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SELF CONSUMPTION: Batteries or Eskom


Tariq
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Trying to figure out if self consumption is worth it, with Eskom at currently R2.10 per kWh and a Pylontech 2000 costing R15,000, unless I am completely wrong in calculating the ROI ( 1 cycle per day ), it comes to over 10 years and even if you threw in Eskom price increases, it can’t be less than 7 years or so, also the battery  money could be earning interest in a certificate of deposit.

    Can somebody tell me where I have gone wrong in my thinking

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In my opinion, if you buy those types of batteries, you use them every day. I drain my to 20% each day, regardless of what Eskom is doing or their prices etc. These batteries are designed to be discharged 6000 times. No point spending that sort of money on a battery and keeping it 100% each day, for the load shedding periods. That's wastage. 

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I went down this hole of calculating the ROI, costs, etc. But what phil mentioned is something that is hard to put a price too. How much is it worth to have some lights when loadshedding happens?

In the end I decided to go for the battery option, but not trying to go off grid completely. This will cost a bunch of $$$ which you will be hard to recover everything. Yes you could get close, but that is also not looking at what might happen in future with regards to battery replacements or hardware failures. It is just to difficult to put a price of that as well.

Now my biggest problem is to keep to my budget and not upgrade too much. Once you start with solar it is very addictive. Anyone want to join a SA club (Solar Anonymous, not South Africa but it is a good play :D 

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33 minutes ago, Plaashaas said:

A cycle on a US2000 is 2.4kW
If you DOD to 20% it would supposedly last 6000 cycles
2.4.kW x 6000 = 14400kW

144000x R2.10 =R30240 (Without any Eskom price increases)

In my case I do not have a grid tie inverter, my inverter need a battery to operate, so I get about 10KWH each day out of my inverter while the battery is only idling and not really cycling during the day, once you add that extra 10KWH + @Plaashaascalculation into the mix it starts looking even better. 

Then it comes down to how much patience you have for load shedding, is it worth not spend money on backup.

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1 hour ago, Plaashaas said:

A cycle on a US2000 is 2.4kW
If you DOD to 20% it would supposedly last 6000 cycles
2.4.kW x 6000 = 14400kW

144000x R2.10 =R30240 (Without any Eskom price increases)

Just remember that no battery would keep its full capacity over its life. IIRC you can expect these batteries to end at around 60% original capacity. So on average:

2.4 * 0.8 (adjustment for average original capacity) * 6,000 * 2.1 = 24,192. You need to compare that against the battery's price. As long as Eskom's price increases are in line with what a risk-free investment would have earned (say keeping your money in your bond), then it future increases would have no impact on this calculation (although you can argue that you have hedged out uncertainty about what those units will cost you, which does have value).

Depending on your municipality, electricity could have a different price and you could also be charged more or less after a certain amount of units.

For me: Buying my batteries (and consequently an inverter) on its own wasn't as much an "investment" in electricity cost savings as it was an "investment" in being able to be hedged against loadshedding. I decided that having the predictability of my evening routine is worth at least something to me. So it was a luxury purchase that require no further justification. Purchasing solar panels was therefore the only cost I need to factor into deciding whether the electricity savings is worth it to me as an "investment".

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1 hour ago, jykenmynie said:

For me: Buying my batteries (and consequently an inverter) on its own wasn't as much an "investment" in electricity cost savings as it was an "investment" in being able to be hedged against loadshedding. I decided that having the predictability of my evening routine is worth at least something to me. So it was a luxury purchase that require no further justification. Purchasing solar panels was therefore the only cost I need to factor into deciding whether the electricity savings is worth it to me as an "investment".

I'm in the same boat there. I wanted predictable energy. Once I had decided that was a goal; I did not really bother looking into ROI too much. All I know is the more I get off the grid, the more predictability I will gain. So far, I have managed to keep my lights on, including every plug in the house during the two load shedding events since the system was installed. At that point, I couldn't care less what the ROI is; I had power. 

The other question I wanted to answer was this: If Eskom magically ended load-shedding, tomorrow - would I still pull the trigger on the solar setup? Yes, yes I would. 

Edited by Rclegg
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1 hour ago, Plaashaas said:

Just 2 more panels babes then I am done 🙂

Just be warned! During load shedding babes is going to watch her favorite program, and you might end up running around like a serious operator monitoring battery view, inverter, watchpower, ICC and whatever to try and not look like the fool who spent that bucks on the rabbit hole😁

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My question was self-consumption, I already have two 2.4 Pylontech’s, which gives me 3.8 kWh’s per cycle, with my 4.2 kWp of solar panels, I could charge additional batteries, so is it worth adding more batteries or just going with Eskom 

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6 minutes ago, Gerrie said:

Just be warned! During load shedding babes is going to watch her favorite program, and you might end up running around like a serious operator monitoring battery view, inverter, watchpower, ICC and whatever to try and not look like the fool who spent that bucks on the rabbit hole😁

I'm pretty much off grid. The only way we know its loadshedding is the messages on the community group. That's why it is becoming more difficult to expand the system. 

Edited by Plaashaas
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23 minutes ago, Tariq said:

so is it worth adding more batteries or just going with Eskom 

I don't think it is worth it. It might be nice, but not worth it.
What is there that you currently cannot do during the 2 hours loadshedding inside that 3.8kW?

And then being smarter with your usage might be a better investment. For instance I am planning to add a little feature to my VenusOS driver that will change the SOC limit when load shedding is announced. Then I can set my min. to 30% and up it to 50% when there is load shedding. This will cost me no extra batteries. Just better use of those that I do have already.

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31 minutes ago, Tariq said:

My question was self-consumption, I already have two 2.4 Pylontech’s, which gives me 3.8 kWh’s per cycle, with my 4.2 kWp of solar panels, I could charge additional batteries, so is it worth adding more batteries or just going with Eskom

This adds considerable context to your economic calculation and involves the "Law of diminishing returns".

A hungry man might pay $100 for a sandwich, but only $50 for another one and probably wouldn't even take a 5th one for free.

The short answer if your battery capacity has already completely fulfilled its purpose:

Then it's not only cheaper going with ESKOM than using battery power, it also doesn't add any personal value that you would be willing to pay a premium for.

We know this because otherwise people would expand their battery capacity ad infinitum, and they don't.

Edited by phil.g00
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2 minutes ago, Louisvdw said:

For instance I am planning to add a little feature to my VenusOS driver that will change the SOC limit when load shedding is announced. Then I can set my min. to 30% and up it to 50% when there is load shedding.

Can you please share that once done? That's something I've been meaning to look into.

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4 minutes ago, Tariq said:

My question was self-consumption, I already have two 2.4 Pylontech’s, which gives me 3.8 kWh’s per cycle, with my 4.2 kWp of solar panels, I could charge additional batteries, so is it worth adding more batteries or just going with Eskom 

Ah, that changes it.

How long does your current batteries last for when used for self consumption? I'm guessing they already easily last through a loadshedding stint?

I doubt you'll get a quick ROI if that is what you are after (you definitely won't if it's financed) and your goal doesn't seem to be going as off grid as possible. For you I would say it will most likely not be worth it. Even if you factor in a very conservative 6% Eskom increase a year along with a 3% loss in capacity in the battery (to get to the ~85% SOH after ~1675 cycles mentioned in the report) you'll only reach R15k worth of battery usage after 9 years at 80% DOD on a US2000 (if my quick math is correct). And that's if you run them down to a 20% SOC daily.

I think a potential factor to consider would be determining how long your 2x US2000's lasts you when being used for self consumption and if it'll be worth adding another.

And like Louis mentioned you can always change the self consumption to not go lower than the percentage needed to easily get you through a loadshedding stint and when we potentially have weeks of non-stop loadshedding next year you can change that to a much higher value or even set it to keep batteries charged which will then cope with an evening and morning loadshedding stint. Yes, it's not exactly part of the question, but that's something that is normally in the back of your mind when figuring out battery capacity (at least for me).

It's a nice to have, definitely, but I think most people are after something that will easily cope with a stint of loadshedding along with the added benefit of using it during the evenings and getting more value out of your PV by charging the batteries with it the next day.

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Too bad feed-in is not a worthwhile option in Cape Town, then my panels would not be loafing half the day, even though the geyser and appliances ( tumble dryer, washing machine and dishwasher ) are hooked up also

Edited by Tariq
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1 hour ago, Tariq said:

Too bad feed-in is not a worthwhile option in Cape Town, then my panels would not be loafing half the day, even though the geyser and appliances ( tumble dryer, washing machine and dishwasher ) are hooked up also

Also in CT and understand what you are getting at. I currently have about 7 to 10kwh of lost solar generation as batteries are full and solar generation is 3 times the active loads from the house during the day. And this will be more in summer. 

My plan is to be as independent of the grid (CoCT) as possible and the only way to do that is to increase my battery bank to cover me for 24 hours. My batteries gets to 20% SOC by about 01:00 if I let it supply the whole house. Currently I have 3 x 3.5kw pylontech batteries with the plan to build it up to 8 batteries in the bank. 10kwh of lost solar generation power per day is a lot. 

It's also more than just ROI for me at this point as I already cut myself off their water supply after they hiked the water tariffs during the drought. Zero water bills for the past 2 years.

CoCT electricity tariffs are some of the highest in the country and at this point I would rather spend another R100k by adding 5 more batteries than giving them a cent more than I have to for them to continue subsidising everybody else. 

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2 hours ago, fredhen said:

It's a nice to have, definitely, but I think most people are after something that will easily cope with a stint of loadshedding along with the added benefit of using it during the evenings and getting more value out of your PV by charging the batteries with it the next day.

In my case, I will keep adding batteries until I can't charge them all during the day using the PV. I want to get as much as I can out of my panels; currently after 10am (When the single Pylontech I have atm is fully charged) My PV drops from 4kw/h to 1.6kw/h (House + pool) - So I am "wasting" up to 12 Kw/h a day - 370 kw/h a month. So for me, adding another one or two batteries is worth it. So happens that the second Pylontech should arrive on Thursday. 

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8 hours ago, Tariq said:

Trying to figure out if self consumption is worth it, with Eskom at currently R2.10 per kWh and a Pylontech 2000 costing R15,000, unless I am completely wrong in calculating the ROI ( 1 cycle per day ), it comes to over 10 years and even if you threw in Eskom price increases, it can’t be less than 7 years or so, also the battery  money could be earning interest in a certificate of deposit.

    Can somebody tell me where I have gone wrong in my thinking

A lot of people will argue ROI back and forth, including this, exclusing that. 

For me it was simple. (Below based on my load profile, including opportunity costs of 10% (I am an accountant and can’t ignore that, and 7% Eskom increases)

Option 1: Backup Only > No Payback

With load shedding a reality, the battery and basic inverter charger that matches your real critical load (eg. TV, Lights, Wifi) is for security and comfort - 2kW Inverter with 2.4kW Pylon. As you charge with Eskom, this can never have payback (unless you have time of use tariffs and can do load shifting like some direct Eskom customers)
 

Option 2: Solar Only, No Battery

For me, this would have meant Panels (Limited to 3,6kWp), String Inverter and No export. Thus self consumption of base load. This is the best payback. For me 3 years and increased use of pool pump.

Option 3: Hybrid

3.6kWp Panels, Hybrid Inverter, 1 3.6kW battery. 12 years payback. For me that was not acceptable as I do not even known if I will live in my house by then. 
But, as I was willing to invest in Option 1 regardless, I subtracted the costs of that option.  Got me to 7 years with increase use of pool pump over baseline. Note - I did most of the install myself.

Bottom line

- one can “argue” any which way to justify your decision. And those qualitative factors are very personal.

- Batteries kill the ROI

- Most quotes I got, the solar middlemen killed the ROI

- Do not over invests, as panels can quickly become idle (see comments above) which will lead to batteries which do not have payback. 

- Export is not an option, even if it is allowed. It is structured in such a way to not make sense. Which makes sense in itself, why will a utility get you to pay zero and have that backup infrastructure coming to your doorstep. 

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IMHO load shedding is not going to get better, it is only a matter of time and it will get worse. I want to be be ready for when (not if) it gets worse. I also waste about 5kwh to 8kwh of solar per day as the batteries are already full by 10am even after the geyser is hot and all washing loads are done. Adding batteries is the only answer for all the solar going to waste. 

One thing I have learned in this country is that we cannot depend on government. We must not have the mentality of: ”the government must provide for us” We need to provide for ourselves. And the sooner we get off grid, the better for us. 
But like I said; this is just my opinion, feel free to disagree. 😊

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