- A zero-export controller stops the system pushing any power to the grid.
- An export-limit controller caps export to a DISCOM-permitted value.
- Use them when net metering is denied by feeder or transformer saturation.
- Best fit is a site with high daytime self-consumption.
- It often still needs DISCOM intimation or approval — verify the state rule.
Net metering is the best deal when the DISCOM allows it, but feeders fill up. When a distribution transformer or feeder is saturated, the DISCOM can refuse to let a new system export. A zero-export or export-limit controller is the fallback: the customer still cuts their daytime bill, and the grid stays protected. This guide shows how the controllers work and when to choose each.
What zero-export means
Zero export means the solar system serves only the site and sends nothing to the grid. A zero-export controller measures the building's load and tells the inverter to throttle its output so generation never exceeds on-site use. The customer cuts the daytime portion of their bill without an export agreement.
Export rules, controller requirements and any intimation duty are set by each State Electricity Regulatory Commission (SERC) and DISCOM, and they vary by state and amendment. Treat the rules here as a working guide and verify the current requirement for your DISCOM and state before you design a non-export system.
When the DISCOM denies export
The DISCOM denies export when the local grid cannot safely absorb more solar. The two common triggers are a saturated distribution transformer and a saturated feeder.
Feeder and transformer saturation
When too much rooftop solar already feeds a transformer or feeder, the DISCOM caps further export to protect the network. A loading limit of about 30 percent of DT capacity is commonly cited, but the figure is state-set and changes — see the DT 30% loading rule and verify the current cap with your DISCOM. A capacity-above-cap or feeder-saturation rejection at feasibility (covered in feasibility rejected) is a common reason to move to zero export.
How the controller works
The controller sits between the meter point and the inverter. It watches the power flowing at the grid connection. The moment it sees power about to flow outward, it signals the inverter to reduce generation so the net flow to the grid stays at zero (or at the set limit).
The controller must work with a CEA-compliant inverter that has anti-islanding protection, and it relies on accurate metering at the connection point. A poor install — wrong CT placement, a slow response setting — can let brief export slip through, which defeats the purpose. The inverter standards guide covers the inverter side.
Your options when net metering is hard
Match the site to the right route. The best economics depend on whether export is allowed, the daytime load, and the value of any surplus.
Source: compiled from CEA standards and SERC export provisions. Export allowances vary by state — verify the current rule with your DISCOM.
Zero-export vs export-limit — which to use
Both stop excess solar reaching the grid, but they fit different situations.
Zero-export: no power to the grid at all
A zero-export controller allows nothing to flow outward. Use it when the DISCOM permits a system only on the condition that it never exports — typically a fully saturated feeder. The trade-off is that any generation above the daytime load is simply curtailed and lost.
Export-limit: a permitted cap
An export-limit controller caps export to a set kW the DISCOM allows, and lets the rest serve the site. Use it where the DISCOM grants a partial export allowance. It captures more value than zero export because some surplus still earns, up to the cap.
Does a zero-export system still need approval?
Often, yes. A zero-export system frequently still needs DISCOM intimation or approval, even though it does not export, because the DISCOM still wants a record of grid-connected generation for safety and planning. Do not assume "no export means no approval".
The exact rule varies by state and changes, so verify the current requirement for the specific DISCOM before you install. Telling a customer no approval is needed, when the state in fact requires intimation, can create a compliance problem later. Get the position in writing where you can.
Designing and sizing it right
A zero-export system pays only if it is sized to the daytime load. Oversize it and you curtail generation you paid for; undersize it and you leave savings on the table.
Size to the daytime load profile
Study the site's daytime consumption — a factory, an office or a shop with strong daytime use is a good fit. Size the array so most generation is consumed on site during sunlight hours. A home that is empty all day is a poor fit for zero export.
Consider storage for valuable surplus
If the site generates a large, useful surplus, a battery may beat zero export by storing that surplus for evening use. It costs more, so compare the payback. The net metering vs battery storage guide weighs the two, and net vs gross vs net-billing compares the metering models where some export is allowed.
Setup checklist
Before you commit a client to a zero-export or export-limit design, run this check.
- DISCOM position confirmed — export denied or capped, in writing where possible.
- Intimation/approval checked — the state rule for non-export systems verified.
- Daytime load studied — generation matched to on-site daytime use.
- Controller proven — works with a CEA-compliant, anti-islanding inverter.
- Metering accurate — CT placement and response setting prevent leak-through.
- Surplus decision made — curtail, cap, or store, with payback compared.
- Customer briefed — they understand surplus above the limit is not paid.
How SuryaHub helps with zero-export projects
A zero-export job has its own paperwork: the metering model, the controller setting and any DISCOM intimation. SuryaHub records all of it on the job, alongside the DISCOM workflow and the project plan, so the system is sized, approved and handed over cleanly — and the customer's expectation on surplus is set in writing. SuryaHub is pre-revenue; real pilots are Suryantra Energy and RGESPL, and the export rules here are scheme facts that vary by state, not guarantees.
Win the job even when export is denied
See how SuryaHub records the metering model and controller on each job.
Related guides
Frequently asked questions
What is a zero-export controller for solar?+
A zero-export controller is a device that stops a solar system from pushing any power onto the grid. It measures the load and tells the inverter to reduce output so generation never exceeds on-site use. It lets solar run when the DISCOM will not allow export to a saturated feeder.
When do you use a zero-export controller?+
You use a zero-export controller when net metering is denied because the transformer or feeder is saturated, or when the site has high daytime self-consumption and does not need to export. It lets the customer cut their daytime bill without an export agreement, where the DISCOM permits a non-export system.
What is the difference between zero-export and export-limit?+
A zero-export controller allows no power to flow to the grid at all, while an export-limit controller caps export to a set value the DISCOM permits and lets the rest serve the site. Zero-export suits a full feeder; an export-limit suits a partial allowance. Both protect the grid from excess solar.
Does a zero-export solar system still need DISCOM approval?+
A zero-export solar system often still needs DISCOM intimation or approval, even though it does not export, and the rule varies by state. Do not assume no approval is needed. Verify the current requirement for the specific DISCOM and state before installing a zero-export or export-limited system.
Is zero-export better than a battery?+
Zero-export is cheaper than a battery but wastes any surplus generated above the daytime load, while a battery stores that surplus for evening use at a higher cost. The better choice depends on the load shape and economics. Compare payback for both before deciding for a client.
How does SuryaHub help with zero-export projects?+
SuryaHub records the metering model, the controller setting and any DISCOM intimation on each job, so a zero-export system is sized, approved and handed over cleanly. SuryaHub is pre-revenue; real pilots are Suryantra Energy and RGESPL.
Sources & references
Export-control standards and the rules behind them come from primary government sources. Export allowances and intimation duties differ by state — always confirm the current rule with your DISCOM and SERC before you design a non-export system.
- Central Electricity Authority (CEA) ↗
Technical and safety standards for grid-connected inverters and export control (verify current).
- Ministry of Power — Rights of Consumers Rules 2020 ↗
Connection rules; export and metering provisions vary by state notification.
- Ministry of New & Renewable Energy (MNRE) ↗
Rooftop solar policy context and capacity guidance.
Written by the SuryaHub team · reviewed against CEA / MoP / MNRE sources · updated 19 June 2026.
Method: Controller behaviour and export rules are compiled from CEA standards and SERC export provisions, re-checked every 30 days. Export allowances and intimation duties are state-specific estimates — verify the current rule with your DISCOM. SuryaHub is pre-revenue; only Suryantra Energy and RGESPL are real pilots.
Change log: 19 Jun 2026 — first published.