Heat pumps in flats: energy strategy at planning stage
Choosing between individual and communal air source heat pumps in a block of flats decides plant space, riser routes, condenser positions and the acoustic case. Here is how the choice plays out at planning stage.
Heat pumps in flats change the planning application, not only the services drawings. Decide between individual units and a communal system before the layouts are fixed, because the two strategies take different space out of the building, land in different places on the elevations, and raise different acoustic questions at the windows immediately above them. Leave the choice to technical design stage and you will be redrawing plans after the officer's first site visit.
For a scheme of any scale the decision also determines what the energy statement can claim, so it belongs in the pre-application discussion.
Individual against communal heat pump strategies
An individual air source heat pump per flat gives each household its own system, its own bill and its own maintenance responsibility. It needs an external condenser within reach of that flat, which in practice means a balcony, a terrace, a recessed plant nook or a bracketed position on the facade.
A communal system puts larger pumps in one place, usually at roof level or in an external plant compound, and distributes heat through a network of risers to a heat interface unit in each flat. One set of plant, one maintenance contract, one point of failure.
| Consideration | Individual pumps | Communal system |
|---|---|---|
| External plant | One condenser per flat, spread across elevations | Concentrated at roof or compound level |
| Internal space | Small cylinder in each flat | Plant room, thermal store, risers, HIU cupboards |
| Visual effect | Repetitive units visible across the facade | Screened plant at roof level, taller parapet |
| Acoustic risk | Many small sources close to windows | Fewer, larger sources further from habitable rooms |
| Resident billing | Individual electricity supply | Heat charges under heat network rules |
| Distribution losses | Negligible | Real, and a cause of corridor overheating |
Neither is the right answer everywhere. Small blocks of six or eight flats with generous balconies usually work better with individual units. Anything with deep plans, single aspect flats or a constrained roof tends towards a communal arrangement. Where a site is being brought forward in phases, the network question interacts with the wider strategy set out in the article on energy masterplanning across a phased site.
Plant space, risers and what they take out of the scheme
Communal systems are space hungry, and the space comes off saleable area. Allow for the plant enclosure, the thermal store, the pumps and controls, and a route for the risers that does not cut through the middle of a flat.
Three consequences show up at planning stage. The roof plant needs screening, which raises the parapet and changes the height shown on elevations and in any daylight or townscape work. The risers need a vertical alignment through every floor, which constrains the core and sometimes the stair. And the heat interface unit cupboard in each flat has to be accessible from common parts if you want maintenance without entering the dwelling, which pushes it towards the entrance hall.
Individual pumps trade that for a cylinder cupboard in each flat and a condenser position outside it. The cylinder is not small, and it competes with the storage the Nationally Described Space Standard expects.
Draw both options at 1:100 before choosing. The version that survives contact with a flat layout is usually obvious once you do.
Where the condensers go and how they read
Officers object to visible plant, and they object hardest to plant that appears in a repetitive pattern on a principal elevation. A block with 24 identical condensers bracketed to the front wall reads as an equipment store.
Positions that tend to be accepted are recessed nooks behind a louvred screen designed as part of the elevation, roof level compounds set back behind a parapet so they are not visible from the street at a reasonable distance, and balcony positions where the unit sits below the balustrade line. Positions that tend to be refused are anything on a roof slope, anything on a facade in a conservation area facing a highway, and anything that projects beyond the building line.
Airflow discipline matters as much as appearance. A condenser needs free air in and out, so a unit boxed into a tight nook either loses efficiency or gets a larger louvre than the elevation was drawn with. Get the clear opening areas from the supplier before the elevations go out.
Two points on permitted development. For a new block the plant is part of the application, so Class G of Part 14 of Schedule 2 to the Town and Country Planning (General Permitted Development) (England) Order 2015 is not the route. For retrofit to an existing block it may be, subject to the conditions in the current text of Class G, which has been amended more than once and should be read fresh rather than from an old note.
Acoustic consequences at balconies and windows
This is the issue that causes refusals. A condenser two metres below a bedroom window is a night-time noise source in a residential building, and the assessment position is your own resident's window, not a neighbour's.
Two frameworks are in play. The MCS planning standard sets a noise limit for domestic air source heat pumps at an assessment position and is the basis for the permitted development condition. Larger communal plant is assessed as commercial sound under BS 4142:2014+A1:2019 against the measured background, with corrections for tonality and for the intermittency of defrost cycles. Internal guideline values in BS 8233:2014 then apply inside the flats.
Practical measures that work: put the plant on the roof rather than the facade where the block is tall enough, set condensers away from openable windows and balcony seating, specify low noise units and confirm the sound power level rather than the sound pressure figure in the brochure, and design the acoustic screen as part of the parapet rather than adding it later.
Night-time setback of the pumps is sometimes offered as mitigation. Be careful with it, because a system that cannot meet the heating demand at 04:00 in February is not a system.
Electrical capacity and the connection enquiry
All electric heating multiplies the electrical load, and the distribution network operator connection is frequently the longest lead item on the programme.
Submit the connection enquiry early with a realistic diversified load, and get the answer in writing before the layout is fixed. Reinforcement can require a substation on site, which needs a footprint, vehicular access for a transformer, and a position that is not in the middle of the planted courtyard the design relies on. A substation added at technical design stage is a material change to a consented layout.
The trade-off between electrical capacity and a gas connection is set out in the article on the all electric decision for new homes, and the answer for flats usually falls differently from houses because the load is diversified across many dwellings.
Metering and billing for residents
A communal heat pump makes the building a heat network, which brings consumer protection obligations. Heat supplied to residents must be metered and billed under the heat network metering and billing regime, and the Energy Act 2023 moved heat networks into regulation by Ofgem with consumer standards attached.
Planning officers increasingly ask about this, particularly where affordable housing is involved and the registered provider will inherit the system. Expect questions about who operates the network, how residents are charged, and what happens to the standing charge if the block is half sold.
Design decisions follow from it. Oversized distribution pipework with poor insulation produces standing losses that residents pay for and that heat the corridors, which is also an overheating problem. A design compliant with a recognised heat network code of practice is the answer, and saying so in the submission saves an argument.
Evidencing the choice in the energy statement
The Energy Statement should do more than report a percentage improvement over the Part L baseline. Set out the options considered, the reason the chosen strategy was selected, and the consequence for the building.
Include the calculation methodology and version, the emission factors used, the plant specification and sound power levels, the riser and plant space allocations shown on the drawings, the distribution loss assumptions, and the connection enquiry reference. Where the London Plan applies, follow the energy hierarchy and the reporting format the Greater London Authority guidance sets out, and address the heat network policy before reaching for individual pumps.
An Overheating Risk Assessment should sit alongside it, because a communal network in a single aspect flat is an overheating question as much as a heating one. Run the two together and the answers stop contradicting each other.
This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. Enter your postcode on PlanScope to see which reports a residential scheme is likely to need.
Frequently asked questions
Are individual or communal heat pumps better for a block of flats?
It depends on the block. Small buildings with generous balconies and shallow plans often suit individual units, since each flat keeps its own system and bill. Deep plans, single aspect flats and constrained roofs push towards a communal system, which concentrates plant and acoustics away from windows but needs a plant room, thermal store and risers.
Do heat pumps on flats need planning permission?
For a new block the plant forms part of the planning application, so the question does not arise separately. For retrofit to an existing building, Class G of Part 14 of Schedule 2 to the General Permitted Development Order may apply, subject to its conditions on siting, volume and noise. Read the current text, because it has been amended.
What noise standard applies to a communal heat pump?
Larger communal plant is normally assessed as commercial sound under BS 4142:2014+A1:2019 against the measured background level, with corrections for tonality and for intermittent defrost cycles. Internal guideline values in BS 8233:2014 then apply within the flats. Domestic scale units are assessed against the MCS planning standard limit at the assessment position.
Why does the electrical connection matter at planning stage?
All electric heating raises the diversified load, and network reinforcement can require a substation on site. That needs a footprint, transformer access and a position that does not sit in the middle of the communal garden the design depends on. Adding one after consent is a material change to the approved layout.
Does a communal system make the building a heat network?
Yes. Heat supplied to residents must be metered and billed under the heat network metering and billing regime, and the Energy Act 2023 brought heat networks into regulation by Ofgem with consumer standards. Officers ask who will operate the network and how residents are charged, particularly where a registered provider inherits it.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.