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Estimating Solar PV generation values throughout the year.

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(@markc)
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93 kWhs
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I'm currently looking into having a solar PV system installed and am wanting to get an idea of what the system can generate throughout the year. 

With the space I have available it looks like the system I can have installed has an estimated production capability of around 6,000kWh.

The first salesperson that has visited was only able to divide 6000kWh by 365 days to state that on average the system will produce 16.4kWh per day. This figure isn't really useful.

What I would like to have is a rough idea on an average kWh SVP production for each month of the year from a 6kw system (without batteries). Based in Sheffield, South facing 40º pitch roof, no shading.

Would anyone know if these figures are calculable?

Thanks

Mark


   
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Mars
 Mars
(@editor)
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We have a 6.16kW array, south facing, 35 degree pitch, no shading and for three years we’ve produced 6MWh annually.

This is last year’s monthly breakdown.

2AEE894A 2CAF 4F63 97FF ED6495F1F9FD

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(@markc)
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Topic starter  

Thanks @Mars. Would you have that data as a spreadsheet or monthly figures? Both for production and export.
Also do you know what your average electricity kWh usage is per month (excluding ASHP).


   
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(@batalto)
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@markc https://re.jrc.ec.europa.eu/pvg_tools/en/tools.html

That should do you

12kW Midea ASHP - 8.4kw solar - 29kWh batteries
262m2 house in Hampshire
Current weather compensation: 47@-2 and 31@17
My current performance can be found - HERE
Heat pump calculator spreadsheet - HERE


   
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Mars
 Mars
(@editor)
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@markc, there doesn’t seem to be a way I can export the data. I’m writing a blog about our solar PV so I’ll put together a table with a month by month breakdown to give you exact numbers.

There’s no way I can separate our ASHP data and usage from our general usage. With the heat pump off, our house uses 20-24kWh per day. We use a lot of power because we’re at home 24/7 with a lot of appliances and stuff running. I’d like to get us below 15kWh per day without the heat pump. 

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Majordennisbloodnok
(@majordennisbloodnok)
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@markc, hope this helps.

 

Although we had our ASHP and solar PV fitted in December last year, early March was the first point we were able to sort out our runaround with UKPN and get the export MPAN to be able to start exporting. As a result, the attached spreadsheet gives daily figures from then for kWh exported, imported and generated along with the ASHP consumption and therefore a calculation of the non-ASHP usage.

We had a minor misconfiguration of our PV and battery setup such that the battery was charging but not always being used in preference to energy imports. There is a hiccup between 18th and 30th May where the installer made an erroneous reconfiguration which had the battery charging from imports and then immediately discharging to export, but after that it has been rock solid and working entirely as intended. Therefore those dates' figures are the only ones which misrepresent usage and export to any significant degree. As for the ASHP, I started only recording the total usage but as you can see there is a point where I switched to recording the heating and DHW separately.

I have also included a second tab (Monthly percentages) which shows each month and the theoretical percentage of a year's energy likely to be consumed or generated in that month. These are standard figures I have gleaned from this forum and elsewhere, allowing me to reasonably accurately extrapolate the figures I do have to give a picture of a full year. I expect you will need to do the same.

For reference, our installation is a 6.5 kWp array linked with a 6kWh battery. The total of 18 panels are on two South-facing slopes except for three that are on an East-facing elevation to catch the earlier sun. Since 15th December 2021, we have generated a total of 4894 kWh, and have, on occasion seen peaks of 6.1 kW but never the full 6.5.

105 m2 bungalow in South East England
Mitsubishi Ecodan 8.5 kW air source heat pump
18 x 360W solar panels
1 x 6 kW GroWatt battery and inverter
Raised beds for home-grown veg and chickens for eggs

"Semper in excretia; suus solum profundum variat"


   
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(@batalto)
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@editor thats a lot of power sans heat pump. We are home all day with children and without heating we use around 15kwh. You must have some hungry stuff

12kW Midea ASHP - 8.4kw solar - 29kWh batteries
262m2 house in Hampshire
Current weather compensation: 47@-2 and 31@17
My current performance can be found - HERE
Heat pump calculator spreadsheet - HERE


   
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(@atommyk)
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@batalto I agree. I mean I appreciate that Mars’ house is much bigger than ours (3-bed semi, 1950ies build) - prior to swapping our tumble dryer, we used about 8-12 kWh per day; now it’s more like 6-9 kWh.


   
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(@derek-m)
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@atommyk

I think that it could be due to all the 'energy saving' devices that Mars has installed. 😎 


   
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(@atommyk)
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🤣 that would be extraordinary 


   
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(@markc)
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Posts: 97
Topic starter  

Thanks for all the data and link to PVGIS. The PVGIS spat out figures that were inline with the data from Majordennisbloodnok.

I have a daily average of 16kWh of non ASHP usage. I'm breaking this down to 12kWh in the day and 4kWh at night.

This would mean that without batteries, May, June, July and August would be generating excess electricity that I couldn't use.
These are also the months where the ASHP is not needed.
From the SEG I imagine this to be worth £50 per year. (1209kWh x £0.04)

So the 6kWp system would generate 4791kWh that I could use. At the current price of £0.34 that equates to £1628 saving per year.

A £9k installation therefore would take 5.5 years to pay for itself.

Screenshot 2022 10 17 at 15.51.35

   
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Majordennisbloodnok
(@majordennisbloodnok)
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Posted by: @markc

Thanks for all the data and link to PVGIS. The PVGIS spat out figures that were inline with the data from Majordennisbloodnok.

I have a daily average of 16kWh of non ASHP usage. I'm breaking this down to 12kWh in the day and 4kWh at night.

This would mean that without batteries, May, June, July and August would be generating excess electricity that I couldn't use.
These are also the months where the ASHP is not needed.
From the SEG I imagine this to be worth £50 per year. (1209kWh x £0.04)

So the 6kWp system would generate 4791kWh that I could use. At the current price of £0.34 that equates to £1628 saving per year.

A £9k installation therefore would take 5.5 years to pay for itself.

Screenshot 2022 10 17 at 15.51.35

Not sure about the SEG, tbh @markc. We went instead with the Octopus agile outgoing tariff which is a variable export rate. Our May, June, July and August figures as you can see in the spreadsheet equate to Octopus paying us £75, £63, £95 and £89 respectively. By my reckoning those four months alone earned us £322 after we'd used all the solar leccy we could. Given that's already £270 over and above your £50 estimate, I'd guess you'd want to factor that into your ROI calculations.

This does, of course, depend on you not using something like Octopus Go; they don't allow both those tariffs together for obvious reasons.

105 m2 bungalow in South East England
Mitsubishi Ecodan 8.5 kW air source heat pump
18 x 360W solar panels
1 x 6 kW GroWatt battery and inverter
Raised beds for home-grown veg and chickens for eggs

"Semper in excretia; suus solum profundum variat"


   
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