A factory owner asked us a fair question last month: why does his neighbour’s unit, roughly the same size, pay a completely different solar tariff structure than his own plant? Both run on solar. Neither owns the same rooftop area. And that, more than anything else, is what decides whether net metering or open access ends up saving more money.

These two routes are not really competing versions of the same idea. They are built for different kinds of consumers, and mixing them up at the planning stage is one of the more expensive mistakes a factory can make when moving to solar.

What Net Metering Actually Means in Maharashtra

Net metering in Maharashtra rules work on a fairly simple principle: you install solar on your own rooftop or premises, and a bi-directional meter is used to track what you draw from the grid against what you send back. You are billed on the net, not the gross.

Maharashtra Electricity Regulatory Commission (MERC) recently raised the net metering capacity limit from 1 MW to 5 MW, which opened this route to a much larger set of industrial consumers than before. But there is a catch that trips up a lot of first-time applicants: the permissible solar capacity is subject to the applicable regulatory and sanctioned-load conditions. A factory running a 400 kW connection cannot install a 700 kW system under net metering just because the roof has proper space for it. If you want to size up, you apply for load enhancement first.

Settlement happens annually; usually it is closed out by March. Surplus units exported during the settlement period may be carried forward as credit, while treatment of any remaining surplus at the end of the applicable settlement period is governed by the prevailing MERC regulations and tariff framework. This is where a lot of factories lose value without realising it: oversizing a system so it exports more than it uses can shift the economics from offsetting higher-value consumption to receiving a lower-value settlement for surplus generation, depending on the applicable settlement mechanism.

Time-of-day billing has also been a basis for how net metering suits consumers above certain demand/capacity thresholds. Solar credits that are generated during the day may interact differently with consumption across applicable time-of-day billing periods, rather than automatically offsetting evening peak consumption on a one-to-one basis. For a factory running a second shift into the evening, that timing detail can considerably change the math on paper savings versus actual bill reduction. 

What Open Access Solar Actually Involves

Open access solar for factories works on a different premise entirely. Instead of generating power on your own site, you procure it from a solar generator elsewhere, often a ground-mounted plant, through a power purchase agreement, and that power is wheeled to your factory over the state grid.

This set-up generally becomes applicable once a factory’s load and eligibility under the applicable open-access framework make third-party or captive procurement viable, particularly where rooftop or on-site land simply isn’t enough to meet actual consumption, or there are any kind of structural difficulties. Solar open access lets a factory tap into utility-scale generation without needing acres of unused land on its own premises.

The trade-off is the charge structure. Open access power comes with charges such as cross-subsidy surcharge, wheeling charges, transmission charges/losses, and, where applicable, additional surcharge and other regulatory/system charges, layered on top of the power purchase cost.

Maharashtra’s open-access economics depend on the applicable consumer category, voltage level, procurement structure and prevailing charges, which is exactly why the economics need modelling for your specific consumer category and voltage level rather than assuming a generic percentage-savings figure you might see floating around.

Let Us Understand Which Route Really Pays Off

For a factory with enough usable roof or land, a sanctioned load that comfortably covers the solar capacity it wants, and consumption patterns that line up with daytime generation, net metering tends to be the more straightforward saver. There is no third-party power procurement arrangement for the rooftop generation itself, no open-access wheeling requirement for that on-site generation, and the payback period on the system itself depends on the project-specific cost, generation, tariff and financing assumptions.

For a factory that has already fully utilised its available rooftop, or runs a large enough load that self-generation on-site can’t cover more than a fraction of demand, open access may become more relevant despite the surcharge structure. Bulk-scale solar generation is often priced low enough that, even after applicable CSS, wheeling, transmission and other charges and losses are added, the landed cost per unit can still be competitive with standard industrial tariffs, particularly for HT and EHV consumers with high monthly consumption.

Neither answer, on its own, provides enough clarity. A mid-sized unit with spare roof area and an eligible sanctioned load may be better served staying within net metering. A larger industrial consumer already procuring power at HT or EHV level, with consumption that outstrips what any rooftop could realistically supply, may be a more natural candidate for evaluating open access.

Can a Factory Use Both?

In practice, some larger industrial consumers run a blended approach. A factory installs rooftop or in-roof solar under net metering to cover whatever load its own structure can host, and separately signs a PPA for open access to cover the demand gap the roof can’t. Whether both arrangements can be combined for a specific consumer depends on the applicable regulatory framework, sanctioned/contract demand, metering arrangement and DISCOM approvals.

The plan has to be deliberate, though. To operate both means tracking two billing mechanisms and two settlement cycles, and making sure the sanctioned load calculations for net metering also don’t get tangled up with the open access procurement volume. Get that sequencing wrong, and you end up paying for capacity you’re not using efficiently under either scheme. This is usually where an engineering-led feasibility study earns its cost back many times over, since sizing errors at this stage are expensive to unwind later.

Seasonal variation adds another layer that has to be considered. Generation drops through the monsoon months because solar irradiation and weather conditions vary, regardless of which route you take, so a factory sizing its system against a sunny-month output figure often ends up short come July and August. Building that dip into the payback calculation upfront avoids a lot of the disappointment we see with rushed system sizing.

Getting the Call Right

The decision comes down to three things: how much roof or land you actually have, what your sanctioned load and consumption profile look like, and whether your usage matches daytime solar generation closely enough to make net metering worthwhile before the applicable settlement mechanism determines the value of any surplus generation.

This is where the engineering assessment matters as much as the policy comparison. At Insteel, as a solar installation company in india built on a structural engineering discipline, we start every factory conversation with a load and site audit before recommending a route, because the wrong choice here isn’t just a paperwork inconvenience. It shows up every month on the electricity bill for years afterwards.