Battery-backed systems cost about 30 per cent more than grid type systems because of the additional cost of batteries. "People who live in areas where the duration of power cut is short should go for a grid-type system with a small power backup. But those who live in areas that witness power cuts of more than two hours should opt for a battery-based system," says Bhalla. The need to replace batteries periodically imposes an additional cost.
A grid-based system takes longer to install since one has to apply to the state utility. Permissions can take 30-45 days. In comparison, an off-grid, battery-backed system takes only two-three days to install.
Government subsidies are available on grid-type systems and not on battery-based systems. They vary from one state to another and range from 20-30 per cent of the cost of the project.
High upfront cost: While a solar-power system makes economic sense from a 25-year perspective, its initial cost is high. Hence many people settle for an inverter-battery system that costs around Rs 15,000.
Let us get an estimate of how much these systems cost. A 3-kw non-battery-based system will cost you around Rs 65 per watt, while a battery-based system will cost around Rs 95 per watt. Thus, the total cost of a 3-kw system will come to around Rs 200,000 (non-battery) or Rs 285,000 (battery-based). For a 5-kw system, the cost will be around Rs 60 per watt for a non-battery-based system and Rs 90 for a battery-based one. For a 10-kw system, it will be Rs 55 and Rs 85 respectively. The per watt cost drops a little as you go for larger systems.
Most households opt for three to six kilowatt systems because their rooftops cannot accommodate larger systems. For each kilowatt that you wish to generate, you need 10 square metres of shadow-free space on the roof.
Opt for an expert vendor: A rooftop solar system for a household needs to be designed and installed properly. "Any part of the roof on which a shadow from a neighbouring building, tree, or wall falls is rendered useless. Power generation can dip by as much as 80 per cent below the installed capacity if a shadow falls on one of the panels," says Bhalla. Even the angle at which the panels are installed has a bearing on output. If these glass-topped panels are not secured properly, strong winds can cause them irreparable damage.
Since these are high-power systems, safety becomes a crucial concern. The wires that are used need to be of a high quality since regular cables tend to degrade in ultraviolet light. The earthing mechanism has to be right. Lightning arrestors need to be installed.
With design and safety both being crucial concerns, it is advisable to opt for players from the organised sector.
Tips for solar power customers
In India, it makes more sense to opt for photovoltaic technology that can provide power to your home, instead of thermal technology used in colder climates for central heating
If your roof is covered in shade most of the day, then having a solar panel installed on it may not be a good idea. Opt for a community-based solution instead
If your roof needs renovation, get it done before installing the solar-power system
Simultaneously consider energy-efficiency upgrades, such as switching to energy-efficient lighting and other products, and use appliances more prudently
Opt for a service provider who offers a warranty of 20-25 years
Go for solar products that meet IEC standards