Frequently Asked Questions

What is an air source heat pump and how does it work?
An air source heat pump (ASHP) is a renewable heating system that transfers thermal energy from the outside air into your home. It uses a refrigeration cycle—comprising an evaporator, compressor, condenser, and expansion valve—to absorb heat from ambient air and upgrade it to a usable temperature for space heating and domestic hot water. Most systems operate on electricity and can deliver heat even when outdoor temperatures drop below freezing.

What types of air source heat pumps are available?

There are two main types:

Air-to-water: Transfers heat to a wet central heating system (radiators or underfloor heating) and hot water cylinder. This is the most common type for UK homes.
Air-to-air: Delivers warm air directly into rooms via fan units. Less common in the UK and not compatible with hot water systems.

What is the Coefficient of Performance (COP)?
COP measures efficiency: it’s the ratio of heat output to electrical input. For example, a COP of 3 means the pump produces 3 kWh of heat for every 1 kWh of electricity consumed. Seasonal Performance Factor (SPF) is a more realistic metric, accounting for year-round operation. Typical SPF values range from 2.5 to 3.5 in UK climates.

Do air source heat pumps work in cold weather?
Yes. Modern ASHPs are designed to operate efficiently in temperatures as low as -15°C. They use inverter-driven compressors and variable-speed fans to maintain performance in fluctuating conditions. However, efficiency does decrease slightly in colder weather, so proper system sizing and insulation are critical.

What are the installation requirements?

Outdoor unit: Requires clear airflow and must be mounted on a stable surface, typically a concrete pad or wall bracket.
Indoor components: Includes a hot water cylinder and control unit. Space is needed for pipework and buffer tanks if required.
Electrical supply: A dedicated circuit and RCD protection are typically required. Installers may need to upgrade the consumer unit.

What heating systems are compatible?
ASHPs work best with:

Underfloor heating: Low flow temperatures (30–45°C) match pump output.
Oversized radiators: Designed to operate efficiently at lower temperatures (typically 45–55°C).
Hot water cylinders: Must be compatible with heat pump flow temperatures and have sufficient coil surface area.

How long does installation take?
A standard domestic installation takes 3–5 days, including commissioning and system balancing. Complex retrofits may take longer, especially if insulation upgrades or radiator replacements are needed.

Is planning permission required?
In Scotland and most of the UK, ASHPs are considered permitted development if they meet noise and placement criteria. Units must be at least 1 metre from the property boundary and comply with MCS Planning Standards. Properties in conservation areas or listed buildings may require additional permissions.

What maintenance is required?

Annual servicing: Includes refrigerant checks, electrical inspection, cleaning filters, and verifying system pressures.
User checks: Keep the outdoor unit clear of leaves, snow, and debris. Monitor system performance via the control panel or app.

How long do air source heat pumps last?
With regular maintenance, ASHPs typically last 15–20 years. Key components like compressors and fans are designed for long-term use, and many manufacturers offer warranties of 5–7 years.

Can I combine it with other renewable technologies?
Yes. ASHPs integrate well with:

Solar PV: Reduces running costs by powering the pump with self-generated electricity.
Battery storage: Enhances energy independence and load shifting.
Smart controls: Optimise performance based on weather forecasts and occupancy.

Are grants or incentives available?
Homeowners in Scotland may qualify for:

Home Energy Scotland Loans and Grants: Interest-free loans and cashback options for eligible properties. Installers must be MCS-certified to access these schemes.