Before diving into the models, it’s important to understand how heat pump performance is measured. The Coefficient of Performance (COP) represents the efficiency of a heat pump at any given moment. In simpler terms, it tells you how much heat (in kW) the pump produces for every kW of electricity it consumes. A COP of 3, for example, means that for every unit of electricity used, the pump generates three comparable units of heat.

However, real-world conditions – such as temperature variations between indoor and outdoor environments – means that the COP will fluctuate. That’s where SCOP, or Seasonal Coefficient of Performance, comes in. SCOP gives a more accurate picture by averaging the heat pump’s efficiency over the course of an entire year, factoring in all the seasonal changes. This makes SCOP a more reliable metric for comparing heat pumps in everyday use.

A crucial factor that significantly affects a heat pump’s efficiency is the flow temperature of your central heating system. This is the temperature to which the heat pump needs to heat the water before it circulates through your radiators or underfloor heating system.

As a rule of thumb, the lower the flow temperature, the more efficient the heat pump will be. Heating water to lower temperatures requires less energy, making your system more economical to run. In this comparison we will focus on standard systems using flow temperatures of 45°C and 50°C. In certain cases, like with the Aira model, we’ll use the flow temperature recommended by the manufacturer or installer.

The technology behind heat pumps has evolved quite a bit over recent years, and so have the benchmarks for efficiency. Just a decade ago, a SCOP of 2.75 was considered acceptable. Today, a modern heat pump should achieve a SCOP of at least 3.2 to be considered efficient.

The Microgeneration Certification Scheme (MCS), which certifies heat pumps in the UK, has set a minimum SCOP of 2.8 at a flow temperature of 35°C. However, most modern models far surpass this requirement. To ensure you’re getting the best value for your investment, aim for a SCOP of 3.5 or higher.

To keep the comparison simple we will take 8kW models, or the manufacturers nearest output, to
compare how efficient they are against each other.

Brand & Model

45°C SCOP

50°C SCOP

Aira 8kW

3.80

Octopus Cosy 6kW

3.36

3.21

Samsung 8kW

3.69

3.40

York 7kW

4.27

3.90

Mitsubishi 8.5kW

3.84

3.64

Vaillant 7kW

3.90

3.65

Aira and Octopus have taken the leap to design and create their own heat pump.

Octopus Cosy 6
While Octopus is known for its affordability, the Cosy 6 is currently one of the lowest-performing heat pump available in the UK, as shown in the table below. Although the lower upfront cost may appeal to homeowners, the heat pump’s poor SCOP means it’s unlikely to deliver significant energy savings in the long run. Additionally, with MCS (Mircogeneration Certification Scheme) likely to raise its minimum SCOP standards soon, the Cosy 6 may lose its certification unless improvements are made.

Aira Heat Pump
Aira, originally installing Vaillant units, has now branched out to offer its own heat pump. With better efficiency ratings than the Cosy 6, Aira’s heat pump is a more attractive option for those prioritizing long-term performance. However, like Octopus, Aira only allows its own engineers to install and maintain their units, which could limit support options down the road.

A fan favourite of independent installers is the Mitsubishi Ecodan. Good performance rating, sound levels and a great support team it’s understandable installers with less experience choose this brand of heat pump as their go to, with Mitsubishi’s support team there to help them along the way and the customer having a high SCOP at the end of it.

The Mitsubishi Ecodan heat pump’s only big negative is not having a built in circulation pump. Having this built into the air source heat pump unit itself, like it is with the York heat pump, means it can modulate and run the heat pump more efficiently compared to it being installed externally at a fixed speed.

Mitsubishi’s best unit in the range is the 8.5kW with the worst being the 14kW. The 14kW is a double fan unit that requires planning permission due to it’s size and is much louder than the rest of the range.

Based on our analysis, the York heat pump stands out as the clear leader in efficiency, outperforming all the competition in terms of SCOP. It’s superior performance makes it an excellent choice for homeowners looking to maximize energy savings and reduce environmental impact. Your Energy is one of only a few installers in the UK with exclusive access to York, making us your go-to provider for the most efficient heat pump on the market!

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