PhilT

Your 11.2kW PUHZ version uses R410 coolant and a twin rotary compressor. The latest 11.2kW PUZ version uses R32 coolant and a scroll compressor. The good news is that the quoted overall performance ratings are similar between these two models so, as others have suggested, your PUHZ setup just needs more effort to find the efficiency sweet spot. If you haven't already, I would strongly recommend an inspection/service to ensure no faults.

which exact model do you have?

It makes the "future proofing" decisions harder, as getting just the inverter first would allow the addition of a V2x device later. Hopefully we won't have to wait to much longer for that!

R u sure? This is the link I saw https://www.solaredge.com/uk/products/ev-charger#/

I see SolarEdge have an all-in-one Inverter/charger available, very interesting, what are people's views on the pros and cons vs separate units?

regarding compatibility of SE optimisers with other inverters, they say:- "Benefits of the SolarEdge P370i universal optimizer Stand-alone optimization technology (IndOP™) - allows operation with any inverter and does not require any additional interface hardware"

might be worth the risk if, as they claim, they will be a pioneer in rolling out V2x technology - what's your view on what those consequences are?

Appreciate the possibilities if you are able to do/manage everything yourself. Although my house is a self build I'm now too old unfortunately so this is a 3rd party commercial installation of ASHP, new HP compatible DHW tank, header tanks, six new radiators, all plumbing, controls and electricals and took 2 guys a whole week to install. £15k gross less £9k RHI grant.

Does anyone have the Octopus outgoing fixed 7.5p SEG with their PVs and if so is the import variable rate available at the current 28 - 29p ish or does it have to be linked to a previously set fixed import rate?

That's about right. My 11.2 version is similar

good ideas - limit the array to less panels mounted horizontally at the highest possible position on the roof (which has a couple of gables anyway so makes even more sense) and my roof is already quite steep at 42deg. I like joe90's idea but don't have UFH unfortunately, and my house is a 30 year old self build, but I could try running the ASHP heating more during the day to make a kind of 'air thermal store' to cover the evening period.

Still mulling this over and struggling to understand how I could replicate the the high % usage figures achieved by others. Jun-Sep I'm using c. 6kWh/day total, of which 1kWh/day is ASHP doing DHW - could be replaced by PV 3kWh but that will have virtually no impact on usage or cost. So from the biggest 4 months PV output of c. 1,600kWh I will only be able to use around 600kWh. The months of Mar/Apr/May & Oct/Nov are potentially more promising, but during those months the ASHP uses most energy before 9am and after 6pm. Would appreciate some help identifying anything I might be missing, and any other opportunities.

Thanks everyone for your help which gives me some confidence it's worth doing. Are there any other key issues and watchouts, when appraising supplier quotes, and generally?

Great many thanks

Yes sorry it wasn't a loaded question I was simply after some hard data on how much PV power is generated by month so I could get a better idea of how much can be used at different times of the year

150 vs 400 that seems extraordinary given the daytime hours and irradiance power difference between Dec/Jan and June/July, nevertheless very good to hear most of it can be used so thanks!

Interesting. How much power would you estimate an average (3kW?) rig generates in December/January between 11am and 4pm?

11.2kW ASHP and looking at a 9 x 410 PV generating c. 3.8MWh pa. With the ASHP I'm now using 75% of my electricity in Oct-Mar vs 50% with total consumption at 6MWh pa of which the ASHP is using around 50%.

I couldn't find anything on this specific question but if there is, and some kind soul could point me in the right direction, I'd be much obliged. I have an ASHP, installed June 2021. With energy prices increasing and likely to remain high for some time I'm rather belatedly looking at PV, but the seasonal and daily timetable of use by ASHP compared to PV seems so far out of sync, my spreadsheet analysis struggles to get anything more than 50% self-use. Does any ASHP+PV user out there have actual annual PV usage figures split between self-use and export?

If cost is your main priority then gas (no PV), if energy/CO2 reduction then go for ASHP. I was faced with a similar choice 18 months ago but went with ASHP as the RHI grant made the net cost comparable to gas. Now the whole picture has changed due to inflation and grant reduction so my installation net cost has doubled (c. £6k to £12k). If that had been the case 18 months ago I may have gone for gas. Personally I would not consider PV as I don't have an electric car and my hot water usage is so tiny in the summer, they just don't make any financial sense for my situation, yours may be different.

It's fine if time is not an issue but in the depths of winter the DHW cycle needs to be as short as possible

Menu item 3 in the DHW settings determines operation time. Mine is still set at the default 60min which will not be enough for yours if your coil is only 1.5sq m. Until you find a more permanent solution try setting it to the maximum 120min

Agreed it was bad! 16/21 = only 76% efficiency. The CoP for those 3 winter months theoretically would be 16/21 x 9,779 = 7,450, divided by 1,674 = 4.4. I suspect many/most gas households have this issue so the claim of potentially huge energy savings is still valid, IMO.

the point at issue was about energy saving not cost saving. Which supplier gives you 28p - I'll be switching to them!

To the first point - not in the context of the original post - it's a new build so safe to say a good standard of insulation and glazing will already have been planned, so the question then becomes is it worth getting a heat pump? Answer yes absolutely compared to other forms of heating such as gas. To the second point, in the 3 coldest months Dec/Jan/Feb my heat pump used 1,674kWh compared to gas the same period one year earlier of 9,779kWh so that's where the energy saving is actually most impressive.