While the PV system costs have come down considerably, roof top systems provide altogether a new market to the urban households who are looking to take advantage of net metering benefits offered by the Discoms to the consumers. Here are the five key considerations which you should have while selecting a solar rooftop system for your roof.
Ensure what is being offered.
Solar rooftop system installation is basically a system integration, and it is important to know what is the make of the systems offered to you as a part of your solar PV systems. Ensure that makes of following components are from reputed companies.
AC and DC cables
Junction Boxes and combiner boxes
Monitoring system and protection system
2. Assess your roof available to meet the requirement
The best orientation for a rooftop solar PV system is on a south-facing roof; hence it is important that the roof has a south facing option available to install solar PV system. A flat horizontal roof is also eligible for solar PV facing clear sky and having shadow free area. The amount of roof space needed for a Rooftop Solar PV systems is determined on the basis of your selection of your PV generating capacity. Typically a rooftop system requires about 100 ft2 area to house a 1 kW power.
3. Assess your expected generation in advance
PV systems produce the most electricity during October to March when the sun is shining. Energy production will vary, of course, depending on geography and climate. A typical 1 kW roof top PV system will produce about 1600-2000 kWh in a year depending on the location. If we consider a typical household demand of 12000 Units a year, then a typical 5 kW rooftop system will meet about 60-70% of the annual household electricity demand.
4. Assess your savings
The electricity generated from rooftop systems are still more expensive than conventional grid electricity, however it all depends on how much is the opportunity cost of displaced electricity. If the displaced electricity is a combination of grid and DG based electricity, in that case the cost of displaced electricity is about 9 Rs/unit which makes solar PV system much more attractive to the roof top installer. The rooftop PV systems will cost about 60-70 Rs/Wp and depends on the size of installation. The residential consumers are also eligible for 30% capital subsidy while the commercial and industrial consumers can take advantage of accelerated depreciation upto 80%. The interest on the debt component affects significantly on the savings estimated through a solar rooftop system.
5. Evaluate the PPA option
It is important to evaluate the option of installing self owned or a third party owned system. Typically in case of rooftop PV systems, the third party signs a PPA with the building owner and sell the solar electricity as a part of onsite generation to displace his costly DG based power generation. As long as this system is completely off grid, there is no problem in terms of meeting the regulatory compliances, however in case of grid interactive systems, if the solar PV installer at a building installs the PV plant, and go for net metering, there are no guidelines from Government of India for net metering of solar electricity. Also it is not clear that the PPA signed by the third party who sells is solar electricity to the building owner as well as to the grid in the event of non-captive requirement s, is he legally allowed to sell the electricity to both parties. The third party sale can be done under the group captive mode where the buyer should have stake in a Solar PV at least 26% and should have at least 51% of solar electricity. Rest of the electricity can be sold to the grid.