PhilT Posted August 17, 2022 Share Posted August 17, 2022 (edited) 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? Edited August 17, 2022 by PhilT Link to comment Share on other sites More sharing options...
JohnMo Posted August 17, 2022 Share Posted August 17, 2022 You don't mention size of ASHP nor PV array size. We have 3.1kW of PV and gas boiler (so should be easier for you to self use). Since middle of June I have exported 43kWh (5 to 600kWh generated), this was only exported because my immersion was miss reading and only charging the cylinder to 55 degC. This has since been fixed and now exporting nothing. Link to comment Share on other sites More sharing options...
joe90 Posted August 17, 2022 Share Posted August 17, 2022 1 hour ago, PhilT said: the seasonal and daily timetable of use by ASHP compared to PV seems so far out of sync, I have an ASHP and considering PV, with UFH and a large DHW tank I plan to time the ASHP to come on at at 11am and off at 4pm, therefore if the sun is shining the ASHP will use as much as it needs, and you can override it if required. Link to comment Share on other sites More sharing options...
ProDave Posted August 17, 2022 Share Posted August 17, 2022 It is not JUST the ASHP that uses electricity. ANYTHING consuming electricity in your house will use at least some of the PV. If you are talking of a normal sized array with a 3.68kW inverter it is pretty easy to self use almost all you generate. I am certainly self using 95% just by switching use of the big appliances to the middle of the day and diverting excess PV to the immersion heater. However Octopus do seem to be offering a tariff now that actually pays a decent rate for export, not the insulting rate of 5p per kWh so that may change the equation. Link to comment Share on other sites More sharing options...
joe90 Posted August 17, 2022 Share Posted August 17, 2022 40 minutes ago, ProDave said: However Octopus do seem to be offering a tariff now that actually pays a decent rate for export, But does that rule out DIY instal? Link to comment Share on other sites More sharing options...
PhilT Posted August 17, 2022 Author Share Posted August 17, 2022 1 hour ago, JohnMo said: We have 3.1kW of PV and gas boiler (so should be easier for you to self use). Since middle of June I have exported 43kWh (5 to 600kWh generated), this was only exported because my immersion was miss reading and only charging the cylinder to 55 degC. This has since been fixed and now exporting nothing. 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%. Link to comment Share on other sites More sharing options...
PhilT Posted August 17, 2022 Author Share Posted August 17, 2022 1 hour ago, joe90 said: I have an ASHP and considering PV, with UFH and a large DHW tank I plan to time the ASHP to come on at at 11am and off at 4pm, therefore if the sun is shining the ASHP will use as much as it needs, and you can override it if required. Interesting. How much power would you estimate an average (3kW?) rig generates in December/January between 11am and 4pm? Link to comment Share on other sites More sharing options...
JohnMo Posted August 17, 2022 Share Posted August 17, 2022 (edited) Little confused. In Jan your output from PV for the month will be around 150kWh, some days the output will be zero, but if we average to 31 days of equal generation, 4.8kWh per day. Even getting a CoP of 4, that less than 2 hours of running the heat pump. So full use from PV without any other loads. In summer you are generating circa 400kWh per month, 13kWh per day, a couple of hours doing hot water, would 5.6kWh, other background uses, washing machine, dishwasher etc plus immersion to bump up cylinder temp to max, all the PV is used. Edited August 17, 2022 by JohnMo missed context Link to comment Share on other sites More sharing options...
joe90 Posted August 17, 2022 Share Posted August 17, 2022 1 hour ago, PhilT said: Interesting. How much power would you estimate an average (3kW?) rig generates in December/January between 11am and 4pm? See what @JohnMo says above. All I am saying is it’s best to use what’s available, when it’s available. Link to comment Share on other sites More sharing options...
PhilT Posted August 17, 2022 Author Share Posted August 17, 2022 59 minutes ago, JohnMo said: Little confused. In Jan your output from PV for the month will be around 150kWh, some days the output will be zero, but if we average to 31 days of equal generation, 4.8kWh per day. Even getting a CoP of 4, that less than 2 hours of running the heat pump. So full use from PV without any other loads. In summer you are generating circa 400kWh per month, 13kWh per day, a couple of hours doing hot water, would 5.6kWh, other background uses, washing machine, dishwasher etc plus immersion to bump up cylinder temp to max, all the PV is used. 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! Link to comment Share on other sites More sharing options...
PhilT Posted August 17, 2022 Author Share Posted August 17, 2022 1 minute ago, joe90 said: See what @JohnMo says above. All I am saying is it’s best to use what’s available, when it’s available. 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 1 Link to comment Share on other sites More sharing options...
JohnMo Posted August 17, 2022 Share Posted August 17, 2022 https://re.jrc.ec.europa.eu/pvg_tools/en/ Use the tool, to get a good estimate of output by month Link to comment Share on other sites More sharing options...
PhilT Posted August 17, 2022 Author Share Posted August 17, 2022 Just now, JohnMo said: https://re.jrc.ec.europa.eu/pvg_tools/en/ Use the tool, to get a good estimate of output by month Great many thanks Link to comment Share on other sites More sharing options...
joe90 Posted August 17, 2022 Share Posted August 17, 2022 5 minutes ago, PhilT said: it wasn't a loaded question Ha, those who know me here know I am a Luddite and I do not “do” data, I just tend to copy people who get it Right 🤣🤣🤣🤣 my whole build was finger in the air (and lots of copying others) 🤷♂️ Link to comment Share on other sites More sharing options...
ProDave Posted August 17, 2022 Share Posted August 17, 2022 2 hours ago, joe90 said: But does that rule out DIY instal? Afraid so. You need an MCS install to claim any sort of export payment. 1 Link to comment Share on other sites More sharing options...
jayc89 Posted August 17, 2022 Share Posted August 17, 2022 Novice question - what happens to the power generated from a PV if the household demand is low, the immersion is no longer calling for heat (i.e. it's already at temp), you don't want to export any of it and you don't have a battery array? Link to comment Share on other sites More sharing options...
jamieled Posted August 17, 2022 Share Posted August 17, 2022 If it's physically limited from exporting (as opposed to you not wanting to export) then I think generation would drop as there's no demand. Link to comment Share on other sites More sharing options...
ProDave Posted August 17, 2022 Share Posted August 17, 2022 2 minutes ago, jayc89 said: Novice question - what happens to the power generated from a PV if the household demand is low, the immersion is no longer calling for heat (i.e. it's already at temp), you don't want to export any of it and you don't have a battery array? Well it just gets exported. I export about 100kWh per year for no payment. Most of that is when the PV maxes out at mid day and generates a few hundred watts more than the immersion heater can sink. Link to comment Share on other sites More sharing options...
Dillsue Posted August 18, 2022 Share Posted August 18, 2022 9 hours ago, jayc89 said: Novice question - what happens to the power generated from a PV if the household demand is low, the immersion is no longer calling for heat (i.e. it's already at temp), you don't want to export any of it and you don't have a battery array? Unless youve specifically installed a system to monitor export and throttle generation if you start exporting, any excess just goes to the grid. Unless youve got a DNO restriction on what you can export, I cant see a reason why you would not want to let excess go to the grid. Link to comment Share on other sites More sharing options...
patp Posted August 18, 2022 Share Posted August 18, 2022 Not strictly on topic but can anyone help? We were in desperate straits last Christmas time. Living in our caravan on a campsite we needed to get a meter fitted asap so that we could move to site and finish the build. Eventually got hold of Octopus and put our plight (husband/site manager just diagnosed with cancer and both in our seventies) to them regarding the 3 month lead time on installations. They put us on "emergency fit" and turned up a day later to install our, 3 phase capable, meter! Since then I have heard absolutely nothing from them! That means no bills! We do have 46 solar panels so are not expecting to owe a lot (?) but it is still concerning. Husband's health got worse (chemo attacked his heart and gave him heart failure) so that is my excuse for not chasing harder but should I be jumping up and down at them? Electrician is so busy I cannot get hold of them to come and talk it through reference our generation v usage so that I can stop worrying or go into panic mode! For info we have an ASHP and the usual array of domestic appliances. Link to comment Share on other sites More sharing options...
joe90 Posted August 18, 2022 Share Posted August 18, 2022 Morning Pat, sorry to hear this , can you not estimate your usage from you meter readings so you could be aware of the cost in the future? Link to comment Share on other sites More sharing options...
jayc89 Posted August 18, 2022 Share Posted August 18, 2022 48 minutes ago, Dillsue said: Unless youve specifically installed a system to monitor export and throttle generation if you start exporting, any excess just goes to the grid. Unless youve got a DNO restriction on what you can export, I cant see a reason why you would not want to let excess go to the grid. I was thinking a DIY installation where, as I understand it, you're not legally allowed to export back to the grid? Link to comment Share on other sites More sharing options...
markc Posted August 18, 2022 Share Posted August 18, 2022 @patp octopus are renowned for taking time to connect to 3 phase meters, and as Joe says, use your readings to estimate your bill or post here and we can estimate for you. 1 Link to comment Share on other sites More sharing options...
joe90 Posted August 18, 2022 Share Posted August 18, 2022 4 minutes ago, jayc89 said: I was thinking a DIY installation where, as I understand it, you're not legally allowed to export back to the grid? No, if you DIY (like I am going to) you cannot claim £ fir the generation to the grid, it’s just used as a dump fir unused lecky. So use as much as you can, if you had an EV you could dump to this. Link to comment Share on other sites More sharing options...
Kelvin Posted August 18, 2022 Share Posted August 18, 2022 Sorry to hear this Pat. Octopus can be hard work to deal with. The Octopus CEO is a guy called Greg Jackson. Here’s his email address: greg@octopus.energy I had cause to email him about a long outstanding issue I had and it got resolved. Good luck. Link to comment Share on other sites More sharing options...
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