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Solar PV Performance Thread - Post your monthly output

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    #482
    DrPhilG
    Registered Users Posts: 12,221 ✭✭✭✭DrPhilG


    KCross wrote: »
    And you havent addressed the main thing that has been pointed out.... you seem to have allocated ALL the generation to day rate electricity...

    Where have I done that?


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    #483
    KCross
    Registered Users Posts: 12,077 ✭✭✭✭KCross


    DrPhilG wrote: »
    Where have I done that?

    I said “seems”... €900 looks like all your generation (€900/15c=6000kWh).


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    #484
    DrPhilG
    Registered Users Posts: 12,221 ✭✭✭✭DrPhilG


    KCross wrote: »
    I said “seems”... €900 looks like all your generation (€900/15c=6000kWh).

    Gotcha. Not sure where you got the 6000kWh from.

    No sense ripping the arse out of this, we clearly agree to disagree.


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    #485
    KCross
    Registered Users Posts: 12,077 ✭✭✭✭KCross


    DrPhilG wrote: »
    Gotcha. Not sure where you got the 6000kWh from.

    No sense ripping the arse out of this, we clearly agree to disagree.

    The 6000kWh comes directly from your €900 figure. It’s not a case of agreeing or disagreeing. It should be data driven if you are calculating savings.

    How many kWh’s do you estimate your system will generate for a full year?


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    #486
    unkel
    Registered Users Posts: 64,916 ✭✭✭✭unkel


    KCross wrote: »
    How many kWh’s do you estimate your system will generate for a full year?

    Let's have an optimistic guess, shall we?
    DrPhilG wrote: »
    2.8kWp on the garage, south facing.
    3.4kWp on the house, west facing.

    In Donegal, so maybe 2.5MWh from the garage and 2.5MWh from the house?

    5MWh in total. Let's be very optimistic and say 35% is used during the day for stuff that could not be run at night. Another 10% is used for charging the car, 25% is used for heating water and 30% is going back to the grid without payment. Seems realistic enough?

    So the total annual saving is:

    0.35 * 0.14 (day rate) * 5000 = €245
    0.10 * 0.07 (night rate) * 5000 = €35
    0.25 * 0.05 (heat your house with an efficient oil or gas boiler) * 5000 = €63

    So total saving about €343

    Cost of install about €6k (net of near €4k subsidy)?

    So not taking into account any financing cost or opportunity cost of money or even any maintenance or breakages, you are looking at a 17 year pay back

    Realistically, your battery will be all but useless by then and your inverter, eddi and zappi will have all been replaced at that stage

    In other words, the system will never pay for itself. That's the cold harsh reality. Still the right thing to do, to go renewables. But let's not kid ourselves on the finances...


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    #487
    championc
    Registered Users Posts: 6,074 ✭✭✭championc


    And as I said earlier, you cannot call €200 of this a PV saving since it's not a saving limited to PV owners.

    You have simply claimed that your PV itself is saving you €700 per year. My own wouldn't be near this in savings but of course, everyone's consumption and pattern is different.

    You are possibly like my wife in that all she is interested in is as to roughly how much is our spend on electricity with pv vs without pv.
    I think PV is saving me about €300 per year. Excluding the €200, how are you doing so far, since your installation was completed ?


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    #488
    DrPhilG
    Registered Users Posts: 12,221 ✭✭✭✭DrPhilG


    championc wrote: »
    And as I said earlier, you cannot call €200 of this a PV saving since it's not a saving limited to PV owners.

    I'm really not trying to be an arse, but I don't understand this point.

    Where did this figure of €200 come from? Where did I say it was part of my estimated €900?

    I'm not saving €200 by switching. I'm staying at the same price by switching. If I didn't switch I'd probably lose about €200 a year. By switching I stay at the same cost. If I didn't have solar, I wouldn't be counting that as a €200 saving.

    People seem to think that if my annual bill drops by €900, its because the panels saved me €700 and switching supplier saved the other €200.

    My estimate of €900 is what I expect my bill to reduce by SOLELY because of PV generation. Not because of switching supplier which is a given for every person, every year.

    I'm estimating that €900 based on my average monthly savings so far which are (I'll have to check the numbers tomorrow) a bit over €400 after 4 months. Likely to be less over winter of course, but I also still have the best months still to come.

    I appreciate that a more accurate figure will be reached by analysing the numbers from the inverter and I'll do that at the end of the 12 month period. For now, a rough guide of costs this period compared to the same period pre-solar is fine by me.


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    #489
    championc
    Registered Users Posts: 6,074 ✭✭✭championc


    Ok, now I get you. So if you don't switch, your cost goes up by about 200, but surely by switching, you just maintain the same level - you're just saving the same 200 you saved last year.

    In any case, the rolling 12 months total will be interesting for sure.


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    #490
    garo
    Registered Users Posts: 1,874 ✭✭✭garo


    unkel wrote: »
    Let's have an optimistic guess, shall we?

    In Donegal, so maybe 2.5MWh from the garage and 2.5MWh from the house?
    ...

    Sorry but these are not optimistic numbers. Also attributing 35% to day use is pretty miserly. And a 30% export while having an EV and an Eddi is ridiculously high. While I think Dr Phil is a tad optimistic, you are being way too conservative and calling it an “optimistic guess”. I saved 450 from a 4.8kWh system in 2020. And yes I did the full breakdown. My system generated 4230kWh of which I exported 1051. I don’t have an Eddi and didn’t have a Zappi until late September and by my estimates less than 200kWh went into heating water and almost nothing displaced night time usage.


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    #491
    unkel
    Registered Users Posts: 64,916 ✭✭✭✭unkel


    DrPhilG wrote: »
    My estimate of €900 is what I expect my bill to reduce by SOLELY because of PV generation.

    So you use all of the 5MWh you produce per year yourself without sending a single unit back to the grid, without a single unit going to Eddi and without a single unit going to Zappi? And you value each and every unit at €0.18, which is a very high undiscounted rate?

    Seriously?


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    #492
    garo
    Registered Users Posts: 1,874 ✭✭✭garo


    @Dr PhilG 900 is a bit high tbh. You have a 7.2kW system? You will be lucky to get more than 6500kWh. To save 900 you need to be using all but 500 of it at day rate. So no Zappi or Eddi usage as that doesn’t count as day rate.
    When you produce 40-50 kWh on good days in May you simply won’t be able to use it all on day rate. Unless you have big fish tanks or a data centre.


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    #493
    graememk
    Moderators, Home & Garden Moderators Posts: 5,855 Mod ✭✭✭✭graememk


    As your monthly stats have been posted here.

    Ive worked out what you have saved so far from Aug - Jan
    * you didnt have the august stats for eddi&zappi so I made them the same as sept.

    Generated 1538.9 Kwh
    Exported 224.9kwh
    Eddi 106kwh - (@€;0.06) - €6.36
    Zappi 198.85kwh - (@0.074) - €13.92

    That gives you a self use of 1009.15kwh - (@0.15) -€151.37

    Total saving so far from solar is €171.65

    you electricity bill has been €400 lower on the same period, 171.65 was from the solar, and the other 229 have been from switching to a cheaper plan.


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    #494
    DrPhilG
    Registered Users Posts: 12,221 ✭✭✭✭DrPhilG


    championc wrote: »
    Ok, now I get you. So if you don't switch, your cost goes up by about 200, but surely by switching, you just maintain the same level - you're just saving the same 200 you saved last year.

    Correct. So I wouldn't call it a saving. I'd call it maintaining the status quo.

    I was never counting that into the estimated 900 saving on last year's bill.

    Maybe I'll hit the 900, maybe I won't. I'm just estimating based on the results so far.


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    #495
    stiofan85
    Registered Users Posts: 505 ✭✭✭stiofan85


    Very interesting thread and very helpful.

    Does anyone have any thoughts on the yield for the money paid vs sitting in the bank? Since interest rates are so low, an investment of, say €4k on PV, saving €340 a year using Unkel's numbers - that's ~9% return tax free. Is that wishful thinking in terms of justifying the cost?


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    #496
    DrPhilG
    Registered Users Posts: 12,221 ✭✭✭✭DrPhilG


    graememk wrote: »
    the other 229 have been from switching to a cheaper plan.

    I didn't switch to a cheaper plan.


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    #497
    garo
    Registered Users Posts: 1,874 ✭✭✭garo


    Then your usage must have gone down as you become more aware of your consumption.


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    #498
    garo
    Registered Users Posts: 1,874 ✭✭✭garo


    graememk wrote: »
    As your monthly stats have been posted here.

    Ive worked out what you have saved so far from Aug - Jan
    * you didnt have the august stats for eddi&zappi so I made them the same as sept.

    Eh? August would be at least 30% higher than Sep no? Unless he gave the August generation stats but not Zappi/Eddi.


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    #499
    unkel
    Registered Users Posts: 64,916 ✭✭✭✭unkel


    graememk wrote: »
    Total saving so far from solar is €171.65

    And this of course includes stuff like putting on a dish washer or washing machine while the sun is shining. These could have been put on at night at the night rate, so the real saving when you do that is €0.08 per kWh, not €0.14 per kWh

    So that figure in reality is a good bit lower again...

    Lookit, I'm a big fan of renewables and we should all install a lot more. But let's not delude ourselves with false hopes & figures


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    #500
    garo
    Registered Users Posts: 1,874 ✭✭✭garo


    stiofan85 wrote: »
    Very interesting thread and very helpful.

    Does anyone have any thoughts on the yield for the money paid vs sitting in the bank? Since interest rates are so low, an investment of, say €4k on PV, saving €340 a year using Unkel's numbers - that's ~9% return tax free. Is that wishful thinking in terms of justifying the cost?

    No it’s not wishful thinking. Those are the numbers. Though I doubt you will get a system that saves 340 for 4K. Maybe 5k after grant. But 6-7% return after tax is what I calculated. There’s the little matter of principal as the PV is a depreciating asset but you still come out ahead. 3% after tax return was what I calculated using conservative estimates of lifetime. It’s probably higher now as install prices have dropped in the 18 months since I got the install.


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    #501
    unkel
    Registered Users Posts: 64,916 ✭✭✭✭unkel


    Even a very low return percentage like 2-3% would be much better than your money sitting in a savings account, doing nothing. It's quite possible that not long from now you will actually have to pay for money sitting in a bank and also quite possible we will see an era of much higher inflation than we have become used too - which would erode the real value of any savings you have in a bank account

    So by all means, do some proper sums, but do invest in renewables if you can and the figures make (at least some) sense!


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    #502
    stiofan85
    Registered Users Posts: 505 ✭✭✭stiofan85


    unkel wrote: »
    So by all means, do some proper sums, but do invest in renewables if you can and the figures make (at least some) sense!

    TBH it's primarily an environmental choice. Have been slowly making all the right changes - A3/Heat Pump house, little/no meat, grow a lot of our own veg/source from local farmer, don't fly, EV recently, reduce/reuse/recycle. Last up is Solar PV and I'd say it's hardest per my post in PV quotes thread - A3 means no grant so the sums are a bit harder to justify even with the environment as primary motivation. This thread has actually confirmed my sums so very helpful. Will probably get it in over the summer with a significant dose of DIY.


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    #503
    graememk
    Moderators, Home & Garden Moderators Posts: 5,855 Mod ✭✭✭✭graememk


    garo wrote: »
    Eh? August would be at least 30% higher than Sep no? Unless he gave the August generation stats but not Zappi/Eddi.

    Yeah it was before the myengei app update. Was being optimistic!


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    #504
    garo
    Registered Users Posts: 1,874 ✭✭✭garo


    stiofan85 wrote: »
    TBH it's primarily an environmental choice. Have been slowly making all the right changes - A3/Heat Pump house, little/no meat, grow a lot of our own veg/source from local farmer, don't fly, EV recently, reduce/reuse/recycle. Last up is Solar PV and I'd say it's hardest per my post in PV quotes thread - A3 means no grant so the sums are a bit harder to justify even with the environment as primary motivation. This thread has actually confirmed my sums so very helpful. Will probably get it in over the summer with a significant dose of DIY.


    Yeah if you do a good bit of DIY the sums would make sense. You just need to have a keen eye, shop around and don't commit till you get a good price.


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    #505
    garo
    Registered Users Posts: 1,874 ✭✭✭garo


    @DrPhilG


    I made a mistake, your install is 6.2 and not 7.2kW. So 2.8 S and 3.4 W assuming a good 35 degree tilt, PV-GIS gives 5200 kWh. No way you save 900 Eur on that. Even if you used every single kWh for day-time use you'd need to be paying 17.3c per kWh. So 900 is simply not possible. Energia's new plan is 14.22c but even if you were on the older 16c plan the theoretical max you can save is 840.


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    #506
    unkel
    Registered Users Posts: 64,916 ✭✭✭✭unkel


    garo wrote: »
    @DrPhilG


    I made a mistake, your install is 6.2 and not 7.2kW. So 2.8 S and 3.4 W assuming a good 35 degree tilt, PV-GIS gives 5200 kWh. No way you save 900 Eur on that. Even if you used every single kWh for day-time use you'd need to be paying 17.3c per kWh. So 900 is simply not possible. Energia's new plan is 14.22c but even if you were on the older 16c plan the theoretical max you can save is 840.

    ;)

    Linky


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    #507
    unkel
    Registered Users Posts: 64,916 ✭✭✭✭unkel


    Nice performance now anyway here in Dublin. 2.3kW and that's not counting my single east facing panel.


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    #508
    slave1
    Moderators, Sports Moderators Posts: 18,746 Mod ✭✭✭✭slave1


    Glad to see some common sense when it comes to financial savings, I had plenty of installers telling me I'd save a grand a year and when questioned was told prepared by accountant and using 19c day rate, enough said.
    As an accountant myself it beggers my belief when I see such little common sense application and/or trying to fool people, does my head in.
    Looking at previous years bills is a total waste of time as usage/rates etc can be so very different.

    Totally agree that just normal base load should be savings at day rate, you should know your base rate as it's an easy read of the meter a few times a day for a week or so, base loads varies very little you will soon see.
    Everything else should be night rate as charging your EV, washing machine, dryer, dishwasher etc should all be operated at night rate.
    I saw one guy try to be clever and just divide the day and night rate and use an average but remember 9 hours night rate and 15 hours day rate so you cannot use a simple average, at least you should weight it.
    Also, if looking at Payback everything needs to be included, don't go leaving out that BER cost.

    I'm brutal with my savings, all at night rate and just 4 units base load at day rate in Winter, no point in fooling anyone especially me.

    Now the Sun is better it's a case of experimenting and moving likes of washing machine to around 11am, dryer too etc.

    My stuff for sale on Adverts inc. outdoor furniture, roof box and EDDI

    My Active Ads (adverts.ie)



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    #509
    KCross
    Registered Users Posts: 12,077 ✭✭✭✭KCross


    garo wrote: »

    I made a mistake, your install is 6.2 and not 7.2kW. So 2.8 S and 3.4 W assuming a good 35 degree tilt, PV-GIS gives 5200 kWh. No way you save 900 Eur on that. Even if you used every single kWh for day-time use you'd need to be paying 17.3c per kWh. So 900 is simply not possible. Energia's new plan is 14.22c but even if you were on the older 16c plan the theoretical max you can save is 840.

    Exactly. Its technically not possible. Not sure Phil is up for accepting that though. :)

    The debate about switching providers is irrelevant. Comparing bills from previous years is irrelevant.

    You can only go off the stats from your inverter (or MyEnergi app) and decide how much of it is to be calculated at day rate and how much of it is night rate (car/eddi/washing-machine etc) and thats your ROI.

    Everything else is irrelevant.


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    #510
    idc
    Registered Users Posts: 548 ✭✭✭idc


    KCross wrote: »
    The debate about switching providers is irrelevant. Comparing bills from previous years is irrelevant.

    You can only go off the stats from your inverter (or MyEnergi app) and decide how much of it is to be calculated at day rate and how much of it is night rate (car/eddi/washing-machine etc) and thats your ROI.


    Funny thing is if I was to tell my wife about the ROI she'd probably still ask whats the difference between the bills!! Difference between night/rate, changing supplier she doesn't care about - just the overall difference be it solar or whatever :)


    One nice feature of my system is you can populate the prices and time periods and it calculates Feed-in (obviously zero so far), self-consumption and load shifting. (only installed end of september and only started load-shifting part way through january when i moved to day/night rate)


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    #511
    Bobeagleburger
    Registered Users Posts: 45,280 ✭✭✭✭Bobeagleburger


    If you don't have an EV, is it still worth moving to night time electric?

    3300 kWh approx usage per year.

    Paying 13.75c with Energia for daytime units.


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