In short
- Who can: HT and EHT consumers in Tamil Nadu with a contracted demand of 63 kVA or more — factories (HT I) and commercial buildings (HT III) alike. LT connections cannot take open access.
- What a grid unit really costs: a unit that solar replaces costs about ₹8.17 for a factory and ₹10.24 for a commercial building, once the morning peak rate and the 5% electricity tax are counted.
- What solar costs at your meter (plant at 33 kV, your factory at 11 kV, assumed ₹4.00 solar price): about ₹7.16 through third-party, about ₹5.66 through group captive, after the network charges, surcharges and line loss listed on this page.
- The saving: a factory saves about 12% with third-party and about 31% with group captive. A commercial building saves about 26% and 45%, because its TNEB rate is higher.
- Watch out: TNPDCL has proposed an extra ₹0.63 a unit on third-party open access from October 2026. Group captive does not pay it.
- Our offer: send your last three HT bills. Within two working days you get a one-page sheet with your own numbers.
Rates checked against the sources listed below on 29 September 2026. Illustrative default values — request a site-specific quotation.
Who this is for
Factories, mills and IT services
Spinning and weaving mills, engineering units, foundries, pumps and motors, auto parts, food processing, and companies doing IT services. TNEB energy charge ₹7.50 a unit.
Commercial buildings
Malls, hotels, private hospitals, offices, banks, cinemas, marriage halls, supermarkets. TNEB energy charge ₹9.40 a unit — so the saving per unit is bigger.
Does your connection qualify?
Look at your EB bill. Two things decide it:
- Your tariff is HT (for example HT I or HT III) or EHT. If it says LT, open access is not allowed in Tamil Nadu, whatever your load. Your route is solar on your own roof or land.
- Your contracted demand is 63 kVA or more. That is Tamil Nadu's threshold under TNERC's Green Energy Open Access Regulations 2025 (notified 18 September 2025). The national rule is 100 kW, so Tamil Nadu is more open than the national floor.
Many mid-sized HT units qualify without knowing it. If you are between 63 kVA and a few MW, send us three bills and we will compare.
What a TNEB unit really costs you
Your HT bill has a fixed part and a per-unit part. Open access only replaces the per-unit part. From TNERC Tariff Order No. 6 of 2025 (effective 1 July 2025, still in force):
Solar makes power from about 7 am to 5 pm, so part of it falls in the costly 6–10 am peak. Taking about 15% of solar units as peak units and adding the 5% tax, each TNEB unit that solar replaces costs you about ₹8.17 in a factory and ₹10.24 in a commercial building (about ₹10.75 with the lighting add-on). That, not ₹7.50, is the number to compare against.
What it costs to bring a solar unit to your meter
When you buy from a solar plant elsewhere, its power travels through TANTRANSCO's high-voltage lines and TNPDCL's local network. You pay for the trip, and some power is lost on the way. Solar gets a concession: half the normal network charges, and 70% of the cross-subsidy surcharge (TNERC Orders 5 of 2019 and 9 of 2020, carried into the 2025 regulations).
Why your voltage changes the answer
Your supply voltage is printed on your EB bill. It matters because the higher the voltage, the fewer units are lost on the way and the less of the local network you use.
- Plant at 33 kV, you at 11, 22 or 33 kV (most factories and buildings): 5.35% to 6.58% of the units are lost, wheeling applies, and we count transmission too.
- Plant at 110 kV, you at 110 kV (EHT consumers): only 3.91% is lost. Wheeling may not apply at all at this level; we still include it until we see it waived on a real bill.
Where a rule is unclear, we count the charge. If it turns out not to apply, your saving is bigger than shown, not smaller.
The full comparison: TNEB vs third-party vs group captive
Cost per unit at your meter, with every charge and loss counted, at an assumed solar price of ₹4.00 (an assumption for the arithmetic, not an offer).
Swipe the table sideways to see all three routes.
| Per unit | TNEB today | Third-party | Group captive |
|---|---|---|---|
| Factory (HT I), plant 33 kV → you 11 kV | ₹8.17 | ₹7.16 saves 12% | ₹5.66 saves 31% |
| Factory (HT I), 110 kV → 110 kV | ₹8.17 | ₹7.00 saves 14% | ₹5.50 saves 33% |
| Commercial (HT III), plant 33 kV → you 11 kV | ₹10.24 | ₹7.57 saves 26% | ₹5.66 saves 45% |
| Commercial (HT III), 110 kV → 110 kV | ₹10.24 | ₹7.41 saves 28% | ₹5.50 saves 46% |
| If the proposed ₹0.63 surcharge is approved (33 kV → 11 kV) | — | Factory ₹7.79, saves 5% Commercial ₹8.20, saves 20% | No change |
How much the solar price matters (plant 33 kV, you 11 kV): at ₹3.50 a unit, a factory saves about 19% with third-party and 37% with group captive. At ₹4.50, third-party saving for a factory shrinks to about 5% — and turns into a loss if the ₹0.63 surcharge comes in — while group captive still saves about 24%. For commercial buildings, both routes stay clearly cheaper than TNEB. Illustrative default values — request a site-specific quotation.
Third-party or group captive? Both have real advantages
Simple: you just buy the power
Good: no investment; one power purchase agreement; little paperwork; easier to exit or switch supplier when the contract ends; suits buyers who cannot hold shares in a power company, such as trusts, government-linked bodies and many listed firms.
Watch: pays the cross-subsidy surcharge and any additional surcharge TNERC orders; no banking, so power your meter can't use at that moment is not credited; savings are thin for factories at higher solar prices.
Best for: commercial buildings (the saving holds up well), and factories with steady daytime load that get a low solar price.
Own a slice, skip the surcharges
Good: no cross-subsidy surcharge and no additional surcharge — about ₹1.40 (factory) to ₹1.80 (commercial) a unit today, and about ₹0.63 more if the proposed additional surcharge is ordered; electricity tax only 10 paise a unit; banking allowed within the month; the saving survives surcharge changes.
Watch: the buyers in the group must together own at least 26% of the plant company and together use at least 51% of its power every year, and no buyer can count more than its share towards the test unless it holds 26% or more (Rule 3, Electricity Rules 2005, as amended March 2026); if the yearly check fails, the surcharges are billed back; more paperwork; harder to exit; your equity is tied up for the plant's life.
Best for: factories that can invest and have steady daytime load; any buyer who wants the lowest, most stable cost.
Since 13 March 2026 (Electricity (Amendment) Rules, 2026), a company, its holding company and fellow subsidiaries can count together as one captive user, which makes group captive easier for business groups. It is an equity decision, so your chartered accountant will be part of it. We work with your CA on the company structure and the yearly check.
Banking: who gets it, and on what terms
Banking means solar units you can't use when they are made are held by the grid and given back later.
- Third-party open access: no banking. A unit your meter can't use at the moment it arrives is not credited to you.
- Group captive: banking allowed. The grid keeps 8% of what you bank. Accounts are settled every calendar month with no carry-forward. Units banked in normal hours come back in normal hours, night in night; units banked in the peak can be used in any slot. What is left unused at month-end is paid for at 75% of the renewable tariff, or of the latest bid tariff where none is set. (TNERC GEOA Regulations 2025)
That is why third-party solar only works for the part of your load that runs in daylight. What the banking rules mean for night shifts →
Night shifts and seasonal load: look at wind
Solar makes power in daylight only. In the windy season, Tamil Nadu's wind often keeps generating into the evening. For a mill, hotel or hospital that runs round the clock, a wind or wind-plus-solar supply can fit the load far better than solar alone. We find generators for both. Aran manufactures solar equipment; wind is a route we facilitate, not a product we sell.
Rooftop first, open access for the rest
Power made and used on your own premises skips transmission, wheeling, both surcharges and line losses, so it is usually the cheapest unit you can get. We always size your roof first, then use open access or group captive for the load the roof can't cover. Zero-investment rooftop solar →
What is about to change
- TNEB tariffs: a yearly rise of up to 6% was due from 1 July 2026. It had not been ordered when we checked. It would raise your saving.
- Surcharges: for 2026–27 TNERC's earlier plan sets the cross-subsidy surcharge at ₹2.06 (HT I) and ₹2.66 (HT III) and wheeling at ₹1.03, awaiting an order. The additional surcharge petitions above are pending.
- Solar concessions: TNERC published draft renewable energy tariff regulations on 1 June 2026. We found nothing in them on these concessions, but the final text is not out.
We re-check these every week and update this page when an order is issued.
What we handle for you
- You send your last three HT bills on WhatsApp, and tell us your shift hours.
- Within two working days you get a one-page sheet: your cost on TNEB today, under third-party and under group captive, for your tariff, voltage and load. If it isn't worth doing, the sheet says so.
- We find the generator whose supply fits your load: solar for daytime, wind or a mix for evenings and nights. We only propose a match when load, price and term all fit.
- We handle the application through the single window: SLDC for short-term open access, the state transmission utility for medium and long-term, and TNPDCL's consent. The national Green Energy Open Access Rules 2022 give the nodal agency 15 days to decide an application.
- You sign directly with the generator. We look after metering and keep the compliance calendar, including group captive's yearly 26% and 51% check.
How we're paid: the bill sheet costs you nothing. If a deal goes ahead, our fee is a facilitation fee on each unit delivered, agreed in writing before anyone signs. We never buy or resell the power.
Common questions
Can a commercial building take open access in Tamil Nadu?
Yes. Any HT or EHT consumer with a contracted demand of 63 kVA or more can, including HT III commercial buildings such as malls, hotels, private hospitals and offices. Because the HT III energy charge is ₹9.40 a unit against ₹7.50 for factories, commercial buildings usually save more per unit.
Can an LT connection take open access in Tamil Nadu?
No. Under TNERC's Green Energy Open Access Regulations 2025, open access is only for HT and EHT consumers. If your connection is LT, solar on your own roof or land is the way to cut your bill.
What is the minimum load for open access in Tamil Nadu?
A contracted demand of 63 kVA, for HT and EHT consumers, under the TNERC Green Energy Open Access Regulations 2025. The national floor in the Green Energy Open Access Rules 2022 is 100 kW, so Tamil Nadu's threshold is lower.
How much can a Tamil Nadu factory save with open access solar?
At an assumed solar price of ₹4.00, a factory on HT I pays about ₹7.16 a unit landed through third-party against about ₹8.17 for the TNEB unit it replaces, a saving of about 12%. Through group captive it pays about ₹5.66, a saving of about 31%. Your own figure depends on your voltage, load and the price you get, which is what the free bill sheet works out. Illustrative default values — request a site-specific quotation.
Is banking allowed for third-party solar power in Tamil Nadu?
No. Under the 2025 regulations, third-party open access gets no banking. Group captive can bank: the grid keeps 8%, accounts are settled monthly, and units banked in normal or night hours come back in the same slot, while units banked in the peak can be used in any slot.
What is group captive, and what are the 26% and 51% rules?
Group captive means the buyers together own at least 26% of the company that owns the plant and together use at least 51% of the power it makes each year (Rule 3, Electricity Rules 2005, as amended March 2026). If both are met, you don't pay the cross-subsidy surcharge or the additional surcharge.
Do we still pay TNEB demand charges?
Yes. You stay a TNPDCL consumer, and the demand charge of ₹608 per kVA a month continues on the higher of your recorded maximum demand or 90% of your contracted demand. Open access replaces the units you buy, not your connection.
Why does my supply voltage matter?
Fewer units are lost at higher voltages. From a 33 kV plant to an 11 kV connection about 6.58% of the units are lost; from 110 kV to 110 kV only about 3.91%. Your voltage is printed on your EB bill.
Is Aran a power trader?
No. We don't buy or resell electricity. Your power agreement is directly with the generator. We find the match, compare the routes on your real bills and handle the process.
How does Aran get paid?
The bill comparison is free. If a deal goes ahead, our fee is a facilitation fee on each unit delivered, agreed in writing before anyone signs.
Where these numbers come from
- TNERC Suo-motu Tariff Order No. 6 of 2025, dated 30 June 2025, effective 1 July 2025 — energy and demand charges, time-of-day, wheeling, cross-subsidy surcharge.
- TNERC intra-state transmission charges order and TNSLDC charges order, both dated 30 June 2025, for 2025–26.
- TNERC Tariff Order No. 7 of 2022 — open access loss table by voltage, and the approved 2026–27 surcharge and wheeling levels.
- TNERC Orders No. 5 of 2019 and No. 9 of 2020 — solar concessions (50% of network charges, 70% of cross-subsidy surcharge), as described in TNERC's March 2021 consultative paper.
- TNERC Green Energy Open Access Regulations 2025, notified 18 September 2025 — 63 kVA threshold, banking.
- Additional surcharge: TNERC M.P. No. 13 of 2025 (29 April 2025, ₹0.10); ₹0.54 (M.P. No. 44 of 2024, via Mercom); TNPDCL petitions — ₹1.14 via InfraLive (20 August 2025), ₹0.63 and nil for April–September 2026 via DT Next (26 September 2026).
- MoP Green Energy Open Access Rules 2022 — 100 kW national floor, 15-day decision time.
- Tamil Nadu Tax on Consumption or Sale of Electricity Act, 2003 — 5% on grid supply, 10 paise a unit on captive consumption.
- Our own arithmetic: the per-unit transmission figure (at 19% capacity use) and every landed cost on this page.
- Electricity Rules 2005, Rule 3, as amended by the Electricity (Amendment) Rules, 2026 (13 March 2026) — captive and group captive.
Get your one-page power cost sheet
Tell us about your connection. The quickest way is to WhatsApp your last three HT bills; we come back within two working days. No obligation.
Thanks, we've got your details. The fastest next step: send your last three HT bills on WhatsApp.
Send bills on WhatsApp