For a clinic, a showroom, a mill, or a cold room, the KSEB bill is a fixed operating cost. Sonetec’s commercial page uses an energy-charge band of about ₹7.50 to ₹10.50 per unit before fixed and demand charges. At the middle of that band, a roof that actually matches the daytime load has a simple payback in the range the same page already publishes: about 3.2 to 4.2 years. The December rule changes the price of getting there. It does not change how many units a given kilowatt produces.
What changes on 31 December 2026
Two lists are in play, and they are not the same thing.
- List-I is the module. These panels are made by approved Indian manufacturers. Net-metered projects already have to use them.
- List-II is the cell inside the module. A non-List-II module on this job uses cells from a global fab, then an Indian List-I factory laminates the module. A List-II module uses a cell made in India as well.
Domestic cell lines are still ramping, and a large share of that output is tied to subsidised household schemes. That scarcity is why the same wattage costs more once List-II becomes mandatory. MNRE’s 18 July 2026 release (283/53/2026-GRID SOLAR, reported by PIB the same day) said there was no blanket change to the List-II mandate. The relief is narrow: net-metering and open-access projects may be commissioned without List-II cells until 31 December 2026. The earlier window had run to 31 May 2026. The current-notices page on mnre.gov.in carries the same end date in the notice title.
A private plant that never connects for export is a different ALMM case. If the design is behind the meter only, check the current order before treating the cell rule as optional. This article is about plants that will be net-metered with KSEB or commissioned on open access.
The price gap, in two sizes we actually quote
These are Sonetec turnkey planning figures for a standard commercial roof in South Kerala: modules, inverter, structure, protection, and the usual cable run. A high structure, a long cable route, or an LT panel or transformer upgrade moves the number. The cell premium in these examples is about ₹9 per watt, at the top of the ₹6 to ₹9 per watt band we are seeing. That is ₹60,000 to ₹90,000 extra per 10 kW, and about ₹9,000 per kW in the tables below. Generation is the same in both columns: about 1,440 units per kW per year, which is roughly 4 units per kW per day.
The savings column uses ₹9.50 per unit, inside the ₹7.50 to ₹10.50 band on our commercial page. A bill that is mostly fixed demand, or a roof that exports most of its energy, will not match this. Daytime loads — a hospital wing, a showroom, a mill, a hotel laundry — are the ones this model describes.
20 kW — showroom, clinic, small hotel
| Planning figure | Commissioned by 31 Dec 2026 | Commissioned from 1 Jan 2027 |
|---|---|---|
| Modules | List-I, non-List-II TOPCon | List-I modules with List-II cells |
| Turnkey cost | ₹9,20,000 (about ₹46/W) | ₹11,00,000 (about ₹55/W) |
| Extra capital | Baseline | ₹1,80,000 |
| Units in a year | About 28,800 kWh | About 28,800 kWh |
| Energy-charge savings at ₹9.50 | ₹2,73,600 | ₹2,73,600 |
| Simple payback on project cost | About 3.4 years | About 4.0 years |
| Year-1 depreciation if used from Nov–Dec 2026 | 20% · ₹1,84,000 | 20% · ₹2,20,000 |
| Tax saved in that year at an illustrative 25% | ₹46,000 | ₹55,000 |
50 kW — factory, hotel, cold store
| Planning figure | Commissioned by 31 Dec 2026 | Commissioned from 1 Jan 2027 |
|---|---|---|
| Modules | List-I, non-List-II TOPCon | List-I modules with List-II cells |
| Turnkey cost | ₹21,50,000 (about ₹43/W) | ₹26,00,000 (about ₹52/W) |
| Extra capital | Baseline | ₹4,50,000 |
| Units in a year | About 72,000 kWh | About 72,000 kWh |
| Energy-charge savings at ₹9.50 | ₹6,84,000 | ₹6,84,000 |
| Simple payback on project cost | About 3.1 years | About 3.8 years |
| Year-1 depreciation if used from Nov–Dec 2026 | 20% · ₹4,30,000 | 20% · ₹5,20,000 |
| Tax saved in that year at an illustrative 25% | ₹1,07,500 | ₹1,30,000 |
Indicative benchmarks, not a quotation. Simple payback is project cost divided by one year of energy-charge savings. It leaves out demand charges (those stay), degradation, tariff changes, interest, and later years of depreciation. Company tax may be near 25% under section 115BAA or higher. If you claim GST input credit, the depreciable base is generally the cost after that credit. Your CA should sign the schedule we hand over. The 2027 column assumes the same roof and the same generation, with only the cell rule changed.
Why the first-year tax line is 20%, not 40%
Solar power generating systems sit in the 40% written-down-value block under section 32. That rate is real, and it keeps applying to the remaining value in later years. The first year has a second test. If the asset is put to use for fewer than 180 days in the financial year, the Act allows half the block rate in that year.
FY 2026–27 started on 1 April 2026. One hundred and eighty days from then lands around the end of September. A plant commissioned in November or December 2026 is in this financial year, and it is under the 180-day line, so the year-1 allowance in the tables is 20% of cost. A claim that multiplies the full 40% by the tax rate, and treats that as cash back this March, overstates the first-year shield for any plant going in now. Waiting until after 31 March 2027 pushes even the 20% claim into FY 2027–28, and a net-metered plant in that year also pays the List-II price.
Four reasons the clock is the commissioning date
1 · Capital
₹60,000 to ₹90,000 more per 10 kW
Same wattage, same technology, same units. The step-up is the domestic cell. On the examples above it is ₹1.8 lakh at 20 kW and ₹4.5 lakh at 50 kW.
2 · This financial year
20% now, 40% on the balance later
Commissioning before 31 March 2027 puts the plant into FY 2026–27. You will not get a full 40% deduction in year one from a November start. You will get the asset onto the books this year, at the lower hardware price if commissioning also beats 31 December.
3 · The queue
Feasibility, inspectorate, then the meter
A commercial file still needs KSEB feasibility, structure and protection, Electrical Inspectorate approval above the state’s kVA threshold, and a tested bi-directional meter before synchronisation. On a prepared South Kerala file that run is often 30 to 45 days. It is not a promise. From 6 November, a start this month can still aim at 31 December. A start in late November is already tight.
4 · When you use power
9 a.m. to 5 p.m. is the expensive part of the bill
A house exports at noon and imports at night. A showroom, a ward, a loom, or a cold room uses power while the array is producing. At ₹9.50 and the generation above, first-year energy savings are about 30% of project cost. That is a simple ratio, not a promised internal rate of return. Fixed and demand charges continue.
What Sonetec can take from here
We design and install commercial rooftops in South Kerala — Kollam, Thiruvananthapuram, Pathanamthitta, and Alappuzha — from the Chathannoor, Anchal, and Chadayamangalam offices. The 25 kW plant at Dr Pradeep’s Sindhoor Ayurveda Hospital in Kollam is the kind of daytime load this article is about: Luminous NXi 325 and Luminous TOPCon 625 W modules, sized to the hospital’s day bill. Commercial work also uses Microtek where that inverter fits the load.
We do not keep a standing claim of “ready stock” in every wattage, and we do not promise that every file opened in December will be commissioned in December. What we do is the engineering and the liaison: structure design, galvanised frames, chemical anchors where the slab needs them, AC and DC surge protection, the KSEB papers, the inspectorate file when the kVA threshold requires it, and a depreciation schedule your CA can check. The module list is Luminous and Microtek, both bought as List-I for the non-List-II window while that window is open.
Questions owners ask before they sign
Does a commercial business get any subsidy under PM Surya Ghar?
No. Central financial assistance under that scheme is for residential consumers. The ₹30,000 / ₹18,000 slabs and the ₹78,000 cap do not apply to a commercial or industrial connection. The business case is the tariff you stop buying, GST input credit where your registration and use allow it, and depreciation under section 32. The household scheme’s own deadline is a different document — we fact-checked it in Is the government stopping the PM Surya Ghar subsidy?
What if the plant is installed in December 2026 and KSEB commissions it in January 2027?
The cutoff is commissioning. PIB’s 18 July 2026 release, and the notice title on MNRE’s current-notices page, both describe a window to commission net-metering and open-access projects without List-II cells until 31 December 2026. A plant that is on the roof in December and synchronised in January is a 2027 commissioning. It needs List-II cells. That is why the useful date to start a South Kerala file is early November, not the week of Christmas.
Are non-DCR panels a lower grade?
List-I is the quality gate for the module. The panels Sonetec installs on these jobs are Luminous and Microtek TOPCon, with the manufacturer’s product and performance warranty, commonly 25 to 30 years on performance. List-II changes where the cell is made. It does not add watts. Other List-I brands exist. We quote the ones we install and service from these three offices.
Can I claim the full 40% in FY 2026–27 if I commission in December?
You claim half the block rate in year one, because the plant will have been in use for fewer than 180 days. On these examples that is ₹1,84,000 of depreciation on a ₹9.2 lakh plant, and about ₹46,000 of tax at an illustrative 25% rate. The block stays at 40% of written-down value from the next year. If GST credit is claimed, do not also depreciate the GST. Have the CA confirm it before you book the investment.
Price the roof before the cell rule changes
Turnkey commercial rooftop solar in South Kerala. Load from your bills, a structure that matches the slab, List-I TOPCon while the non-List-II window is open, and the KSEB and inspectorate file run in parallel.
Policy source: Ministry of New and Renewable Energy, “ALMM for Solar PV Cells — No blanket exemption/extension…”, PIB release of 18 July 2026, and the matching notice on mnre.gov.in (current notices, end date 31 December 2026, O.M. 283/53/2026-GRID SOLAR). Tax: section 32 of the Income-tax Act and the 180-day rule. Tariffs and costs are planning figures for South Kerala, not a KSEB tariff order and not a fixed quotation. PM Surya Ghar central financial assistance does not apply to commercial connections.