Are solar batteries with rooftop solar economically viable?

For countless Indian households, uninterrupted power is a real challenge. This challenge can now be addressed thanks to rooftop photovoltaics and solar battery storage systems. A rooftop solar solution is an efficient way to harness solar energy, reduce dependence on traditional power sources, and ensure backup energy for your home.

In this blog, we’ll explore how batteries work with rooftop solar systems, the benefits of adding battery storage, the cost considerations, and the available financing options and subsidies that make this transition accessible for Indian consumers.

How Do Batteries Work with Rooftop Solar Systems?

Rooftop solar installations use photovoltaic (PV) panels to convert sunlight into electricity. The energy generated can be  first utilized to meet real-time electricity demands. Any surplus electricity, which exceeds your household’s immediate consumption, can be stored in solar batteries for later use. If the batteries reach full capacity, with an on-grid solution, the excess power is directed to the grid, where it can be sold to offset electricity costs.

Pairing your rooftop photovoltaics with a battery storage system allows you to tap into stored energy during power cuts, which are common across India, at night , or in an off-grid set-up. This hybrid setup ensures greater energy independence, enabling households to reduce reliance on diesel generators or grid electricity and switching to consuming renewable energy instead.

Figure 1

Adding batteries to your rooftop solar solution enhances its efficiency and usability, providing several key benefits:

• Power Backup: Solar batteries store energy that can be used during frequent power outages, ensuring uninterrupted electricity for essential appliances or if you’re working remotely.
• Energy Independence: With a hybrid setup, you reduce reliance on grid electricity or diesel generators, cutting down on expenses and harmful emissions.
• Optimized Renewable Energy Usage: Stored solar energy can be used during peak consumption hours, maximizing the efficiency and value of your rooftop solar system.
• Off-Grid Feasibility: For homes in remote areas where grid access is unreliable or nonexistent, battery integration is essential for off-grid solar solutions.

While integrating batteries increases the upfront investment, the long-term advantages make it a worthwhile addition for many households.

How to Choose Your Solar Battery Capacity?

Choosing an optimised battery capacity for your solar system is a critical step to ensure economic viability. Factors that influence the size of your solar battery to achieve this  include:

• Energy Consumption Patterns: Households with higher evening energy usage may require larger batteries to cover consumption during non-sunlight hours.
• PV Capacity of Your Rooftop Solar System:  To store all the excess energy generated,  it is important to factor in both the PV capacity installed, and the self consumption of generated solar energy. 
• State Regulations: Policies regarding renewable energy and net metering vary across India. Opting for batteries rather than exporting the excess may be more viable in your state.
• Solar Panel Efficiency: The efficiency of your photovoltaic panels directly affects the amount of energy they generate.
• Depth of Discharge: The depth of discharge tolerated by the battery type impacts how much of the stored energy can be used without affecting battery health.

Properly sizing your battery based on these factors ensures economic feasibility of the hybrid system, minimal energy wastage and efficient performance.

Understanding the Costs of Rooftop Solar Solutions

The cost of installing a rooftop solar solution varies depending on factors such as the type of panels, batteries, inverters, and the location of installation. The MNRE benchmark sets the minimum cost as in Table 1. This includes the cost of panels, a basic inverter minimal structure erection material and labour, before subsidy.

Table 1

Beyond 3kW the subsidy is capped at ₹ 78,000, and only available for residential installations. Some states like Pondicherry are providing additional subsidies to encourage renewable energy adoption.  While subsidy isn’t applicable from the 4th kW, the per kW cost of installation decreases with higher system capacity, making larger installations more economical in the long run. Check with your installer for the current market rate.

To compare the same scenario with and without batteries, we ran a few simulations on our advanced calculator. These were done for a residence with four residents, hence assuming 3kW installation and  in Tamil Nadu in the following scenarios:

• without batteries, with a peak consumption in the evening (everybody is out of the house during the day and comes back home in the evening). 
• without batteries, with a peak consumption in the day (some of the residents stay home all day)
• with lithium-ion batteries, with a peak consumption in the evening (everybody is out of the house during the day and comes back home in the evening). 
• with lithium-ion batteries, with a peak consumption in the day (some of the residents stay home all day)

Table 2

As shown above, batteries offer valuable benefits for uninterrupted power supply. However, if budget constraints arise, starting with solar panels alone provides quick payback and significant savings. Opting for a hybrid inverter initially can facilitate battery integration in the future.

Conclusion

Rooftop solar systems, when paired with battery storage, present an unparalleled opportunity for Indian households to embrace clean energy, save on electricity bills, and enjoy uninterrupted power supply. Whether you choose a basic system or a hybrid setup with batteries, a rooftop solar solution is a forward-thinking investment for a sustainable future. If your budget doesn’t allow you to invest in batteries immediately, it is often advisable to pay the difference and opt for a hybrid inverter from the start. This allows integration of batteries relatively easily in the future.

If you’re considering making the switch to solar, now is the perfect time to explore your options. With subsidies and financing support available, there’s never been a better moment to harness the power of the sun!
Looking for financing options? check out Financing Models for rooftop solar energy in India