Frequently Asked Question

1. How much will it cost and how much will be the saving?
The project cost and monthly savings are dependent on capacity of the plant. In the output panel of the calculator, the average monthly saving and total project cost are mentioned.

2. What will be the capacity of the plant? How much roof area is required to install such a plant?
The capacity of the plant depends on the energy demand of the home. As the quantity of home appliances varies, the plant capacity updates. Typically a roof area of 9 Sq. m is required for a 1 kW system.

3. Should I have batteries to store the power? Or Should I sell the extra power to the Grid? Which is economical?
Storing energy in battery (Off-grid system) provides more energy independence than without them (Grid connected system). Because even at nights and less sunshine days, the stored energy will power the house. However, the downside to that is, thebatteries are less efficient and therefore increases the total cost of the system.

4. How much is the CO2 saving if I install a rooftop solar plant?
The annual CO2 saving is mentioned in the result section of the calculator. It is also represented in terms of equivalent trees planted.

5. What are the main assumptions made to develop the calculator?
Some of the assumptions made to develop the calculator are:

Capacity utilization factor – 19% Days of autonomy – 1
Inverter and Battery efficiency – 90% Battery Depth of Discharge – 50%
O&M cost escalation – 5.72% Average emission factor – 0.83 KgCO2/kWh
Discount factor – 14.2% Plant life – 25 years
Tariff increment – 5% every year Roof area per kW – 9 Sq. m

6. Are the calculator results accurate enough for my city?
While attempts have been made to provide accurate results, there are also several assumptions made in the calculator, which could negligibly distort the accuracy of the results. That said, the purpose of the calculator is to provide awareness on various technical and economic aspects of the solar rooftop systems.

7. My city is not included in the calculator. What should I do?
The calculator works based on pin code system. We had made all efforts to include all the regions of the country. If a pin code is missed out, please report it to our team (Krishan Kumar,, we will address the issue immediately.

8. For which kind of rooftop applications the calculator works best?
The calculator works best for residential buildings. It is not a best model for commercial or industrial building applications.

9. Should I get bank loan for my solar plant?
Availing bank loans will increase the monthly expense of the project. The calculator provides options to control the amount of loan and see the results accordingly. If the user finds the result acceptable, bank loan can be availed.

10. Which banks are providing loan for this purpose?
The Ministry of New and Renewable Energy (MNRE) advised all public sector banks to include rooftop solar PV loans in their home loan proposals. Some banks to mention are, Syndicate bank, Bank of India, Dena bank, State bank of India, Punjab national bank, Allahabad bank, Indian bank, Central bank of India andIndian overseas bank.

11. Is there any subsidy from state/central government for the rooftop projects?
Yes, there are. The Ministry of New and Renewable Energy (MNRE) provides 30% central finance assistance (CFA) for all types of residential buildings. In addition to that, there are also state specific incentives.