Supply of electricity is quite unreliable in most parts of India. Due to increased scheduled and un-scheduled power cuts in most of the cities in India, interest in using electricity generated through alternate sources has also increased. However, high capital cost of setting up systems to tap energy through renewable sources is deterrent in taking up large-scale deployments of the same.
Solar power is arguably the cleanest, most reliable form of renewable energy available, and it can be used in several forms to help power your home or business. Solar-powered photovoltaic (PV) panels convert the sun’s rays into electricity by exciting electrons in silicon cells using the photons of light from the sun. This electricity can then be used to supply renewable energy to your home or business.
Residential, grid-connected rooftop systems which have a capacity more than 10 kilowatts can meet the load of most consumers. They can feed excess power to the grid where it is consumed by other users. The feedback is done through a meter to monitor power transferred. Photovoltaic wattage may be less than average consumption, in which case the consumer will continue to purchase grid energy, but a lesser amount than previously. If photovoltaic wattage substantially exceeds average consumption, the energy produced by the panels will be much in excess of the demand. In this case, the excess power can yield revenue by selling it to the grid. Depending on their agreement with their local grid energy company, the consumer only needs to pay the cost of electricity consumed less the value of electricity generated. This will be a negative number if more electricity is generated than consumed. Connection of the photovoltaic power system can be done only through an interconnection agreement between the consumer and the utility company. The agreement details the various safety standards to be followed during the connection.
To understand this process further, let’s look at the solar energy components that make up a complete solar power system.
The roof system
In most solar systems, solar panels are placed on the roof. An ideal site will have no shade on the panels, especially during the prime sunlight hours of 9 a.m. to 3 p.m.; a south-facing installation will usually provide the optimum potential for your system, but other orientations may provide sufficient production. Trees or other factors that cause shading during the day will cause significant decreases to power production. The importance of shading and efficiency cannot be overstated. In a solar panel, if even just one of its 36 cells is shaded, power production will be reduced by more than half. Experienced installation contractors use a device called a Solar Pathfinder to carefully identify potential areas of shading prior to installation.
Not every roof has the correct orientation or angle of inclination to take advantage of the sun’s energy. Some systems are designed with pivoting panels that track the sun in its journey across the sky. Non-tracking PV systems should be inclined at an angle equal to the site’s latitude to absorb the maximum amount of energy year-round. Alternate orientations and/or inclinations may be used to optimize energy production for particular times of day or for specific seasons of the year.
Solar panels, also known as modules, contain photovoltaic cells made from silicon that transform incoming sunlight into electricity rather than heat. (”Photovoltaic” means electricity from light — photo = light, voltaic = electricity.)
Solar photovoltaic cells consist of a positive and a negative film of silicon placed under a thin slice of glass. As the photons of the sunlight beat down upon these cells, they knock the electrons off the silicon. The negatively-charged free electrons are preferentially attracted to one side of the silicon cell, which creates an electric voltage that can be collected and channeled. This current is gathered by wiring the individual solar panels together in series to form a solar photovoltaic array. Depending on the size of the installation, multiple strings of solar photovoltaic array cables terminate in one electrical box, called a fused array combiner. Contained within the combiner box are fuses designed to protect the individual module cables, as well as the connections that deliver power to the inverter. The electricity produced at this stage is DC (direct current) and must be converted to AC (alternating current) suitable for use in your home or business.
The inverter is typically located in an accessible location, as close as practical to the modules. In a residential application, the inverter is often mounted to the exterior sidewall of the home near the electrical main or sub panels. Since inverters make a slight noise, this should be taken into consideration when selecting the location.
The inverter turns the DC electricity generated by the solar panels into 120-volt AC that can be put to immediate use by connecting the inverter directly to a dedicated circuit breaker in the electrical panel.
The inverter, electricity production meter, and electricity net meter are connected so that power produced by your solar electric system will first be consumed by the electrical loads currently in operation. The balance of power produced by your solar electric system passes through your electrical panel and out onto the electric grid. Whenever you are producing more electricity from your solar electric system than you are immediately consuming, your electric utility meter will turn backwards!
Net metering comes as a new concept that promises an environment friendly and power efficient electricity evaluation system. It provides an easy option to produce electricity from renewables and also to get connected to the grid at the same time.
Net metering is a new concept where an instrument which has a special metering and billing agreement between utilities and their customers, facilitates the connection of small, renewable energy-generating systems to the power grid. This new program is being developed to encourage small scale renewable energy systems to ensure that customers always have a reliable source of energy even when their renewable generators are not producing energy, and to provide substantial benefits to the electric power-generating system as well as the environment. When a net metering client’s renewable generator is producing more power than is being consumed, the electric meter runs backward generating credits. Whenever the net metering customer uses more power than is being produced, the meter runs forward normally. Net metering customers are charged only for the net power that they consume from the electricity service provider that has accumulated over a specific period. In other words, if their renewable energy generating systems make more electricity than is consumed, they may be credited or paid for the excess electricity contributed to the grid over that same period. Net metering is also a way to increase the energy in the power grid to keep up with increase in demand during peak power use time, and this is of particular interest to states facing power shortages.
Net metering is a concept that has been talked about extensively in the world of solar. But, what exactly does it mean for you and when will it come to India?
Net metering is basically you generating you own electricity and then feeding whatever you don’t use into the existing grid. The policies in this differ a lot from region to region.
There are two main benefits of net metering:
1. Feed Extra in to Grid: Whatever extra energy you produce, can be fed into the grid. This basically is significantly important because it allows you to bypass using battery bank to store energy that you don’t consume for later. Batteries are expensive with high maintenance, net metering allows for a significant reduction in cost savings.
2. Switch to Grid when you use extra: Imagine that you have your own way of producing electricity; maybe a diesel gen set or solar panels and one day you need extra electricity to power your new air-conditioner, but your generated electricity isn’t enough. Net metering will allow you to take electricity that you are not able to cover from your system with grid electricity.
Ideally, net metering stands to benefit consumers substantially. Not only will you be able to save money by cutting the cost of batteries but you might also earn money by feeding extra electricity into grid.
Small scale or residential component of solar relies heavily on net metering. Net metering will reduce the cost of installing a solar system significantly because now you no longer need a battery bank. Also, net metering will allow you to earn money by feeding in the extra energy into the grid, this will bring the return on investment down significantly.
In this system, you have a single new bi-directional meter. When you consume electricity from the grid (or your electricity supply), the meter readings will move forward; but, when you produce electricity and send it to the grid, the meter readings shall move backward. Suppose you use 10 units of electricity in a day and produce 8 units, your meter will show a reading of 2 units. And if you use 10 units of electricity and produce 12 units, then your meter will show -2 units. Your bill at the end of month will be based on net units consumed/produced. If you generate extra electricity in any month, the surplus is carried over to the next month and netted. At the end of a year, if your total production is more that what you consumed, then you will get paid for the next surplus electricity produced at the cost decided by your state’s electricity regulatory commission.
In this system, there are two meters: one measures your electricity consumption and the other measures your electricity production. Consequently, you get two different bills: one for consumption and other for production. There is no change in the way your consumption is billed (as it happens today), but you get paid separately for the electricity you produce. Again, the cost of electricity that you are paid is decided by the state’s electricity regulatory commission.
Difference between Net metering & Gross metering
If you look at the way electricity is priced (check domestic tariff slabs), the price of electricity is lower when consumption is less and it is higher when the consumption is more. When you ‘net’ your consumption, you don’t get a fixed cost for your electricity production. The price that you get varies, based on your consumption/production, whereas in case of Gross Metering, you get a fixed price for all the electricity you produce
In a solar electric system that is also tied to the utility grid, the DC power from the solar array is converted into 120/240 volt AC power and fed directly into the utility power distribution system of the building. The power is “net metered,” which means it reduces demand for power from the utility when the solar array is generating electricity – thus lowering the utility bill. These grid-tied systems automatically shut off if utility power goes offline, protecting workers from power being back fed into the grid during an outage. These types of solar-powered electric systems are known as “on grid” or “battery-less” and make up approximately 98% of the solar power systems being installed today.
Other benefits of solar
By lowering a building’s utility bills, these systems not only pay for themselves over time, they help reduce air pollution caused by utility companies. For example, solar power systems help increase something called “peak load generating capacity,” thereby saving the utility from turning on expensive and polluting supplemental systems during periods of peak demand. The more local-generating solar electric power systems that are installed in a given utility’s service area, the less capacity the utility needs to build, thus saving everyone from funding costly additional power generating sources. Contributing clean, green power from your own solar electric system helps create jobs and is a great way to mitigate the pollution and other problems produced by electricity derived from fossil fuel. Solar-powered electrical generating systems help you reduce your impact on the environment and save money at the same time!
Grid-Tied, Off-Grid and Hybrid Solar Systems
What are the benefits of grid-connected solar panels vs. living off the grid? Deciding whether or not to grid-tie your solar panels is usually pretty straightforward – the clear-cut benefits of being grid-tied appeals to the majority of homeowners. There are, however, some people that choose to live off the grid.
What would be the best in your situation? Let`s look closer at the benefits and downsides of grid-tied, off-grid and hybrid solar systems.
1) Grid-Tied Solar Systems
Grid-tied, on-grid, utility-interactive, grid intertie and grid back feeding are all terms used to describe the same concept – a solar system that is connected to the utility power grid.
Advantages of Grid-Tied Systems
1. Save more money with net metering
A grid-connection will allow you to save more money with solar panels through better efficiency rates, net metering, plus lower equipment and installation costs:
Batteries, and other stand-alone equipment, are required for a fully functional off-grid solar system and add to costs as well as maintenance. Grid-tied solar systems are therefore generally cheaper and simpler to install.
Your solar panels will often generate more electricity than what you are capable of consuming. With net metering, homeowners can put this excess electricity onto the utility grid instead of storing it themselves with batteries.
Net metering (or feed-in tariff schemes in some countries) play an important role in how solar power is incentivized. Without it, residential solar systems would be much less feasible from a financial point of view.
Many utility companies are committed to buying electricity from homeowners at the same rate as they sell it themselves.
2. The utility grid is a virtual battery
Electricity has to be spent in real time. However, it can be temporarily stored as other forms of energy (e.g. chemical energy in batteries). Energy storage typically comes with significant losses.
The electric power grid is in many ways also a battery, without the need for maintenance or replacements, and with much better efficiency rates. In other words, more electricity (and more money) goes to waste with conventional battery systems.
According to data national, annual electricity transmission and distribution losses average about 7% of the electricity that is transmitted. Lead-acid batteries, which are commonly used with solar panels, are only 80-90% efficient at storing energy, and their performance degrades with time.
Additional perks of being grid-tied include access to backup power from the utility grid (in case your solar system stop generating electricity for one reason or another). At the same time you help to mitigate the utility company`s peak load. As a result, the efficiency of our electrical system as a whole goes up.
Equipment for Grid-Tied Solar Systems
There are a few key differences between the equipment needed for grid-tied, off-grid and hybrid solar systems. Standard grid-tied solar systems rely on the following components:
• Grid-Tie Inverter (GTI) or Micro-Inverters
• Power Meter
Grid-Tie Inverter (GTI)
What is the job of a solar inverter? They regulate the voltage and current received from your solar panels. Direct current (DC) from your solar panels is converted into alternating current (AC), which is the type of current that is utilized by the majority of electrical appliances.
In addition to this, grid-tie inverters, also known as grid-interactive or synchronous inverters, synchronize the phase and frequency of the current to fit the utility grid (nominally 60Hz). The output voltage is also adjusted slightly higher than the grid voltage in order for excess electricity to flow outwards to the grid.
Micro-inverters go on the back of each solar panel, as opposed to one central inverter that typically takes on the entire solar array.
There has recently been a lot of debate on whether micro-inverters are better than central (string) inverters.
Micro-inverters are certainly more expensive, but in many cases yield higher efficiency rates. Homeowners who are suspect to shading issues should definitely look into if micro-inverters are better in their situation.
Most homeowners will need to replace their current power meter with one that is compatible with net metering. This device, often called a net meter or a two-way meter, is capable of measuring power going in both directions, from the grid to your house and vice versa.
You should consult with your local utility company and see what net metering options you have. In some places, the utility company issues a power meter for free and pay full price for the electricity you generate; however, this is not always the case.
2) Off-Grid Solar Systems
An off-grid solar system (off-the-grid, standalone) is the obvious alternative to one that is grid-tied. For homeowners that have access to the grid, off-grid solar systems are usually out of question. Here`s why:
To ensure access to electricity at all times, off-grid solar systems require battery storage and a backup generator (if you live off-the-grid). On top of this, a battery bank typically needs to be replaced after 10 years. Batteries are complicated, expensive and decrease overall system efficiency.
Advantages of Off-Grid Solar Systems
1. No access to the utility grid
Off-grid solar systems can be cheaper than extending power lines in certain remote areas.
2. Become energy self-sufficient
Living off the grid and being self-sufficient feels good. For some people, this feeling is worth more than saving money. Energy self-sufficiency is also a form of security. Power failures on the utility grid do not affect off-grid solar systems.
On the flip side, batteries can only store a certain amount of energy, and during cloudy times, being connected to the grid is actually where the security is. You should install a backup generator to be prepared for these kinds of situations.
Equipment for Off-Grid Solar Systems
Typical off-grid solar systems require the following extra components:
• Solar Charge Controller
• Battery Bank
• DC Disconnect (additional)
• Off-Grid Inverter
• Backup Generator (optional)
Solar Charge Controller
Solar charge controllers are also known as charge regulators or just battery regulators. The last term is probably the best to describe what this device actually does: Solar battery chargers limit the rate of current being delivered to the battery bank and protect the batteries from overcharging.
Good charge controllers are crucial for keeping the batteries healthy, which ensures the lifetime of a battery bank is maximized. If you have a battery-based inverter, chances are that the charge controller is integrated.
Without a battery bank (or a generator) it’ll be lights out by sunset. A battery bank is essentially a group of batteries wired together.
DC Disconnect Switch
AC and DC safety disconnects are required for all solar systems. For off-grid solar systems, one additional DC disconnect is installed between the battery bank and the off-grid inverter. It is used to switch off the current flowing between these components. This is important for maintenance, troubleshooting and protection against electrical fires.
There`s no need for an inverter if you`re only setting up solar panels for your boat or something else that runs on DC current. You will need an inverter to convert DC to AC for all other electrical appliances.
Off-grid inverters do not have to match phase with the utility sine wave as opposed to grid-tie inverters. Electrical current flows from the solar panels through the solar charge controller and the bank battery bank before it is finally converted into AC by the off-grid-inverter.
It takes a lot of money and big batteries to prepare for several consecutive days without the sun shining (or access to the grid). This is where backup generators come in.
In most cases, installing a backup generator that runs on diesel is a better choice than investing in an oversized battery bank that seldom gets to operate at it`s full potential. Generators can run on propane, petroleum, gasoline and many other fuel types.
Backup generators typically output AC, which can be sent through the inverter for direct use, or it can be converted into DC for battery storage.
3) Hybrid Solar Systems
Hybrid solar systems combines the best from grid-tied and off-grid solar systems. These systems can either be described as off-grid solar with utility backup power, or grid-tied solar with extra battery storage.
If you own a grid-tied solar system and drive a vehicle that runs on electricity, you already kind of have a hybrid setup. The electrical vehicle is really just a battery with wheels.
Advantages of Hybrid Solar Systems
1. Less expensive than off-gird solar systems
Hybrid solar systems are less expensive than off-grid solar systems. You don`t really need a backup generator, and the capacity of your battery bank can be downsized. Off-peak electricity from the utility company is cheaper than diesel.
2. Smart solar holds a lot of promise
The introduction of hybrid solar systems has opened up for many interesting innovations. New inverters let homeowners take advantage of changes in the utility electricity rates throughout the day.
Solar panels happen to output the most electrical power at noon – not long before the price of electricity peaks. Your home and electrical vehicle can be programmed to consume power during off-peak hours (or from your solar panels).
Consequently, you can temporarily store whatever excess electricity your solar panels in batteries, and put it on the utility grid when you are paid the most for every kWh.
Smart solar holds a lot of promise. The concept will become increasingly important as we transition towards the smart grid in the coming years.
Equipment for Hybrid Solar Systems
Typical hybrid solar systems are based on the following additional components:
• Charge Controller
• Battery Bank
• DC Disconnect (additional)
• Battery-Based Grid-Tie Inverter
• Power Meter
Battery-Based Grid-Tie Inverter
Hybrid solar systems utilize battery-based grid-tie inverters. These devices combine can draw electrical power to and from battery banks, as well as synchronize with the utility grid. The bottom line is this: Right now, for the vast majority of homeowners, tapping the utility grid for electricity and energy storage is significantly cheaper and more practical than using battery banks and/or backup generators.
Issues with Net-metering for India – even when its essential…
Net-metering can potentially drive widespread implementation of distributed generation by incentivizing end-users to adopt localized power generation through technologies such as solar. In theory, net-metering is the proverbial silver bullet designed to help India achieve greater energy security through generation at point of consumption (distributed generation). In addition to helping consumers reduce their energy bills, it is also supposed to help stabilize the national, regional and state grids, provide financial relief to the distribution companies (DISCOMs) through consumer default risk mitigation and reduction of AT&C losses, and help cut down the per-capita energy footprint. Unfortunately solar adoption through net-metering has not picked up, even in 12 states and union-territories where it has been implemented. Both DISCOMs and end-consumers are reluctant to adopt net-metering.
• Net-metering is crucial for India if it wants to achieve energy security by 2022
• Improvement in inverter technology and innovation in financial incentives is required for large scale adoption of net-metering
• While technological improvements will enable market growth, financial innovations will drive the growth
• There are two main reasons for the disappointing adoption of net-metering by the consumers: the tariff structure (a policy matter) and grid-reliability (a technical concern). Both issues are relevant for the residential, commercial and industrial segments. In this post, I have focused on the residential segments since it exemplifies the issues well.
• Reason 1: Tariff structure (a policy issue)
• Net-metering allows customers who generate their own electricity from solar to feed unused electricity back into the grid and be compensated for that. If the energy supplied by the consumer to the grid (selling) is at a special, usually higher, tariff rate than the one at which electricity is bought from the grid (buying), then it is called a “feed-in-tariff”. However, if the selling and buying are at the same tariff-rate (usually the buying rate), then it is called net-metering. And herein lies a problem.
• Residential (and agricultural) tariffs are purposefully and artificially kept low (through subsidy) to influence the voters (e.g. Delhi elections). The actual average tariff rate varies widely in each state ranging from approximately Rs. 2.8/unit in Chhattisgarh to Rs. 6.15/unit in Maharashtra for MSEDCL consumers. In the highest consumption slab, they can even reach Rs. 11/unit in certain states. Residential rooftop solar PV systems today, on the other hand, produce electricity at a fairly constant cost across the country of approximately Rs. 10/unit – reducing yearly as system prices drop.
• Thus a net-metering customer in Chhattisgarh will have to sell electricity at a loss of almost Rs 7/unit. Only residential customers in the highest consumption of some states benefit as they can sell at a profit and recover their investment within a few years.
• DISCOMs recover the revenue lost due to subsidy for residential and agricultural users by levying extra charges on the commercial and industrial segments. If one removes this “cross subsidy” then the tariff rates will become more realistic and net-metering for all users will make more financial sense.
• However, since there is no sign of change in vote gathering mechanisms and thus removal of cross subsidy in the near future, feed-in-tariff comes across as a possible solution. Unfortunately, feed-in-tariff is just not possible in India is because of the simple reason that the DISCOMs are in financial deficit – they have no money to pay the users. Lack of viable financial incentives is, thus, restricting end customer’s adoption of net-metering.
• For net-metering to make financial sense, the solar industry, its financiers and the Indian government will have to introduce innovative financial incentives (may be such as tax-credits) to make choosing solar through net-metering easier for consumers.
• Reason 2: Grid reliability (a technical issue)
• One of the key requirements for any energy source to connect to the grid is the availability of “anti-islanding protection”. Anti-islanding protection is a way for the inverter to shut itself off and stop feeding power into the grid, when it senses a problem with the power grid, such as a power outage. This requirement is crucial because when problems arise with the power grid, it is assumed that workers will be sent to deal with it, and the power lines need to be completely safe – i.e. not have electricity flowing from all the nearby PV grid-tie systems – so that the workers can fix them without putting their lives in danger.
• Most of the states in India, unfortunately, suffer from frequent power outages, mostly due to load shedding rather than problems in the grid’s infrastructure. Thus when the grid shuts off, the solar PV inverter will also turn off completely, preventing the owner from using the generated energy for themselves. With high unreliability of the grid, a lot of the electricity generated by the solar PV system will be wasted. This is a key reason for consumers to adopt solar with net-metering.
• The anti-islanding protection is an essential safety feature that cannot be removed. Thus, the solution is technological innovation. Inverter manufacturers will have to make their inverters capable of cutting off the connection to the grid in case of grid failure, while still being able to operate (acquire reference voltage) and provide solar energy for use. If such a provision is available then net-metering customers can still use their grid-connected PV systems even during power outages.
• In essence, consumers are seeking better incentives and a resolution of technical obstacles before they invest in residential solar PV systems. Policy makers, meanwhile, are coming up with multiple mechanisms to incentivize net-metering adoption from both sides to help DISCOMs improve their financial health and to enable a reliable energy supply. Unfortunately, this is just one side of the story. DISCOMs are wary of net-metering for various reasons. Policy makers are working hard to convince them to accept it as a viable solution. This convoluted state of affairs is, unfortunately, working against net-metering and India’s progress to achieve energy security.
How do you size the Solar PV system?
One of the biggest challenges with an “Off Grid” system is that your appliance are connected to the solar PV system. So, you have to figure out your appliances wattages, daily usage etc. to calculate the right size of your Solar PV system. This entire calculation can be somewhat complex and confusing.
With a “Grid Connected” system, the calculation is extremely simple. You just have to take your electricity bill and look up the value called: “Sanctioned Load” or “Connected Load”. Depending on your state’s policy, you can install a system equivalent to 100% to 150% of the connected load value that you have on your bill. So, for instance, if your connected load is 10 kW, then in some places you can install a maximum of 10 kW solar PV system whereas in other places you can install upto 15 kW. But, in no case can you exceed 150% of the connected load for a “Grid Connected” system.
The next challenge that you have to tackle is: shadow analysis. To get the optimum output from a Solar PV system, you need to ensure that you have enough shadow-free area that can hold the system. Typically (based on current levels of efficiency of solar panels), you need a shadow-free area of 90-100 sq ft to install 1 kW of Solar Panels. The panels have to face south and should be inclined at 15-18 degrees (depending on the city).
You have to make sure that:
1. There is no external body (like buildings, trees) that casts shadow on panels during the day.
2. Panels are placed in such a way that they get maximum sunshine throughout the day at the right angles.
Shadow Analysis can help you calculate the rooftop area that can be utilized and based on that (using 90-100 sq ft per 1 kWp) you can calculate the maximum size solar PV system that you can install. As mentioned earlier, you cannot exceed more than 100%-150% (depending on state) of the sanctioned load. Please take help of your Solar PV installer to get the shadow analysis done accurately. There are software available that can be used to do this analysis too (they can predict shadows depending on seasons and location). Do not go blindly by what an installer says; you may have to pay some money upfront to get this done, but then it will have better outcomes in the long run.
Can your roof hold the panels?
Typically solar panels are quite light, but once you have decided the place to install solar PV, you need to make sure that the roof should be able to handle the solar PV system. If you have asbestos sheets that are old, you may want to change them with tin sheets that are long-lasting. Your roof should be sturdy enough to hold the panels. If your roof is quite high and there is a lot of wind, you need to understand the setup with your installer to make sure that the installation is safe enough. If needed, you shall have to take permissions from your municipal corporation to make sure you do not miss any safety parameters.
As batteries are eliminated, the maintenance required for such a system is quite less. The chief maintenance activity would be to clean the solar panels regularly so that dust does not accumulate on them. The other electrical components may have some wear and tear on regular basis (depending on the quality of the product) and would need fixes. To give a rough idea, maintenance cost is typically assumed to be 1%. In general, it is recommended to go for high quality components so that you just fit and forget the system and it keeps generating electricity for you.
Approvals from electricity distribution company
You need to take approvals from your electricity distribution company. This is because they are the ones who shall purchase electricity generated by your system. Before you start your project, you have to submit a form with your electricity distribution company (which can be done either online or offline). In the form, you will have to list out all the technical details of your PV project, along with your electricity bills and other relevant documents. The electricity distribution company will also do their feasibility study before you go ahead and install the system.
Once the system is installed, the electricity distribution company will sign an agreement with you which is called a “Power Purchase Agreement” or PPA. This agreement will lay out the terms and conditions at which the electricity distribution company will purchase electricity from you. This should be in line with the terms setup by the State Electricity Regulatory Commission and will lay down the terms of purchase.
Once everything is set up (from the system’s perspective) and the PPAs are signed, your electricity distribution company will install the “Net Meter” in your premise. Please note that your old meter may give way to this new meter (if you have a net-metering arrangement). If you have gross metering, then you will get an additional meter. Your system will start functioning once everything is set and connected.
Cost and Economics work out
Just like any other appliance, you will get products with varying costs in the market for Solar PV as well. But then just like any other appliance, you have to be aware of the quality of the product so that your expectations are matched with the product’s performance. Tier 1 manufacturers would be expensive, but their products will perform better over a longer period, whereas the cheaper ones may not perform so well over time. The benchmark costs of Solar PV rooftop “Grid Connected” system has varied between Rs 75,000/kWp and Rs 1,00,000/kWp in the last few years. In fact, if you check the prices right now, the quotations that you would get would vary between Rs 60,000/kWp and Rs 90,000/kWp (for decent quality systems).
If your connected load is 5 kW and you have enough space to install a 5 kWp system, then it would cost roughly Rs 3,75,000. Typically a 1 kWp panel would generate about 1300-1400 units of electricity per year (it will be more on days with abundant light and less on days with low light). So a 5 kWp system would offset about 6500 units from your electricity bill every year. If your average per unit cost is Rs 7 then that works out to savings of Rs 45,500 per year. At Rs 7 per unit, you will recover cost of project in 8 years (without subsidy) and in 5 years (with 30% subsidy). If the cost per unit is more, then the cost recovery will be faster.
The option of Solar PV Rooftop “Grid Connected” system looks quite lucrative for places with fairly regular and continuous supply of electricity. A majority of such places in the country are cities with higher tariffs and reliable electricity supply. It can be a great method to not only reduce electricity bills, but also the generated power can be routed to places which have a shortage of electricity. If you do have one such place in mind where you can install the system, give solar PV rooftop “Grid Connected” system a thought.