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Wet grinder uses lot more instantaneous power than you think. more like 1000+ watts and its an inductive load, so if you are already close to maxing out your pcu, it will trip.

the disadvantage with offgrid systems is they will generate only as much as your critial loads need and waste rest of the energy.

The advantage of a hybrid inverter is, some good ones come with a CT coil that can be installed near your meter and apart from powering your critical loads, they can sent power towards your non critical loads as well and then if they need more power, that is imported from the grid.

The CT will prevent the inverter from sending power towards the meter hence nullifying the need for netmetering.

However, cost definitely comes into picture.

i would bet on LFP batteries if you have the money, but there is surely some uncertainity about reliability, so its needs to be a well thought out decision.

With 4 x150ah batteries, if you go for solar tubular batteries from Exide they come with 5 years full replacement warranty, they are rated at 1200+ cycles at 80% DOD. So when you only discharge to 50%, it should last 3000 cycles. Nothing stopping you from discharging to 80% and getting a warranty claim at 3 year mark.

When choosing the inverter make sure its the high voltage type mppt input. So at a latter stage you want to go to grid tie, both inverters can share the same panel with a simple DC switch.

Since you are in Bangalore, its better to go off grid because of the high fixed santioned load charges every month.
You could probably lower the sanctioned load to just 0.5kw after going off grid solar.

Also in most cases DIY solar off grid installation with batteries is still cheaper then grid tie installation with subsidy.

A 2.5 to 3L Wet grinder hardly consumes 150w. Same goes to washing machine in cold cycle.

Since its a new house install bldc ceiling fans, get a 5 star inverter AC, these have no inrush current and can run on the inverter.

Use induction stove, washing machines all on solar (in off grid solar installation, you need to milk every watt produced by solar). Use a smart sockets or timer switch to switch ON appliances one at a time. Reason being is with 150ah lead acid batteries you can only charge at max of 15A to 20A (so 48v x 20A is only 960w). So the excess solar all needs to be utilized by heavy appliances or EV charger.

Thank you for the feedback. As aim120 indicated below, today's solar tubular batteries have much higher life cycles and are rated 1200-1500 cycles even at 80% DOD. They cost higher though at around 18k+ for 150Ah.

This is supported by most off-grid inverters as per my understanding, but would definitely reconfirm.

Thank you very much for all your suggestions. Yes, the power consumption calculation I did above already considers BLDC fans and will definitely look at smart sockets as well to ensure maximum utilization.

Had a very basic query for members here. For some reason, I am actually more confused about the topic after watching Youtube videos.

For an OnGrid system, does the power generated from the solar panels directly go into the Grid without servicing any load from the house (i.e. Do the appliances in the house continue to pull power from the Grid?)

Let me explain some scenarios:
1. If the load in your house is say 1kw at a certain point, and the generation from the solar panels is 500w, then 500 additional watts will be used from the grid along with the generated 500w. So that way, the 1kw load is satisfied.

2. If the load in your house is 1kw, and the generation is 2kw, then the house load of 1kw is used up directly and the rest goes to the grid.

The meter that records the import and export of electricity is called as a bidirectional meter.

In case 1, the meter would count the 500w used from the grid as imported power.
In case 2, the 1kw power that goes out to the grid is calculated as exported power.

The power that gets used up directly from the panels in the house would not even be shown in the bidirectional meter. That's why usually there is another meter that's wired to the solar panels that's exclusively going to count the generated power. But now I am going more into specific implementations.

The solar DC from panel is converted to AC via a inverter and then sent via the bi-directional meter to the grid without servicing the home (when grid power supply goes down, your inverter will stop supplying power), in hybrid inverter its serves the home and exports the remaining.

The on grid/grid tie inverter will analyze the grid voltage, it then increases the voltage slightly by 0.1v or lower to reverse the flow of the electrons into the grid. So your appliances is technicaly still consuming the power you produced. Since electricity is going to go to first to load which is near.

Thanks. I am not sure if I am imagining it, but both your explanations seem to point the in the opposite direction.

The reason for my concern all of a sudden is the news going around that KSEB is planning to introduce gross metering instead of net metering.

As far as I understand this particular concept, it would only become a concern if the On Grid setup always sends the power generated to the grid directly and the house continues consuming power sent from the Grid (at least as far as the bidirectional meter is concerned).

In this case, the units consumed would take us into Non telescopic billing in some months (just my estimations for now since we haven't really spent a proper year in this old house to date). With gross metering we would end up paying Rs. 6.2 per unit for all the units consumed in the month while I am sure KSEB pays a lot less for the units we generate through Solar.

I'd imagine that this is why news articles mention that Solar adopters would take 10+ years to break even.

First of all, there is only one set of electricity cables from the grid to your house. So, you cannot send power as well as receive it via the same cable. Electricity can only go in one direction at a time. So, as far as I can see and also what I experience with my grid tie system, the inverter will first serve the house first and then serve the grid.
As Aim mentioned, this control is achieved via a small voltage increase/decrease by tracking the voltage/phase of the grid.

The main difference with net metering and gross metering is that, in net metering, the cost incurred will be imported units - exported units. So, if you import 200 units and export 100 units, you will be charged for 100 units at the applicable slab.
In gross metering, you will be charged for 200 units at your applicable slab, and reimbursed for 100 units at the agreed upon rate (usually less than the rate you would pay).

The main reason why gross metering will take longer to break even is that, the generation and consumption patterns are usually different. For example, large loads like water heater tend to be used early in the morning when solar generation is not much. So all of this is on the grid. Applicants like refrigerators work 24/7 but the generation is only between 10 and 4. So, what you would see is that, over half of your consumption is usually directly from the grid just due to the time of the day. In net metering, even if you use the heater in the morning, that gets offset by the power sent back in the afternoon.
In gross metering the calculation is not so. That's why gross metering takes longer to break even.

As far as I know, net and gross metering only differ by how the calculation/billing is done. The actual electrical connections and even the meter is the same in both cases. I would be happy to be corrected as I am not that experienced with gross metering.

Both net metering and gross metering will send power to the grid via the same incoming cable. Its only bills different.
As said in my earlier post, you are still consuming what you have produced.
But in most Hybrid inverter you have a seperate AC out for house and seperate AC out for Grid.

Unfortunately this trend of shifting to gross metering is happening world wide due to the greed of the power companies. So many end up using batteries, atleast you get backup. Also in Karnataka you need to pay 117/kw every single month as fixed charges as sanctioned load and can export the power= equal to the sanctioned load.

So in the future when we have EV with V2L, like Ioniq 5, EV6 and Atto 3. You can charge the batteries of the EV and use the V2L of 3.3kw to power heavy appliances.

When car companies like Tata (which have high cycle LFP batteries) as they said in auto expo start implementing V2V, one can DC super charge other EV vehicles, I am sure there will be some app developed for the owners of EV to sell the power. This will solve the availability and wait time for charging and also give no reason to with grid tie inverters.

As you can imagine, it is impossible to run your house in such a way that it is continuously consuming equal to or more than what your solar is generating. You can try your best but it is still challenging. If you need best usage of solar enery for home loads, you then need a hybrid inverter with a battery bank connected to it and battery set as top priority for home loads. But then with this you are cycling the battery and it might end up costing way more than what you would save if you had to pay if using gross meter apart from the initial cost of hybrid inverter and batteries.

LFP batteries are best used for this purpose due to they high cycle count. I converted my setup to a hybrid with a lfp battery and hybrid inverter due because i am crazy but it does not make much economic sense to the average person.

I still don't cycle the battery since i am on netmetering, so why stress the battery when the grid can be your battery. Hopefully the battery lasts for ever this way.

with my current model, my energy monitor tells me i use a max of 30-35 of the solar power directly without sending to the grid. rest goes to the grid and comes back when solar is not available. might be slightly better in summer, but i have not checked and am unable to check back since i moved systems and lost data.

Hi,

Thanks for the reply. I am away from my home and also had no internet access to respond. Once I go back which is still a few months will try DIY setups to monitor.
I did manage to get some readings with the help of my parents over phone call.

The issue repeats often only on sunny days during the peak power time resulting in over voltage cut off. So, I was wonder what are the chances that Grid fluctuates only during peak generation time on sunny days but stays within range during cloudy days?


So, I asked my parents to hook up a digital multi-meter to our house power outlet and monitor the voltage continuously for couple of days. The interesting observation is that in the inverter datasheet it shows that in low light/evenings the voltage is lower than our house plugs which makes sense but during the the day the voltage in our house power outlet increases eventually which is what inverter is shelling out. This means the rise in voltage is from inverter side not the grid, I'm aware that to export the power the inverter has to have higher voltage than the grid. So, I asked in home to disconnect solar inverter using isolator switch when the voltage is higher around the peak time. Immediately after the disconnection the voltage in the house power outlets drops back to 230-235ish but when the inverter is connected back to the grid(and the house) the voltage rises to 255-260+ and cuts off as safety precaution but without any error code. Repeated this for couple of days at different times to make sure the observation is not erroneous.

My doubt is that inverter is having an issue. May be the MPPT is not doing its job properly to figure out the optimal voltage and current. I even calculated for the voltage drop due to the distance between inverter and the load which should be less than 1.2% in worse case scenario. Accounting for voltage increase due to the distance should not cross 250V.

Tired of communicating with installer/inverter team. They keep playing blame game on each other and on other components though all are brand new and in warranty. Still figuring out the way to solve it.

Folks here who are planning to get solar rooftop, make sure the installer is technically sound. It is a worthy installment for sure, just needs a better people to handle it. Ask around in forums and do proper research in choosing the components.

I'm having an issue in understanding the net metered bill in Karnataka. We got our first bill finally after months. In the bill the energy exported is much lower than the energy generated after consumption. I understand if there is a small difference in units here and there but the difference is a bit significant. I want to know anyone here to give some clarity on the billing.

In our 1st month bill and 2nd month bill energy import and export doesn't add up to total generated units. There is a difference of 322 units so far between total generated shown in the inverter and shown in the meter. That is for every month loss of around 80.5 units (4 month old plant).

1.) Is the billing process done by the same person who bills the regular meter? I'm told a separate person JE (Junior Engineer) comes to bill the solar installations.

2.) If above is true then we have not seen anyone come to our house and take the readings before billing but they just come directly with the bill already prepared on 1st of the month. I am not sure how are they able to record the import/export units without visiting the site. The bill generated date and delivered date are the same and the bill is A4 sheet with lot of columns which requires a computer printer.

I understand your concerns completely - been through it personally and have even gone and met the accounts folks at bescom to reconcile and understand their process. My initial bills never reconciled and I have left it at that and now keep a close watch on the recent bills. They show you a ton of adjustment transactions + meter readings against your account, all manual, which for me was next to impossible to sit and reconcile!

Here is how it works for me:

• For net meter - Ours is a monthly billing cycle and a separate meter reader comes home between 1st-6th of the month and takes the reading and hands it over to the subdivision accounts office, they then manually enter in the numbers and generate a bill based off an excel template and prints them and deliver back to home usually around last week of the month. Any amount we are due gets deposited only after another month or two and the deposit dates are pretty random.
• Solar generated power=solar meter reading=Units exported + Solar units consumed (I have a consumption CT and get this off it)
• The meter readings and bill details are not available online and none of central customer care/accounts depts can help you with net meter issues. You will need to head out to your subdivision accounts dept, catch hold of the net meter reader to know the exact contact who is doing the billing.
• Any bill amounts which are due from our end (months where it is net +import) don't get adjusted in the next/subsequent months - they come up and remain as arrears and you need to clear them with a payment.
• I have heard of positive experiences from folks in other subdivision with bills over email and timely deposits etc but ours is still not streamlined and a bit messy.

For normal meter - The meter reader visits home and keys in the numbers into his handheld device and generates the bill on the spot. The reading numbers and bill details are also available online.

My normal meter billing cycle/dates and net meter billing cycle/dates are different and not the same.

Any idea how they are monitoring to make the adjustments and meter reading against accounts? As far as I know, they have to enter the property and take the reading, there is no remote monitoring right?

Here is where the problem is, for us


Yes, we have seen the normal meter reader visiting for reading and printing the bill which is usually mid month but have not seen anyone come for solar meter reading.

Well, here is how it works.
The net meter can measure electricity coming in (import). It can measure electricity going out (export). But it will NOT measure solar-generated-electricity getting consumed directly by you.

Let me explain. Below is how the connections are:

House load --- solar --- net meter --- grid

Now, whatever the solar panels generate, it will go to serve the house first, and anything extra goes to the grid. So let's assume you are generating 1kw but consuming only 300watts. The rest 700watts goes out through the bi-directional meter. So the meter is accounting for 700watts but the 300 is what gets used up directly and is not going to be measured by the bidirectional meter.

So, in your case, about 80 units seems to be about what you consume.directly from the solar plant.