Understanding heat pumps: how they work, what they cost, and their efficiency compared to oil, gas or LPG heating systems

hannahharvey2
Oct 7
4 min read

When it comes to heating your home efficiently and sustainably, heat pumps are leading the charge. At Limitless Energy, we design and install advanced systems from Vaillant and Mitsubishi Electric for homeowners across Swansea, Neath, Port Talbot, Brecon, Bridgend, Cardiff, Carmarthenshire, and the Gower Peninsula.

If you’ve ever wondered how heat pumps actually work, what they cost to run, and how they compare with traditional gas, oil, or LPG boilers, here’s everything you need to know.

How Do Heat Pumps Work?

A heat pump doesn’t create heat by burning fuel; it moves and amplifies existing heat from outside air, the ground, or water into your home. Even on cold days, there’s usable heat energy in the air.

Using a refrigerant circuit and compressor, the system absorbs low-grade heat outdoors, raises its temperature, and transfers it inside through your heating and hot water system.

The process runs on electricity, but because it transfers far more energy than it uses, a heat pump can be over three times more efficient than a standard boiler.

Here’s how it works:

Absorption – The pump draws in air from outside and absorbs heat into a refrigerant.
Compression – The refrigerant is compressed, raising its temperature.
Heat Exchange – This high-temperature refrigerant transfers heat to your home’s heating and hot water systems.
Expansion – The refrigerant cools, and the cycle repeats.

Takeaway:

Because heat pumps transfer heat instead of generating it, they’re incredibly efficient.

Efficiency Explained: COP and SCOP

To measure efficiency, we use two key terms:

COP (Coefficient of Performance): Efficiency under set conditions. Example: COP = 4 means 1 kW of electricity produces 4 kW of heat.
SCOP (Seasonal Coefficient of Performance): The real-world seasonal average across the heating year.

Most modern air-source heat pumps achieve SCOPs between 2.8 and 4.0 in UK homes — that’s 280–400% efficiency, compared with:

Gas boilers: around 90–94%
Oil boilers: around 85–90%
LPG boilers: around 90%

In simple terms, for every £1 you spend on electricity for your heat pump, you could get £3–£4 worth of heat.

What Does a Heat Pump Cost to Run?

To compare like-for-like, let’s assume a typical South Wales home requires 12,000 kWh of heat per year for space heating and hot water.

System	Fuel Cost (per kWh)	Efficiency	Energy Needed	Annual Running Cost
Air Source Heat Pump (SCOP 3.2)	27p (standard electricity)	320%	3,750 kWh electricity	~£1,012 / year
Air Source Heat Pump (SCOP 3.2)	15p (Vaillant + OVO tariff*)	320%	3,750 kWh electricity	~£563 / year
Gas Boiler	7p	90%	13,333 kWh gas	~£933 / year
Oil Boiler	9p	88%	13,636 kWh oil	~£1,227 / year
LPG Boiler	10.5p	90%	13,333 kWh LPG	~£1,400 / year

Prices reflect October 2025 UK averages. *Other heat pump and EV tariffs are available.

Takeaway:

On a standard tariff, heat pumps are similar in cost to gas but cheaper than oil or LPG.
With a discounted electricity tariff for EV or battery storage (such as Octopus Go! or E.on Next), or solar PV, a heat pump can outperform gas on running costs.
If you’re replacing an oil or LPG boiler, the savings can be significant.

Vaillant aroTHERM plus installed in Swansea

Heat Pump options:

We install a variety of heat pump models: CTC, Stiebel Eltron, Vaillant or Mitsubishi. Each has their own benefits and at Limitless Energy we work to find the right solution for every home.

Here's a headline overview on two products we often recommend - Vaillant aroTHERM plus and Mitsubishi Ecodan.

Vaillant Heat Pumps

Vaillant aroTHERM plus air-source models are among the most advanced available in the UK.

Efficiency: Up to 5.2 SCOP under ideal conditions (typically 3.0–4.0 in real homes).
Performance: Works efficiently even at –25 °C.
Smart Tariffs: Vaillant’s partnership with OVO Energy offers the Heat Pump Plus tariff — a discounted electricity rate of around 15p/kWh, cutting running costs dramatically.

Mitsubishi Ecodan Heat Pumps

The Mitsubishi Ecodan range is another excellent option for Welsh homes, particularly where higher flow temperatures are required.

SCOP: Around 3.0–4.0 depending on system design.
Hot Water Output for R290 range: Up to 70–75 °C, ideal for older radiator systems.
Low Noise: Exceptionally quiet operation — perfect for urban and rural locations alike.

Real Efficiency: Why Design Matters

Efficiency depends on more than just the model—it’s about how well the system is designed and installed. At Limitless Energy, we tailor each installation for optimal performance, considering:

Insulation and airtightness – A well-insulated home allows your heat pump to work more efficiently. (Consider reducing draughts under floor or around windows & doors)
Flow temperature – Lower flow temperatures improve performance (e.g., with 40-50 degrees for underfloor heating or large radiators).
Smart controls – Weather-compensated systems automatically adjust output for maximum efficiency.
Electricity tariff – Time-of-use or renewable-friendly tariffs can further reduce running costs. (for example E.on Next, Octopus Cosy or Octopus Go!)
Solar integration – Pairing your heat pump with solar PV and battery storage can cut bills even further.

Why Homeowners in South Wales Are Switching

Across Swansea, Neath, Port Talbot, Brecon, Bridgend, Cardiff, Carmarthenshire, and the Gower Peninsula, homeowners are choosing heat pumps for their:

Lower carbon footprint
Reduced dependence on fossil fuels for safer and cleaner homes
Potential savings on running costs
Eligibility for government grants like the Boiler Upgrade Scheme (£7,500)

Ready to Make the Switch?

At Limitless Energy, we provide expert heat pump installation, solar PV, battery storage, and EV charging solutions across South Wales. We’ll assess your home, design a bespoke system, and help you understand your potential savings before you commit.

Switch to cleaner, safer, cheaper heating today.

📞 Call us on 01792 361638 🌐 Visit www.limitless-energy.co.uk

Serving Swansea, Neath, Port Talbot, Brecon, Bridgend, Cardiff, Carmarthenshire, and the Gower Peninsula