- Status
chetansha
Juggernaut
Off grid does not make economic sense nor is it environmentally friendly as it uses battery for storing power.
What is you inverter specs, while it would be ideal to have matched panels. You can mix them with a higher rated panel depending on the inverter specs, it will offcourse result in some less then optimum output but it will work.
It does make economic sense depending on whether you build the solar yourself or get a installer .
For me it was simple, since I installed every single thing myself from scratch, with zero subsidy with the best possible components, it worked out cheaper then a On grid/grid tie solar with subsidy.
Last edited:
N
NotMyRealName
This is something very few people understand and just fall into the whole "solar" hype instead.
The only way you save money using solar is by installing (more than) enough panels for your load and then if you have nighttime use, use the grid. Batteries are the single biggest hurdle to solar being profitable. It's very simple math.
Nope, the recurring battery costs will never be as cheap as paying the grid for power, which works out to a small fraction of the cost of batteries and their replacements and their replacements and their replacements... ... ...
I have answered this numerous times. In the other thread bunch of good discussion in this thread https://techenclave.com/threads/looking-for-a-home-ups-that-is-smart.186404/page-7#post-2171539
N
NotMyRealName
Sure, there's been a lot of discussions there and a WHOLE lot of calculations but never summarised into what really matters.
Assuming panel life is 20 years, over that time period:
1. What is the total cost of batteries, their maintenance and replacements
2. Alternatively, how much do you pay the grid for nighttime use only. (Since your panels are enough for your daytime load)
Very simple. Answer this without bias or twisting facts to suit the narrative. I have friends who work selling and installing consumer solar products and they say it never works out cheaper than grid.
For me it costed 56k for 7.2kw lead battery pack with 5 years no questions asked full replacement warranty. In my personal experience with those type of batteries then last about 7 years on average. But like I said in those thread On grid/grid tie means when the grid supply fails you get no power from solar. So people buy another regular inverter and batteries, which they forget to mention.
A typical single battery inverter is only good for lights and fans and electronic devices, its not adequate for large appliances.
In my case I have yet to install/buy the panels due to covid. But I have calculated and accumulated lot of load data.
In my case I need to run a pressure pump without which I will not get hotwater from solar water heater(grid tie is ruled out), I intend to take the hot water line to the Dishwasher( also lg dishwasher starts from first if power fails which is unacceptable), washing machine, when those two are not running and if its in summer it will substituted by 1.5 five star inverter acs and a .8ton 5 star inverter ac( which consume less then 300w and 200w respectively after it reached the set temperature).
In night time use there is a 50w load from the inverter self consumption, 50w load for router,cameras, 8tb external HDD, intel J5005 based PC-NVR/NAS and 50 to 150watt load from refrigerator depending on whether its cooling or defrosting. Fans are BLDC, right now they are not switched On in the night but in summer they will be running so about 80w for all the fans in summer. 1kw for the dishwasher when it has cold water(not sure how much it will consume when fed with hot water. When there was a power cut yesterday the inverter was showing a amp draw of 2.8 to 3.2amps constant at 12am.
So let say the solar panels star producing the power at 9am to 4pm, they will probably still be producing power even before to power loads less then 100w.
I did do a test back in jan2020 where I switched off the input mains to the inverter, my batteries give a backup of 26hrs (no air conditioner running) at which point they have about 30% battery left give or take 5%.
Since then I have added a dishwasher, more cameras. So it safe to say that without air conditioners I will get a full 24hrs of back up.
But the biggest difference to my calculations of cost vs others is that I installed and got everything at wholesale prices and zero labor, this itself saved me lakhs vs a the average joe who buys them from a dealer and get them installed.
My inverter again doesn't require batteries, it can work directly with just solar and if the load exceeds what the solar panels make, they take the remaining from the grid.
N
NotMyRealName
The whole problem, I've realised, is that most solar providers know the basics of plug and pray without understanding how to tailor solutions to requirements. When i say i want a solar setup without batteries, but running on the panels without grid and then switching to grid only when the output is insufficient they are stumped. Just one guy said something like, that will need a hybrid inverter which is available only in Australia/NZ etc.
Your last para indicates you have such an inverter already. So what you said in the first para is not applicable to you even though you're grid tied technically.
So anyway, till we factor in the two simple questions i posed earlier, we cannot calculate cost effectiveness in the overall scheme of things.
Your last para indicates you have such an inverter already. So what you said in the first para is not applicable to you even though you're grid tied technically.
So anyway, till we factor in the two simple questions i posed earlier, we cannot calculate cost effectiveness in the overall scheme of things.
One thing every one is forgetting in my state power corporation charges 7.50rs per unit if i cross 400 unit consumption upto 400 unit they charge 3rs per unit(if i consumes 600 unit they will charge 4500rs from me but if i consumed 400 they will charge 1200 rs)if i can keep those unit to 400 with help of solar plant then i can save more then 3000rs per bill. @adder i also installs most of stuff my self.i have 2.5kv solar inverter,2 tubular batteries with 1200 watt panels it cuts down main supply line as soon sun rises.if i need power in between i can override it.
Thats because those solar providers only install grid tied ones, where the profit margin is huge. I would have gone with grid tie model and saved even more on cost but they the escoms won't allow it, you have to buy from their approved installers, where the escoms and installers make good money even more with subsidy.
I could have downsized my batteries, my wiring and what not just like the installers but because I did it myself, I got the best bang per buck which will be superior to any installer here in india.
Now that I have the 7.2kw batteries its good to see my washing machine with heater on and dishwasher running when there is no power. Hell I switched on a twin cylinder 3hp air compressor on backup, it probably would have been too much if I had small sized batteries.
In 5 years time I will mostly would have switched to Lifep04 batteries and they should have cycle life of 8000 and upon which still have more then 70% capacity after that.
what hybrid inverter?all types inverters are common in india.my inverter operates on both solar panel and batteries at same time.it charges batteries from solar panels if sun is out it charge batteries from grid power also.if i want totally solar charging all i have to do is turn a switch and it will not consume grid power for charging batteries.i have another sensor installed which cut down grid power when sun comes out.can you elaborate more on this? hybrid inverter
thanks
@adder You seem very knowledgeable about solar and after quickly glancing through the other thread, you and rdst seem to be planning to build a Tesla power-wall equivalent of your own, super interesting!. I would be interested in that project as well, but I don't know much about these things, will read up from now. Whenever you begin the project please loop me in as well if you guys plan to do a group buy.
For now, I am looking to install a 5kw on grid system at my home in BLR, thinking of going with Vikram/Waree Mono 390 panels and IQ7+ micro inverters. Checked with BESCOM and a couple of suppliers, they are quoting about 3.5L for the whole project. Any suggestions or advice you have would be sincerely appreciated.
For now, I am looking to install a 5kw on grid system at my home in BLR, thinking of going with Vikram/Waree Mono 390 panels and IQ7+ micro inverters. Checked with BESCOM and a couple of suppliers, they are quoting about 3.5L for the whole project. Any suggestions or advice you have would be sincerely appreciated.
rdst_1
Juggernaut
I had enquired and researched about the Micro-inverter route, but it doesn't make sense at all if you are going for a 5kW setup. Micro-inverters are good if one wants to start small, with just a couple of panels and then keep adding panels one-by-one. So in that case, one doesn't have to buy a big inverter which is generally more costly. But for a 5kW setup, just buy a good 7.5-10kW (for future-proofing) hybrid inverter (like the models discussed in the other thread). Adder swears by Exide Solar batteries and rightly so. In fact even for my normal Sukam 3.5kVa inverter, I am going to buy the same Exide Solar batteries only.
Both, me and Adder, have spent quite some time trying to make Solar work and he will be the first one to go ahead with his setup and I'll have to wait because govt supplied electricity is very cheap in my state.
But when finally LiFePo4 batteries become cheap in India, I'll definitely setup my own solar setup as well.
Yes I will inform people here and we can start a GO but COVID has put a lot of brakes on everyone, including getting cheap batteries from china.
Another option I am thinking of getting used batteries from scrapped /accident EV, while the batteries in them may have a life of only 60 to 80% depending on the chemistry, for static storage for solar its would work great if the EV battery is of lifepo4 and the price would be just a tad more expensive then lead acid. If the EV a regular NMC or NCA chemistry then they have lower cycle life then lead acid battery, although after 5 year mark the lead acid will have a steep dive in capacity while the NMC or NCA would have stagnated.
Tesla model 3 and Y cars in china will switch to lifepo4 so we can expect some good cheap cells in used market.
Micro grid inverters sadly cost a lot more, its good for large scale solar plants but for residentual use it doesn't make sense. The prices you have got is high not sure how much the micro inverter is to blame.
Another option I am thinking of getting used batteries from scrapped /accident EV, while the batteries in them may have a life of only 60 to 80% depending on the chemistry, for static storage for solar its would work great if the EV battery is of lifepo4 and the price would be just a tad more expensive then lead acid. If the EV a regular NMC or NCA chemistry then they have lower cycle life then lead acid battery, although after 5 year mark the lead acid will have a steep dive in capacity while the NMC or NCA would have stagnated.
Tesla model 3 and Y cars in china will switch to lifepo4 so we can expect some good cheap cells in used market.
Micro grid inverters sadly cost a lot more, its good for large scale solar plants but for residentual use it doesn't make sense. The prices you have got is high not sure how much the micro inverter is to blame.
i can help you in panels.Buy vikram panels these are really good penals and tried and tested.price you mentioned is insane.a 10kv solar system costs around that much price with tata panels which are most are most expensive one.i enquired about panel for chetansha which he had asked.solar panel prices have gone way down dont get yourself looted.adani mono panels are around 22 and simple one 20rs,tata ones are 25,26rs per watt vikram panel is same around adani.havent used these iq7 micro inverter so cant say anything.we are using solar inverter with batteries so we bring down DC cable from rooftop to solar inverter directly.my cousin have installed one controller like thing it draws 30% extra dc power from panels.sorry i forgot name of that equipment.if you are spending that much money buy 5kv solar inverter with batteries and panels.simply dont pay that much amount
N
NotMyRealName
Didn't you say earlier that your inverter doesn't require batteries? So why are you using them? For when there is no panel output AND the grid is offiine?
Btw, this thread has now gone into the same hypothetical discussions and calculations as the other thread and we've added Li-ion battery tech to it again just like the other one.
It's pretty obvious, if you were to just calculate, that batteries kill the entire VFM or ROI calculations and Li even more so. Neither you nor @rdst_1 have actually implemented a setup nor are giving cost figures which i simply asked above. Till then all the calculations remain hypothetical and based not on reality but wild assumption. It's just endless discussion without a final figure.
Let me repeat the question once again (copy paste from above):
Assuming panel life is 20 years, over that time period:
1. What is the total cost of batteries, their maintenance and replacements
2. Alternatively, how much do you pay the grid for nighttime use only. (Since your panels are enough for your daytime load)
Unless the cost of #1 is lower than the cost of #2 it makes no sense. Please PLEASE answer this question before going on with endless discussions and calculations. Because if we can't answer this then we simply don't have enough data and our entire premise may be faulty.
We're not even calculating the cost of the panels, installation (whether self-done or otherwise) etc. (everything except the batteries) because that's daytime running. And we're assuming that it will pay off cheaper than using grid power in the daytime. It may turn out that even that is more expensive than just paying your grid bills and forgetting about solar in the first place.
So i asked this guy about an inverter which is grid-tied as in it will power the load directly off the panels when there is enough panel output (sunlight) but will feed off the grid when it's too dark (or night). Without batteries at all. His answer was that this requires a 'hybrid' inverter, as in normal inverters will not do the task without batteries in the setup.
@Julian yes it doesn't require batteries its optional. but ON GRID/GRID TIE inverter DOES NOT give back up when power supply fails, for me running a pressure pump is critical, running a Air con in summer when the power fails is critical. Hence the need for batteries. Now I would have loved too get the panels first and then the batteries, while lead acid battery prices have remained stagnant, not so the case with solar panels. Each year the price seem to be dropping by 10%, on top of that since 2019 there was duties applied on solar cells imported from china and the duty was supposed to reduce every year, to give indian makers to become competitive, that was until india china clash, now god knows whats the current situation about the drop in duties.
To your question on battery and maintenance cost
I told you the cost at which I got 56k for 7.2kw and @rdst_1 t got a even lower quote for the Exide battery.
They are guaranteed for 5 years, but they last on average 7 years and they become unusable by 8 to 9 year mark, meaning the capacity would have dropped below 50%, at 9 year mark the cells inside can become bad. Let say at 5 year mark still within warranty, you can stress the battery by running deep 100% cycles and kill the cell and still get a new replacement. What exide guy told me was that if a cell becomes dead within warranty or if runtime is really low they will replace the battery free of cost.
Having had past experience with C10 batteries it lasted 9 years for me before the APC smart UPS started showing the replace battery led.
Maintaince its needs distill water top up every 10months based on bangalore weather.
So if you go with grid tie, you will still need to buy batteries for your current inverter or buy both the inverter and battery.
2nd question
In my city the prices for night are the same as day. Unless its summer the daily night time load will come to about 2.6kw to 2.9kw, in summer with the AC running 4.5kw daily when no solar is generating. Its hard to calculate that in cost because putting solar off grid will itself lower my slab rate, I am currently hitting the Rs7.8 slab every month and the 1st and 2nd slab averages to Rs4.76 for the first 100units. Next 100 units cost Rs6.75 and the last slabe one costs Rs 7.8 and I consume every month more then 400units (split between 2 meters which I load balance to make the slabs even), in summer it crosses the 500, this year due to dishwasher it may cross the 600 units, then again in summer the dishwasher consumes less since I would have started to give the dishwasher with 60C hot water supply from solar water heater. So I cannot permute exactly in cost due to slabs how much I will save. But it will be a lot just due to the fact that the slab goes down.
So with my current batteries it does well for every single night other then summer, unless I want to discharge the batteries to 80%, in which case the batteries should last only 3 years i.e there capacity drops below 60% but since exide replaces no questions asked within 5 years, I could in theory discharge them to 80% every day and after I get new batteries get another 3 more years.
As far as lifep04 goes, the prices I got in 2019 was Rs17700 incl 18% GST for 12.8v 100ah equivalent PRISMATIC format battery,(you will still need a BMS which costs extra 1k) to compare a exide 100ah lead acid battery costs 10k to 11k, but lifep04 battery has 3x to 5x more life, again unlike lead acid battery they will still work with 70% capacity there after.
Now you said unless cost 1 is less then cost 2, its will not make sence, its not black and white.
In my case I would have any way spent atleast on two 150ah batteries for my regular APC smart UPS. IF you have a ON grid inverter, answer this question if power fails will you light candles.
To your question on battery and maintenance cost
I told you the cost at which I got 56k for 7.2kw and @rdst_1 t got a even lower quote for the Exide battery.
They are guaranteed for 5 years, but they last on average 7 years and they become unusable by 8 to 9 year mark, meaning the capacity would have dropped below 50%, at 9 year mark the cells inside can become bad. Let say at 5 year mark still within warranty, you can stress the battery by running deep 100% cycles and kill the cell and still get a new replacement. What exide guy told me was that if a cell becomes dead within warranty or if runtime is really low they will replace the battery free of cost.
Having had past experience with C10 batteries it lasted 9 years for me before the APC smart UPS started showing the replace battery led.
Maintaince its needs distill water top up every 10months based on bangalore weather.
So if you go with grid tie, you will still need to buy batteries for your current inverter or buy both the inverter and battery.
2nd question
In my city the prices for night are the same as day. Unless its summer the daily night time load will come to about 2.6kw to 2.9kw, in summer with the AC running 4.5kw daily when no solar is generating. Its hard to calculate that in cost because putting solar off grid will itself lower my slab rate, I am currently hitting the Rs7.8 slab every month and the 1st and 2nd slab averages to Rs4.76 for the first 100units. Next 100 units cost Rs6.75 and the last slabe one costs Rs 7.8 and I consume every month more then 400units (split between 2 meters which I load balance to make the slabs even), in summer it crosses the 500, this year due to dishwasher it may cross the 600 units, then again in summer the dishwasher consumes less since I would have started to give the dishwasher with 60C hot water supply from solar water heater. So I cannot permute exactly in cost due to slabs how much I will save. But it will be a lot just due to the fact that the slab goes down.
So with my current batteries it does well for every single night other then summer, unless I want to discharge the batteries to 80%, in which case the batteries should last only 3 years i.e there capacity drops below 60% but since exide replaces no questions asked within 5 years, I could in theory discharge them to 80% every day and after I get new batteries get another 3 more years.
As far as lifep04 goes, the prices I got in 2019 was Rs17700 incl 18% GST for 12.8v 100ah equivalent PRISMATIC format battery,(you will still need a BMS which costs extra 1k) to compare a exide 100ah lead acid battery costs 10k to 11k, but lifep04 battery has 3x to 5x more life, again unlike lead acid battery they will still work with 70% capacity there after.
Now you said unless cost 1 is less then cost 2, its will not make sence, its not black and white.
In my case I would have any way spent atleast on two 150ah batteries for my regular APC smart UPS. IF you have a ON grid inverter, answer this question if power fails will you light candles.
Last edited:
N
NotMyRealName
We're doing a basic cost analysis. Let's give solar the benefit of the doubt. So we'll assume everything is ideal and the grid never fails. Or for my critical equipment like PC/covid ventilator i have a separate UPS. I'm not looking at the practical applications. We're starting with cost to check the feasibility itself first. We work from the ideal, perfect calculation and then add our problem areas later.
Let's assume our day/night load is the same. Say 1000W. Let's say we're looking at a 50% DoD. That should give us a battery life of 7 years right? Please correct me and change figures as you see fit. So for the 20-year period we're looking at replacements twice. So that's 3x the cost of the batteries. Now how many batteries do we need to power 1KW down to 50% DoD for the nighttime hours? I just need an educated guess not a super accurate figure.
2nd part, say we don't have this setup at all for a clean slate. What is our bill for using the grid for the nighttime hours when we would be using the above battery setup. That's the power bill for 20 years. Again rough estimate.
How can you say it's not black and white? If your power company bill for 20 years totals 5 lakhs and your batteries with 2 replacements at the end of every 7 years totals 7.5 lakhs, isn't that clearly a bad deal?
The daytime running (utility bill minus panel etc. setup cost) is another calculation after we've nailed this one first. I want a straightforward equation, not figures here and there which don't add up. Thanks for all your inputs mate.
Let's assume our day/night load is the same. Say 1000W. Let's say we're looking at a 50% DoD. That should give us a battery life of 7 years right? Please correct me and change figures as you see fit. So for the 20-year period we're looking at replacements twice. So that's 3x the cost of the batteries. Now how many batteries do we need to power 1KW down to 50% DoD for the nighttime hours? I just need an educated guess not a super accurate figure.
2nd part, say we don't have this setup at all for a clean slate. What is our bill for using the grid for the nighttime hours when we would be using the above battery setup. That's the power bill for 20 years. Again rough estimate.
How can you say it's not black and white? If your power company bill for 20 years totals 5 lakhs and your batteries with 2 replacements at the end of every 7 years totals 7.5 lakhs, isn't that clearly a bad deal?
The daytime running (utility bill minus panel etc. setup cost) is another calculation after we've nailed this one first. I want a straightforward equation, not figures here and there which don't add up. Thanks for all your inputs mate.
- Status