Residential · Air-to-Air
Air-to-Air heat pumps — frequently asked questions
Straight answers to the questions we hear most from homeowners considering Air-to-Air. For anything specific to your home, ask Current — our AI adviser can talk through the right setup for your rooms and how you actually use them.
System types & design
- What's the difference between single split, multi-split, and Multi+?
- Single split is one outdoor unit serving one indoor unit — the simplest setup, suited to a single room or open-plan space. Multi-split is one outdoor unit serving several indoor units (typically 2–6), each controlled independently — the usual choice for several rooms without hot water from the same outdoor unit. Daikin Multi+ is a multi-zone Air-to-Air system that also produces domestic hot water from one outdoor unit, connecting up to four indoor units plus a 120 L or 230 L tank. For most UK homes that only need heating and cooling, multi-split is enough; choose Multi+ when you specifically want rooms and hot water from one outdoor unit.
- What are my options for the indoor unit?
- Wall-mounted is the most common and cost-effective, mounted high on a wall. Ceiling cassette sits flush into the ceiling for a more discreet look, but needs adequate ceiling void depth. Ducted (concealed) is the most invisible option, hidden above the ceiling with air delivered through discreet grilles — the most expensive and disruptive to retrofit. Floor-standing sits at floor level, useful where wall or ceiling mounting isn't practical. All four heat and cool equally well; the choice comes down to how much visible unit you're willing to accept versus how much you want to spend on concealment.
- What should I know about the outdoor unit?
- It houses the compressor and does the actual work of extracting or rejecting heat. A single-split has one outdoor unit per indoor unit; multi-split and Multi+ size one outdoor unit for the combined — though rarely simultaneous peak — demand of the connected rooms (and, for Multi+, the hot water tank). Placement matters: it needs unobstructed airflow clearance to run efficiently, and noise, boundary distance, and proximity to bedroom windows should all be considered at the design stage, not worked around afterward.
Refrigerant
- R32 or R290 — does it actually matter which one I get?
- It's a fair, informed question to ask in 2026, though it shouldn't be the only thing you decide on. R32 has been the standard UK refrigerant since around 2018–2020, with a Global Warming Potential (GWP) of 675 — a major improvement on what it replaced, though not the lowest-carbon option now available. R290 (propane) has a GWP of just 3 and tends to perform better at very low outdoor temperatures, but is more flammable, which means stricter installation safety requirements and sometimes a modest cost premium. Day-to-day performance — efficiency, capacity, noise, controls, warranty — matters more than refrigerant type alone, but it's still worth asking your installer which one a given system uses and why.
- Why is refrigerant choice time-sensitive right now?
- From 1 January 2027, new UK and EU regulations require new heat pump and split air conditioning systems rated 12kW or below to use a refrigerant with a GWP below 150 — R32 (675) doesn't meet that threshold, R290 (3) comfortably does. This doesn't affect systems already installed, which remain legal to run and service. But it means R32 choice is likely to narrow after 2027, making R290 the more future-proof specification for a new installation from here on.
Hot water
- Does an Air-to-Air system give me hot water as well as heating and cooling?
- As a rule, no — a pure Air-to-Air system heats and cools air only, and for most manufacturers this is a structural limitation, not something some installers include and others skip. If you want Air-to-Air plus hot water, the usual routes are: a separate Air-to-Water or hot-water-only heat pump running alongside it, retaining or installing a standard immersion or existing water heating solution, or choosing Air-to-Water as your primary system instead if combined hot water and space heating matters more than Air-to-Air's zoned control and cooling. There is one notable exception worth knowing about: Daikin's Multi+ range combines multi-zone Air-to-Air space heating and cooling with domestic hot water from a single outdoor unit — genuinely one system rather than two run alongside each other. It's not yet how the market works as a whole, so ask specifically if this is the configuration you want, rather than assuming any multi-split system offers it.
Brands & reliability
- Is it worth paying more for Daikin or Mitsubishi?
- They're widely regarded across the UK installer trade as the most reliable, longest-track-record brands, with decades of heat pump and VRF-specific manufacturing experience and the widest, most experienced installer networks — which matters as much as the hardware itself, since a poorly commissioned excellent unit underperforms a well-commissioned good one. That said, brands like Mitsubishi Heavy Industries, Panasonic, Toshiba, LG, Samsung, and specialist manufacturers like Vaillant and Grant produce genuinely competitive systems, often at a lower price point, and several have moved faster into R290 refrigerant. Premium brands are the lower-risk, well-trodden choice, particularly for a first heat pump purchase; strong second-tier brands can offer real value if you're comfortable with slightly less brand-name certainty.
Control & everyday use
- Does the app actually matter, or is it a gimmick?
- It genuinely matters. A good app gives you independent scheduling and temperature control per room, reliable remote access that works over typical home wifi, and useful per-zone energy reporting so you can see what's actually costing you money. This is central to what makes Air-to-Air distinctive — heating just the home office from 8am, or pre-cooling a bedroom before a hot evening — so a clunky or unreliable app undermines the main reason many people choose the system in the first place.
Health & air quality
- Does Air-to-Air affect indoor air quality, not just temperature?
- Yes, and it's worth taking seriously. Indoor units draw room air across a filter before conditioning and recirculating it — most systems include at least a basic dust filter, and many mid-to-premium models offer finer filtration for smaller particles and pollen. Filter cleaning isn't optional maintenance, either: a dirty filter reduces both air quality and system efficiency, so it directly affects your running costs. As an air conditioning-style system, Air-to-Air also removes some moisture from the air when cooling, which can improve comfort in humid weather, and well-managed indoor humidity in winter helps reduce condensation and mould risk in poorly ventilated rooms.
Maintenance & lifespan
- How long does an Air-to-Air system last, and what maintenance does it need?
- A well-installed, well-maintained system typically runs 15–20 years, though outdoor units can need earlier replacement in harsh coastal or heavily-used settings. It doesn't need annual gas safety servicing the way a boiler does, but regular filter cleaning (every few weeks to a couple of months, more often with pets) and a periodic professional check of refrigerant levels, electrical connections, and outdoor unit condition are genuinely worthwhile — similar in spirit to servicing a car even when nothing seems wrong.
- What's actually covered by the warranty?
- There are three separate warranties, often confused. The parts/product warranty is typically 2–5 years as standard, sometimes extendable. The compressor warranty is often longer, since it's the most expensive single component to replace. The installation/workmanship warranty comes from your installer, not the manufacturer — and a manufacturer's product warranty typically doesn't cover a fault caused by poor installation, so it pays to understand where the line sits. Extended warranties are often available but usually require the system to be registered and serviced on schedule by an accredited installer — worth checking the specific conditions rather than assuming a longer period applies automatically.
Is it right for my home?
- Why are people increasingly choosing Air-to-Air even when their existing heating works fine?
- Air-to-Water tends to get chosen out of necessity, when a boiler needs replacing. Air-to-Air is increasingly chosen for what it adds that an existing system can't: cooling during hotter summers, independent room-by-room control, or heating for a space — an extension, loft, or garden room — the existing system doesn't reach well. Common cases include home offices needing independent control during work hours, conservatories and garden rooms that are hard to keep comfortable year-round with radiators, loft conversions and extensions poorly served by extending a wet system, and increasingly, bedrooms, for summer sleep comfort.
- Can Air-to-Air work alongside solar panels or an existing heating system?
- Yes to both. Running an Air-to-Air system from self-generated solar is a strong practical pairing, particularly in summer when cooling demand and solar generation both peak. It also pairs well with an existing or new Air-to-Water system — Air-to-Water handling whole-home heating and hot water, Air-to-Air handling cooling and zoned comfort in specific rooms — which is an increasingly common combined specification rather than a contradiction.
Still have a question specific to your home? Ask Current — it can walk through the right system, zone by zone, based on how you actually use your rooms.