Delhi Solar Calculator (TPDDL)
Rooftop solar payback for North Delhi homes on Tata Power-DDL, with the Delhi top-up, generation incentive and 200-unit subsidy.
https://calculators.nirajiitr.com/energy/solar-calculator-delhi-tpddl
Your home
About 504 units a month on the TPDDL tariff. Use a year's average if your bill swings with the seasons.
Fine-tune
Sized to cover a year of your consumption, at 5.1 peak sun hours a day in Delhi.
About 100 sq ft per kW. Leave at 0 for no limit.
Typical for an on-grid system from an empanelled vendor. Replace it with your quote.
Indian residential tariffs have historically risen 4-7% a year.
Monocrystalline panels typically lose about 0.5% a year.
A 4 kW system makes about 478 units a month, 95% of your use. Your bill drops from ₹3,000 to about ₹0 in year one.
- Installed cost
- ₹2,20,000
- PM Surya Ghar subsidy
- − ₹78,000
- State top-up
- − ₹78,000
- Delhi Government top-up to PM Surya Ghar
- Net cost to you
- ₹64,000
- Saving in year one
- ₹53,248
- Return (IRR)
- 85.2% a year
- over 25 years, before tax
- CO₂ avoided
- 97 tonnes
- over 25 years
- You pay29%
- Central subsidy35%
- State top-up35%
Year-by-year cash flowShowHide
| Year | Units made | Bills without solar | Bills with solar | Upkeep and EMIs | Running total |
|---|---|---|---|---|---|
| 1 | 5,733 | ₹36,048 | ₹0 | ₹0 | -₹10,751 |
| 2 | 5,705 | ₹37,851 | ₹0 | ₹0 | ₹44,214 |
| 3 | 5,676 | ₹39,743 | ₹0 | ₹0 | ₹1,00,986 |
| 4 | 5,648 | ₹41,730 | ₹0 | ₹0 | ₹1,59,660 |
| 5 | 5,620 | ₹43,817 | ₹0 | ₹0 | ₹2,20,336 |
| 6 | 5,592 | ₹46,008 | ₹0 | ₹2,200 | ₹2,64,143 |
| 7 | 5,564 | ₹48,308 | ₹0 | ₹2,200 | ₹3,10,252 |
| 8 | 5,536 | ₹50,724 | ₹0 | ₹2,200 | ₹3,58,775 |
| 9 | 5,508 | ₹53,260 | ₹0 | ₹2,200 | ₹4,09,835 |
| 10 | 5,481 | ₹55,923 | ₹0 | ₹2,200 | ₹4,63,558 |
| 11 | 5,453 | ₹58,719 | ₹0 | ₹2,200 | ₹5,20,077 |
| 12 | 5,426 | ₹61,655 | ₹0 | ₹30,200 | ₹5,51,532 |
| 13 | 5,399 | ₹64,738 | ₹0 | ₹2,200 | ₹6,14,070 |
| 14 | 5,372 | ₹67,975 | ₹0 | ₹2,200 | ₹6,79,844 |
| 15 | 5,345 | ₹71,373 | ₹0 | ₹2,200 | ₹7,49,017 |
| 16 | 5,318 | ₹74,942 | ₹0 | ₹2,200 | ₹8,21,759 |
| 17 | 5,292 | ₹78,689 | ₹0 | ₹2,200 | ₹8,98,248 |
| 18 | 5,265 | ₹82,624 | ₹0 | ₹2,200 | ₹9,78,672 |
| 19 | 5,239 | ₹86,755 | ₹0 | ₹2,200 | ₹10,63,227 |
| 20 | 5,213 | ₹91,092 | ₹0 | ₹2,200 | ₹11,52,119 |
| 21 | 5,187 | ₹95,647 | ₹0 | ₹2,200 | ₹12,45,566 |
| 22 | 5,161 | ₹1,00,429 | ₹0 | ₹2,200 | ₹13,43,795 |
| 23 | 5,135 | ₹1,05,451 | ₹0 | ₹2,200 | ₹14,47,046 |
| 24 | 5,109 | ₹1,10,723 | ₹0 | ₹2,200 | ₹15,55,570 |
| 25 | 5,084 | ₹1,16,260 | ₹0 | ₹2,200 | ₹16,69,629 |
How it works
The bill you enter is worked backwards through your DISCOM's slabs, fixed charges, surcharges and duty to the units you use. The panels' yearly output is set against that use under net metering, and each month is re-billed on what is left. Because the units solar removes come off your most expensive slab first, the saving per unit is often well above the average rate on your bill. Tariffs rise by the escalation rate each year while the panels slowly lose output; maintenance, an inverter replacement in year 12 and any loan repayments are taken off, and the running total gives the payback year.
Saving₍y₎ = [Bill(U) − Bill(U − G₍y₎/12)] × 12 × (1 + e)^(y−1), G₍y₎ = kW × H × 365 × PR × (1 − d)^(y−1)- U
- Units you use a month, worked out from your bill
- G₍y₎
- Units the panels make in year y
- H
- Peak sun hours a day in your state
- PR
- Performance ratio: the share of rated output that reaches the meter, 0.77 here
- e
- Yearly rise in electricity prices
- d
- Yearly loss in panel output
Worked example
A Delhi home on TPDDL with a ₹3,000 monthly bill and a flat RCC roof, assuming prices rise 5% a year.
- 1Working the bill back through the TPDDL slabs, charges and duty gives about 504 units a month
- 2At 5.1 peak sun hours, 4 kW makes about 478 units a month, 95% of that use
- 34 kW at ₹55,000 per kW costs ₹2,20,000; PM Surya Ghar pays ₹78,000 and the Delhi Government top-up to PM Surya Ghar ₹78,000, leaving ₹64,000
- 4The first year saves ₹53,248, and the saving grows as tariffs rise
The system pays for itself in about 1.2 years and leaves the household about ₹16,69,629 ahead over 25 years.
Frequently asked questions
How does Delhi's 200-unit free electricity interact with solar?
Delhi pays the whole bill for homes using 200 units or fewer in a month and half the bill, up to ₹800, between 201 and 400. Solar that brings a 500-unit home's net use down below 200 therefore wipes out more than the units it replaces: the bill drops to zero. The calculator applies both tiers to the net units after solar.
What is PPAC and why does it matter for solar?
The Power Purchase Adjustment Cost is a percentage surcharge on energy and fixed charges that DERC lets DISCOMs levy as power costs rise; for TPDDL it is 16% from June 2026, on top of the 7% pension trust surcharge. Every unit solar removes also removes its share of these surcharges.
How does net metering settle on TPDDL?
Net metering with a yearly settlement, plus a generation-based incentive under the Delhi Solar Policy paid on every unit the panels produce for the first five years.
How much is the PM Surya Ghar subsidy?
₹30,000 per kW for the first 2 kW and ₹18,000 for the third, so ₹30,000 for 1 kW, ₹60,000 for 2 kW and ₹78,000 for 3 kW or more. It is paid into your bank account after the DISCOM inspects and commissions the system, and only for installations by an empanelled vendor using ALMM-listed panels, applied for through pmsuryaghar.gov.in.
Why is my saving per unit higher than my average rate?
Residential tariffs are telescopic: the first units are cheap and each slab above costs more. Solar takes units off the top of your bill, so it removes the dearest ones first. A home in a ₹10-plus slab saves that rate on every unit the panels cover, even if the bill averages out lower.
Why not simply fit the biggest system my roof will hold?
The central subsidy stops rising at 3 kW, and under net metering surplus units are usually bought back at the regulator's average power purchase cost, often ₹2-3 a unit, far below what you pay for grid power. Sizing to your own consumption earns the full retail rate on every unit. The calculator suggests that size; override it to see what a bigger system does to the return.
Related calculators
- Solar ROI Calculator IndiaEnter your electricity bill and state to see the rooftop system you need, your PM Surya Ghar subsidy, payback period and 25-year return.
- Delhi Solar Calculator (BSES Rajdhani)Rooftop solar payback for South and West Delhi homes on BSES Rajdhani, with the Delhi top-up, generation incentive and BRPL's PPAC.
- Uttar Pradesh Solar Calculator (UPPCL)Rooftop solar payback for Lucknow, Noida and the rest of Uttar Pradesh, with the UPNEDA top-up of ₹15,000 a kW on UPPCL's slabs.