Bihar's Draft Rooftop Solar Rules: What the 500 kWp Cap Means for Your Factory

Published Nov 6, 2026

Rooftop SolarPolicy

Bihar is rewriting its rooftop solar rules, and factories should pay attention. The state regulator has proposed a cap on net metering and a new low rate for surplus solar power.

The message for a plant head or CFO (Chief Financial Officer) is simple: size solar to what your factory actually uses. Here is what the draft says, what is still unsettled, and what to do now.

What has Bihar proposed for rooftop solar?

The Bihar Electricity Regulatory Commission (BERC) has proposed capping net metering at 500 kWp (kilowatt-peak) or the consumer's sanctioned or contracted load, whichever is lower. Larger systems would move to gross metering. Surplus power left at the end of the financial year would be paid at 50% of the feed-in tariff.

The proposal is a draft Second Amendment, 2026, to BERC's rooftop solar net and gross metering regulations. SolarQuarter's report on the draft amendment sets out four main points:

Net metering minimum: 1 kWp.
Net metering maximum: 500 kWp, or your sanctioned or contracted load if that is lower.
Gross metering: capacity can go up to your full sanctioned or contracted load.
Year-end surplus: paid at 50% of the feed-in tariff approved for that year.

Mercom India's report confirms the 500 limit and the 50% rate, though it writes the cap as 500 kW. Check the unit in the final text, because it can change how much panel capacity you may install.

Are these rules final?

No. As of 6 November 2026, we could not find a final notified version. Treat every number below as a proposal that could change.

Written comments were due by 28 October 2026. Reports listed public hearings in early November, with 2 November for the feed-in tariff petition and 3 November for the amendment. The notice for the amendment is listed on the BERC website, which is the place to watch for the final text.

How does the draft differ from Bihar's current rules?

The main change for large consumers is a fixed ceiling on net metering. A summary of the 2018 regulations ties system size to your sanctioned or contracted load, with no separate 500 kWp limit.

The summary of the 2018 Bihar regulations also shows other limits that matter for a project:

Cumulative net metering of 100 MW per year in a discom's (distribution company's) supply area.
Cumulative capacity at a distribution transformer of no more than 80% of that transformer's capacity.
A check meter for systems above 20 kW.

That summary dates from 2018, so ask your discom which limits apply today. The transformer limit in particular can decide a project at a crowded industrial feeder.

What happens to surplus solar power under the draft?

Surplus still unadjusted at the end of the financial year would earn 50% of the approved feed-in tariff. That is likely to be far less than the value of a unit your factory uses itself.

The discoms have asked BERC for a feed-in tariff of ₹2.71 per unit for FY 2026-27, in a petition filed by North Bihar Power Distribution Company Limited and South Bihar Power Distribution Company Limited. If both proposals are approved as they stand, year-end surplus would earn about ₹1.36 per unit.

Compare that with your own bill. A solar unit used on site avoids your full variable charge for that time of day. A unit left over in March would earn about ₹1.36 under these proposals. That gap is why oversizing is likely to become an expensive habit in Bihar.

Does a Bihar factory above 500 kWp lose out?

Not automatically, but it has a harder choice. A factory that needs more than 500 kWp would no longer get net metering on the whole system under the draft. Gross metering would remain open up to its sanctioned or contracted load.

Under gross metering, the discom pays for the electricity you inject at the approved feed-in tariff, according to the 2018 summary. Your factory continues to buy its power at the normal tariff. So the deal depends on the gap between ₹2.71 (if approved) and your grid rate.

Question	Net metering (draft)	Gross metering (draft)
Size limit	500 kWp or sanctioned load, whichever is lower	Up to full sanctioned or contracted load
Where solar power goes	Used on site first, surplus exported	Injected into the grid and paid for
Value of each unit	Avoids your grid charge when used or adjusted	Feed-in tariff (₹2.71 sought for FY 2026-27)
Year-end surplus	50% of the feed-in tariff	Not applicable: injected units are paid at the feed-in tariff
Best suited to	Factories with steady daytime load	Sites that want capacity beyond the net metering cap

The draft also says the state government may take up larger rooftop projects through other mechanisms. No details were reported, so do not plan around this yet.

How should a Bihar factory size rooftop solar under the draft?

Start from daytime load, not roof area. A plant that matches your solar-hours consumption protects the value of nearly every unit it produces.

We covered the full method in our guide on how to size rooftop solar for a factory. For Bihar, four checks matter most:

Pull 12 months of bills. Our guide on how to read your factory's electricity bill shows which charges solar can cut.
Map your weekly offs and shutdowns. Solar still generates on a Sunday, and those units become exports if the plant is idle.
Test the size against the cap. Check 500 kWp, your sanctioned load and your transformer capacity. The lowest limit decides your net metering size.
Estimate year-end surplus. Run your numbers with surplus at 50% of the feed-in tariff, and see if the plant still works.

Why time-of-day billing matters too

Solar value is not the same at every hour. Under the FY 2026-27 Bihar tariff order, consumers with contract demand above 10 kW, except agriculture, are billed on Time of Day (ToD) rates from 1 April 2026. Check the rate your bill shows for solar hours, and use that in your savings estimate, rather than an average rate.

Is the Bihar green tariff an alternative to rooftop solar?

It serves a different goal. The green tariff buys a renewable claim at extra cost. Rooftop solar aims to lower your per-unit cost.

The same tariff order lets consumers choose renewable energy at an additional ₹0.68 per unit. That may help a company chasing a quick sustainability target. It adds to the power bill, though, so it does nothing to reduce your energy cost.

Does the draft affect zero investment solar?

It affects the sizing, not the idea. Under the OPEX solar model, a developer funds and owns the plant, and you pay per unit. A plant that exports less and serves your load fits this model well.

The reports do not set out specific rules for RESCO (Renewable Energy Service Company) projects under net metering. The feed-in tariff petition does refer to "prosumers or third-party owners" under gross metering, and the 2018 summary refers to self-owned and third-party-owned systems. Confirm your structure with the discom before signing.

If you plan to buy the solar plant outright, the same logic applies with more force, since you carry the cost of any capacity that earns only the surplus rate. Either way, our comparison of CAPEX vs OPEX rooftop solar sets out the trade-offs.

Should a Bihar factory wait for the final rules?

Do the groundwork now, and sign once you know the final numbers. Most of the useful work does not depend on the final text.

Collect 12 months of bills and your load pattern.
Get your roof checked and your sanctioned load confirmed.
Ask your discom about transformer capacity and any queue at your feeder.
Ask the developer to model the plant at 500 kWp and at your sanctioned load, using the 50% surplus rate.

It is also worth asking how the final rules treat systems already approved. The reports we read do not say, so get this in writing from your discom.

Once a plant is live, good solar plant monitoring shows how much power is being exported, so you can spot a growing surplus before year-end.

FAQ

What is the proposed net metering limit in Bihar?

BERC's draft proposes a limit of 500 kWp or the consumer's sanctioned or contracted load, whichever is lower. It is not final until BERC notifies it.

What rate would Bihar pay for surplus rooftop solar power?

Surplus left unadjusted at the end of the financial year would be paid at 50% of the approved feed-in tariff. If the ₹2.71 per unit sought for FY 2026-27 is approved, that works out to about ₹1.36 per unit.

Can a Bihar factory install more than 500 kWp of rooftop solar?

Under the draft, yes, through gross metering, up to its full sanctioned or contracted load. Injected power would then be paid at the approved feed-in tariff.

Has BERC approved the ₹2.71 feed-in tariff?

Not in the reports we read. The figure comes from a discom petition, and BERC directed a public notice and hearing on it.

Does the draft mention batteries?

The reports we read do not mention storage. A battery storage system could in theory shift surplus to later hours, but test the cost against the value of those units.

About SustVest

SustVest is a rooftop solar developer in India, ranked among the CRISIL Top-10 rooftop solar project developers (#5, 2026). It runs 80+ distributed solar plants (about 30 MW) across 13 states for commercial and industrial clients, and it funds, builds, owns and maintains plants under its OPEX model with zero upfront cost. Talk to SustVest about a rooftop solar plan for your factory.