without a Hot Water Cylinder?
Yes, a heat pump can work without a conventional hot water cylinder, but your home will still need a way to produce domestic hot water.
An air-to-water heat pump used for both central heating and hot water will normally use a cylinder because it does not provide instant hot water like a combi boiler. If you remove the cylinder, you could use the heat pump for space heating only and provide hot water through another system.
Possible alternatives include an air-to-air heat pump with separate water heating, an instantaneous electric water heater, certain heat batteries or a hybrid arrangement retaining a boiler. Some indoor heat-pump units also incorporate a cylinder inside the casing, although these are not genuinely cylinder-free.
Can You Use a Heat Pump Without a Hot Water Tank?
If you are considering a heat pump without a hot water cylinder, the short answer is yes — but only if you have another suitable way to provide domestic hot water.
A standard air-to-water heat pump does not normally behave like a combi boiler. It cannot instantly produce a large flow of hot water every time you open a tap. Instead, most UK installations use the heat pump to warm water stored in a cylinder ready for showers, baths and taps. Energy Saving Trust specifically notes that standard air source heat pumps do not provide hot water on demand in the same way as a combi boiler.
However, a conventional cylinder is not the only possible arrangement. A heat pump can provide space heating only, while another appliance handles hot water. Air-to-air heat pumps usually work this way. Heat batteries, instantaneous electric heaters and some specialist integrated systems can also change how much conventional hot-water storage you need.
The right solution depends mainly on your available space, hot-water demand, heating system and whether you want to use the Boiler Upgrade Scheme.
Considering a heat pump? Compare heat pump options and request a free quote from Getfreequote.co.uk.
Heat Pump Hot Water Options Compared
| System | Conventional Cylinder Needed? | How Hot Water Is Provided | Main Consideration |
|---|---|---|---|
| Air-to-water heat pump | Usually | Heat pump heats stored water | Most common whole-home arrangement |
| Air-to-water for heating only | Not necessarily | Separate water heater | Two separate systems to consider |
| Air-to-air heat pump | Usually not for heating | Separate hot-water appliance | Usually cannot provide domestic hot water itself |
| Heat pump + heat battery | Not always | Thermal storage | Product and design suitability matter |
| Hybrid heat pump + combi | Potentially no | Boiler heats water on demand | Fossil-fuel hybrid is not BUS eligible |
| Integrated heat-pump cylinder | No separate cylinder | Cylinder is built into indoor unit | Still contains stored hot water |
Why Do Most Air-to-Water Heat Pumps Need a Hot Water Cylinder?
An air-to-water heat pump transfers heat from outside air into your home’s water-based heating system. That water can supply radiators or underfloor heating and can also heat domestic water through a cylinder.
The heat pump itself uses an evaporator, refrigerant, compressor, condenser and expansion valve to move heat into the property. You can read the detailed process in Getfreequote’s guide to how air source heat pumps work.
The important distinction is what happens when you turn on a shower.
A gas combi boiler can produce a high heating output almost immediately. A typical domestic heat pump is designed to work more steadily and efficiently. Storing hot water allows it to heat the water in advance rather than trying to meet a large instantaneous demand.
Energy Saving Trust therefore advises households considering an air source heat pump to plan for hot-water storage. It says cylinder size should reflect the household’s normal hot-water use.
Can an Air-to-Water Heat Pump Work Without a Cylinder?
Yes. There is no requirement for an air-to-water heat pump to heat domestic hot water in every possible installation.
For example, the heat pump could supply your radiators or underfloor heating while another electric appliance provides water for your taps and showers.
That arrangement separates two jobs:
Space heating is handled efficiently by the heat pump.
Domestic hot water comes from a separate system.
This can solve a genuine problem in flats, small terraces and former combi-boiler homes where finding space for a 200- or 250-litre cylinder may be difficult.
However, replacing the cylinder with another appliance does not remove the hot-water requirement. It simply changes how that requirement is met.
What Are the Alternatives If You Do Not Have Cylinder Space?
Air-to-air heat pump with separate hot water
An air-to-air heat pump warms rooms directly through indoor fan units rather than circulating hot water through radiators.
Most air-to-air systems do not provide domestic hot water, so you can pair one with a separate electric water-heating solution. Energy Saving Trust notes that there are exceptions, including at least some systems capable of contributing to stored hot water, but these are not the standard arrangement.
This option may be particularly relevant to smaller homes and flats without an existing wet central-heating system.
Heat battery
A heat battery stores thermal energy in a compact material rather than keeping a large volume of hot water in a traditional cylinder.
Some designs can provide domestic hot water while using less space. Energy Saving Trust has documented a flat where the occupants selected a heat battery specifically because they did not have enough room for a conventional cylinder.
The suitability of this approach depends on the product, required flow rate, household demand and complete heating design.
Instantaneous electric water heating
Energy Saving Trust also identifies instantaneous hot-water heaters as an option where cylinder space is unavailable.
They heat water electrically when required, so there is no large store.
However, direct electric water heating works differently from heat-pump water heating. Your installer should therefore compare expected energy use, electrical requirements and available flow rates rather than assuming that removing the cylinder automatically improves efficiency.
Integrated cylinder systems
Some heat-pump systems package the cylinder, hydraulic equipment and controls inside one tall indoor unit.
These can make an installation tidier and reduce the amount of separate equipment required.
They are often described as space-saving systems, but they are not truly cylinder-free. Hot water is still being stored; the cylinder is simply integrated into the appliance.
Can a Heat Pump Work Like a Combi Boiler?
A conventional domestic air-to-water heat pump should not normally be treated as a direct heat-pump version of a combi boiler.
The issue is power.
A shower can require a substantial amount of heat over a short period. Providing that heat instantly would require much greater output than the property normally needs for space heating.
Storing hot water allows a smaller heat pump to build up that energy gradually.
This is why the question should not simply be, “How can I remove the cylinder?”
A better question is:
What is the most practical way to meet my household’s peak hot-water demand within the space available?
A proper heat pump survey should assess household occupancy, showers, baths, cylinder or storage space and expected recovery time before the final design is agreed.
What If You Currently Have a Combi Boiler?
This is where cylinder space becomes most important.
Homes with combi boilers often have no airing cupboard because the boiler already provides hot water on demand. Replacing it with an air-to-water heat pump can therefore require finding space that the existing heating system never needed.
Do not assume this automatically rules out a heat pump.
Possible solutions include converting another cupboard, using part of a utility room, choosing a compact or integrated unit, investigating alternative thermal storage or using a different heat-pump configuration.
Getfreequote’s guide to checking whether your home is suitable for a heat pump covers cylinder space alongside heat loss, radiators, electrics and outdoor-unit positioning.
Can You Keep Your Existing Hot Water Cylinder?
Potentially.
Replacing every existing cylinder is not automatically necessary.
Current MCS heat-pump design requirements state that an existing cylinder may be reused, but its insulation, mechanical condition, size and compatibility must be checked. The cylinder must also suit the manufacturer’s requirements. Heat-pump cylinders typically require a larger heat-exchanger surface than traditional boiler cylinders because heat pumps usually operate at lower temperatures.
MCS also requires domestic hot-water demand to be calculated and an appropriately sized cylinder specified. The desired reheat time should be agreed with the customer.
See the current MCS Heat Pump Design Standard for the technical requirements.
Therefore, an existing cylinder should be assessed rather than automatically accepted or rejected.
What Does the Boiler Upgrade Scheme Mean for Cylinder-Free Systems?
The funding rules matter if you are considering an unconventional arrangement.
As of September 2026, the standard Boiler Upgrade Scheme grant in England and Wales is £7,500 for an eligible air-to-water heat pump. Qualifying off-gas properties replacing oil or LPG can receive £9,000 until 31 March 2027. Residential air-to-air heat pumps can currently receive £2,500.
Ofgem states that a BUS-funded heat-pump system must be capable of meeting the property’s full hot-water requirement, either through the heat pump itself or together with an eligible supplementary appliance. Fossil-fuel hybrid heat-pump systems are not eligible.
This means a cylinder-free design should be checked as a complete system, not just as an individual heat pump.
For current funding details, see Getfreequote’s Boiler Upgrade Scheme 2026 updates and the official GOV.UK Boiler Upgrade Scheme guidance.
How to Decide Whether You Should Go Without a Cylinder
Start with your hot-water needs rather than the equipment catalogue.
Ask your installer to establish:
- How much hot water your household normally uses.
- Whether several showers or baths are used close together.
- Whether an existing cylinder can be retained.
- Which indoor locations could accommodate a compact or integrated store.
- Whether a heat battery or separate water heater is technically suitable.
- What electrical upgrades an alternative system would require.
- Expected hot-water running costs.
- How quickly stored hot water would recover after heavy use.
- Whether the complete design remains eligible for any grant you intend to claim.
A cylinder may initially look inconvenient, but it can be the simplest way of providing strong hot-water performance for a family.
Conversely, installing a large cylinder simply because it is conventional makes little sense if another properly designed solution suits the property better.
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Frequently asked questions
Find clear answers to common questions about heat pumps and hot-water cylinders, including combi-boiler replacement, instant hot water, cylinder alternatives, air-to-air systems, hybrid arrangements, cylinder reuse, sizing, heat batteries, flats and Boiler Upgrade Scheme eligibility.
No. A heat pump used only for space heating does not necessarily need a domestic hot-water cylinder. However, another system must then heat water for showers, baths and taps.
An air-to-water heat pump normally uses a cylinder when it provides domestic hot water. Air-to-air heat pumps usually require a completely separate hot-water system.
Yes, but the hot-water arrangement normally changes. Instead of heating tap water instantly, most air-to-water heat-pump installations store hot water in a cylinder.
Standard domestic air-to-water heat pumps generally do not provide high-flow instantaneous hot water like a combi boiler. Stored hot water is normally used instead.
Possible alternatives include certain heat batteries, instantaneous electric water heating or a separate hot-water heat pump. Suitability depends on household demand and system design.
Most do not. They normally heat rooms through indoor fan units, with a separate appliance providing domestic hot water. A limited number of specialist systems can also contribute to hot-water production.
Technically, a hybrid arrangement can use a heat pump for heating and the boiler for hot water. However, fossil-fuel hybrid heat pumps are not currently eligible for the Boiler Upgrade Scheme in England and Wales.
Possibly. The installer must check its size, insulation, mechanical condition and heat exchanger compatibility. Current MCS design requirements specifically allow an existing cylinder to be assessed for reuse.
Heat pumps commonly operate at lower water temperatures. MCS notes that heat-pump cylinders therefore tend to require a greater heat-exchanger surface area than cylinders designed around combustion boilers.
There is no universal size. Current MCS design rules calculate domestic hot-water demand from bedrooms or known occupancy, then require the cylinder to be sized alongside heat-pump capacity and required recovery time.
You normally need to wait while the heat pump reheats it. The recovery time depends on cylinder size, temperature, heat-pump output and heat-exchanger performance.
It can be. Energy Saving Trust has documented installations where a heat battery was selected specifically because there was insufficient room for a conventional hot-water cylinder.
Sometimes, but structural support, frost protection, heat loss, pipe routes, servicing access and applicable water-system regulations all need consideration. The proposed location should be approved as part of the system design.
An air-to-water system usually needs stored hot water if it serves taps and showers. Flats with limited space may instead consider air-to-air heating, compact storage or another separate hot-water solution.
Potentially, because the rules assess the complete heating system rather than simply requiring a particular cylinder. However, the combined system must satisfy current heating and hot-water requirements, so the design should be confirmed by the participating installer.
Can You Use a Heat Pump Without a Hot Water Tank? Final Answer
Yes. You can install a heat pump without a conventional hot water cylinder, but a standard air-to-water heat pump cannot simply replace a combi boiler and produce unlimited hot water instantly.
If the heat pump is providing both central heating and domestic hot water, a correctly sized cylinder remains the normal UK solution.
Where space is limited, alternatives can include a heat battery, separate electric water heating, an air-to-air system or a compact integrated arrangement. A hybrid system can also retain combi-style hot water, although fossil-fuel hybrids do not qualify for the Boiler Upgrade Scheme.
The best solution depends on the property rather than a universal rule. Before ruling out a heat pump because you have no airing cupboard, have the installer assess the available space, hot-water demand and alternative configurations.
