Direct Answer
For most factory owners in West Bengal, third-party open access solar is not the practical route. WBERC's Open Access Regulations 2022 put the distribution licensee first in allotment priority, and — per a Bengal Chamber 2025 paper — stacked wheeling and CSS charges frequently make third-party renewable procurement commercially less viable. In the CESC area, wheeling alone runs 164.60 paise/kWh for FY2025-26, and the CSS is capped at 20% of the category tariff, exempted only for captive own-use proportional to equity. The realistic path is behind-the-meter rooftop solar under the Rooftop Solar Prosumers Regulations 2025 (net billing or gross metering), with group captive structures for larger loads.
TL;DR
- Third-party open access in West Bengal is structurally disadvantaged: the licensee gets first priority on open access allotment, and stacked charges make third-party renewable procurement frequently commercially less viable, per the Bengal Chamber's 2025 paper.
- In the CESC area, FY2025-26 wheeling is 164.60 paise/kWh, and CSS (T − ACS + R) is capped at 20% of the category tariff, with exemption only for captive own-use in proportion to equity.
- Rooftop solar now runs on the WBERC Prosumers Regulations 2025 — net billing or gross metering, with the feed-in tariff set by the 20 August 2025 suo-motu order — and WBSEDCL adjusts injected energy against at most 90% of annual consumption.
How West Bengal's open access framework works
Open access in West Bengal is governed by the WBERC (Open Access) Regulations 2022, notified in the Gazette as 75/WBERC with effect from 1 August 2022, with a draft First Amendment circulated in October 2024. Two design choices work against third-party renewable buyers.
The first is allotment priority: when open access capacity is contested, the distribution licensee comes first — a third-party solar supplier is effectively queued behind the utility's own requirements. The second is the cumulative charge burden, which the Bengal Chamber's 2025 paper concluded frequently makes third-party renewable procurement commercially less viable in the state. For how other states structure the same charges, see our open access solar guide for India.
The CESC-area charge stack for FY2025-26
Kolkata and the surrounding industrial belt fall in the CESC distribution area, where the applicable FY2025-26 charges illustrate the stacking problem:
| Charge element | CESC area, FY2025-26 | What it means for a buyer |
|---|---|---|
| Wheeling | 164.60 paise/kWh | Payable on energy injected, per the wheeling schedule of 25 March 2025 |
| CSS formula | T − ACS + R | Capped at 20% of the category tariff |
| CSS exemption | Captive own-use only | Proportional to equity holding in the plant |
Read that table as a third-party buyer and the arithmetic is unforgiving: wheeling on every unit injected, then a CSS that can reach a fifth of the category tariff — and the exemption applies only to captive consumers using the power themselves, in proportion to equity. A third-party PPA buyer holds no equity and gets no exemption. The exemption clause is the pivot of the whole analysis: it points at ownership structures, not purchase structures.
WBSEDCL practice: the 90% adjustment cap
Outside the CESC area, WBSEDCL's practice on net injection adds its own constraint: energy injected into the grid is adjustable against a maximum of 90% of annual consumption. Plants sized close to or above annual consumption will routinely have surplus that earns little or nothing. Size the plant to your stable daytime base load, not to your roof's theoretical capacity.
Rooftop prosumers: the 2025 regime
The bigger structural shift came in 2025. The WBERC Rooftop Solar Prosumers Regulations 2025 (Gazette 81/WBERC, 31 July 2025) recast the rooftop framework, with the feed-in tariff set by the Commission's suo-motu order of 20 August 2025. The regime is now net-billing or gross-metering based rather than full net metering — injected energy is valued at the set FiT against your consumption at retail rates, not offset one-for-one.
Compared with the one-for-one net metering still available in much of North India — including Delhi-NCR and Haryana, where Sun Wave Technologies serves industrial rooftop clients — net billing changes the optimal plant size. Every self-consumed unit is worth far more than every exported unit, so the plant that maximises self-consumption, not nameplate capacity, wins.
What a West Bengal factory should realistically do
Given the framework above, the sensible strategy runs through ownership, not open access purchases:
- Start with a captive rooftop plant. Own (or host under a captive OPEX structure) a rooftop system sized to daytime load. Captive own-use attracts the CSS exemption proportional to equity, avoids third-party allotment risk, and fits the 2025 prosumer regime. Our Kolkata industrial solar guide covers site-level specifics.
- Understand your metering settlement. In the CESC area, follow the prosumer regulations and the FiT set on 20 August 2025; under WBSEDCL, model the 90% annual adjustment cap into your sizing.
- Use group captive for larger loads. Where the load exceeds one roof, a group captive plant — consumers holding at least 26% equity and self-consuming — preserves the captive exemptions at scale. Our group captive solar guide explains the structure end to end.
- Treat third-party open access as a last resort. Only pursue it if delivered cost stays competitive after wheeling, CSS and allotment risk — with the full charge stack confirmed in writing.
- Check the roof before the spreadsheet. Structural capacity, shading and roof rights determine whether the captive rooftop option exists at all — our guide to roof structural load assessment for solar covers what to check.
Route comparison at a glance
| Route | Charges you bear | Practical viability in WB |
|---|---|---|
| Third-party open access | Wheeling + CSS (capped at 20% of category tariff), no exemption | Weak — licensee-first allotment and stacked charges, per Bengal Chamber 2025 |
| Captive rooftop (own use) | CSS exemption proportional to equity; net billing at the set FiT | Strong — the default for most C&I buyers |
| Group captive | Captive exemptions preserved with 26%+ equity | Viable for loads beyond one roof |
Frequently Asked Questions
Is third-party open access solar viable in West Bengal?
Usually not. The WBERC Open Access Regulations 2022 give the distribution licensee first priority in allotment, and per the Bengal Chamber's 2025 paper, stacked wheeling and CSS charges frequently make third-party renewable procurement commercially less viable. Most C&I buyers are better served by captive rooftop or group captive structures.
What are the open access charges in the CESC area?
For FY2025-26, wheeling in the CESC area is 164.60 paise/kWh per the wheeling schedule dated 25 March 2025. The CSS is computed as T − ACS + R and is capped at 20% of the category tariff. The CSS exemption applies only to captive own-use, in proportion to the consumer's equity holding in the generating plant.
How does rooftop solar metering work in West Bengal now?
Under the WBERC Rooftop Solar Prosumers Regulations 2025 (Gazette 81/WBERC, 31 July 2025), rooftop systems operate on a net billing or gross metering basis, with the feed-in tariff for injected energy set by the Commission's suo-motu order of 20 August 2025. Self-consumed units avoid the retail tariff entirely, so maximising self-consumption is the design goal.
What is the 90% rule under WBSEDCL?
In WBSEDCL's practice, energy injected into the grid is adjustable against a maximum of 90% of the consumer's annual consumption. Plants sized near or above annual consumption will have surplus energy that earns little, so size the plant to stable daytime load rather than available roof area.
Can a factory in West Bengal use a group captive solar plant?
Yes, and for larger loads it is usually the right structure. Consumers holding at least 26% equity in the plant and self-consuming the output are treated as captive, preserving the CSS exemption third-party buyers do not get. Combined with rooftop captive systems, this covers most industrial needs in the state.
Where can I read more about industrial solar in Kolkata specifically?
Our utility guides — WBSEDCL net metering for industry and CESC net metering for commercial and industrial consumers — cover the two main distribution areas in detail.
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