Rooftop Solar Systems: What is it, and how much money can they save for households?

Solar power is gaining popularity very quickly. It is not only considered as an option that is essential to reduce carbon footprint emissions and to tackle climate change, but also to be a viable alternative to the conventional power production methods for saving homeowner’s money in the long run.

How frequently do you see solar rooftops in India? Unless you are residing in a tier 1 city, chances are slim that you have come across more than two to three of them in your neighborhood. But this landscape is rapidly changing. Very soon you would find it difficult to spot a house without a solar rooftop.

In a study by the US Department of Energy, it is estimated that solar energy can account for 40% of the United States’ electric supply by 2035 and 45% by 2050. With this estimation, there is clear indication that solar energy is the way forward for many countries having large populations including India and China.

In addition to the above, solar energy will also become a quintessential factor in meeting the power needs and demands of the future.

The largest contributor to this power generation across the globe will not be any governmental or industrial entity but homeowners and direct consumers like us. Homes, commercial buildings, and units will have rooftop solar systems that will power the lights, television, and other electrical appliances we use on a daily basis.

In this post, we will understand the schematics of Rooftop Solar Systems and how much they can realistically save in the long run and contribute in the future.

What is Rooftop Solar System?

Rooftop solar system is a series of solar panels installed on rooftops of residential homes, commercial buildings, institutions, and industrial buildings. These systems are used to harness the sun’s energy and convert it into electrical power. This can be done by adding a device known as an inverter that converts the DC power generated by the solar panels on the rooftop to AC power as most appliances/devices run on AC.

Benefits of Rooftop Solar Systems

Low gestation period - Break even in 4-7 years under optimal conditions
Utilization of unused or under-utilized space on the rooftop
Minimal transmission and distribution losses
Cost-effective with low maintenance charges
Ecological security through reduced carbon footprint

Types of Rooftop Solar Systems

There are three types of rooftop solar systems that are employed commonly today.

On Grid Solar System
On Grid Solar System is a rooftop solar system that is integrated with the main grid supply. This system allows power to be used from the grid supply only when the rooftop solar system is unable to supply the required power.

These systems are connected to the public electricity grid and have no battery storage. Any solar power that is generated from an on-grid system (and not used in your house) is exported onto the electricity grid. This allows the homeowners to also leverage the metering system and earn revenue from the unused electricity.
Off Grid Solar System
Off Grid Solar System employs battery storage and will not be connected to the electricity grid. This system is designed in such a way that it has enough power generation and battery storage capabilities to meet the home’s requirements even in the depths of winter when there is no or little sunlight.

This rooftop solar system is not linked to the main grid and can run on its own with its battery. So, the solar power generated from the rooftop solar system charges the battery which is then used to power various applications. This system is more expensive than the ‘On Grid System’ as there are batteries and other components used.
Hybrid Solar System
A hybrid solar system combines the best from the grid-tied solar system and the off-grid system: it can interact with the utility grid and store energy in a battery. This system allows homeowners to store power in batteries for their daily use, when the power grid goes down or when the electricity grid is not connected. These systems provide power to offset the grid power when the sun is shining and will even send excess power to the grid for credit, which can be used later.

In this system, the on-grid and off-grid systems work in tandem. Though a battery is used, the advantage here is that after the battery is fully charged the excess power generated is fed to the grid which generates additional revenues for the consumer.

Feasibility of using rooftop solar systems to generate power in homes

Availability of sun light - Availability of sun light is a major factor when it comes to the use of rooftop solar systems. In most parts of India, year-around sunlight makes it convenient for homeowners to use solar rooftops. So, it is imperative to see how much sunlight is available and based on that calculate the number of panels that need to be installed.
Design of the property - Design of the home or property also plays an important role when it comes to employing a solar rooftop in many cases. Solar panels that are installed on the rooftop have to face upward to get maximum exposure to the sun. In some cases, there might be the need of grills and stands because the home design might not be ideal for reaping maximum efficiency.
Neighborhood factors - The neighborhood or surrounding area is a key factor to decide whether rooftop solar systems can be employed or not. In cases where there are trees next to the home or high-rise buildings in the surrounding area, it may affect the efficiency making it difficult for homeowners to get the most out of their solar panels.
Climate factors - Climate factors are directly influential in the use of rooftop solar systems. For example, too much rain will not only reduce the amount of power generation but might also decrease the life of the solar panels. Frequent ice falls during heavy rains might even damage the solar panels. It is important to understand the climate of any locality before installing solar systems.

How much money can rooftop solar panels save in real world conditions?

While the advantages and benefits of using solar energy is evident, the question that many ask is still basic. Will installing rooftop solar panels save money? The answer is ‘Yes’. Although solar panels my seem to be expensive, there are huge savings that homeowners can enjoy as they go.

While the rooftop solar installations are a long-term investment due to the upfront costs involved in the installation and setup of these systems, they have very minimal, or no-costs involved in maintenance for at least 6-8 years depending on the conditions. So, the break-even can be expected in the long-run. While you can see the reduced electricity bills immediately.

Let’s deep dive and see how much we can realistically save using the rooftop solar systems.

Scenario 1:

5KW Rooftop Project is employed in a house where there is an average use of 300 KWh/month.

Average monthly usage: 300 KWh
Average cost per KWh charged: Rs. 5.5 (Depends on the electricity board)
Cost of power: Rs. 1,650/month
Generation potential from 5KW installation: 600 units/month
Extra power generated: 600-300 = 300 units
Total revenue by selling back to the electricity board: Rs. 1,650

So, in the above case the homeowner will end up making an average profit of Rs. 1,650 every month by installing a rooftop solar system.

Scenario 2:

5KW Rooftop Project is employed in a house where there is an average use of 1000 KWh/month.

Average monthly usage: 1000 KWh
Average cost per KWh charged: Rs. 5.5 (Depends on the electricity board)
Cost of power: Rs. 5,500/month
Generation potential from 5KW installation: 600 units/month
Power usage: 1000-600 = 400 units
Total cost incurred after deducting solar power usage: Rs. 2,200
Total money saved every month: Rs. 3,300

So, in the above case the homeowner will save Rs. 3,300 on an average every month by installing a rooftop solar system.

In most cases, the homeowners are estimated to save a huge percentage of their monthly electricity bills by employing the rooftop solar system in their homes. Since there is an upfront cost involved, homeowners will need time to collectively be profitable.

Time required to break-even on the investment

Solar power systems, as we know, already are a long-term investment that enables smart savings in the long run. Typically, the cost of setup depends on the number, amount and capacity of the components installed.

In India, typically with the government subsidies involved, homeowners can break even on their investment with 2-3 years for a 5Kwh power system and without the government subsidies, it might take 3-5 years for the same.

Considering this scenario, a lot of homeowners are already ready to invest in the rooftop solar power systems in their homes.

Some of the successful implementations by Enphase:

Conclusion:

Rooftop solar system is becoming a common household entity in the recent times. These systems provide advantages like lower electricity bills, reduced carbon footprint, and potentially higher home values.

While the magnitude of the gains from the rooftop solar systems can vary widely from one house to another depending on various factors, with careful planning and implementation, homeowners can not only transition to green electric power supply at minimal recurring expenses but also sell the unused power to the electricity board generating revenues and further savings.

References
Solar Futures Study
Solar Futures Study

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