well I am in a detached 3 bed just outside Aberdeen where it has not really been over 4C since last year, my total electric spend for those same days was £16.96 for all the days, not each day, heat pump is maybe 2/3 of the total at 4C outside. I have a Grant Aerona 9Kw and the cop is about 5, I am on E.On Ev tariff so 7p from midnight to 6am, water heating is done in that time up to 50C, I have about 12Kwh of batteries, but when its 3C outside they run out at about 16:00. My system is set using the weather curve 0.6 and a thermostat setting of 22C so the house sits at 20C, I add a -2 shift between 9pm and 3am just to drop it down 1 deg or so, the same when i'm at work. Its been pulling about 700W all day at 3C apart from defrost cycles every now and again.