Many online tools give you a shiny payback period. But do they factor in panel degradation or annual maintenance? Most don’t.
This is where the calculator on this page changes the game. It considers things like panel degradation, tariff escalation, maintenance costs, and even financing options. This isn’t just a quick estimate. It’s a realistic simulation that helps you understand your potential savings over 25 years.
Let’s walk through the main factors the calculator uses. These are the levers that determine if and when solar pays off for you.
The first step is deciding how big your system should be. For reference, a 1 kW solar system in India generates approximately 4 to 5 units (kWh) of electricity daily.
The gross cost varies, but you should always look at the net system cost after subsidies. Under the PM Surya Ghar: Muft Bijli Yojana, the central government provides a Central Financial Assistance (CFA) of Rs. 30,000 per kW for the first 2 kW and Rs. 18,000 per kW for the additional one kW. For a typical 3 kW system, this brings the total subsidy to Rs. 78,000. So, if a vendor quotes you Rs. 1,65,000 for a 3 kW setup, your net cost becomes around Rs. 87,000 after subsidy. This is exactly why the calculator is pre-filled with that specific value.
The savings from solar directly offset what you pay the power company. If your monthly bill is low, the savings will be proportionally lower. The calculator allows you to input your exact monthly bill. For a household consuming around 400 units per month, annual electricity expenses often fall between ₹40,000 and ₹50,000.
Here’s a logical argument for solar that many miss. Grid electricity tariffs almost never go down.
According to ICRA, an average tariff hike of 4.5% is needed to revive discoms. Meanwhile, Goa recently approved an average hike of 4%. Over the long term, a 5% yearly escalation is a conservative and reasonable estimate. By using this in our calculator, you see the true value of locking in your electricity rates today with solar.
While a 1 kW system generates 4–5 units daily in good conditions, the actual figure for a 3 kW system in Indian cities ranges from 12 to 15 units per day. This generation is one half of the savings equation. The second half is self-consumption.
The calculator defaults to an 80% self-consumption rate. This is a realistic average for most households who run appliances like ACs, refrigerators, and fans during the day. The remaining 20% is exported to the grid. The export rate you receive is generally lower than the retail tariff you pay, often around ₹3 per unit. This value can vary by state, but the calculator’s default is a solid benchmark for planning purposes.
Here is where many free calculators cheat. They assume your solar system generates the same amount of power in year 25 as it did in year 1. That is simply false.
According to NREL (National Renewable Energy Laboratory) data, the median degradation rate for modern solar panels is 0.5% per year. By year 25, your panels will still be producing around 88% of their original rated output. This is a critical variable. A panel operating at 0.5% per year degradation will still be delivering about 87.5% of its original power after 25 years, making it a solid long-term investment.
Additionally, solar systems require basic upkeep. In India, basic cleaning and annual maintenance contracts typically range from ₹3,000 to ₹8,000 per year. Many estimates place this cost at roughly ₹1,000–₹2,000 per kW annually. The calculator includes this as an annual cost so you don’t get a shock later.
You have options. One major benefit of the PM Surya Ghar scheme is the availability of collateral-free loans.
The calculator lets you input your loan interest rate and tenure. Under the government’s scheme, you can access a loan of up to ₹2 lakh at an interest rate as low as just 6%. For loans between ₹2 lakh and ₹6 lakh, the rate aligns with standard home loan rates. For reference, many banks currently offer solar financing at rates between 7% and 9%. This opens the door for homeowners who don’t want to pay the full amount upfront.
Once you hit “Calculate,” the tool generates several key outputs.
First, it estimates your payback period. For a typical residential consumer in India, the payback period usually ranges from 3 to 6 years. When you combine lower hardware costs with rising grid tariffs, payback periods tighten further, especially for homes consuming 200–400 units a month and running daytime loads (like fridges, fans, and work-from-home equipment) on solar.
Second, it shows the 25-year savings and net profit. After the payback period, the electricity you generate is essentially free for another two decades.
Finally, the calculator includes a FD comparison. It projects how much your net system cost would grow if you invested it in a fixed deposit at a given rate. If the 25-year solar profit surpasses the FD maturity value, you get a thumbs-up. This is a fair comparison because it accounts for the opportunity cost of your capital.
Beyond the math, there is the planet.
A solar system doesn’t just save you money. It actively reduces your environmental footprint. For context, coal-based grid electricity emits roughly 0.9 kg of CO₂ for every unit (kWh) generated.
A typical residential system can avoid a substantial amount of CO₂ over its lifetime. For instance, a 5 kW system can cut around 6 tonnes of CO₂ per year—the equivalent of taking two cars off the road for a full year. The calculator uses a factor of 0.82 kg of CO₂ saved per unit of solar power generated, showing you the clean air impact of your investment.
Relying on generic claims isn’t helpful. This simulator uses verified data points, including the NREL degradation benchmark, the specific PM Surya Ghar subsidy structure, and realistic tariff escalation rates.
The best recommendation is to adjust the sliders and input fields to match your specific situation. Then, click calculate. Seeing the numbers for your unique scenario is the most reliable way to determine if going solar is the right decision for your home and your wallet.