Generating electricity is easier than ever. Drastic price decline in the last decade, combined with policy incentives for rooftop systems, have allowed consumers to install solar system on their rooftop. However, given that it is expensive to store electricity, systems are often connected to the grid so that surplus can be exported to the grid and deficit can be imported from the grid. Two arrangements are often defined by governments when designing the regulations for solar rooftop system – Gross and Net metering.
Gross metering is a mechanism in which the entire energy generated by your solar system is exported to the grid at a certain rate. In this case, the energy generated from your system is not consumed by you in any capacity. Once the energy is generated from your solar system it is transferred to the grid, and the grid further sells the energy to the power consumers at a certain tariff rate. In the case of gross-metering, a unidirectional meter is installed to track the total export of electricity from the solar system to the grid.
In the case of net-metering, the power generated by the solar system is first used for self consumption and if there is any leftover surplus energy, only then it is transferred to the grid in exchange for compensation. It is also a net preserver of energy usage. What this basically means is that home owners are in a position to monitor and control the amount of energy they use during the day or at night. When you’re away your home may generate extra electricity using solar energy. You may buy some expensive batteries to store that extra energy to use it at night but there’s another option to send extra power produced back to the grid and that’s what we call as net metering.
Net-metering requires installing of a bi-directional meter because in net-metering both the import and export of energy is taken into account to calculate the net consumption of electricity. Gross metering makes sense for those property owners who have idle space and don’t need to generate solar power for their own consumption. They can install a solar system to utilize the idle space and export the entire generated energy to the grid in exchange for financial benefit. Net metering ensures reduced electricity bills and makes sure that the produced energy is not wasted with no need for installation of a battery storage system that can be expensive for some people. It takes some pressure off electric grids while proving beneficial for the environment as well as preserving the natural energy produced.
Experts point out that this ‘gross metering’, though well-intended, has one major problem.
- If you have a rooftop solar plant and wish to sell power to the discom, you have to build the infrastructure needed to evacuate the power. You need to put separate cables all the way from the solar inverter to the gross meter, which has to be installed separately. The cost of this additional infrastructure will in most cases be much higher than the cost of the solar PV systems themselves.
- Furthermore the produced power from the solar power plant, if bought by the electricity board, is at a much lower price than that sold to the consumer.
Net- metering is quite beneficial. However, the interconnection processes still remain taxing in many parts of the country despite the states announcing the net metering policies for rooftop solar.
Here are few common challenges in Net metering listed below –
- The solar energy produced by a photovoltaic system is largely dependent on the availability of sunlight. The power generated can vary drastically because of many reasons. This leads to rapid voltage fluctuations that can impair the transmission network, and in some cases overheat the power lines. Inverters are designed to regulate the PV system voltage. Voltage fluctuations can take place due to improper functioning of the inverter and can be a problem if the fluctuations move outside the specified values. To avoid any such scenario, voltage fluctuations need to stay within specific limits beyond which the system is required to automatically disconnect from the grid.
- Electrical disturbances, generating harmonics is created by the presence of non-linear components in the system. It can overload equipment, interfere with the telephone circuit and lead to metering errors. The total, individual and current harmonic disturbances produced by a PV system should not be allowed to exceed 5%, 3% and 8% respectively so that it does not affect the quality of the power in the grid.
As of date, 30 states and Union territories in India have implemented the policy to support “Grid Connected” Solar PV. Those are :-
- Andhra Pradesh
- Himachal Pradesh
- Madhya Pradesh
- Tamil Nadu
- Uttar Pradesh
- West Bengal
- Andaman and Nicobar
- Dadar and Nagar haveli
- Daman and Diu
Most Indian states like Tamil Nadu, Maharashtra, Rajasthan and Uttar Pradesh are abruptly hinting to change to Gross metering by withdrawing Net meter benefit. These four states constitute nearly 45% of rooftop solar capacity in India and with such decisions, the upward slope of growth in rooftop solar might get affected.
Opinionated from experts, the regulators are restricted by the financial troubles and it would be better to arrive at the tariff rates with best interests for everyone.