What a 1.5 MW Solar Plant Costs and Needs: Roof, Connection, Approvals

A 1.5 MW rooftop solar plant for a factory indicatively costs about ₹3.6 to ₹3.9 crore excluding GST, at ₹24,000 to ₹26,000 per kW, the lower end of our published C&I band. It needs roughly 1.5 lakh sq ft of shadow-free roof, generates about 1.8 lakh units a month in north India, and connects on the HT side, with approvals running through the DISCOM and the state electrical inspector.

What does a 1.5 MW plant cost, and how does it scale?

Our published benchmark for turnkey commercial and industrial rooftop solar is ₹24,000 to ₹32,000 per kW, excluding GST, falling as plants grow. We publish cost pages for 100 kW, 250 kW, 500 kW and 1 MW. We do not publish one for 1.5 MW, so the figure below is scaled from the 1 MW page and is a planning number, not a quotation.

The scope behind the band is modules, inverters, mounting structure, DC and AC cabling, earthing and lightning protection, protection and metering, installation, testing and commissioning, and the DISCOM liaison. It excludes roof strengthening, HT-side works where the site needs a new bay or transformer, batteries, land for a ground-mount alternative and statutory fees. At 1.5 MW the HT scope is the swing item: an existing bay keeps you inside the band, and a new bay, cable run or protection panel is priced from the single-line diagram, not per kW. For smaller plants see the 100 kW and 250 kW pages.

Roof or ground: how much area does 1.5 MW need?

Plan on about 100 sq ft of shadow-free roof per kW, so about 1.5 lakh sq ft for 1.5 MW. That is rarely one roof. Expect five to ten sheds with different heights and orientations, and subtract skylights, vents and parapet shadows. A shadow study turns the brochure area into your real one, and the solar plant area calculator gives a first screen. If the roofs fall short, the alternatives are a carport, a ground-mount on spare industrial land, or a smaller rooftop plant plus open access for the balance. Our calculators use about four acres per MW for ground-mount, so plan for something near six acres at this size, and see when ground-mount beats the roof.

The roof must also carry the load. At this scale you are adding structure to several buildings, and old sheds and asbestos or pre-engineered metal roofs need a structural check before the layout is fixed. The solar roof load calculator is a first look, not a certificate.

How much will it generate?

Our planning figure for the northern belt is about 120 units per kW per month. For 1.5 MW that is about 1.8 lakh units a month, or about 21.6 lakh units a year. Rajasthan and Gujarat run higher; the East and North East run lower; fog, dust and orientation move the monthly figure. To turn units into rupees, multiply by what each unit would otherwise cost you on the bill, and separate the units you use on site from those exported. The solar payback calculator shows payback as scenarios by self-consumption share instead of a single number.

Connection voltage, metering and the open access question

A megawatt-class plant is connected on the HT side, at 11 kV or 33 kV depending on the DISCOM's supply code and the feeder. We could not confirm a fixed capacity-to-voltage rule from a primary source, so the DISCOM's feasibility study is the decider. The CEA connectivity standards for distributed generation are framed for connections below 33 kV, so if the DISCOM asks for 33 kV, ask which technical standard it applies.

Three rules shape the economics at 1.5 MW:

• The net-metering ceiling. The Electricity (Rights of Consumers) Rules, as amended in 2021, raised the net-metering limit to 500 kW, with the sanctioned load as the other limit. For larger plants, arrangements such as net billing, net feed-in or gross metering are for the state commission to decide. PIB's year-end reviews date the amendment differently, so read the gazette. A 1.5 MW plant is beyond the central ceiling, and the state's regulation then decides how export is settled.
• Sanctioned load or contract demand. The plant should be sized against what your connection allows and what the daytime load can absorb. A plant larger than the daytime load exports, and export is usually the least valuable unit.
• Open access. The Green Energy Open Access Rules, 2022 lowered the open access limit from 1 MW to 100 kW, and PIB notes that approval is to be deemed granted if not decided in 15 days. A consumer at 1.5 MW is above the older threshold and the new one, but state adoption varies. Our open access solar page compares it with rooftop captive.

Inverter architecture and protection

At 1.5 MW the choice is a fleet of string inverters, typically 25 to 30 units in the 50 to 60 kW class, or a few central inverters. We usually favour strings for serviceability: a failed string inverter is a small share of output replaced from stock, while a failed central unit can idle a large block. Central inverters can win where roofs are large, uniform and close to the inverter room. See string vs central inverters at 500 kW to 2 MW.

Whatever the architecture, protection decides whether the plant stays on. Reverse-power, over and under voltage and frequency relays must coordinate with your existing scheme. The transformer must absorb reverse flow at peak generation minus minimum load, which is a holiday afternoon for most plants. DG interlocks must stop the plant back-feeding a generator set, and our guide on grid interconnection protection covers this.

Approvals in order, and a realistic timeline

1. Check sanctioned load, contract demand and transformer headroom, then freeze the capacity.
2. Prepare the design and single-line diagram, including the HT bay and metering.
3. File the DISCOM application. Under the central rules as amended in February 2024, the feasibility study for rooftop systems above 10 kW is to be completed in 15 days, with deemed approval if it is not; state processes for HT plants may run differently.
4. Obtain the electrical inspector's approval of the drawings, then install and test.
5. Arrange inspection, meter installation and synchronisation.

On modules, MNRE's office memorandum of 4 August 2026 exempts net-metering projects from the ALMM cell list (List-II) only if commissioned by 31 December 2026; the module list (List-I) still applies. Private captive behind-the-meter plants are outside both lists. Your contractor should state which regime your plant falls under; see ALMM.

There is no honest single timeline at this size. Site work is measured in months, and the time is dominated by procurement lead time, the DISCOM feasibility, the inspector's visit and the HT bay. Ask each bidder for a dated programme that separates those four.

How Secured Engineers helps

We design in-house, take MEPF and solar under one contract, and file the DISCOM net-metering application and the CEIG file in-house, so the HT side of a 1.5 MW plant is one scope with one owner. Our offices are in Noida (Delhi NCR) and Ludhiana, with 535+ projects across 18+ states and 89.77% repeat clients. Our solar EPC pages describe modules, inverters and structure.

Start with the solar calculator using your last twelve bills. Then send the bills and your sanctioned load by WhatsApp, call +91 70099 85817, or ask for a free proposal, and we will tell you what size your connection and the state's rules support before you buy.