Open access solar is a mechanism that allows large electricity consumers to purchase solar power from a remote solar plant and receive it through the existing electricity grid. Unlike rooftop solar where panels are installed on your premises, open access solar involves no installation at your site. The power is generated elsewhere and wheeled to you.

For large businesses consuming significant electricity, open access can offer lower per-unit solar power costs than rooftop solar. But it comes with regulatory complexity and minimum consumption thresholds that make it unsuitable for smaller consumers.

How open access solar works

A consumer who qualifies for open access enters into a Power Purchase Agreement (PPA) with a solar developer. The developer builds or owns a solar plant, generates electricity, and injects it into the grid.

The state transmission company and DISCOM then “wheel” this power to the consumer’s premises. The consumer pays the DISCOM wheeling charges, transmission charges, cross-subsidy surcharge, and any other applicable charges for this transportation service.

The net per-unit cost of solar power through open access is the PPA rate plus all wheeling and ancillary charges. When this total falls below the retail commercial tariff from the DISCOM, open access is financially attractive.

Who qualifies for open access?

Open access eligibility is governed by state electricity regulatory commissions and varies significantly by state. The key threshold is typically the consumer’s contracted demand or sanctioned load.

In most Indian states, open access is available to consumers with a contracted demand of 1 MW (1,000 kW) or above. Some states have lower thresholds: certain states allow open access from 100 kW.

For most small and medium businesses, open access is not applicable because their consumption does not meet the threshold. Rooftop solar is the appropriate mechanism for consumers below the open access threshold.

Large manufacturers, large commercial facilities, data centres, hospitals, and hotels are the typical open access beneficiaries.

State-wise open access thresholds

State	Typical threshold for open access
Rajasthan	1 MW and above
Gujarat	1 MW and above (lower in some categories)
Maharashtra	1 MW and above
Karnataka	1 MW and above
Tamil Nadu	1 MW and above
Andhra Pradesh	1 MW and above
Telangana	1 MW and above

Note that some states have created special categories for renewable energy open access with lower thresholds. Check with your state electricity regulatory commission for the current applicable rules.

What charges apply under open access?

The total cost of open access solar power includes several components beyond the PPA rate:

Transmission charges: Paid to the state transmission company for using the high-voltage grid.

Wheeling charges: Paid to the DISCOM for distribution of power through the lower-voltage grid to your premises.

Cross-subsidy surcharge: A levy designed to compensate for the subsidy provided to domestic consumers that is partly funded by commercial tariffs. This is often the most significant additional charge and varies by state.

Scheduling and standby charges: For grid balancing and backup supply.

The sum of all these charges can be Rs 2 to Rs 5 per unit depending on the state. Whether the total open access cost is lower than the DISCOM tariff depends on state-specific charges.

Open access vs rooftop solar: which is better?

For consumers above the open access threshold, the comparison depends on your state’s specific charges.

Rooftop solar advantages: no wheeling charges, simpler process, available to any size consumer, PM Surya Ghar or MSME subsidies may apply.

Open access advantages: no upfront capital investment (under PPA model), potentially lower per-unit cost for large consumers, no roof space requirement.

Many large consumers use both: rooftop solar to cover the maximum feasible on-site generation, and open access to cover remaining consumption.

How to pursue open access solar

If your consumption exceeds your state’s threshold, the process involves:

Applying to your DISCOM for open access connectivity approval.

Engaging a solar developer who offers PPAs for open access projects in your state.

Signing a PPA specifying the supply rate, term, and conditions.

Obtaining connectivity approval from the state load despatch centre.

The full open access process is more complex than rooftop solar and typically requires legal and technical advisory support. Several solar developers and energy consultants specialise in facilitating open access for industrial consumers.

Summing up

Open access solar is a mechanism for large electricity consumers, typically with demand above 1 MW, to access solar power without installing panels on their premises. It is not relevant for most small businesses or residential consumers. For large industrial and commercial consumers, it is a powerful tool to reduce electricity costs, complementing rather than replacing rooftop solar.