Soleco are the only heat pump designed specifically for use with borehole water rather than a closed brine or water/glycol loop. Given the underground water represents a huge constantly refreshed heat source this should achieve a better COP than the closed loop alternative.
Heat Pumps have been available for many years often sold with wildly exaggerated COPs. To tackle this we welcomed the introduction of EN14511 which dictates the way in which the formal COP should be calculated. For open loop systems it should be calculated at a source water on 10C and a source water off of 7C, and for closed loop the figures are 0C source water on and -3 source water off. The key measure being that the difference (TD) in the in and out temperature is the same at 3C.
The formula for heat taken from water is
Kw = 4.18 x TD (°C) x Flow (L/Sec)
Soleco publish on these pages their official MCS certificate giving the COP at these conditions. The Kensa data sheet states the COP is calculated using the methodology in EN14511 but using design conditions namely brine in at 0C and water out at -4C, giving an increased TD of 4C. This increases the relative heat generated from the water by 33% massively improving the COP calculation. It is interesting to note why they do not publish their MCS certificate in full with the formally COP? Is it because it is much lower than Soleco?
The accrediting agency when asked would only comment that all the Kensa units achieved the minimum standard namely a COP of at least 3.5.
So I am unable to answer the question due to a lack of clarity around the statistics offered by Kensa.
Soleco units, we believe are very efficient and better than many equivalent units on the market, in our informal testing our data suggests that an open loop heat pump has at least a 10% better COP than the exact equivalent closed loop system.