Air-Source Heat Pumps (Commercial): Heat pumps for landlords

Why air-source heat pumps are the default choice for landlords

For most landlords looking at low-carbon heat across a let portfolio, the commercial air-source heat pump is the obvious starting point. It needs no boreholes, no ground works and no land take, which means the lowest disruption to a building that is occupied by tenants and earning rent. That matters when you cannot afford a long void to dig up a car park or a yard. An air-source system can be largely pre-assembled, sited in an external louvred compound or on a roof plant deck, and brought online with a live cutover measured in hours rather than weeks. For a landlord juggling lease obligations, service-charge budgets and tenant goodwill, that speed and low disruption is often worth more than the marginal efficiency a deeper technology might offer. Cascaded modular units also scale neatly, from a single small office demise to a large mixed-use site, so the same technology suits almost every building in a varied portfolio.

The pressure to act is real and it sits squarely on the landlord. Heat is the single largest source of carbon in most let buildings, the gas boiler is usually the culprit, and Minimum Energy Efficiency Standard and EPC expectations keep tightening on the people who own the asset rather than the people who occupy it. Replacing an ageing gas or oil boiler with an air-source heat pump removes on-site combustion entirely, improves the building's energy profile, and turns an unpredictable gas bill into something you can model and plan around. It also gives you a credible answer when a tenant, a lender or a valuer asks what your net-zero plan for the building actually is. The strongest moment to act is when a gas or oil boiler is reaching the end of its life, because then you are comparing the heat pump against the genuine cost of a like-for-like replacement rather than against doing nothing, and that comparison is where the case for landlords becomes compelling.

What a typical install looks like and how we size it

For a let commercial building we usually design an air-source system in the 40 to 500 kW thermal range, scaling from a single unit up to cascaded banks of 4 to 12 units as the heat load grows. The plant footprint is modest, typically 20 to 200 square metres for an external louvred compound or a roof plant deck, which is far easier to accommodate in a tenanted building than any ground array. A system that size delivers in the region of 80,000 to 1,000,000 kWh of heat a year and saves between 15 and 180 tonnes of CO2 annually. We never size by floor area. Sizing comes from a proper heat-loss survey and at least 12 months of gas or oil consumption, because the peak heat demand and the annual demand profile, not the building's footprint, decide the plant.

The cardinal rule on every design is to lower the flow temperature, because every degree of reduction lifts the seasonal efficiency. We design for a flow temperature of 45 to 55C wherever the emitters allow it, since that is where an air-source SCOP of 3.0 to 4.0 is realistically achieved, and that SCOP is the single figure that decides your running cost. Where a building has high-temperature radiators sized for an old gas boiler, that does not rule out a heat pump, it simply tells us to pair lower flow temperatures with selective emitter upgrades. Because air-source efficiency dips in the coldest weather, we size and, where appropriate, design in a peaking strategy for the rare extreme days rather than oversizing the plant for a worst case that occurs only a handful of times a year. The result is a system matched to what the building genuinely draws, not an optimistic maximum that a landlord pays for and never uses.

Costs, payback and tax relief

A commercial air-source project for a let building typically lands between £60,000 and £600,000 depending on the heat load, the emitter upgrades required and any electrical supply work, with a simple payback in the region of 8 years. The single biggest financial lever for a landlord is capital tax relief. A heat pump is qualifying plant and machinery, so a company paying UK corporation tax can claim full expensing, a 100% first-year deduction with no upper cap that is permanent from April 2026, worth up to 25p of tax saved per pound spent at the 25% rate. Unincorporated landlords use the Annual Investment Allowance instead, up to a million pounds of qualifying spend at 100%. Wiring and ancillary works may fall outside full expensing but typically qualify for the Annual Investment Allowance, so it is always worth confirming the treatment with your accountant.

On the running-cost side, the honest answer is that it depends on the SCOP and the tariff. Electricity currently costs more per unit than gas, but a heat pump delivering an SCOP of around 3.5 produces 3.5 units of heat per unit of electricity, which offsets most of that unit-price gap, and the position improves as gas carbon levies rise and the grid decarbonises. The headline £7,500 Boiler Upgrade Scheme is domestic-only and does not apply to commercial premises, which is exactly why the commercial funding playbook in our grants and funding guide matters, and why our cost guide sets out worked numbers rather than a single headline figure.

Funding routes in detail

The named routes that landlords should look at depend on the building and the tenant. Public bodies and public-sector occupiers can access the Public Sector Decarbonisation Scheme administered by Salix, which funds the cost over and above a like-for-like fossil-fuel replacement for buildings such as schools, NHS estate and local-authority property, with capital grants running from tens of thousands to multi-million pounds. Where a building serves an eligible industrial process, the Industrial Energy Transformation Fund supports fuel-switching to heat pumps, typically at a 30 to 50% intervention rate. A landlord developing or expanding a multi-building scheme should look at the Green Heat Network Fund, which can cover up to 50% of eligible costs.

For any private landlord taxed in the UK, full expensing or the Annual Investment Allowance is the dependable backbone of the business case, available on every qualifying project regardless of sector. We map which of these you qualify for before quoting and build the application around the project rather than treating funding as an afterthought, because the grant windows are competitive and the eligibility rules are specific. Getting the funding strategy right at feasibility, rather than after the design is fixed, is one of the clearest ways a specialist earns its keep for a landlord.

Compliance and sector considerations

Air-source installs carry a specific compliance set that a landlord cannot afford to get wrong. Systems up to 45 kW thermal generally need MCS certification, or a recognised commercial equivalent, to access most grant routes; above 45 kW thermal we design to CIBSE and BSRIA standards with BS EN 14511 and BS EN 14825 performance ratings so the quoted figures are comparable across suppliers. Most commercial air-source installs fall under permitted development, but they are subject to size, siting and noise limits, and a BS 4142 acoustic assessment is commonly required to show the external unit will not disturb neighbours or tenants in adjoining demises. Listed buildings and conservation areas need consent before any external plant goes in.

Refrigerant handling is carried out by F-Gas certified engineers under the UK F-Gas Regulation, and the refrigerant phase-down of high-GWP gases is steering modern units toward R32 and, for higher duties, natural refrigerants. Large heat pumps add meaningful electrical load, so we confirm available supply capacity early; a DNO supply upgrade can be the longest-lead item in the whole project and we start that conversation at feasibility so it does not blindside the programme. For a landlord, the value of getting every one of these points checked up front is that the project lands without nasty surprises mid-installation, which is precisely when a surprise is most expensive in a tenanted building.

How we approach this kind of project

Our method is built to protect a landlord from the over-promised quote. We start from your actual half-hourly meter data and at least 12 months of consumption, not an estimate, and we model running cost and carbon at current and forecast prices so you see real numbers before you commit. We design for self-consumption and a low flow temperature to lift the SCOP, and we survey your existing emitters and pipework first so you only pay for the upgrades the building genuinely needs rather than a blanket strip-out.

We submit any G99 grid application and open the DNO conversation early so the longest-lead item is not what holds up your project, and where a building has an asbestos-cement roof or aged plant room, we check it before we quote rather than discovering it on the day. You receive a fixed-price proposal specified to BS EN 14825, and the installation carries an insurance-backed warranty. We plan the changeover around your operating calendar, typically spring or autumn rather than a peak-heat week, and we can keep the existing boiler live through commissioning so a demise is never without heat. We would rather lose a job to honest maths than win it on a number we cannot stand behind.

An illustrative example

As an illustrative composite, and not a real named client or project, consider a landlord-operated care building of around 70 beds running a pair of ageing gas boilers nearing failure, with a year-round heating and hot-water demand. The design was a 180 kW cascaded air-source heat pump of six modular units with selective emitter upgrades and a retained boiler held for peak backup. Modelled heat delivered was in the region of 360,000 kWh a year at an SCOP of about 3.6, an illustrative saving near £22,000 a year against the prior gas cost for a payback close to 7.5 years, with roughly 55 tonnes of CO2 saved annually, around an 85% cut in on-site combustion. It was installed in autumn around the operating calendar, the old boilers were kept live through commissioning so the building was never without heat, and full expensing delivered first-year tax relief on the qualifying spend. Every figure here is illustrative and depends on your building, tariff and emitters.

If your portfolio includes year-round buildings or a process load, compare this with our pages on commercial ground-source heat pumps and the hybrid boiler-replacement retrofit route. When you are ready, read the cost guide and the funding routes, then request a feasibility from your meter data or browse the heat pump FAQs first.