On-Grid vs Off-Grid vs Hybrid Solar for Factories

Direct answer

For most Indian factories, a grid-connected (on-grid) solar plant with net metering is the right choice. It is the cheapest to install, needs no batteries, and displaces grid power at ₹7–12 per unit with solar generated at an effective ₹2.5–3.5 per unit. Hybrid (solar plus battery) makes sense when you also want backup power or evening-peak savings — but batteries add roughly 30–60% to system cost. Off-grid almost never makes sense for a factory that already has a grid connection.

TL;DR: Start on-grid. Add storage only when a specific, quantifiable problem — diesel bills, outages, evening peak tariffs — justifies it.

How on-grid solar works for a factory

A grid-tied plant feeds your factory's loads first; surplus units flow back to the grid through a bidirectional meter. Under net metering, those exported units offset imported units on your bill — you pay only for the net. Under net billing (used in some states and above certain caps), exports are credited at the DISCOM's average power purchase cost — roughly ₹2.80–5.50 per unit nationally — far below the ₹7–12 retail tariff you pay for imports.

Key facts that shape the decision:

• The Ministry of Power's consumer rules set a national net-metering floor of 500 kW or sanctioned load (whichever is lower); most states cap commercial net metering at 1 MW, and above the cap projects move to net billing, open access or group-captive structures.
• Exporting power without a net-metering or open-access agreement is a violation — DISCOM meters detect reverse flow and will trip or penalise it. Factories on saturated feeders may be required to install zero-export controllers that throttle the plant in real time.
• Factory day-shift load (8 AM–5 PM) overlaps solar generation hours well, so most of the plant's output displaces grid imports directly — no storage needed to capture the value.

That overlap is why on-grid dominates. A plant sized to your daytime load converts nearly every unit into a saved grid unit at retail tariff.

When off-grid makes sense (and when it does not)

Off-grid — solar plus enough battery to run the factory independently — is rational only where no grid exists or extension is prohibitively expensive: telecom towers, mining sites, remote cold stores. A factory consuming 10,000 units a month would need 8–10 hours of battery autonomy to run independently, and the system must be engineered for the worst monsoon week, not the average day. With battery replacement cycles of 8–15 years, duplicating infrastructure the DISCOM already provides is almost never a good investment.

If your business has a grid connection, treat off-grid as a thought experiment, not an option.

Hybrid solar: when a battery earns its keep

A hybrid system pairs a grid-tied plant with a battery energy storage system (BESS). In 2026, three value streams justify it:

1. Replacing diesel. DG sets cost ₹18–28 per kWh all-in (fuel, maintenance, operator, depreciation) — versus ₹7–11 per kWh for grid-charged battery backup including round-trip losses. A 500 kVA DG running 200 outage hours a year can cost ₹18–25 lakh annually in energy alone. Batteries also switch over in milliseconds versus 10–30 seconds for a DG start, protecting CNC lines and PLCs from the dip.

2. Time-of-day arbitrage. Regulators now mandate ToD tariffs for C&I consumers with at least a 40% spread between evening peak and solar-hour rates. A battery charged from midday solar and discharged at the evening peak captures the full spread. Industry sizing examples for a 1 MW plant with a ~450 kW/1,125 kWh battery show ₹4–7 lakh a year in arbitrage and resilience value — against roughly ₹50–65 lakh of added capex.

3. Regulatory positioning. A March 2026 draft amendment to the Electricity (Rights of Consumers) Rules proposes allowing state commissions to mandate storage for renewable installations above 500 kW; Maharashtra already requires storage procurement planning for new large renewables. Treat these as direction of travel, not current law — but they signal that storage will increasingly be part of C&I planning.

BESS prices have collapsed: the Power Ministry reported storage service tariffs falling from about ₹10.18 per kWh in 2022-23 to about ₹2.1 per kWh by late 2025 in competitive auctions (a tariff for storage service — not the installed purchase price, which for C&I-scale systems runs roughly ₹15,000–40,000 per kWh depending on size). The CEA has also firmed up fire-safety expectations: setback distances, fire-rated containers, detection and suppression systems, and third-party audits — real design and cost line items that belong in your quote.

What each option costs and earns

For a qualifying CAPEX rooftop, Sun Wave's reference pricing is ₹23,000/kW at 100 kW and ₹22,000/kW at 500 kW (ex-GST; final pricing follows site survey and engineering scope). Industry-wide, industrial rooftop systems run ₹35–50 per watt installed.

A 100 kW on-grid plant at the ₹23 lakh reference generates roughly 1.45 lakh units a year in North India. Displacing grid power at ₹7–10 per unit saves about ₹10–14.5 lakh a year. With 40% year-one accelerated depreciation (old tax regime; not available under Section 115BAA) and GST input credit, effective payback compresses to roughly 2.5–4 years across that tariff band, with post-tax IRRs above 20%. The same plant as a hybrid with meaningful backup would add ₹20–40 lakh of battery capex and stretch payback toward 5–7 years — which is exactly why the battery decision must be driven by outage cost or peak-tariff exposure, not added as a default.

How to choose: a 5-question framework

1. How reliable is your grid? Fewer than a few hours of outage a month → on-grid. Chronic outages costing real production loss → hybrid with backup for critical loads.
2. What does an outage cost you per hour? spoiled product, restart scrap, idled labour — quantify it before a salesperson does.
3. Are you on a ToD tariff? If evening peaks dominate your bill, arbitrage value strengthens the battery case.
4. What is your DG fuel bill? If diesel is running as primary backup more than occasionally, solar-plus-storage displaces it at 60–75% lower cost per backup unit.
5. What is your load pattern? Single day shift → on-grid captures most value. Two shifts with heavy evening load → hybrid or open-access supply deserves evaluation.

Frequently Asked Questions

Which solar system is best for a factory in India?

For most factories, a grid-connected (on-grid) solar plant with net metering is the best choice: lowest cost, no batteries, and payback of roughly 2.5–4 years with accelerated depreciation. Hybrid systems with batteries suit factories with costly outages or strong evening-peak tariffs.

Is a battery necessary for industrial rooftop solar?

No. Grid-connected plants without batteries are the standard for Indian industry. Batteries add value only when they displace diesel generation, shift load across time-of-day price gaps, or protect production from outages that cost more than the storage premium.

How much does a hybrid solar system cost compared to on-grid?

Batteries typically add 30–60% to system cost. For a mid-size factory plant that can mean ₹20–60 lakh extra, stretching payback from about 2.5–4 years to 5–7 years. The premium is justified when diesel displacement or outage-cost avoidance is worth more than the added capital.

Can solar power run a factory at night?

On-grid solar cannot — the plant shuts down after dark and the factory draws grid power. Hybrid systems can run backed-up loads at night from stored solar, and off-grid systems rely entirely on batteries. For most factories, net-metered exports during the day and grid imports at night is the cheaper combination than storing energy on-site.

What happens to on-grid solar during a power cut?

A grid-tied inverter shuts down during an outage (anti-islanding protection) even if the sun is shining, because it must not energise a dead line and endanger line workers. If outage protection matters, you need a hybrid design with battery backup or a DG-synchronised system.

What is the payback period for factory solar in India?

On-grid CAPEX plants typically pay back in 2.5–4 years with 40% accelerated depreciation and GST input credit, depending on your grid tariff (₹7–12 per unit across most industrial states) and self-consumption share. Hybrid systems run longer at roughly 5–7 years.

Sources: Ministry of Power, Electricity (Rights of Consumers) Rules and March 2026 draft amendment; PIB release on BESS auction tariffs (Dec 2025); Mercom India and IEEFA BESS market analyses (2026); CEA draft BESS safety regulations (2025); published case data and market cost guides (2026); Sun Wave reference pricing (sunwavetech.com, Sep 2026).