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Roof Top Solar PV System for residences - my experience

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I noticed some discussions on Roof Top Solar PV System for residences. I would like to share my experience and assumptions.

I have installed a SPV system on my roof top as a back up to grid supply 4 years ago, and is functioning satisfactorily although some improvements in the overall operation of the system is desirable and achievable.

Assumptions first:

  1. Renewable energy sources are the future; and solar power has the most advantages;
  2. Conventional power sources are fast depleting and getting costlier; social and environmental cocerns with these sources are huge and cannot be ignored any longer. Their real cost to the society is much more than what we see now as electricity prices.
  3. In order to make use of SPV systems work effectively, the electricity demand has to be managed carefully.  Usage of heavy duty appliances such as fridges, ACs, washing machines, water pumping, electric iron box, etc should be avoided as far as possible OR carefully managed. My requirement was only for lighting, PC, TV, and cell phone recharging.
  4. Some financial risk taking is involved for individuals if we want to hasten the wider use of these renewable energy sources.
  5. Living in a village a decent backup for the grid power was necessary for me to be able to use my PC at any time.
  6. Also I wanted to demonstrate to otheres (especially the authorities: I demonstrated my SPV system to the state energy minister in 2009) the efficacy of these systems.


  • a. A system of capacity  [50*2 watts, 125 AH battery, control cubicle (for charge controlling, changing over from grid to solar and vice versa, preference to charge the battery either from grid or from solar, a switch and few indicating lamps), iron stand, testing and commissioning all included] was quoted for about Rs 80,000 in 2008. Warranty of 20 years for the panels, and 5 years for the battery was obtained. I held back about Rs. 10,000 as performance gaurantee. The supplier never asked for this money; so huge must be the profit.
  • b. The system is functioning satisfactorily for my uses: CFLs, TV, PC, two small table fans, two small table lamps, and power sockets for charging the cell phoness. System is connected to the AC wiring of the house, and hence the soalr power can be used anywhere in the house.
  • c. Once the battery is charged fully (say about 4 hours of sunlight), I can manage without grid supply for one whole day.  Supply changeover from grid to solar and vice versa isgenerally smooth and is almost un-noticeable.
  • d. I also have a decent after-sales-service as can be expcted in a rural environment.
  • e. Since the system is modular in nature no. of panels can be added; accordingly the cable and control cubicle may also need to be changed.


  • i) The price for a simialr system has come down by more than 50% in 2012.
  • ii) The system can be very useful in most parts of Karnataka including Bangalore. There will be some charging of the battrey even on cloudy and rainy days, but to a reduced extent;
  • iii) If we know our load requirements well and are ready to accept small sacrifices SPV systems can provide good service.
  • iv) Most residences will not need more than 2 kW capacity fo the system, if we manage the usage carefully
  • v) Best usage is to make use of all the solar energy generated during day time; and keep the battery energy only for lights, TV and PC for the night.;
  • vi) There can be no doubt that responsible usage of the scarce energy resource we have cannot be compromised. We have to decide whether some of the appliances such as fridge, AC, washing machine, micro wave oven etc. are indispensable.
  • vi) Small size water pumping sets should be of problem. Best to sue them during day time.
  • vii) Cost of 1 KW SPV system can be less than Rs. 2 lakhs; one has to shop around for best buy. Bangalore may offer many good options.
  • viii) Before finalising the buy it is advisable to check with one or two who are already using the system; preferanly consult a professional
  • iX) Since the system is modular one can go for a smaller systen to start with, and decide to updgrade depending on one's experience and needs
  • x) There can be no doubt with more and more people opting for sush systems the prices will come down further and better systems will be made available.
  • xi) Subsidy may be available for sytems of capacity  more than 1 kW; need to very with KREDL, Bangalore and MNRE, Delhi.
  • xii) As always the pioneers will have to bear some extra costs and risks; but that is why they are called as pioneers.
  • xii) As a thumb rule about 1 kW of SPV can be installed in a surface of 60 Sq. ft. Even if it is 100 Sq. ft per kW it is adeqaute in most cases. A  house built on a 30*40 Feet site can offer a surface of more than 500 sq. ft. Hence getting a minimum of 5 kW of solar power capacity is feasible on most of the roof tops.
  • xiii) Installing SPV for a group of house will become little bit more complicated not only in the cost, design and operation, but there may be licensing issues to be considered. some one has to take the ownership of the entire system and may have to get license from the electricity regulator. I am not sure about this and hence need to be checked with KERC, Bangalore.



silkboard's picture

thanks, welcome, and some questions

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Gret post Shankar, and welcome to Praja. So looks like you built your system in 2008.

So looks like:

Once the battery is charged fully (say about 4 hours of sunlight), I can manage without grid supply for one whole day.

And this is for your needs:

CFLs, TV, PC, two small table fans, two small table lamps, and power sockets for charging the cell phoness.

So how about any heavy appliances, I am guessing you would have a pump for water. May be a Fridge?

Also, great to hear this:

I also have a decent after-sales-service as can be expected in a rural environment.

Really, in a rural area? Good to hear that. What is typically required as part of after-sales-service? Battery?

Bang on regarding the price:

Cost of 1 KW SPV system can be less than Rs. 2 lakhs; one has to shop around for best buy. Bangalore may offer many good options

One more question. So its been 3.5 years now for you. How are the batteries doing?

silkboard's picture

also, system is not exactly modular

198 users have liked.

Another thing, from what I know, the system is NOT exactly modular.

There are three peices to the system we have

  • Panels
  • Batteries
  • Charging/Conditioning unit

Can add more panels, can add more batteries. But the conditioning unit is rated 24V, and if I want to go from 1 Kw to 2 Kw tomorrow, I am told I will need a 48V conditioning unit.

However, they told me that if I start at 2Kw, then I can go to 3Kw or 4Kw capacity using the same 48V conditioning unit.

I don't know if that is plug to entice people to go for 2Kw systems, or if there is any technical limitation to making the system modular from 1Kw onwards itself.

Shankar Sharma's picture

Roof Top Solar PV System for residences - my experience

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Sorry for the delay in reponse.

The battery, a dry one, is doing fine. Does not require much of maintenance; just topping up with distilled water once in a while; I think it is once a year.

I have no fridge, no washing machine, or any other heavy gadgets. The 1 HP water pump is used only when there is grid supply.  During 4 months of rainy season I even minimise this usage by collecting rain water for all the uses except for drinking and cooking.

I believe the whole philosophy of renewable energy sources revolves around the distinction between real needs, pleasure wants and vulgar luxuries.  We have to make individual choices in this regard.  If our interest towards roof top SPV system is to meet the energy requirements of all our gadgets (whether essential or not), then SPVs in the present form may not fit the bill; and/or may cost hugely.

I chose to install SPV system on my roof top knowing clearly well that all my electricity needs are not going to be met by it. I wanted to experinec it myslef before I advocated it in my articles. Also I wanted to do my bit in popularisign it and to bring down the initial price of the system. I also have a solar hot water syatem. I believe both these systems have been of great benefit to my family, and I am also happy that I am doing my bit in reducing the dependence on the grid supply, which also has benefits from global warming perspective.

Whatever the problems I have been facing is with the electronics in the control cubicle. A component in it got burnt out twice in 4 years due to lightening here. The local rep. provided me a back up control cubicle while the orignal was sent to Bangalore for repairs. It took 2 days first time and 10 days second time to repair. Do not know how to overcome this problem. Comapred to the poor power supply from the grid for the villages, such inconviniences seem trivial. When the whole street/village is without power (which is very often here since we are fed from a rural feeder passing through thick vegetation) I can meet most of my electricity needs comfortably.

The problems I have faced in the SPV system may not be so heavy in places like Bangalore where the repairs can happen quickly. People may also have many choices, and I also undersand the SPV systems have improved cosiderably since I got mine.

No particular maintenence is needed frequently. I need to clean the solar panel once in a while. I just pour few liters of water on it. Since I am in a relatively dust free environment even this need is not great. Battery is doign well; has 5 year warranty on it.

When we say SPV is modular, we dont mean that everything in it is modular. The SPV panels are modular in the sense that additional panels can be added if the overall system (battery and the invertor) are of adequate capacity. These also can be replaced if we have an understanding with the company. One may get a small discount for the new ones in exchange for the old ones, becuase the supplier can use them elsewhere. I have such an understanding with my supplier.

One may also consider having 1 KWp of solar panel and go for 2 or 3 kVA invertor to reduce the overall cost. Such a combination may allow the usage of some appliances during day time through solar energy.

Initially it is ideal to take care to have a good design keeping in view one's own requirements for the next 5-6 years. I chose to have a 500 VA invertor for 100 Watts peak panels so that I can add another 100 or 200 Watts panel without having to change the invertor. That supports a small exhaust fan in the kitchen for small durations. There seems not much of a price difernce between invvertor of two different capacities. Adequate enquiries will help.

Such care in configurations can really be helpful. But unless one is from an electrical engineering background it is advisable to seek help from the experts. I do not mid helping in such configuration considerations, if one wants it.

But I have no hesitation to recommend the deployment of such SPV systems in all places possible. I am workign with many individauls and NGOs to lobby the govt. to bring in the feed-in-tariff mechanism. With more people using SPVs it will be easier to implemen the feed-in-tariff mechanism.



Surya Prakash

Commander V Joshua's picture


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Quite impressed with Mr Shankar Sharma's missionary zeal. Would like to correspond on the subject directly and my mail a/c is

avanimoola's picture


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Mr Sharma, I am quite impressed with your initiative of risking a large sum on the try. The experience you have gained and publicised should spur others too. 

I was under the impression that the investment would be quite high on the lines of what you have spent. But a few trips to SP Road  and talks with  some good dealers in solar  panels & accessories indicate a better costing. The general unit cost  for a Solar Panel per watt of  net energy is around Rs 90.

add to this the cost of a Controller. My enquiries bought me to the following set-up.

A 124 watt system of solar power will need 4 Panels of 36 or 37.5 watt panels connected in series. This will give 124 watts at 12 Volts( or slightly higher). this can charge a Battery of 12 Volts 88 AH or 125 AH comfortably.

Since I have a UPS of 800 VA already it is not necessary to invest on a Battery, Charging system or Inverter. I can connect the output of the solar Panel (around 10 Amps max at 13.2 Volts) to the UPS to Charge the Battery during daytime. During Nights, this can be used to light up the house.

Some changes may be required , like moving the UPS to a place nearer to the Solar panel which may be in I Floor, and some wiring for a smooth changeover  to BESCOM when sun plays truant. 

With some observation and experience the unit can beupgraded with more panels and maybe one more Battery, so that entire lighting load (including fans, TV and 1/2 hp pump ) can be taken care of.

With the general level of earning of a middle class family in bangalore it appears that the investment is not heavy. The additions can be in instalments without pinching the budget.

We in India should term ourselves lucky to have a tropical climate most of the year.

Right now I am in the US and see the immense awarenes here for solar lighting in homes and offices. Solar panels are available in 'Home Store'  and similar  outlets which sell workshop and 'do-it yourself' stuff.

As soon as I return to India in Jan 2013, I propose to install a Solar lighting  system in my house at Bangalore.

There is a very good Business potential too,  if some entreprenur offers to install Solar opanels on Housetops in Bangalore. 

I am an electrical Engineer and am willing to join hands with an invester /team.

R Vasudevan 


RamSolar's picture

Roof Top Solar PV

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Hi, I hear that there are manufacturers who are offering Rs50/W to Rs60/Wtoday for Mono/Poly Crystalline solar cells. We can get this bargain by forming a group and negotiate for better deal. The big cost is gonna be the Inverter since we normally require low power rating of around 3KW.


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