TNEB Solar Bill Calculator & Solar Savings Calculator (Updated 2026)
Calculate your rooftop solar bi-monthly generation, TANGEDCO net billing offset, PM Surya Ghar central subsidy (up to ₹78,000), and investment payback ROI in Tamil Nadu.
System Investment & Tariff Breakdown:
| Breakdown Item | Without Solar | With Solar | Savings / Value |
|---|---|---|---|
| Bi-monthly Units | 600 Units | 0 Net (750 Gen) | 600 Saved |
| Bi-monthly Bill Amount | ₹3,035 | ₹0.00 | ₹3,035 / Cycle |
| Gross Solar Plant Cost | - | ₹1,95,000 | ₹1,95,000 |
| PM Surya Ghar Central Subsidy | - | - ₹78,000 | DBT Credit |
| Net Customer Out-of-Pocket Cost | - | ₹1,17,000 | ₹1,17,000 |
Recommended System Specs & Feasibility:
- ⚡ Meter Type: Bi-directional Net Meter
- ☀️ Solar Panels: 6 × 550W DCR Modules
- 🔌 Phase Requirement: Single Phase (1-Phase)
- 🏛️ Subsidy Scheme: PM Surya Ghar (Direct Bank DBT)
What is a TNEB Solar Bill Calculator
A TNEB solar bill calculator works out how much you can save on your TANGEDCO electricity bill by installing a rooftop solar system, and how long it takes for that system to pay for itself. You enter your current bi-monthly consumption and the solar capacity you’re considering, and the tool calculates your expected generation, your new net billed units after solar offset, the PM Surya Ghar subsidy you qualify for, and your payback period.
Rooftop solar in Tamil Nadu works through something called net metering. TANGEDCO installs a bi-directional meter at your connection, so during the day, when your solar panels generate more power than your home is using, the extra units get exported to the grid. At night or on a cloudy day, when your panels aren’t producing enough, you draw units back from the grid as usual. At the end of the billing cycle, TANGEDCO only charges you for the difference, meaning total units consumed minus total units your system generated. This is what actually determines whether your bill drops a little or goes all the way down to zero.
This calculator does that offset math for you, along with the subsidy and cost numbers, so you’re not left guessing whether a 2 kW system or a 3 kW system makes more sense for your household.
Why You Need to Use This Tool
Here’s a real scenario that shows why this calculation matters. Say a family consumes 800 units in a bi-monthly cycle. Without solar, under the TNEB domestic slab structure, that bill comes to around ₹5,070 for that cycle, which adds up to roughly ₹30,420 a year.
Now say the same family installs a 3 kW rooftop solar system. In Tamil Nadu, a 3 kW system generates around 750 units in a bi-monthly cycle, based on the state’s average of 4 to 4.5 units per kW per day. Here’s what happens to the bill:
- Net billed units: 800 consumed minus 750 solar generated = 50 net units
- 100% Free Slab: The first 100 units are 100% free under TANGEDCO’s domestic LT-1A tariff subsidy
- Total Payable: Since 50 units falls entirely within that free slab, the new bill comes to exactly ₹0.00
That’s a bi-monthly saving of ₹5,070, or about ₹30,420 a year, from a single system. Most people don’t realize how close they can get to a zero bill until they see the actual offset calculation, because it’s not just “solar reduces my bill a bit.” Crossing from a paid slab into the free slab can wipe out the entire bill, not just part of it.
There are a few practical reasons to run these numbers before you install anything:
Sizing your system correctly
Going bigger than you need means paying for capacity that just exports excess power at a lower pooled rate, while going too small means you’re still paying for a chunk of your consumption every cycle. The calculator shows you the exact bi-monthly generation for each capacity size, so you can match it to your actual usage instead of guessing.
Understanding the real subsidy amount
Under PM Surya Ghar: Muft Bijli Yojana, the central government subsidy isn’t a flat percentage, it’s tiered by capacity. A 1 kW system gets ₹30,000, a 2 kW system gets ₹60,000, and 3 kW or above is capped at ₹78,000 for a single domestic connection. Knowing this before you talk to a vendor stops anyone from quoting you a system size that doesn’t actually maximize your subsidy.
Working out your real payback period
Installation isn’t free, and knowing your net out-of-pocket cost after subsidy, against your actual annual savings, tells you exactly how many years until the system has paid for itself. In Tamil Nadu, this typically works out to 3 to 4.5 years, after which you’re getting free electricity for the remaining life of the panels.
Checking your sanctioned load before you commit
Your solar plant capacity can’t exceed the sanctioned load on your TNEB connection. If your sanctioned load is 2 kW and you want to install a 3 kW system, you’ll need to apply for a load enhancement through TANGEDCO’s portal first. Running the numbers early avoids a surprise mid-installation.
Key Features of Our TNEB Solar Bill Calculator
The calculator uses the region’s real average of 4 to 4.5 peak sunshine hours and units per kW per day, which works out to roughly 250 units per kW over a bi-monthly TNEB billing cycle. This isn’t a generic national average, it’s calibrated to what a Tamil Nadu rooftop system actually produces.
Plan your rooftop space and target generation with our verified Tamil Nadu benchmarks:
| Solar Capacity | Roof Area Needed | Daily Generation | Bi-monthly Units (TNEB) | Annual Generation |
|---|---|---|---|---|
| 1 kW | 80 to 100 sq.ft | 4 to 4.5 units | 250 units | ~1,500 units |
| 2 kW | 160 to 200 sq.ft | 8 to 9 units | 500 units | ~3,000 units |
| 3 kW | 240 to 300 sq.ft | 12 to 13.5 units | 750 units | ~4,500 units |
| 5 kW | 400 to 500 sq.ft | 20 to 22.5 units | 1,250 units | ~7,500 units |
| 10 kW | 800 to 1,000 sq.ft | 40 to 45 units | 2,500 units | ~15,000 units |
The tool applies the correct tiered subsidy automatically, ₹30,000 for a 1 kW system, ₹60,000 for 2 kW, and a maximum of ₹78,000 for 3 kW and above on a domestic connection, so you know your real out-of-pocket cost before you sign anything with a vendor.
A lot of solar calculators stop at “this is how many units your panels will generate.” This one goes further and shows how that generation interacts with TNEB’s progressive slab structure, where rates climb from free up to ₹6 to ₹11 per unit as consumption rises. Offsetting 500 or 750 units can pull you out of a high slab entirely, not just trim a few units off the top, and the calculator reflects that properly.
Beyond the immediate bill drop, the tool calculates how many years it takes for your net installation cost to be recovered through savings, and projects your total savings across the panel’s 25-year warranty period. A 3 kW system, for instance, can work out to ₹6 lakh to ₹8 lakh or more in lifetime savings after accounting for the installation cost.
The calculator flags whether your intended solar capacity fits within your current sanctioned load, and lets you know if a load enhancement application is needed first, so you’re not caught off guard midway through the installation process.
While the PM Surya Ghar cash subsidy applies to domestic (LT-1A) connections, the calculator also accounts for commercial (LT-V) installations, which don’t get the DBT subsidy but can claim a 40% accelerated depreciation tax benefit instead.
Why We Are the Best Option for This
Most solar calculators available online either use a generic national irradiance figure that doesn’t reflect Tamil Nadu’s actual sun hours, or they stop at estimating your bill reduction without factoring in how TNEB’s slab structure actually responds to that offset. Neither approach tells you the real story, which is that solar savings in Tamil Nadu often aren’t linear. Crossing a slab boundary can matter more than the raw number of units offset.
We built this tool around TANGEDCO’s actual net metering formula, net billed units equal total consumption minus total solar generation, and layered the real domestic slab rates on top of that, so the ₹0 bill scenario you see isn’t a rough guess, it’s the same math TANGEDCO applies to your account.
We also don’t stop at the subsidy number. Between the tiered PM Surya Ghar structure, the sanctioned load rule, and the phase connection requirements (single phase generally works up to 3 or 4 kW, three phase is required for 5 kW and above), there are enough moving parts that a plain “your bill drops by X” estimate misses half the picture. This calculator accounts for all of it.
Frequently Asked Questions