The drawings are in, the portal shows the application at technical feasibility, and then nothing moves. Or the status flips to rejected with a reason that says nothing about your drawings. In many of these cases the DISCOM has found no fault with the design. It has looked at the distribution transformer (DT) that feeds the premises. Rooftop solar already booked on it leaves too little room.
This guide is for the EPC project or operations lead who files net metering applications. You may have to explain a pending or rejected status to a client. The guide covers what the check tests and the DT limits in four state frameworks. It also gives a worked headroom example, a pre-application check, and the options when the transformer is full. For the wider filing workflow, see the DISCOM net metering process by state. For drawing-side rejections, see DISCOM net metering rejection reasons.
Quick answer. Transformer feasibility is the DISCOM check of whether the local distribution transformer can take more rooftop solar. It compares solar already connected plus your proposed kW with a state cap on the transformer rating. The cap is 70% in Maharashtra, 80% in Karnataka, 90% in Tamil Nadu and the full rating in Gujarat. If it fails, you can resize, wait in the queue, or ask for augmentation.
Every limit below was read from the regulator or DISCOM document on 31 October 2026, and each is dated in the text. Limits change, so treat the table as a dated snapshot and confirm the current instrument before you quote a client.
What is a transformer feasibility check for rooftop solar?
A transformer feasibility check is the part of the DISCOM’s technical feasibility study that tests the network, not the consumer’s drawings. The DISCOM takes the application for net metering and finds the distribution transformer serving the connection. It then asks whether the solar capacity on that transformer, including your system, stays inside the state cap.
The regulations name the inputs. In Maharashtra, the study looks at four inputs. They are the AC voltage level, the sanctioned load or contract demand, the rated AC output voltage, and the cumulative capacity available on the relevant transformer. This is set out in Annexure 1 of the MERC Rooftop Regulations, 2019. In Gujarat, the field report records the 11 kV feeder and the transformer capacity. It also records the rooftop capacity already connected and already approved on that transformer, and whether the total is within the rating. The source is the GERC Fourth Amendment, 2024.
Tamil Nadu’s format is the most explicit. The TANGEDCO report asks for the DTR capacity in kVA, the connected load, the solar already connected in kW and the proposed solar in kW. It then tests whether the total is at most 90% of the transformer capacity. This is the Annexure E format in TANGEDCO’s salient features document for TNERC Order No. 8 of 2021.
One point is easy to miss. In every instrument read for this article, the cap counts solar capacity against the transformer rating. It does not look at how much the consumer actually exports.
Which national rules set the clock?
Rule 11 of the Electricity (Rights of Consumers) Rules, 2020, as amended on 22 February 2024, sets two national rules. The technical feasibility study must be completed within fifteen days, and if the outcome is not intimated in that time, the proposal is presumed technically feasible. Complete applications up to 10 kW are deemed accepted without a feasibility study. The text is quoted in the GERC explanatory memorandum, and the Ministry of Power Annual Report 2023-24 describes the same change.
The documents read for this article do not say how a state treats a deemed-accepted small system when its transformer is already at the cap. If your 8 kW application lands on a full transformer, get the outcome in writing.
What distribution transformer limits do DISCOMs use?
Each state commission sets its own cap, and the caps differ. The table gives the limit, the instrument and its date for the four states in this guide.
| State and DISCOM | Cap on cumulative rooftop solar per DT | Instrument and date | Can the DISCOM go higher? |
|---|---|---|---|
| Maharashtra (MSEDCL) | 70% of rated capacity of the DT or feeder | MERC Rooftop Regulations, Reg 5.2, notified 30 December 2019 | Yes, after a detailed load study by the licensee |
| Gujarat (state-owned DISCOMs) | Not more than the capacity of the DT (100% of rating) | GERC Regulations, Reg 5, as replaced by the Second Amendment, Notification 2 of 2020, dated 23 January 2020 | Not applicable |
| Karnataka (BESCOM) | 80% of rated capacity of the DT, for plants below 150 kW | KERC order of 1 June 2023 and BESCOM guidelines of 5 August 2023; repeated in KERC DSPV Regulations, Reg 8.2, notified 19 August 2026 | Not stated |
| Tamil Nadu (TANGEDCO, renamed TNPDCL on 27 June 2024) | 90% of DT capacity for net metering and net billing | TNERC Order No. 8 of 2021, dated 22 October 2021, as summarised by TANGEDCO | Not stated |
Figures such as 30% or 40% appear on installer pages. None of the current instruments read for this article carries them, so do not quote them to a client.
Maharashtra: 70%, with a load-study exception
Regulation 5.2 of the 2019 MERC regulations caps the cumulative capacity of all rooftop systems on a transformer or feeder at 70% of its rated capacity. The proviso lets the licensee allow more after a detailed load study. Regulation 4.1 allocates capacity transformer by transformer, first come, first served. Regulation 5.3 requires the licensee to publish transformer-wise capacity every quarter in the Annexure 6 format.
MERC’s explanatory memorandum for the 2023 draft first amendment said the proviso already allows connectivity above 70% after a study. It proposed no change (MERC, August 2023). The Second Amendment, 2024 in the Maharashtra Gazette of 29 August 2024 does not amend Regulation 5.2. Energetica India reported on 23 September 2026 that MERC has published new draft rooftop regulations, so recheck before you rely on this row.
Gujarat: from 65% to the full transformer rating
The original GERC regulations of 18 June 2016 capped cumulative capacity at a transformer at 65% of its peak capacity. The Second Amendment of 23 January 2020 replaced that proviso. Cumulative capacity now shall not exceed the capacity of the distribution transformer, as the consolidated regulations show. The Fourth Amendment of 4 September 2024 substitutes Regulation 5.1. It requires the licensee to update available transformer capacity yearly and report it to the Commission, and it does not change the cap.
Karnataka: 80%, with a kW to kVA conversion
BESCOM’s guidelines of 5 August 2023 connect each plant below 150 kW to the existing DT. The total of existing and proposed plants on it shall not exceed 80% of rated capacity (BESCOM guidelines). They add that a 100 kVA transformer allows 68 kW, which is 80 kVA converted at 0.85. For plants above 150 kW, the same guidelines apply an 80% limit on the rated current carrying capacity of the 11 kV line instead.
The KERC DSPV Regulations, 2026 repeat the 80% figure in Regulation 8.2. The 2026 text does not restate the 0.85 conversion, so ask the sub-division which factor it applies.
Tamil Nadu: 90%, plus 70% on the HT gross metering side
TANGEDCO’s summary of the TNERC order caps cumulative solar under net metering or net billing on a distribution transformer at 90% of its capacity. Gross-metered HT systems on a power transformer are capped at 70%. I found no later final TNERC regulation that replaces the 2021 order, so confirm with TNPDCL that it still governs.
How can the same transformer pass in one state and fail in another?
Because the caps differ, a transformer with the same rating and the same solar load gives different answers by state. The example below is illustrative.
Assumptions. A 250 kVA distribution transformer. Rooftop solar already connected or booked on it: 140 kW. Your proposed system: 40 kW, which would bring the total to 180 kW. Each state’s cap is applied to the rating as the instruments describe it.
| State rule | Cap on rating | Cap used for comparison (kW) | Headroom for new solar (kW) | Result for 40 kW |
|---|---|---|---|---|
| Maharashtra, 70% | 175 kVA | 175 | 35 | Fails in full; 35 kW fits |
| Gujarat, full rating | 250 kVA | 250 | 110 | Passes |
| Karnataka, 80% at 0.85 | 200 kVA | 170 | 30 | Fails in full; 30 kW fits |
| Tamil Nadu, 90% | 225 kVA | 225 | 85 | Passes |
The Maharashtra, Gujarat and Tamil Nadu rows compare kW of solar directly with kVA of transformer, which is how the TANGEDCO format works. The MERC text refers only to rated capacity and does not state a conversion. If a sub-division applies a power factor, the Maharashtra headroom shrinks. Karnataka uses the conversion in the BESCOM guidelines.
BESCOM’s own worked example shows the next step. Take a 100 kVA transformer with 60 kW already connected and a new 50 kW application. The guidelines call the application feasible for partial capacity only, 8 kW, against the 68 kW allowed. A partial approval is a normal outcome, so size the client’s expectations before the application, not after.
What do feasibility pending and rejected mean?
Portal wording differs by state, so the table below maps outcomes that the documents describe, not exact portal text.
| What you see | What the documents say it can mean | Next action |
|---|---|---|
| Pending, inside the clock | Normal review. National clock is 15 days. Gujarat sets 3 days for the letter, 10 days for the field report and 2 days after it. | Wait. Do not buy equipment before sanction. |
| Pending, past the clock | Rule 11(7): if the outcome is not intimated in 15 days, the proposal is presumed technically feasible. | Ask in writing for the outcome, citing the rule and the state regulation. |
| Pending, waiting list | MSEDCL’s SOP keeps the application in a waiting list in chronological order when transformer capacity is inadequate, if the consumer chose that option. | Keep the option on. An SMS goes to the sub-division and the applicant when the transformer is augmented. |
| Pending, no transformer reason | MSEDCL’s SOP also keeps applications pending for live arrears. | Check dues first. Do not assume a capacity problem. |
| Rejected for capacity | MSEDCL’s SOP rejects by SMS if the consumer did not choose the waiting list. BESCOM’s guidelines have the sub-divisional officer cancel the application if it is not technically feasible. | Ask for the transformer figures behind the decision, then resize or reapply. |
| Approved for less than applied | BESCOM can approve partial capacity. MERC Regulation 9.8 says the approval states the maximum permissible capacity. | Accept the lower figure or queue the balance. |
| Estimate issued | In Gujarat, the letter after the technical report can carry an estimate for system strengthening, payable within 30 days. | Decide whether to pay, resize, or wait. |
In Maharashtra, the 2024 amendment of Regulation 9.7 requires a notice to rectify, within 15 days or longer where needed, before rejection at a transformer. It keeps the chronological order but drops the 2019 proviso that required written reasons for a rejection on inadequate transformer capacity. Ask for the reasons in writing anyway.
How do you check transformer headroom before you apply?
The DISCOM holds the transformer data, so the check is a set of requests plus a calculation. Run these steps before you sign the client.
- Identify the transformer. On the MSEDCL portal, the consumer number brings up the billing details including the DTC code, according to the MSEDCL rooftop SOP. Elsewhere, the section office can name the DT, and TANGEDCO’s format records the substation, feeder and pole.
- Get four numbers. The transformer rating in kVA, the solar connected, the solar approved but not yet commissioned, and the peak load. Gujarat’s report counts capacity already connected and already approved. MSEDCL’s SOP works from the capacity sanctioned on the DTC. Booked but unbuilt systems use up headroom.
- Apply the state cap. Use the table above and the unit rule your sub-division follows.
- Look for the published list. MERC Regulation 5.3 requires quarterly transformer-wise data. GERC Regulation 5.1 requires a yearly update to the Commission. TANGEDCO’s summary requires a monthly website update. I could not confirm where each DISCOM posts these, so if you cannot find the table, ask the sub-division in writing.
- Check the other gates. Capacity may not exceed sanctioned load or contract demand in Maharashtra (Regulation 6.2) or Tamil Nadu. MSEDCL’s SOP also requires no arrears at application.
- Decide the plan. Size to the headroom, or apply for the full size and choose the waiting option, before the client commits to equipment.
The transformer figures come from the DISCOM. The site-side data comes from you. Heaven Designs’ site survey and feasibility services cover the site side, which includes contour and soil surveys and observations on access, obstructions and usable area. They do not replace the DISCOM’s transformer figures. Doing both in parallel means the design is ready when headroom is confirmed.
What can you do when the transformer is full?
You have five options, and the rules treat them differently. Match the option to what the regulation allows in your state.
| Option | Rule basis | Who acts and who pays | Trade-off |
|---|---|---|---|
| Smaller system | BESCOM guidelines (partial capacity); MSEDCL SOP (consent letter to reduce applied capacity); MERC Reg 9.8 | Consumer chooses | Fastest, but lower generation |
| Hold your place in the queue | MERC Reg 9.7 (chronological order); MSEDCL SOP waiting list | Consumer waits | No end date until the DISCOM augments |
| Ask for augmentation | Rule 11(8); MERC Reg 9.7(a); GERC Reg 5.1; KERC Reg 8.3 | See below | Cost and time depend on state and size |
| Ask for a load study | MERC Reg 5.2 proviso | Licensee decides | Maharashtra only; at the licensee’s discretion |
| Phase the project | Apply for the headroom now, queue the balance | Consumer | Two cycles of paperwork |
Who pays for a transformer upgrade?
It depends on the state and the system size. Rule 11(8) says the upgrade is carried out by the licensee or the consumer, as the case may be. The cost of strengthening, including the transformer, goes into the licensee’s revenue requirement. This applies to systems up to 5 kW, or a higher capacity set by the State Commission.
- Maharashtra. Regulation 9.7(a), added in 2024, has the licensee carry out the upgrade within the Supply Code timeline. The cost goes into its annual revenue requirement. The text does not limit this to small systems.
- Gujarat. Under the Fourth Amendment, strengthening for up to 6 kW goes into the licensee’s revenue requirement. Above 6 kW, state-owned DISCOMs recover per kW charges approved by GERC (LT systems up to 100 kW, HT systems up to 1,000 kW). Other DISCOMs pass the augmentation cost to the consumer. When an estimate is issued, the applicant pays it within 30 days. The licensee then has 15 days from payment and the signed agreement to finish the work.
- Karnataka. Regulation 8.3 says the licensee takes up system improvement work beyond the interconnection point. Regulation 8.5 puts the service line up to the interconnection point on the consumer.
- Tamil Nadu. I found no augmentation clause in the documents read. Ask TNPDCL in writing.
Does consumer load help?
Not directly. The cap counts solar capacity against the transformer rating, so raising the consumer’s own load does not change the test. The practical lever is the Maharashtra load study. The MERC proviso lets the licensee exceed 70% after a detailed study, and the Annexure 6 table shows the peak loads the study would use. Ask for it with the transformer’s peak load data. The licensee may allow it, but is not obliged to. A non-exporting design is not a confirmed way around a full transformer, and our zero export solar design guide explains what to ask the DISCOM first.
How long should the feasibility check take?
Timelines below come from the cited rules only. State clocks count days or working days differently, so read the unit.
| Source | Clock | Date |
|---|---|---|
| Electricity (Rights of Consumers) Rules, rule 11(7) | Study completed in 15 days, else presumed feasible | 22 February 2024 |
| Same rules, rule 11(7A) | Complete applications up to 10 kW deemed accepted without a study | 22 February 2024 |
| MERC Annexure 1, as amended | Acknowledgement in 3 working days; study in 15 days | 29 August 2024 |
| GERC Regulation 7 table | Letter to field in 3 days; field report in 10 days; consent letter 2 days after report | 4 September 2024 |
| KERC DSPV Regulations, above 150 kW up to 1,000 kW | Acknowledgement in 3 working days; feasibility in 10 working days | 19 August 2026 |
| KERC DSPV Regulations, up to 150 kW LT | The application is the approval to start work; no feasibility step in the table | 19 August 2026 |
I did not confirm a current Tamil Nadu clock for this guide. Ask the section office for the date the 15-day clock started.
What should you do while you wait?
Use the wait to close the site-side gaps. A confirmed site layout, usable area and obstruction list mean the design starts as soon as headroom is known. If you are scoping rooftop projects across several states, you can request design samples to see the drawing set before you commit. For a Maharashtra file, see the MSEDCL net metering guide. For the plant-side transformer that steps up generation at larger sites, see transformer selection in solar power plants. For ground projects, the solar feasibility study guide covers evacuation capacity at the substation.
The central rules changed in February 2024, and the state frameworks have changed since, as the DISCOM net metering compliance update tracks. Quote the instrument and its date to the client, not a bare percentage.
FAQ
Does transformer feasibility apply to systems up to 10 kW?
The national rule deems complete applications up to 10 kW accepted without a feasibility study. Maharashtra and Gujarat wrote it into their own regulations in 2024. The documents read do not say how a deemed-accepted system is treated if the transformer is already at its cap, so confirm in writing.
Are limits set in kW or kVA?
The instruments compare solar capacity with the transformer rating. BESCOM’s guidelines convert kVA to kW at 0.85. TANGEDCO’s format compares kW directly with kVA. The MERC text states neither, so ask your sub-division which it applies and which solar figure it books.
Do systems that are approved but not yet built count against the cap?
In Gujarat, yes. The technical report counts rooftop capacity already connected as well as approved on the transformer. MSEDCL’s SOP works from the capacity sanctioned on the DTC, which points the same way. That is why a transformer can look empty on site and still be full on paper.
Can the DISCOM reject me without telling me why?
In Maharashtra, Regulation 9.7 requires a notice to rectify before rejection. The 2019 text also required written reasons for a rejection on transformer capacity, and the 2024 substitution does not repeat that proviso. Request the reasons in writing under your state’s regulation.
How often do the caps change?
Maharashtra’s 70% has stood since December 2019, while Gujarat moved from 65% to the full rating in January 2020. Karnataka’s 2026 regulations replaced its 2016 rooftop regulations, and trade press reports new Maharashtra drafts. Recheck the instrument before each client quote.
Before you file
Confirm the transformer, the headroom and the state cap before you promise a client a system size. To have the site-side data prepared while the DISCOM runs its study, start with site survey and land feasibility services. You can also message us on WhatsApp or write through the contact page. We reply within 1 business day.