Mrs OCB does her weekly visit to her office tomorrow, and mini-OCBs are back at school, so tomorrow will be fitting of Tado system. At least with that I'll have more control over the heating.
@Flyin'Dutch' - all good advice, but most are already in place.
I should get round to replacing the oven and hob tbh, but almost all lighting has been LED for quite some years, dryer has been heat pump system for the past 7 or 8 years (onto our 2nd one now), house is modern 20mm double glazed (except for the veranda which got made into an extension, it's 10mm but I have blinds which help a lot) + house has good roof insulation etc.
As @Miscellaneous mentioned, most of the improvements we could make would cost multiples of the savings - so even though there are no low hanging fruit, I am now looking at ideas.
Energy reduction:
Real-time electricity usage monitor - one that feeds into Home Assistant or similar. Low cost/high benefit.
As I'll probably be getting an EV in the near future, will be looking to completely replace my main board and add night meter. Ideally, I’d like to have reporting out of each circuit breaker for power consumption for that circuit - but I’m probably wishing for too much there! Cost - moderate/benefit - well, mainly depends on me getting an EV TBH.
Real-time reporting for gas usage. Nothing I’m aware of “off-the-shelf” and actually available for my analog meter. Will be (re)introducing camera system to record meter. This time though I’ve found an Instructibles type solution that uses raspberryPi + cloud based AI for number recognition + it hosts a small DB and dashboard. Will be doing the same for my water meter as well.
DIY house thermal survey. I’ve been toying for years with the idea of getting IR camera add-on for my iPhone (e.g FLIR ONE). I think now is the time to release my inner geek
Smart lighting for the problem areas (aka the areas the kids leave the bliddy lights on constantly…). Probably not worth it in terms of cost/benefit since lights are only a few watts - but again, my inner geek will enjoy it.
New oven and hob. This would entail an entire new kitchen - so…err, definitely not cost effective.
External cladding. Jury is still out on that one.
Various minor tweaks around the house, like curtain behind the already draught-proofed front door etc. Low cost - but Mrs OCB appears to have an impassible blocker on such things based on aesthetics.
Other
Already mentioned, either PV or mix PV and PT roof panels - both would benefit from fitting of an immersion heater. If I fit an immersion heater, I'd be tempted to construct a ground source loop to uplift incoming water's temp a bit. Cost - high. Payback period would be 8-12 years.
Wood burning “cassette” - a high efficiency burner for the living room. Cost - moderate to high, benefit would mainly be in comfort. Price per kWh for wood where I am is in theory attractive - but I believe the reality is I need to dry a sufficient volume of wood for a couple of years before it genuinely becomes economical.
Ground source/air to air heat pump. V.high cost, payback 15+ years. As the radio adverts say here about such systems, you’re buying the system for your kids!
WFH “somewhere hot” during winter….