Posted by: @ian-s

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Did the initial online quote with Octopus, energy provider, requested a call but currently finding it impossible to get anyone to talk to me. Was hoping to get a rough idea of amount of energy used by their heat pumps to get an idea if it is worth increasing my solar battery storage.

Depending on your flow temperature you should get a SCOP (seasonal coefficient of performance - energy out/energy in averaged over the whole heating season) of around 4 with a good system, so on average the energy use is likely to be very roughly one quarter your gas use.  This assumes that you currently heat your house and it doesn't cool too much at any time eg overnight (a modest cooling of a degree or so because you have switched the heating off for a few hours doesn't actually make much difference to energy consumption).  If your house cools a lot for substantial parts of the day the consumption may be more than this because you usually try to operate heat pumps on 24x7 or thereabouts.   

However during the depths of winter your COP will drop as low as 3 when its very cold outside.   So if your house loss really has a loss of 6kW it will need 6kW*24h to heat =144kWh on a day when its at design temperature all day, which means you will consume about 48kWh of electricity.  A more typical mid season day will be less than half that because you will be running at a higher COP and higher outdoor temperature.

If you have even annual gas readings you can do a sense check on loss calculations and also inspect your max gas use which will tell you about likely electricity use.  If you have half hourly meter readings you can do a more sophisticated analysis by plotting against average OAT, which can, with the right conditions, give a pretty accurate readout of house loss.  The challenge with older houses that have been upgraded is that surveyors dont always take into account the upgrades and/or the u-values of the materials are not necessarily accurately known.  Also estimating the loss due to air changes can be a challenge with older houses.  This generally leads to an overestimated loss, sometimes by a factor of 2, which causes issues.  That said you aren't going to get a heat pump much smaller than 6kW anyway and if your rads are oversized it doesnt matter, you just run at a lower FT and higher COP.  The real problems come when a (say) 6kW house is estimated at (say) twice that figure and since yours is coming out at 6kW you are hopefully not in that territory.

Feel free to most more questions/ask for further explanation.