Dillsue

Work out average daily consumption for each month. Put 20 units of each day or whatever the average is if its less than 20, into a battery at 8.5p=£1.70/day cost for 20 units to use during peak rate. At peak rate of 32p/unit the 20 units used during peak time would have cost £6.40 so there's £4.70/day saving. December's saving would be £4.70x31=£145.70. With my usage I'd get that Nov-Feb, a bit less Mar and Oct and quite a bit less for the summer when the HP isn't running and the PV is going full chat. Total for me is just under £1100/yr. 30kwh of Fogstar batteries and 6kw solis inverter is just under £4k. I'm also hoping to be increasing PV export by exporting most of what we currently use by using the battery and off peak eleccy rather than the PV. Not as lucrative as the peak to off peak saving but it's a bit more in the savings pot. That's a rough estimate based on current Octopus Go rates and doesn't include charge/discharge losses. With 30kwh of batteries I think I'll be able to use more than 20kwh of off peak eleccy which will hopefully offset the system losses?? Figures pan out for me so just fine tuning things before taking the plunge

Didn't the company send in a quote for remedial work together with a service report??

If you use Excel it's straight forward to do room by room heat loss calcs. Work out the area of each surface x U value x temp diff and that's your heat loss. If a surface has an element with a differing U value ie a window or door, deduct that elements area from the main surface and work out that elements loss separately, if it has a differing U value. Add all the losses for each surface of the room, 4x walls+floor+ceiling, and youve got the room loss. Repeat for each room and you've got the whole house loss. Simples:) After that you need to account for ventilation losses and I can't remember how I calculated that without opening up my laptop which I haven't got access to!! Someone else will likely guide you on that??

I believe IOG needs an Octopus approved EV charger which we don't have so we're stuck with the basic Go. Assuming you do all those calculations automatically with a bespoke system then that level of automation is beyond where I want to go with this, but....... If the battery inverter supports it, I suppose I could configure the inverter to dump what's in the battery to export after we've gone to bed?? Any suggestions for inverters that might do this??

The battery inverter will be a separate inverter to the 2 x PV inverters so that's OK. The physical layout is problematic as both PV systems connect to consumer units at the back of the house whereas the ASHP that will be the biggest battery load is fed from a CU at the front by the DNO incomer. I'd need to get a chunky cable from the back to the front to take the PV to the Henley block. That's doable if this is a solution. So PV needs to be connected nearest DNO incomer then CT connected between PV connection and house load?? Battery connected anywhere on house side of CT?? Have you done this....be awesome if thats a solution??

If I charge the battery from PV then I'm charging at 15p/unit(export rate) rather than 8.5p/unit(off peak rate). If I power the house from PV rather than drawing off peak battery charge then it's the same....15p to self use PV and 8.5p to use the battery. I appreciate your description is the normal PV/battery set up but I'm just trying to see if it's possible to force export of all PV generation and use the battery until it's empty then use any available PV followed by the grid if there's no PV.

What's the rationale for switching between the tariffs?

A flip side to the companies approach maybe that the guy that attended for the service is an employee with a set schedule of services to complete in the day with householders taking time off work to wait in for him to arrive. If he gets drawn into doing unscheduled work there's a fair chance he'd mis subsequent appointments and the company would have an unhappy customer or two??

I'm looking to install batteries to charge on discounted off peak to then supply the house during peak time. We have significant PV that we get paid to export at 15p/unit. On our current Octopus Go tariff we could charge the battery at 8.5p/unit so it will help our £ROI if we can let all our PV go to export and run the house on off peak rates via the battery. I can't see a way to stop us using the PV when it's available so is there a way to force house loads to use the battery and not draw on the PV??

If the Go rate disappeared I assume I'd be able to jump onto the Cosy rate if that wasn't withdrawn as well??

That's true, if the available surplus remained static which don't beleive is the case. AFAIK there's still considerable wind power still to be installed to reduce the peak time reliance on gas. If that's the case then that wind power will need somewhere to go during off peak periods which could include any batteries I get:). Assuming I've not dropped a clanger in my calcs then what I have in mind will easily pay for itself in 3-4 years and it's a fair bet cheap TOU tariffs will last that long, if not much longer

Demand is 24/7 from the HP which is the biggest user. EV gets charged in the 8.5p off peak period every few days. The rest is consumption that can't really be shifted in any meaningful way.....asking the missus to cook overnight isn't an option. The majority of heating emitters are radiators so I don't have the thermal capacity to boost heat into a big slab using a Cosy like tariff. Ramping the HP up and down to track a Cosy like tariff would likely give us swings in temperature which I'd like to avoid.....we've just had 3 months of a steady 21 degrees with the HP running WC 24/7

The 20kwh/day is battery capacity charged at 8.5p off peak and discharged to offset 32p peak use.....daily usage can be way more than that. ASHP has gobbled an average of 40kwh/day on its own over the last week in freezing temps. We've already got PV but it doesn't do much in the winter

Maybe I'm missing something but has the system been seen to be over pressured and lifting the relief valve that likely feeds the tundish?? OPs video shows the tundish dripping with the pressure guages showing around 1 bar?? At that pressure the relief valve shouldn't be passing which suggests a leaking relief valve?? Giving the releif valves manual actuator a full turn or 2 to lift the relief valve may well get it to reseat??

So a year on from this chat and I wonder if things have changed significantly from an environmental and £ROI perspective?? Having just had our Octopus Go day rates go up to 32p/unit I've been looking at getting batteries to charge with off peak rates and use during peak rate times. Having put in an ASHP in the autumn our usage has jumped up significantly and Nov and Dec total usage averaged around 30kwh/day. If we could shift 20kwh/day of that and most of our usage for the rest of the year to off peak rates that would be quite a saving. Other than the Octopus rates changing and charge/discharge losses what else needs factoring in??