India Rooftop Solar PV – Frequently Asked Questions
This section provides answers to the questions that we frequently encounter from our clients. Each answer is provided as a snapshot with a ‘Read more’ link that provides a much more detailed discussion on each topic.
Rooftop solar power is much cheaper than power from diesel generators. Solar PV generates power at a cost of about Rs. 4.5-5/KWh while diesel generates power at about Rs. 16/KWh.
Whether solar is more expensive than grid power depends on your current tariff. Solar power is not cheaper than grid power for many consumers but in some cases, such as consumers paying a commercial tariff, solar power may be cheaper than grid power.
A rooftop solar PV system costs approximately Rs.1,00,000 per kWp (Kilowatt Peak) including installation charges but without batteries. The cost breakup for a 1 kWp system is given below
Component Rs. PV modules (Crystalline) 52,000 Inverters 23,000 Balance of System (cables, etc.) 17,000 Installation 8,000 Total 1,00,000
Whether solar power can replace your diesel consumption entirely depends on a number of factors such as the nature and timing of the load, the extent of load shedding, the area of roof available, etc. Some of the factors that constrain the supply of rooftop solar power include
- Solar power is generated only during the daytime on non-rainy days
- Solar power may not handle the heavy starting currents required by heavy machinery
- The output of the solar plant varies as the sun moves across the sky, and as clouds move across the sun
- Limited roof area constrains the capacity of solar PV plant that can be installed
Due to these reasons many energy consumers find that rooftop solar power may not support their entire load all the time. Solar power ideally acts in conjunction with diesel generators, taking up part of the load and saving, but not eliminating, the diesel expenditure.
The area required by a rooftop PV plant depends on the extent of shade-free space available and solar panel efficiency. A solar PV system typically requires 100-130 SF (about 12 m2) of shade free roof area per kW of capacity at current crystalline panel efficiency levels.
The amount of electricity generated by a rooftop solar PV plant depends on the location, orientation of the roof, panel efficiency, and ambient temperature. As a rule of thumb, a 1 kWp plant will generate about 4 kWh (units) of electricity a day on average in a year.
A rooftop solar PV system primarily comprises of Solar PV Modules (panels), Inverters, and Mounting Structures. If battery backup is required Batteries and Charge Controllers would also be integrated with the system.
Solar panels typically have 5-year manufacturer’s warranty with additional performance warranty of 90% of rated power output for first 10 years, and 80% of rated power output for the next 15 years. Other system components (inverters, mounting structures, batteries, junction boxes, etc.) typically have 1-year manufacturer’s warranty extendable to 5 years.
Each component of the plant should conform to various IEC (international) or IS (Indian) standards.
Panels should conform to IEC 61215/IS 14286 for design qualification and type approval, IEC 61730 for safety, and IEC 61701/IS 61701 for salt mist corrosion (for use in coastal areas).
The capacity of the rooftop solar plant you require to power your facility should be calculated keeping in mind your requirements, your constraints, and the amount of sunlight available. Rooftop space is the most likely constraint that will limit the size of your solar plant. If the size of the plant is not sufficient to power your entire facility, you can choose between powering light loads, powering critical loads, and using a solar-diesel hybrid.
Not all rooftop solar plants generate power during a power failure; only some do. The difference lies in the inverter and the functionality it supports. Grid-interactive and hybrid inverters supply electricity even during a power failure while grid-tied and off-grid inverters don’t.
There are 3 alternatives to building your own rooftop solar plant
a) 3rd Party Sale – Where a solar IPP sells power to the energy consumer using grid infrastructure to deliver the power. Many charges are applicable in addition to the cost of power
b) Group Captive – Where a group of energy consumers or a plant developer and consumers jointly own a power plant. Charges are similar to 3rd Party Sale except cross-subsidy charges are not applicable
c) BOO(T) – Under the Build Own Operate (Transfer) model the solar system provider bears the investment of installing the plant on the consumer’s rooftop, and the consumer only pays for power generated by the plant. This model has the least charges over the cost of power
What are the various policies and regulations (subsidies, incentives, permissions) that I should
consider for my rooftop solar systems?
There are various solar policies that incentivise rooftop solar in India. Central government schemes include 80% accelerated depreciation, capital subsidy of 30% and more based on location, and Renewable Energy Certificates (RECs). Some states have further incentives under their own solar policies.
Permissions primarily deal with ensuring the grid isn’t congested by receiving approval from local power distribution authorities.