☀️ Solar
🆓 Free
🇮🇳 PM Surya Ghar
☀️ Solar Panel Calculator
Enter your monthly electricity consumption and instantly get your recommended solar system size, how many panels you need, exact cost after PM Surya Ghar or ITC subsidy, year-one savings, payback period and a full 25-year financial projection. Works for India, USA and UK.
☀️ Solar System Calculator
Region
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Recommended System Size
️ Government Solar Subsidies
🇮🇳
PM Surya Ghar: Muft Bijli Yojana (2024)
India - Central Government Scheme
Subsidy slabs:
• Up to 1 kW: ₹30,000 subsidy
• 1–2 kW: ₹30,000 + ₹18,000 per additional kW
• 2–3 kW: ₹78,000 + ₹9,000 per additional kW (max ₹78,000 for residential)
• Above 3 kW: Fixed ₹78,000 subsidy
Eligibility: All residential consumers with grid-connected homes. Must use empanelled vendors via the National Portal.
How to apply: Visit pmsuryagarh.gov.in Register Apply for subsidy Get empanelled vendor Install Claim subsidy.
Benefit: Also get 300 units free electricity per month for eligible beneficiaries.
• Up to 1 kW: ₹30,000 subsidy
• 1–2 kW: ₹30,000 + ₹18,000 per additional kW
• 2–3 kW: ₹78,000 + ₹9,000 per additional kW (max ₹78,000 for residential)
• Above 3 kW: Fixed ₹78,000 subsidy
Eligibility: All residential consumers with grid-connected homes. Must use empanelled vendors via the National Portal.
How to apply: Visit pmsuryagarh.gov.in Register Apply for subsidy Get empanelled vendor Install Claim subsidy.
Benefit: Also get 300 units free electricity per month for eligible beneficiaries.
🇺🇸
US Federal Solar Tax Credit (ITC)
30% of total system cost
The Inflation Reduction Act extended the Investment Tax Credit (ITC) at 30% through 2032. For a $20,000 system, you get $6,000 back as a federal tax credit. Many states offer additional incentives (net metering, state tax credits). Check dsireusa.org for state-specific incentives.
🇬🇧
UK - Smart Export Guarantee (SEG)
Export payments for excess generation
The UK discontinued the Feed-in Tariff in 2019. The Smart Export Guarantee (SEG) requires energy suppliers to pay for exported electricity. Typical SEG rates: 3-15p/kWh exported. No upfront subsidy, but 0% VAT on residential solar installations applies. Home Upgrade Grant may apply for low-income households.
Solar System Sizing & ROI
System Size Calculation
Daily kWh needed = Monthly kWh / 30
System Size (kW) = Daily kWh needed
/ (Sun hours × (1 - System Loss%))
Example: 300 kWh/month, 5.5 sun-hrs, 20% loss
Daily kWh = 300 / 30 = 10 kWh
System kW = 10 / (5.5 × 0.80) = 2.27 kW
Recommend 2.5 kW (round up to nearest 0.5)
Annual Generation & Savings
Annual Generation (kWh) = System kW × Sun hrs
× 365 × (1 - Loss%)
Annual Savings = Annual kWh × Electricity Rate
Example: 2.5 kW system, 5.5 hrs, 20% loss, ₹8/kWh
Generation = 2.5 × 5.5 × 365 × 0.80 = 4,015 kWh
Savings = 4,015 × ₹8 = ₹32,120/year
Payback Period & ROI
Net System Cost = Gross Cost - Subsidy
Simple Payback = Net Cost / Annual Savings
25-Year ROI = (Total Savings over 25 yrs - Net Cost)
/ Net Cost × 100%
Note: Savings increase each year as electricity
prices rise. Panel output decreases ~0.5%/year
due to degradation (most panels have 25-yr warranty).
Net Metering
When your solar system generates MORE than you use:
Excess units fed back to the grid
Credited at a buy-back rate (usually 2-4 ₹/unit)
When you use MORE than your system generates:
Draw from the grid at normal tariff rates
Net bill = Units consumed from grid × tariff
- Units exported × buy-back rate
With net metering, systems can reduce bills to near
zero for many households.
Frequently Asked Questions
A typical Indian home consuming 300 units (kWh)/month needs a 2.5–3 kW solar system - roughly 6–8 panels at 400W each. The formula: System size (kW) = Daily kWh ÷ (Peak sun hours × (1 – System losses %)). Higher consumption, fewer sun hours in your city, or higher system losses all mean a larger system. Use the calculator above with your actual monthly bill figure for a precise recommendation.
PM Surya Ghar: Muft Bijli Yojana (launched 2024) offers central government subsidies: ₹30,000 for systems up to 1 kW; ₹30,000 + ₹18,000/kW for the 1–2 kW range; ₹78,000 + ₹9,000/kW for 2–3 kW - capped at ₹78,000 for residential connections. Eligible households also get 300 free electricity units per month. Apply at pmsuryagarh.gov.in: register with your electricity consumer number, apply online, get a site inspection, hire an empanelled vendor for installation, then claim your subsidy directly to your bank account.
With electricity tariffs of ₹7–9/unit and PM Surya Ghar subsidies applied, most Indian residential systems pay back in 4–7 years. After payback, the system generates free electricity for another 18–21 years against a 25-year panel warranty. Over 25 years, the ROI for Indian homes is typically 300–500% - outperforming most fixed-income investments with zero market risk.
Net metering allows your solar system to feed surplus electricity back to the DISCOM grid. When your panels generate more than you are consuming - usually daytime hours when you are at work - the excess units go to the grid and you earn a credit. Your monthly bill only charges you for net units consumed (units drawn minus units exported). For systems sized correctly to your consumption, this can reduce bills to near zero or even generate a credit balance.
Yes, though at reduced output. Solar panels generate electricity from diffuse light, not just direct sun. On overcast days, output typically falls to 10–25% of peak capacity. During India's monsoon season, systems still produce meaningful power - especially in southern and western states where monsoon is more predictable. Northeast India and areas with prolonged cloud cover may benefit from adding battery storage or slightly oversizing the system to compensate.
Very little. Monthly: wipe panels with a soft cloth and water - dust and bird droppings reduce output by 5–25% if left uncleaned. Annual: check wiring and MC4 connectors for corrosion, inspect the inverter display for fault codes, verify no new shading obstructions have appeared. Inverters typically need replacement once in 25 years (lifespan 10–15 years, cost ₹15,000–40,000). The panels themselves require no other maintenance and carry a 25-year performance warranty from reputable brands.
On-grid (grid-tied): connected to the DISCOM grid; net metering available; no battery needed; lowest cost; automatically shuts down during grid outages (safety standard). Off-grid: completely independent with battery bank; works during outages; higher cost; ideal for areas with poor or no grid supply. Hybrid: grid-connected plus battery storage; most expensive but most flexible - get net metering benefits when the grid is up and backup power during outages. Battery prices are falling, making hybrid increasingly cost-effective in 2025.
Not recommended for on-grid systems. Grid-connected installation in India requires: an empanelled vendor (mandatory for PM Surya Ghar subsidy eligibility), DISCOM approval and net metering agreement, a licensed electrician for grid interconnection, and compliance with CEA safety regulations. DIY installation voids panel warranties and subsidy eligibility. Professional installation is typically 15–20% of system cost and includes all approvals, net metering paperwork, and a workmanship warranty.
Solar Panel Calculator - System Size, Cost & ROI Explained
Going solar is one of the smartest financial decisions a homeowner can make right now - but only if you size the system correctly and know the numbers before you talk to any vendor. This calculator works through the complete picture: how big a system your home actually needs, what it costs after government subsidies, how much you save every year as electricity rates rise, and exactly when the system crosses from being a cost to generating pure profit.
Quick example - 300 kWh/month household in India (5.5 sun hrs, ₹8/unit, 20% losses): System size: 2.5 kW 7 panels (400W). Gross cost: ₹1,37,500. PM Surya Ghar subsidy: ₹48,000. Net cost: ₹89,500. Year-1 savings: ₹32,120. Payback: ~2.8 years. 25-year total savings: ₹11.2 lakh. 25-year ROI: ~1,152%.
How the System Size Calculation Works
The calculator converts your monthly consumption into the minimum solar capacity needed to cover it, accounting for real-world losses:
- Daily kWh needed = Monthly kWh ÷ 30
- Raw system size (kW) = Daily kWh ÷ (Peak sun hours × (1 – System loss %))
- Recommended size = Raw size rounded up to the nearest 0.5 kW
- Panels required = System kW × 1000 ÷ 400W per panel (rounded up)
System losses (typically 15–25%) account for wiring resistance, inverter inefficiency, dust, and temperature. Peak sun hours vary by location - Rajasthan gets 6–6.5 hours daily while northeast India averages 4–4.5 hours. Using the right sun hours figure for your city makes the size estimate significantly more accurate.
Understanding the Cost & Subsidy Figures
🇮🇳 India - PM Surya Ghar Subsidy
- Up to 1 kW: ₹30,000 flat subsidy
- 1–2 kW: ₹30,000 + ₹18,000 per additional kW
- 2–3 kW: ₹78,000 + ₹9,000 per additional kW
- Above 3 kW (residential): fixed ₹78,000 cap
- Bonus: 300 free units/month for eligible households
- Apply at pmsuryagarh.gov.in via empanelled vendor only
🇺🇸 USA - Federal ITC | 🇬🇧 UK - SEG
- US ITC: 30% of total system cost as federal tax credit (through 2032, Inflation Reduction Act)
- $20,000 system $6,000 tax credit. Net cost: $14,000
- Many US states offer additional net metering and state credits - check dsireusa.org
- UK: No upfront subsidy; Smart Export Guarantee pays 3–15p/kWh exported
- UK: 0% VAT on residential solar installations
Reading the 25-Year Projection
The projection models two real-world effects that dramatically impact long-term returns:
- Panel degradation (~0.5%/year): Solar panels slowly lose output over time. A panel generating 400W today produces roughly 390W in year 5 and 350W by year 25. Most premium panels carry a 25-year performance warranty guaranteeing at least 80% output at end of life.
- Electricity price inflation (~5%/year in India): Every year your electricity tariff rises, the value of each unit your solar system generates also rises. This compounding effect is why the annual savings numbers accelerate over time - your solar system is essentially a hedge against electricity price inflation.
The payback year (marked with in the table) is when cumulative savings equal your net installation cost. Every year after that is pure return on investment - with no risk, no market volatility, and a government-backed net metering framework protecting your earnings.
On-Grid vs Off-Grid vs Hybrid - Which One Should You Choose?
This calculator focuses on on-grid (grid-tied) systems, which are the right choice for the vast majority of urban and semi-urban Indian homes. Here's a quick comparison to help you decide:
- On-grid: Connected to the DISCOM grid. Net metering credits excess generation. No battery required - lowest cost. Power cuts off during grid outages (safety requirement). Best ROI for areas with reliable grid supply.
- Off-grid: Completely independent with battery storage. Ideal for remote areas or locations with frequent long outages. Higher upfront cost due to battery bank. No net metering benefit.
- Hybrid: Grid-connected with battery backup. Best of both worlds - net metering when grid is up, backup power during outages. Highest upfront cost but maximum flexibility. Increasingly popular as battery prices fall.
Is Solar the Right Decision for You Right Now?
Solar makes strong financial sense if most of these apply to your situation:
- Monthly electricity bill above ₹1,500 (India) / $80 (US) / £60 (UK)
- You own the property and the roof is in good condition
- South-facing roof (India/US) with no major shading from trees or buildings
- Your DISCOM offers net metering - most urban DISCOMs do as of 2025
- You plan to stay in the property for at least 5 years
- Your current tariff is ₹6/unit or higher - and electricity costs only go one direction
If fewer than three of these apply, the calculator still gives you an honest payback figure so you can decide with real numbers rather than a vendor's sales pitch.
How this calculator works, and where the numbers come from
The Solar Panel Calculator applies the standard formula for this calculation to the values you enter and updates the result as you type. The calculation itself happens in your browser, and the page explains the method so you can check any result by hand.
Please note: Results are estimates. Tariffs, appliance ratings and local rules vary; electrical work should follow local codes and be done by a qualified person.