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January reckonings..........

Winter is the season when we tend to become more aware of our heating systems and more crucially, how much they cost us to run. Although outside temperatures are uncharacteristically mild at the moment, they have been much lower. For example, the lowest recorded temperature this year was -12.4 ºC in Kinbrace, Sutherland (19th January) Brrrrr....

The relationship between conventional fuels - such as oil and gas - and the heat output is straightforward, and usually just dependent on the efficiency of your boiler. With heat pumps however, the relationship is a little more complex due the variable efficiencies of the heat pumps. Often referred to as COPs (Coefficient of performance) these are dependent on the input temperature (outside air or ground) and the flow temperature of the heating system. The efficiency of air source heat pumps in particular, is affected by the outdoor temperature. At colder temperatures the efficiency of the system is reduced compared with that at a more ambient temperature of 7 ºC for example, so for each unit of electricity that you pay for - you will receive less heat.

The above graph was plotted from real data (obviously not in the UK!), and shows the typical shape of an efficiency curve for an air source heat pump varying with air temperatures. The COPs are lower than we would expect from the latest generation of heat pumps - they should typically achieve a COP of up to 4.5 at ºC, decreasing to around 3 for -3<ºC. An interesting feature of this graph is the scattering of the readings. This level of variance illustrates just how much scope there is within the heating system to optimise the efficiency, and how poor practices can increase your fuel bills over the longer term. This is another reason why good system design and installation is so crucial!

#OrangehouseRenewables #Renewableenergy #ASHP #Efficiency #COP #AirSourceHeatPump

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