Air to Water vs Air to Air Heat Pumps: Lancashire Comparison

Air to water heat pumps cost £8,000 to £14,000 installed (before up to £7,500 in government grants) and provide both heating and hot water through radiators or underfloor heating. Air to air heat pumps cost £1,500 to £4,000 per room and deliver heating through wall-mounted fan units, similar to air conditioning. For most Lancashire homes with an existing wet central heating system, air to water is the better choice. For flats, rooms without radiators, or homes needing supplementary heating, air to air has distinct advantages.

How Air to Water Heat Pumps Work

An air to water (A2W) heat pump extracts heat from the outside air and transfers it to water, which circulates through your central heating system – radiators, underfloor heating, or both. It also heats your hot water cylinder, replacing the boiler’s function entirely.

The outdoor unit looks like a large air conditioning unit and sits on a base outside your home. It connects via insulated pipes to the indoor components – typically a hot water cylinder and the existing central heating pipework. The system runs at lower flow temperatures than a gas boiler (35 to 50 degrees versus 60 to 75 degrees), which is why some radiators may need upgrading to larger models.

A2W heat pumps are the standard choice for Lancashire home heating because they integrate with existing wet heating systems. Most homes in Blackburn, Preston, Chorley, Burnley, and across the county have radiators connected to a gas boiler. Swapping the boiler for an A2W heat pump keeps the radiators and pipework largely in place, minimising disruption.

How Air to Air Heat Pumps Work

An air to air (A2A) heat pump, commonly known as an air conditioning unit, extracts heat from outside air and delivers it directly into your rooms through wall-mounted indoor units. Each indoor unit heats (and in summer, cools) the room it is installed in. There is no water circuit involved – warm air is blown directly into the space.

A2A systems use a single outdoor unit connected to one or more indoor units (known as a multi-split system). A single outdoor unit can typically serve two to five indoor units, each in a different room. Each indoor unit has its own thermostat and remote control, giving independent temperature control in every room.

The key limitation of A2A heat pumps is that they do not heat water. You still need a separate system for domestic hot water – typically a gas boiler, immersion heater, or hot water heat pump. This means A2A systems cannot fully replace a boiler in the way that A2W systems can.

Cost Comparison

Here is what each system type costs for a typical three-bedroom Lancashire semi:

• Air to water heat pump (whole house) – £8,000 to £14,000 before government grant. After government grant (currently up to £7,500, subject to eligibility): £500 to £6,500. Includes outdoor unit, hot water cylinder, controls, and connection to existing heating system.
• Air to air heat pump (three rooms) – £4,500 to £9,000. No grant available. Includes outdoor unit and three indoor wall units. Does not include hot water.
• Air to air heat pump (single room) – £1,500 to £3,000. No grant available. Useful for heating a single problem room like a conservatory or home office.

The government grant makes A2W heat pumps significantly more affordable. After up to £7,500 in grants, a whole-house A2W system can cost less than fitting A2A units in three rooms. This is the main reason A2W dominates the Lancashire market for full house heating.

A2A systems do not currently qualify for the government grant because they do not provide hot water. The government may revise this in future, but for now, A2A installations are entirely self-funded.

Efficiency and Running Costs

Both types of heat pump are efficient, but A2A systems have a slight edge on raw efficiency numbers:

• Air to water SCOP – 3.0 to 4.5 (delivers 3 to 4.5 units of heat per unit of electricity). Effective cost: 5.5p to 8p per kWh of heat.
• Air to air SCOP – 3.5 to 5.0 (delivers 3.5 to 5 units of heat per unit of electricity). Effective cost: 5p to 7p per kWh of heat.

A2A is more efficient because it eliminates the water circuit, reducing energy losses in pipes and the cylinder. However, A2A does not provide hot water, so you still need gas or electric for that. When you factor in the separate hot water cost, the total energy bill is often similar.

For a three-bedroom Lancashire semi, approximate annual heating costs:

• Gas boiler (90% efficient) – £950 to £1,200
• Air to water heat pump – £600 to £850 (heating and hot water combined)
• Air to air heat pump + gas hot water – £500 to £750 (heating) + £100 to £150 (gas hot water) = £600 to £900 total

Which Lancashire Homes Suit Each Type?

Air to water is better for:

• Homes with existing wet central heating (radiators and pipework) – the vast majority of Lancashire houses
• Homeowners who want a single system for heating and hot water
• Properties where the government grant makes the investment affordable
• Homes planning to go fully off gas in the future

Air to air is better for:

• Flats without wet heating systems, especially those with electric panel heaters or storage heaters
• Supplementary heating for specific rooms (conservatories, extensions, home offices) that are poorly served by the existing central heating
• Properties where summer cooling is also desired
• Small homes or studios where the cost of a full A2W system is disproportionate
• Holiday homes or rentals where simple, low-maintenance heating is preferred

Noise, Aesthetics, and Practicalities

Outdoor units. Both systems have an outdoor unit. A2W outdoor units are generally larger (800mm to 1,000mm tall) than A2A units (600mm to 800mm), though this varies by model. Noise levels are similar at 38 to 55 dB. For Lancashire terraced houses where outdoor space is limited, the smaller A2A outdoor unit may be easier to accommodate.

Indoor units. A2W systems are invisible indoors – they use your existing radiators. A2A systems require wall-mounted indoor units in each heated room, which are visible and take up wall space. The units are typically 800mm to 1,000mm wide and mounted high on the wall. Some people find them unattractive, while others do not mind the modern look.

Air movement. A2A units blow warm air into the room, which some people find uncomfortable, particularly if the unit is above a seating area. Proper positioning (blowing across the room rather than down onto occupants) and using the quiet mode setting mitigate this. A2W systems heat via radiators with no air movement – the same silent warmth as a gas boiler system.

Maintenance. Both systems need annual servicing. A2A indoor units also need filter cleaning every few months (a five-minute DIY job). A2W systems have the additional maintenance of the water circuit, including annual checks of the expansion vessel, pressure, and antifreeze levels.

The Summer Cooling Bonus

A2A heat pumps can reverse their operation to provide cooling in summer. This is a genuine bonus during Lancashire’s occasional heat waves, though the county’s climate means cooling is only needed for a few weeks per year at most.

A2W heat pumps can also provide cooling if connected to underfloor heating (chilled water flows through the floor, reducing room temperature). This does not work with radiators, and the cooling effect is much milder than A2A air conditioning. For homes with underfloor heating on the ground floor, it is a pleasant bonus but not a replacement for full air conditioning.

Can I use air to air heat pumps for my whole house?

Yes, but you would need an indoor unit in most rooms, which adds up in cost and visual impact. A multi-split system with five indoor units costs £7,500 to £12,000 – comparable to an A2W system but without the government grant subsidy and without hot water provision. For a whole-house solution, A2W is usually more practical and more cost-effective after the grant.

Do air to air heat pumps work well in Lancashire’s cold winters?

Yes. Modern A2A heat pumps from brands like Daikin, Mitsubishi, and Samsung operate efficiently down to minus 15 to minus 25 degrees. Lancashire rarely sees temperatures below minus 5 to minus 10, so A2A units perform well throughout winter. Efficiency drops slightly in very cold weather, but output remains adequate for heating.

Can I get the government grant for an air to air heat pump?

No. The government grant currently covers only air to water heat pumps, ground source heat pumps, and biomass boilers. Air to air heat pumps are excluded because they do not provide domestic hot water. This may change in future policy revisions, but for now, A2A systems must be self-funded.