Four years ago my wife and I embarked upon our decarbonisation journey. My daughter, then aged 4.5yrs, had subtly changed our mindset about the cost vs return on investment of renewable heating & micro-generation. It was an equation we no longer calculated solely in financial terms, but rather cost vs collective benefit to humanity and her generation. Over time a niggling but increasing moral obligation to do what we could gnawed away at us. *

So we embarked upon removing the old oil boiler and fitting a shiny new 10kW ASHP with £5K BUS grant contribution. We fitted 3.6kW of Solar PV, and we retrospectively added 13kW of BESS. Our heat pump install was done well and the ASHP has been flawless from the get-go, but the commissioning and handover were non-existent. Over the years we've learned through trial and error. We've benefitted from the huge contribution of knowledge this forum has provided - thank you @editor and all. A host of parameter settings needed to be adjusted, and numerous small tweaks made here and there. Over a couple of winter heating seasons we optimised the ASHP CH and DHW control and efficiency and found that elusive weather compensated heating curve sweet spot. If only it could have done it for us out of the box!

We soon realised however that we needed to load shift our electricity import to cheap rates, to allow the ASHP to run continuously for best efficiency while remaining a cost-effective means of heating compared to burning oil. So we added 2x 6.5kW BESS. We work the BESS hard, charging it whenever Cosy has a low rate 3x a day, to leverage the advantage and load shift most of our import to Cosy low rate. (Around 88-90%)

We've recently completed our journey having sold our two jalopy petrol and diesel cars, both with 130K+ miles on them and getting increasingly expensive to keep on the road. The cars owed us nothing. We've gone Chinese - like most things these days - with BYD. A new Dolphin Surf EV and an ex-demo Seal U DM-i PEHV. We've never bought new or nearly new cars before, so this was new territory. Our daily commutes are now all-electric, with the hybrid having a 1300kg towing capacity for our trailer tent family holidays. EV fast chargers on campsites are still anathema in the UK, but on some sites you can cheekily granny charge at 10A load from the electric hook-up.

Both cars are fantastic - we're well impressed with the quality vs value of them. The small EV returns 5miles/kWh, costing 2p a mile on Octopus Cosy cheap rate, less when solar surplus contributes. More Apps on our phones, more head-scratching and yet more settings! We installed a Zappi 7.5kW home charger at home, which is very capable but I didn't find it very intuitive. I've now found the sweet spot where it will timed boost at 7.5kW on the two Cosy cheap overnight rate periods, and granny charge at 1.5kW ECO+ setting at other times drawing from the BESS. Using the BESS that way gives us up to 10hrs of low rate charge overnight in a 'granny-boost-granny-boost' pattern, which no EV tariff offers. We can fully charge the EV overnight that way, but we've never had the battery lower than 45% charge yet on a 200 mile range city EV car used predominantly in a rural environment. One car gets plugged into the Zappi, and if needed one granny charges from an outdoor socket at 2kW. Whichever needs more juice overnight goes on the Zappi. I can charge the PEHV for free at work during the day. What we now save on petrol and diesel per month more than pays for the PCP on the small EV.

* I should add that in the current geopolitical climate where Billionaires send rockets into space for fun, and missiles are fired at anything that moves in the Middle East, our C02 savings seem futile, but we sleep easier knowing we've done our little bit.

Thank you to all who have helped us along this journey. It has been quite a ride!