Solar Savings & System Calculator Pro
Calculate your recommended rooftop solar system capacity (kW), panel count, immediate monthly electricity bill savings, 25-year cumulative ROI, government subsidies, and consult our built-in AI Solar Optimizer.
Energy Usage & Sun Availability
System Pricing & Subsidies
Financing Model & Inflation Analysis
25-Year Cumulative Savings Trajectory
Roof Geometry & Panel Configuration
Battery Storage & Backup (Optional)
Photovoltaic Engineering Specification
Verified Environmental Offset (25 Years)
Intelligent System Viability & Optimization Audit
Analyzing your monthly load, roof footprint, local solar irradiation, and utility tariffs to maximize your investment velocity.
Roof Real Estate Efficiency
Optimal Space RatioYour roof area comfortably accommodates the recommended array with adequate safety margins for walkways and fire code setbacks.
25-Year Utility Price Shield
Hedges ₹18,00,000+At an average 4.5% annual tariff escalation, your power company would collect over triple your initial system cost over the next 25 years.
Battery Storage Feasibility
Strategic OptionUnder retail 1:1 net metering, a battery is primarily for blackout resilience. If your utility shifts to Time-of-Use (TOU) rates, battery storage accelerates self-consumption.
Government Incentive Radar
PM Surya Ghar Yojana (₹78,000)Eligible for direct government subsidies and clean energy credits that directly reduce your net turnkey investment.
AI Top Recommendations to Shorten Payback by 1.5 – 2.5 Years:
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Shift High-Load Appliances to Peak Solar Hours (10:30 AM – 3:30 PM): Run air conditioning, washing machines, water pumps, and dishwashers during midday sunlight to maximize direct solar self-consumption.
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Pair with Electric Vehicle (EV) Charging: Charging an EV with rooftop solar reduces running cost to under ₹0.75 per km, significantly multiplying your household energy ROI.
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Bi-Monthly Module Cleaning & Washing: Dust and grime cause a 5% to 12% generation loss. A light quarterly rinse keeps energy harvest at factory-peak levels.
Turnkey System Cost & Subsidy Breakdown
| Description & Engineering Component | Specification / Quantity | Amount |
|---|---|---|
|
Photovoltaic Solar Modules (Tier 1)
High-efficiency Mono-crystalline / TOPCon panels, 25-yr linear power warranty
|
10 Panels (~440W each) | ₹1,08,900 |
|
Inverter & Power Conditioning Unit
Smart MPPT inverter with cloud WiFi monitoring & grid protection
|
4.0 kW Smart Inverter | ₹36,300 |
|
Rooftop Mounting Structure & Racking
Anodized aluminum & galvanized hardware rated for 150 km/h wind speed
|
Full Array Hardware | ₹24,200 |
|
Balance of System (BOS) & Electrical Protection
DC/AC distribution boxes, SPD surge arrestors, UV-resistant solar cables, earthing
|
Turnkey BOS kit | ₹24,200 |
|
Engineering, Labor, Permitting & Net Metering
Licensed electrical labor, structural engineering inspection, utility interconnection filing
|
Certified Turnkey Service | ₹48,400 |
| Gross Turnkey System Cost | ₹2,42,000 | |
|
Government Subsidy / Tax Incentive Benefit (32%)
Direct financial subsidy or tax credit deductible from installation cost
|
- ₹78,000 | |
| NET OUT-OF-POCKET INVESTMENT | ₹1,64,000 | |
Guaranteed 84.8% minimum linear output at Year 25.
Full manufacturer replacement warranty with cloud monitoring.
Complete waterproofing and structural mounting protection.
How Rooftop Solar Sizing & Savings Are Calculated
Our simulation algorithms follow the National Renewable Energy Laboratory (NREL PVWatts) engineering standards to ensure high-accuracy projections.
System kW = (Monthly kWh ÷ 30) ÷ (Sun Hours × 0.78 Derate)
Accounts for inverter DC-to-AC conversion loss, thermal cell derating, dust build-up, and wiring resistance (standard 0.78 factor).
Annual kWh = System kW × Peak Sun Hours × 365 × 0.78
Simulates real-world yearly solar harvest adjusted for local climate insolation and degradation over 25 years.
Payback (Years) = Net Turnkey Cost ÷ Year 1 Electricity Savings
Determines the exact break-even point where cumulative utility bill savings exceed your net out-of-pocket investment.
Lifetime Profit = 25Y Avoided Bills - Net System Cost - Maintenance
Incorporates 4.0% - 4.5% annual utility inflation, 0.5% yearly panel degradation, and inverter replacement around Year 13.
Global Solar Subsidies & Net Metering Guide (2026 Updated)
Check the active financial benefits available for your rooftop solar installation across key regions:
| Country / Region | Primary Subsidy / Scheme | Financial Incentive Value | Net Metering Policy |
|---|---|---|---|
| India (PM Surya Ghar) | PM Surya Ghar Muft Bijli Yojana | Up to ₹78,000 Direct Subsidy | Bi-directional Net Metering across state DISCOMs |
| United States | Residential Clean Energy Credit (Sec 25D) | 30% Federal Income Tax Credit (ITC) | NEM 2.0 / NEM 3.0 (Time-of-Use Export Credits) |
| United Kingdom | 0% VAT on Solar Panels & Batteries | 20% Immediate Tax Exemption | Smart Export Guarantee (SEG) cash per kWh |
| Australia | Small-scale Renewable Scheme (STC) | A$2,200 – A$3,500 Upfront Discount | State Feed-in Tariff (FiT) credits |
| Europe (Germany/EU) | EU Green Deal & 0% VAT | 0% VAT + Guaranteed Feed-in Tariff | Renewable Energy Act (EEG) grid feed-in rates |
| Canada | Canada Greener Homes Loan | Up to C$40,000 Interest-Free Loan | Provincial Net Metering credits (1:1 offset) |
Rooftop Solar ROI, Battery Backup & Maintenance FAQs
Expert answers to the most common questions regarding solar feasibility and installation:
How is my recommended solar system size (kW) calculated?
Your ideal solar system size is determined by taking your monthly kilowatt-hour (kWh) electricity usage, dividing it by 30 days to get your daily energy requirement, and then dividing by your region's average Peak Sun Hours per day. We then apply an industry-standard engineering derate factor of 0.78 to account for inverter conversion losses (DC to AC), ambient temperature derating, dust, and wiring resistance. For example, a home using 560 kWh/month in an area with 5.2 peak sun hours requires approximately a 4.4 kW DC system.
How does Net Metering work with my local electric utility?
Net Metering uses a bi-directional electric meter installed by your power company. During sunny daylight hours, your solar panels often produce more electricity than your home consumes. This surplus electricity is automatically sent backwards onto the local power grid, spinning your electric meter in reverse and generating bill credits. At night, you pull electricity back from the grid, using those credits. At the end of the billing cycle, you only pay for the net difference.
How do I claim government subsidies (like PM Surya Ghar or US Federal ITC)?
In India, you apply through the official National Portal for Rooftop Solar (pmsuryaghar.gov.in) before installation. After your DISCOM inspects and installs the net meter, the subsidy (up to ₹78,000 for 3kW+) is credited directly to your bank account via DBT. In the United States, you claim the 30% Residential Clean Energy Credit on IRS Form 5695 when filing your annual federal tax return.
Do I need a battery storage system (like Tesla Powerwall)?
If your utility offers favorable 1:1 Net Metering, a battery is not mandatory to achieve bill savings; the electrical grid effectively acts as your battery. However, batteries are essential if: (1) You live in an area with frequent blackout storms and need emergency backup power, or (2) Your utility uses aggressive Time-of-Use (TOU) rates where evening power prices are very high.
How long do modern solar panels last and what is the degradation rate?
Tier-1 Mono-crystalline and TOPCon solar panels are engineered to last 25 to 35+ years. Under manufacturer performance warranties, panels degrade at approximately 0.5% per year (or 0.35% for premium heterojunction cells). This means at Year 25, your solar panels will still produce roughly 84% to 88% of their original factory nameplate power output.
What happens during rainy or heavily overcast cloudy days?
Solar panels continue to produce electricity on cloudy days because photovoltaic cells capture both direct beam radiation and diffuse ambient sunlight. Generation drops to roughly 20% to 40% of peak rated capacity on overcast days. Your grid interconnection automatically supplements the difference without any interruption.
Results provided by this calculator are engineering estimates based on standard solar insolation benchmarks, current utility tariffs, and statutory subsidy guidelines. Actual energy yield and financial returns may vary based on exact roof orientation, tilt angle, local weather variations, shading obstacles, and specific utility interconnection agreements. Always obtain a formal structural roof audit and on-site shade analysis from a certified local solar professional prior to installation.
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| Solar Savings Calculator |
Solar Savings Calculator: How to Estimate Your Rooftop Solar Savings A rooftop solar system is a long-term investment, so the first question is always the same: how much will I actually save? The answer depends on your electricity bill, your tariff, your system size and the sunlight at your location.
The Solar Savings Calculator turns these inputs into clear numbers. You get estimated monthly generation, bill savings, net system cost after subsidy and the payback period.
This guide explains how the calculator works, what each input means, and how to read the result.
Table of Contents
- What Is a Solar Savings Calculator
- Why You Should Calculate Before Installing
- Inputs Used in the Calculator
- Formulas Behind the Calculation
- How to Use the Calculator
- Worked Example with Real Numbers
- Central Subsidy Under PM Surya Ghar
- Factors That Change Your Savings
- Limitations of Any Online Estimate
- Frequently Asked Questions
What Is a Solar Savings Calculator
A solar savings calculator estimates how much electricity a rooftop system will generate and how much money that electricity is worth. It compares your current bill with the bill you would pay after installing solar.
It also compares the money you spend on the system with the money you save each year. This gives you the payback period, which is the time taken to recover your investment.
Why You Should Calculate Before Installing
Installers often quote a system size based on a rough guess. A quick calculation helps you check that quote with your own numbers.
- It stops you from buying a system that is too large or too small
- It shows whether the subsidy changes the payback in a meaningful way
- It lets you compare two quotes side by side
- It gives you a realistic savings figure instead of a sales promise
Inputs Used in the Calculator
Each field below affects the result. Use real values from your latest bill wherever possible.
| Input | What It Means | Where to Find It |
|---|---|---|
| Monthly units used (kWh) | Electricity you consume in a month | Your electricity bill |
| Tariff per unit (Rs) | Average rate you pay per unit | Total bill divided by units |
| System size (kW) | Capacity of the solar plant | Installer quote |
| Total system cost (Rs) | Price before subsidy | Installer quote |
| Subsidy amount (Rs) | Government support you receive | Scheme rules or state portal |
| Peak sun hours per day | Effective full-sunlight hours | Typically 4 to 6 in most of India |
| Performance ratio | Losses from heat, wiring and dust | Usually 75% to 80% |
If you do not know the sun hours or performance ratio, keep the default values. They are reasonable for most Indian locations.
Formulas Behind the Calculation
The calculator uses simple, transparent formulas.
Monthly generation (units) = System size in kW x Peak sun hours x 30 x Performance ratio
Monthly savings (Rs) = Monthly generation x Tariff per unit
Annual savings (Rs) = Monthly savings x 12
Net system cost (Rs) = Total system cost - Subsidy
Payback period (years) = Net system cost / Annual savings
Savings are capped at your actual consumption. A system cannot save you more units than you use, unless your state pays for exported units.
Image Tools
How to Use the Calculator
- Enter your average monthly electricity consumption in units.
- Enter your tariff per unit. If unsure, divide your last bill amount by the units consumed.
- Select the system size in kW. A common thumb rule is 1 kW for every 120 to 150 units used per month.
- Enter the total system cost from your installer quote.
- Add the subsidy amount you expect to receive.
- Keep or adjust the peak sun hours and performance ratio
. - Click Calculate to see your monthly savings, yearly savings, net cost and payback period.
Try two or three system sizes. The best size is usually the one that covers most of your consumption without overshooting it.
Worked Example with Real Numbers
The table below uses the following assumptions: 5 peak sun hours, 78% performance ratio and a tariff of Rs 7 per unit. System costs are illustrative and will vary by city, brand and installer.
| System Size | Monthly Generation | Monthly Savings | Annual Savings | Approx. Cost | Subsidy | Net Cost | Payback |
|---|---|---|---|---|---|---|---|
| 1 kW | 117 units | Rs 819 | Rs 9,828 | Rs 70,000 | Rs 30,000 | Rs 40,000 | 4.1 years |
| 2 kW | 234 units | Rs 1,638 | Rs 19,656 | Rs 1,30,000 | Rs 60,000 | Rs 70,000 | 3.6 years |
| 3 kW | 351 units | Rs 2,457 | Rs 29,484 | Rs 1,80,000 | Rs 78,000 | Rs 1,02,000 | 3.5 years |
| 5 kW | 585 units | Rs 4,095 | Rs 49,140 | Rs 2,90,000 | Rs 78,000 | Rs 2,12,000 | 4.3 years |
Notice that the 3 kW system has the shortest payback here. This is because the subsidy reaches its maximum at 3 kW. Capacity above that is fully self-funded.
Central Subsidy Under PM Surya Ghar
For residential rooftop systems, the PM Surya Ghar: Muft Bijli Yojana provides central financial assistance based on system capacity.
| System Capacity | Central Subsidy |
|---|---|
| 1 kW | Rs 30,000 |
| 2 kW | Rs 60,000 |
| 3 kW and above | Rs 78,000 (maximum) |
Special category states and Union Territories receive higher rates. Several states also add their own top-up subsidy. The scheme is for grid-connected residential systems, and the modules must meet domestic manufacturing requirements.
Rules and amounts can change, so confirm the latest details on the official national rooftop solar portal before you apply.
Factors That Change Your Savings
- Location and sunlight: Rajasthan and Gujarat generally get more sun than the northeast or hilly regions.
- Roof direction and tilt: South-facing, unshaded roofs perform best in India.
- Shading: Even partial shade from a tank or tree can reduce output noticeably.
- Dust and cleaning: Dirty panels lose efficiency, so regular cleaning matters.
- Tariff slab: The higher your slab rate, the more each solar unit is worth.
- Panel ageing: Output drops slowly each year, roughly 0.5% annually for quality panels.
- Net metering policy: Rules for exported units differ by state and electricity distribution company.
Limitations of Any Online Estimate
This calculator gives a planning estimate, not a guaranteed result. Actual generation changes with weather, season and equipment quality.
The tool assumes a steady tariff. Real tariffs include fixed charges, duties and slab changes that a simple average cannot capture.
For a final decision, ask your installer for a site survey and a generation estimate for your exact roof. Use this calculator to check whether their numbers look reasonable.
Frequently Asked Questions
1. How accurate is the solar savings calculator?
It is accurate enough for planning. Results depend on the inputs you provide, especially tariff, sun hours and system cost. Expect real-world savings to land within a reasonable range of the estimate, not at an exact figure.
2. What size solar system do I need for my home?
Start with your monthly units. A common thumb rule is 1 kW for every 120 to 150 units per month. A home using 350 units a month would typically look at a 3 kW system. Roof space and budget also matter.
3. Does the calculator include the government subsidy?
Yes. You can enter the subsidy amount, and the tool subtracts it from the system cost before calculating payback. For residential systems, the central subsidy is up to Rs 78,000, and some states add more.
4. How long does it take for solar panels to pay for themselves?
For most Indian homes with a subsidy, the payback period is roughly 3 to 5 years. After that, the electricity from the system is nearly free for the remaining life of the panels, which is typically 25 years or more.
Conclusion
A rooftop solar system can cut your electricity bill for decades, but the right size and a fair price make all the difference. Enter your own numbers into the Solar Savings Calculator, compare a few system sizes, and use the result to evaluate every quote you receive.
