Rooftop solar power systems pay off in long run despite high upfront costs

You can recover your money in four or five years and then enjoy free power. Besides, you will be doing your bit for the environment

With large parts of India, especially those outside the metros, suffering long hours of power outage, one option that households are turning to, albeit in small numbers currently, is to install rooftop solar power systems. While the upfront cost of these systems is high, the customer recovers his investment cost within four-five years, and then enjoys free power for another 20 years (the life of solar panels being 25 years). By opting for this renewable source, you will also be doing your bit for the environment. 

While these systems have become viable both from the technological and economic standpoint, they are not very popular yet. "There aren't enough early adopters of these systems till now whom people can emulate. If there were people in the neighbourhood who had adopted these systems, others would ask them for their recommendation and then adopt them if they received positive feedback. The high upfront cost is another deterrent," says Sachin Bhalla, senior vice president-marketing, Luminous Power Technologies.

On-grid or off-grid based system? Once you decide to install a solar-power system, you need to choose one of two types. The first is a solar-powered system with backup or a battery-based system. Here, the household consumes a portion of the power generated and the surplus gets stored in batteries. In case of an outage, this backup system provides the household with power.

The second is the grid type system. Here, of the power that gets generated, the household consumes a part and the balance is exported to the grid. The advantage of this system is that the customer both imports from the grid and exports to it. "Since the system owner is charged only for the net energy consumed from the utility grid, he achieves considerable cost saving," says Sanjeev Aggarwal, CEO and founder, Amplus. A grid type, or a non-battery-based system is cheaper, but it stores only a limited amount of power in a small backup system. In case of a power cut, the household enjoys backup for only a limited duration.  

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