How much will solar actually cost you after the ₹78,000 government subsidy? Will your payback period be 2 years or 8 years? Should you install 3 kW or 5 kW?
Stop guessing. Every day, hundreds of West Bengal homeowners search “solar subsidy calculator” and find either:
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Government portals that are confusing and don’t explain the math
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Generic calculators that ignore West Bengal’s specific tariffs and sunlight
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Sales pages disguised as calculators that push you to buy immediately
This guide gives you the exact formulas, real numbers, and a step-by-step manual calculation — plus a free tool to verify your results. By the end, you’ll know your precise system size, net cost after subsidy, monthly savings, payback period, and 25-year ROI.
No sales pitch. Just the math.
What You’ll Learn in This Article:
✔ How the PM Surya Ghar subsidy calculator works (official + independent)
✔ Step-by-step manual calculation with real West Bengal numbers
✔ System size recommendation based on your electricity bill
✔ Exact subsidy amount for 1 kW, 2 kW, 3 kW, 5 kW, and 10 kW systems
✔ Net cost after subsidy with GST breakdown
✔ Monthly and annual savings calculation
✔ Payback period formula with tariff escalation
✔ 25-year lifetime savings projection
✔ EMI vs. cash payment comparison
✔ CO₂ savings and environmental impact
✔ How to verify your calculation with official government tools
✔ Step-by-step manual calculation with real West Bengal numbers
✔ System size recommendation based on your electricity bill
✔ Exact subsidy amount for 1 kW, 2 kW, 3 kW, 5 kW, and 10 kW systems
✔ Net cost after subsidy with GST breakdown
✔ Monthly and annual savings calculation
✔ Payback period formula with tariff escalation
✔ 25-year lifetime savings projection
✔ EMI vs. cash payment comparison
✔ CO₂ savings and environmental impact
✔ How to verify your calculation with official government tools
🎯 FREE: Instant Solar Savings Report for Your Home
Get your personalized calculation in 60 seconds:
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Enter your monthly electricity bill → We calculate your ideal system size
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Select your city → We factor in local sunlight and WBSEDCL tariffs
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Get your complete report → Subsidy amount, net cost, payback, 25-year savings
→ Click Here to Check Your Eligibility → ← Takes only 30 seconds. No credit card needed.
Understanding the PM Surya Ghar Subsidy Structure
Before using any calculator, you need to understand the subsidy formula that every calculator uses. This is the foundation.
4.1 The Subsidy Formula (2026 Rates)
The PM Surya Ghar: Muft Bijli Yojana uses a tiered subsidy structure capped at ₹78,000:
Table
| System Capacity | Subsidy Rate | Subsidy Amount |
|---|---|---|
| 1st kW | ₹30,000 per kW | ₹30,000 |
| 2nd kW | ₹30,000 per kW | ₹60,000 (cumulative) |
| 3rd kW | ₹18,000 per kW | ₹78,000 (cumulative) |
| 4th kW and above | ₹0 per kW | ₹78,000 (capped) |
Critical rule: The subsidy is capped at ₹78,000 regardless of system size. A 3 kW system gets ₹78,000. A 10 kW system also gets ₹78,000.
4.2 Who Qualifies for the Subsidy?
Table
| Eligibility | Requirement |
|---|---|
| Property | Must own the residential property |
| Connection | WBSEDCL residential electricity connection |
| Existing Solar | No pre-existing rooftop/ground-mounted solar |
| Income | No upper limit — all income levels eligible |
| Roof | Minimum 100 sq ft shadow-free area per kW |
| Bank Account | Aadhaar-linked account for DBT transfer |
Not eligible: Renters, commercial properties, government buildings, homes with existing solar, CESC consumers (separate process).
How to Calculate Your Solar Savings: Step-by-Step
5.1 Step 1: Determine Your System Size
Your system size depends on your monthly electricity consumption (units/kWh), not your bill amount.
How to find your consumption:
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Check your WBSEDCL bill for “Units Consumed” or “kWh”
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Average the last 12 months for accuracy
System size formula:
plain
System Size (kW) = Monthly Units ÷ 120Why 120? A 1 kW system in West Bengal generates ~120 units per month on average (4-4.5 peak sun hours × 30 days × system efficiency).
Table
| Monthly Consumption | Recommended System Size | Roof Area Needed |
|---|---|---|
| 100-150 units | 1-2 kW | 100-200 sq ft |
| 150-300 units | 2-3 kW | 200-300 sq ft |
| 300-500 units | 3-5 kW | 300-500 sq ft |
| 500-800 units | 5-7 kW | 500-700 sq ft |
| 800-1,100 units | 8-10 kW | 800-1,000 sq ft |
Example: If you consume 350 units/month:
plain
350 ÷ 120 = 2.91 kW → Round up to 3 kW5.2 Step 2: Calculate System Cost (Before Subsidy)
System cost = (Capacity × Per kW Rate) + GST
Current market rates in West Bengal (2026):
Table
| System Size | Per kW Rate | Total Cost (Excl. GST) | GST (5%) | Total Cost (Incl. GST) |
|---|---|---|---|---|
| 1 kW | ₹75,000-₹90,000 | ₹75,000-₹90,000 | ₹3,750-₹4,500 | ₹78,750-₹94,500 |
| 2 kW | ₹70,000-₹85,000 | ₹1,40,000-₹1,70,000 | ₹7,000-₹8,500 | ₹1,47,000-₹1,78,500 |
| 3 kW | ₹65,000-₹80,000 | ₹1,95,000-₹2,40,000 | ₹9,750-₹12,000 | ₹2,04,750-₹2,52,000 |
| 5 kW | ₹60,000-₹75,000 | ₹3,00,000-₹3,75,000 | ₹15,000-₹18,750 | ₹3,15,000-₹3,93,750 |
| 10 kW | ₹55,000-₹70,000 | ₹5,50,000-₹7,00,000 | ₹27,500-₹35,000 | ₹5,77,500-₹7,35,000 |
Note: Per kW rate decreases as system size increases (economies of scale). Premium brands (Tata Power) cost 10-15% more but deliver better efficiency and warranty.
5.3 Step 3: Apply the Subsidy
Table
| System Size | Total Cost (Incl. GST) | Subsidy | Net Cost After Subsidy |
|---|---|---|---|
| 1 kW | ₹78,750-₹94,500 | ₹30,000 | ₹48,750-₹64,500 |
| 2 kW | ₹1,47,000-₹1,78,500 | ₹60,000 | ₹87,000-₹1,18,500 |
| 3 kW | ₹2,04,750-₹2,52,000 | ₹78,000 | ₹1,26,750-₹1,74,000 |
| 5 kW | ₹3,15,000-₹3,93,750 | ₹78,000 | ₹2,37,000-₹3,15,750 |
| 10 kW | ₹5,77,500-₹7,35,000 | ₹78,000 | ₹4,99,500-₹6,57,000 |
GST note: GST is calculated on the full amount before subsidy deduction. The subsidy is a post-installation credit, not a discount.
5.4 Step 4: Calculate Monthly Savings
Monthly Savings = (Monthly Units Generated × Tariff per Unit) – Fixed Charges
West Bengal residential tariffs (WBSEDCL, 2026):
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First 75 units: ₹5.50/unit
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76-150 units: ₹6.20/unit
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151-300 units: ₹7.20/unit
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301-500 units: ₹7.80/unit
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Above 500 units: ₹8.50-₹9.50/unit
Example calculation (3 kW system, 350 units/month consumption):
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Solar generation: 350 units/month (offsets 100% of consumption)
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Average tariff: ~₹7.50/unit (blended rate for 350 units)
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Monthly savings: 350 × ₹7.50 = ₹2,625
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Less: Fixed charges (unavoidable) = ₹50-₹150
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Net monthly savings: ₹2,475-₹2,575
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Annual savings: ₹29,700-₹30,900
With net metering (excess generation credited):
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If you generate 400 units but consume 350, 50 units are exported
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Export credit: 50 × ₹7.50 = ₹375 (offsets future bills)
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Effective annual savings: ₹33,000-₹35,000
5.5 Step 5: Calculate Payback Period
Simple Payback = Net Cost After Subsidy ÷ Annual Savings
Example (3 kW system):
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Net cost after subsidy: ₹1,50,000 (mid-range)
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Annual savings: ₹33,000
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Simple payback: ₹1,50,000 ÷ ₹33,000 = 4.5 years
But this ignores tariff escalation. With 8% annual tariff increase:
Table
| Year | Annual Savings | Cumulative Savings |
|---|---|---|
| 1 | ₹33,000 | ₹33,000 |
| 2 | ₹35,640 | ₹68,640 |
| 3 | ₹38,491 | ₹1,07,131 |
| 4 | ₹41,570 | ₹1,48,701 |
| 5 | ₹44,896 | ₹1,93,597 |
Real payback with escalation: ~3.8 years
5.6 Step 6: Calculate 25-Year Lifetime Savings
Formula: Sum of annual savings with 8% escalation over 25 years, minus maintenance costs.
Example (3 kW system):
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Year 1 savings: ₹33,000
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Year 25 savings: ₹2,25,000+ (at 8% compound growth)
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Total 25-year savings (gross): ₹22,00,000-₹25,00,000
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Less: Total maintenance (₹500/year × 25) = ₹12,500
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Net 25-year savings: ₹21,87,500-₹24,87,500
ROI calculation:
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Investment: ₹1,50,000
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Return: ₹22,00,000+
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ROI: 1,367% over 25 years
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Annualized return: ~11.5%
Complete Calculation Examples for West Bengal
Example 1: Small Home in Kolkata (2 kW System)
Table
| Parameter | Value |
|---|---|
| Monthly bill | ₹2,800 |
| Monthly consumption | 180 units |
| Recommended system | 2 kW |
| System cost (incl. GST) | ₹1,60,000 |
| PM Surya Ghar subsidy | ₹60,000 |
| Net cost after subsidy | ₹1,00,000 |
| Monthly generation | 180 units |
| Monthly savings | ₹1,350 (after fixed charges) |
| Annual savings | ₹16,200 |
| Payback period | 6.2 years (simple) / 5.1 years (with escalation) |
| 25-year savings | ₹10,50,000-₹12,00,000 |
Example 2: Medium Home in Siliguri (3 kW System)
Table
Example 3: Large Villa in Kolkata (5 kW System)
Table
| Parameter | Value |
|---|---|
| Monthly bill | ₹8,500 |
| Monthly consumption | 650 units |
| Recommended system | 5 kW |
| System cost (incl. GST) | ₹3,50,000 |
| PM Surya Ghar subsidy | ₹78,000 |
| Net cost after subsidy | ₹2,72,000 |
| Monthly generation | 600 units |
| Monthly savings | ₹4,800 (after fixed charges) |
| Annual savings | ₹57,600 |
| Payback period | 4.7 years (simple) / 3.9 years (with escalation) |
| 25-year savings | ₹40,00,000-₹45,00,000 |
Example 4: Luxury Bungalow (10 kW System)
Table
| Parameter | Value |
|---|---|
| Monthly bill | ₹15,000 |
| Monthly consumption | 1,100 units |
| Recommended system | 10 kW |
| System cost (incl. GST) | ₹6,50,000 |
| PM Surya Ghar subsidy | ₹78,000 |
| Net cost after subsidy | ₹5,72,000 |
| Monthly generation | 1,200 units |
| Monthly savings | ₹10,200 (after fixed charges) |
| Annual savings | ₹1,22,400 |
| Payback period | 4.7 years (simple) / 3.8 years (with escalation) |
| 25-year savings | ₹85,00,000-₹95,00,000 |
EMI vs. Cash: Which Saves More?
7.1 EMI Calculation Formula
plain
EMI = [P × R × (1+R)^N] ÷ [(1+R)^N - 1]Where:
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P = Principal loan amount (net cost after subsidy)
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R = Monthly interest rate (annual rate ÷ 12)
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N = Loan tenure in months
7.2 EMI Comparison Table
Table
| System | Net Cost | Down Payment | Loan Amount | Interest Rate | Tenure | EMI | Total Interest | Total Cost |
|---|---|---|---|---|---|---|---|---|
| 2 kW | ₹1,00,000 | ₹0 | ₹1,00,000 | 9% | 5 years | ₹2,075 | ₹24,500 | ₹1,24,500 |
| 3 kW | ₹1,42,000 | ₹0 | ₹1,42,000 | 9% | 5 years | ₹2,947 | ₹34,820 | ₹1,76,820 |
| 3 kW | ₹1,42,000 | ₹42,000 | ₹1,00,000 | 9% | 5 years | ₹2,075 | ₹24,500 | ₹1,66,500 |
| 5 kW | ₹2,72,000 | ₹0 | ₹2,72,000 | 9% | 7 years | ₹4,380 | ₹95,920 | ₹3,67,920 |
| 5 kW | ₹2,72,000 | ₹72,000 | ₹2,00,000 | 9% | 5 years | ₹4,150 | ₹49,000 | ₹3,21,000 |
| 10 kW | ₹5,72,000 | ₹0 | ₹5,72,000 | 9% | 7 years | ₹9,210 | ₹2,01,640 | ₹7,73,640 |
Key insight: Even with EMI interest, your monthly payment is often LOWER than your current electricity bill. A 3 kW system EMI of ₹2,947 vs. a ₹4,500 electricity bill = you’re saving ₹1,553/month while paying off your system.
7.2 Solar Loan Banks (PM Surya Ghar Linked)
Table
| Bank | Interest Rate | Max Loan | Tenure | Special Feature |
|---|---|---|---|---|
| SBI | 9.5-10.5% | ₹20 lakh | 5-10 years | Subsidy-adjusted principal |
| HDFC Bank | 9.99% | ₹15 lakh | 5-7 years | Quick approval |
| Axis Bank | 8.5-9.5% | ₹10 lakh | 5-7 years | Solar-specific product |
| Canara Bank | 8.5-9.5% | ₹20 lakh | 5-10 years | PM Surya Ghar partner |
| Bank of Baroda | 9-10% | ₹15 lakh | 5-8 years | Collateral-free |
SolarLogix advantage: We have tie-ups offering 0.5-1.5% below standard rates.
Frequently Asked Questions (20 FAQs)
Calculator & Methodology
Q1: How accurate are solar subsidy calculators? A: Most calculators are accurate within 10-15% for system sizing and 15-20% for savings. Variations come from: actual roof orientation, shading, panel efficiency, and tariff changes. Always get a site assessment for precise numbers.
Q2: Why do different calculators show different results? A: Each calculator uses different assumptions for:
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Peak sun hours (4.0-5.5 for West Bengal)
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System efficiency (75-85%)
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Tariff escalation (5-10%)
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Maintenance costs (0.5-1.5% annually)
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Panel degradation (0.5-0.8% per year)
Q3: Does the calculator include GST? A: Some do, some don’t. Always verify. SolarLogix calculators include 5% GST on the full system cost. The subsidy is deducted after GST calculation.
Q4: What’s the difference between “simple payback” and “real payback”? A: Simple payback = cost ÷ annual savings (ignores tariff hikes). Real payback factors in 8-12% annual tariff escalation, which typically reduces payback by 0.5-1.5 years.
→ Click Here to Check Your Eligibility → ← Takes only 30 seconds. No credit card needed.
Subsidy & Eligibility
Q5: The calculator shows ₹78,000 subsidy. Will I definitely get it? A: Only if you meet ALL eligibility criteria: property ownership, WBSEDCL connection, no existing solar, DCR-compliant panels, WBSEDCL-empanelled installer. The calculator assumes eligibility — verify yours separately.
Q6: Can I get more than ₹78,000 subsidy? A: Some states offer top-up subsidies. West Bengal’s state nodal agency (BEE) may offer additional benefits, but as of 2026, the primary subsidy is capped at ₹78,000 centrally. Check current state notifications.
Q7: What if my sanctioned load is less than my recommended system size? A: You can only install up to your sanctioned load. If your load is 3 kW but you need 5 kW, apply for load enhancement with WBSEDCL first (₹1,500-₹3,000 fee). The calculator should be adjusted accordingly.
Q8: Does the subsidy calculator work for commercial buildings? A: No. PM Surya Ghar is residential-only. Commercial calculators use different subsidy structures (accelerated depreciation, tax benefits) and typically show higher payback periods.
Financial & Savings
Q9: Should I trust the 25-year savings figure? A: It’s a reasonable projection if you assume:
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Panels last 25 years (Tata Power warranty covers this)
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Inverter replaced once (at year 10-12, ₹40,000-₹60,000)
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Tariffs rise 8% annually (historically accurate for WBSEDCL)
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Minor maintenance annually (₹500-₹1,000)
Q10: Why is my payback period longer than the calculator shows? A: Common reasons: higher-than-expected system cost, lower generation due to shading, delayed subsidy disbursement, or choosing a smaller system than recommended.
Q11: Can I calculate savings for a partial system (not full offset)? A: Yes. If you install 2 kW but consume 350 units, the calculator should show:
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Solar generation: 240 units
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Grid consumption: 110 units
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Savings: 240 × tariff (not 350 × tariff)
Q12: How do I factor in net metering benefits? A: Net metering credits are typically 1:1 in West Bengal (1 unit exported = 1 unit credited). Most calculators assume net metering is operational. If your area doesn’t have net metering yet, reduce savings by 10-15%.
Technical & Installation
Q13: The calculator says I need 5 kW but my roof is only 400 sq ft. What do I do? A: Install the maximum capacity that fits. 400 sq ft ≈ 4 kW with high-efficiency panels (400W+). The calculator’s “recommended” size is ideal; “feasible” size depends on roof area.
Q14: Does the calculator account for panel direction and tilt? A: Advanced calculators (MYSUN, Vikram Solar) do. Basic calculators assume South-facing, 20-25° tilt. East/West-facing roofs reduce output by 10-15%. Flat roofs with elevated structures perform optimally.
Q15: What about monsoon season impact on calculations? A: Most calculators use annual averages that already factor in monsoon dips (June-September: 20-25% lower generation). Don’t manually reduce figures further.
Q16: Can I calculate for battery storage (hybrid system)? A: Most basic calculators don’t include batteries. Hybrid systems cost ₹3-₹5 lakh extra for 5-10 kWh storage. Calculate separately: battery cost ÷ (backup savings + enhanced self-consumption).
Comparison & Decision
Q17: Is it better to calculate online or get a manual quote? A: Use online calculators for initial research and budgeting. Get 2-3 manual quotes from WBSEDCL-empanelled installers for precise, site-specific numbers. SolarLogix offers free detailed quotes that refine calculator estimates.
Q18: How do I compare calculator results from different companies? A: Normalize by checking:
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Are GST and subsidy handled the same way?
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Is maintenance cost included?
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What tariff escalation rate is assumed?
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Are net metering benefits included?
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Is the panel degradation rate realistic (0.5-0.8%/year)?
Q19: Should I calculate for 3 kW or 5 kW if I’m between sizes? A: If your roof and budget allow, size up. The marginal cost per kW decreases (₹65,000/kW for 3 kW vs. ₹60,000/kW for 5 kW), and you get more lifetime savings. The subsidy cap at ₹78,000 means larger systems have lower “subsidy per kW” but still excellent ROI.
Q20: Can I recalculate after installation to track actual vs. projected savings? A: Absolutely. SolarLogix provides a monitoring dashboard that compares projected vs. actual generation monthly. Most systems perform within 5-10% of calculator estimates in Year 1.
🎯 Stop Guessing. Calculate Your Exact Solar Savings Now.
In 60 seconds, know:
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✅ Your ideal system size
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✅ Exact ₹78,000 PM Surya Ghar subsidy
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✅ Net cost after subsidy
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✅ Monthly & annual savings
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✅ Payback period (with tariff escalation)
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✅ 25-year lifetime savings
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✅ EMI options vs. cash payment
→ Click Here to Check Your Eligibility → ← Takes only 30 seconds. No credit card needed.
🎁 GET YOUR FREE PERSONALIZED SOLAR SUBSIDY CALCULATION
What You’ll Receive (Instant + Emailed):
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Recommended System Size — Based on your actual bill
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Subsidy Breakdown — ₹30k + ₹30k + ₹18k = ₹78,000 explained
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Net Cost After Subsidy — Including GST, no hidden charges
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Monthly Savings — Customized to WBSEDCL tariffs
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Payback Period — Simple + real (with escalation)
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25-Year Projection — Total savings, ROI, CO₂ avoided
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EMI Comparison — 3 bank options, interest, tenure
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Site Assessment Offer — Free validation of calculator results
Calculate Now (60 Seconds):
→ Click Here to Check Your Eligibility → ← Takes only 60 seconds. No credit card needed.
SolarLogix – Engineered Energy. Assured Performance.
Official Tata Power Solar Authorized Channel Partner | WBSEDCL-Empanelled Installer
Contact Methods:
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Phone: +91 833-788-7888 (24/7 support)
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WhatsApp: +91 833-788-7888 (instant response)
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Email: contact@solarlogix.in
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Website: www.solarlogix.in
Service Areas:
West Bengal (all districts): Kolkata, Siliguri, Darjeeling, Jalpaiguri, Malda, Cooch Behar, Raiganj, Bankura, Birbhum, Bardhaman
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Our Commitment:
“Every homeowner deserves transparent numbers before making a solar decision. Our calculator is built on real West Bengal data — not national averages — so you get answers you can trust.” — Akhil Sonthalia, Founder
