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20 kW Solar System Price in Chennai

A 20 kW on-grid solar system costs ₹9.6 to ₹10.8 lakh installed in Chennai in 2026, including 8.9% GST, and a 25 kW system costs ₹12 to ₹13.5 lakh. A GST-registered business pays ₹8.8 to ₹9.9 lakh for 20 kW once it claims the GST back.

20 kW is the smallest size that is clearly a business system: a showroom, a clinic, a school block or a small office with its ACs running all day. It is also where Tamil Nadu's lowest LT registration fee band ends, so 25 kW brings a few small changes. Below are both prices, the rules, and the payback on real bills.

20 kW and 25 kW at a glance

• 20 kW price₹9.6 to 10.8 lakh
• 25 kW price₹12 to 13.5 lakh
• 20 kW units a yearabout 32,000
• 20 kW units a monthabout 2,660
• 20 kW roof1,600 to 2,000 sq ft
• 20 kW panelsabout 33 to 36

Chennai on-grid rooftop, 2026, at about 1,600 units per kW a year and 550 to 600 Wp panels.

20 kW and 25 kW solar prices in 2026, before and after GST

Both sizes sit in the same per-watt band, so 25 kW costs exactly a quarter more. The ex-GST column is what a GST-registered business really pays, because it claims the 8.9% back as input tax credit. A school, trust or home without registration pays the incl-GST figure. Our note on GST on a solar power plant explains the 70:30 split behind the 8.9%.

Both prices include modules, inverter, mounting structure, DC and AC cabling, earthing and lightning protection, the generation meter, CEIG and TNPDCL liaison, installation, commissioning and two years of maintenance.

What pushes a 20 kW quote up or down

• Roof. A showroom or workshop with a metal sheet roof costs less per kW than a school or office on RCC that needs an elevated structure.
• Modules. Non-DCR modules cost about ₹14.3 to ₹14.9 per Wp ex-works; DCR modules about ₹23 to ₹26 a watt.
• Inverter brand, and whether 20 kW runs on one inverter or two.
• Structure height over water tanks, parapets or a play area.
• Cable run from the roof down to the LT meter board.

For prices at every size from 10 kW to 1 MW, see the commercial solar cost per kW guide.

Who installs 20 kW: shops, clinics, schools, small offices and large homes

The tariff your connection sits on decides what each solar unit is worth, so it decides the payback more than the panels do.

• Shops and showrooms pay LT V at ₹10.45 a unit for all units. They run lights and ACs from opening to closing, so almost every solar unit is used on site. See solar for retail showrooms.
• Clinics and small nursing homes are also on LT V. Daytime OPD hours line up well with solar output. See solar for hospitals.
• Private schools pay LT IIB(2) at ₹9.40 a unit. Sundays and the summer holidays push more units into export, which the worked example below allows for. See solar for schools and colleges.
• Small offices are on LT V and usually close on Sundays.
• Large homes stay on domestic net metering up to their sanctioned load, with the subsidy capped at ₹78,000.

If your load is smaller, the 15 kW system page covers the step just above 10 kW. If you run cold rooms, kitchens or a full building of ACs, start at the 30 kW system.

What 20 kW and 25 kW generate in Chennai, and the roof they need

These use the Chennai district yield of about 1,600 units per kW a year. Other Tamil Nadu districts run from about 1,550 to 1,700. Output drops by about half a percent a year as the panels age.

Can 20 kW run a commercial building? Compare it with your bill. 20 kW makes about 5,300 units in a two-month bill cycle. If your bill shows that much or more, and most of it is used in daylight, 20 kW will offset most of it. If your bill shows far less, you will export the difference at a much lower rate.

Allow 80 to 100 sq ft of shade-free roof per kW. Stair rooms, water tanks and neighbouring buildings take more space than most owners expect, so the survey maps shade before the layout is fixed.

Subsidy at 20 kW depends on whose name is on the meter

There is no single answer on subsidy at this size, because three kinds of buyer install 20 kW.

The Tamil Nadu top-up is for homes registered on PM Surya Ghar from 5 August 2026, for the first one lakh consumers. The society rate applies to common facilities up to 500 kW. At 25 kW a society needs 9 or more houses to claim the full ₹4.5 lakh.

Businesses get no PM Surya Ghar money, whatever the size. Their support is tax: accelerated depreciation at 40% a year on the written-down value, if the business has taxable profit for it to reduce. Your CA should model it. The solar power plant subsidy guide covers each buyer type, and solar for apartments covers societies.

Above 10 kW in Tamil Nadu: CEIG, generation meter, net feed-in and the ₹500 fee band

Every system above 10 kW follows the same set of TNERC rules, whether it is on a shop or a home. At 20 and 25 kW they are:

• CEIG approval before commissioning. Our CEIG approval guide shows the steps; we file and attend the inspection.
• A separate generation meter with demand recording, at the owner's cost and included in our price. Above 20 kW, TNPDCL also fits a check meter.
• A feasibility study by TNPDCL within 15 working days of registration, then approval within 5 working days, valid for 6 months.
• Registration fee: ₹500 for anything up to 20 kW. A 25 kW system falls in the next band and pays ₹600.
• Capacity cap: the plant cannot exceed your sanctioned load. Check yours first with our post on the sanctioned load limit.
• Application on the TNPDCL rooftop portal (USRP).

A business goes on net feed-in. Imports are billed at your tariff; exports are credited in money at ₹3.37 a unit, the rate for 11 to 150 kW plants. Credit carries forward, and on 31 March you choose payment or carry-over. The solar export unit price guide covers the rates.

A network charge of ₹1.60 a unit applies to every unit generated on LT, in full for LT V and LT IIB. LT IIIB industries pay ₹0.80 in 2026-27 because the state pays half. A home above 10 kW pays 75% of the charge, ₹1.20 a unit. The charge is currently levied and under challenge in the Madras High Court.

Payback for a shop on LT commercial versus a home above 10 kW

Annual saving = (self-used units × tariff) + (exported units × ₹3.37) − (all units × network charge). The showroom is open seven days and uses 90% of its solar. The school uses 75%, because it is shut on Sundays and through the summer holidays. The showroom is GST-registered; the school is not, so it pays the incl-GST price.

Both paybacks are before depreciation and ignore the 25% peak surcharge that LT V and LT IIB pay from 6 to 10 am, part of which solar offsets. The fixed charge of ₹110 per kW a month stays on both bills. Try your own figures in the commercial solar ROI calculator.

A large home at 20 kW

A home pays 75% of the network charge above 10 kW: 32,000 × ₹1.20 = ₹38,400 a year. On net metering it saves its slab rate on every unit it uses, but anything left at 31 March lapses unpaid. Say the house uses 20,000 of the 32,000 units. Under net metering the other 12,000 are lost. If it opts for net feed-in instead, they earn 12,000 × ₹3.37 = ₹40,440, which barely covers the network charge. Either way the surplus earns almost nothing, so a home should size 20 kW only to the units it actually uses. Our post on net metering versus net feed-in shows how to switch.

25 kW: when the extra 5 kW pays and when it does not

Going from 20 to 25 kW adds ₹2.2 to ₹2.5 lakh before GST and about 8,000 units a year. Whether that pays depends entirely on where those 8,000 units go.

A unit used on site is worth ₹8.85 after the network charge. A unit exported is worth ₹1.77. So take 25 kW only if your site uses roughly 110 units or more in daylight on a typical working day. Three smaller points also change at 25 kW: the registration fee rises from ₹500 to ₹600, TNPDCL adds a check meter because the plant is above 20 kW, and your sanctioned load must be at least 25 kW.

If your daytime use is well beyond 25 kW, the 30 kW system costs less per watt, at ₹46 to ₹52.

What a 20 kW quote should include

Two 20 kW quotes can differ by a lakh and both look complete. Check each one for:

• The total with and without 8.9% GST, and the per-watt figure for each.
• Module make, wattage and count (33 to 36 panels at 550 to 600 Wp), and whether they are DCR or non-DCR.
• Inverter make and AC rating, which must not exceed your sanctioned load.
• Structure type and height, and whether any roof repair is included.
• The generation meter, CEIG approval and TNPDCL registration, included or left to you.
• Earthing pits, lightning protection and cable lengths named line by line.
• Two years of maintenance, and the AMC price after.

Our guide on whether your solar quote is too high works through a real quote line by line.

Other commercial sizes

20 kW solar systems, common questions

What is the price of a 20 kW solar system in Chennai?

₹9.6 to ₹10.8 lakh installed in 2026, including 8.9% GST, or ₹48 to ₹54 a watt. A GST-registered business pays ₹8.8 to ₹9.9 lakh after input credit.

What does a 25 kW solar system cost?

₹12 to ₹13.5 lakh including GST, or ₹11 to ₹12.4 lakh before GST. It sits in the same per-watt band as 20 kW.

How many units does a 20 kW solar system produce per day?

About 88 units a day on average in Chennai: about 2,660 a month and 32,000 a year. A 25 kW system makes about 110 a day.

Can a 20 kW solar system run a commercial building?

It can offset most of the bill for a building that uses about 5,300 units or more in a two-month cycle, mostly in daylight: a showroom, clinic, school block or small office. Larger loads need 30 kW or more.

How much roof space and how many panels does 20 kW need?

About 1,600 to 2,000 sq ft of shade-free roof and 33 to 36 panels of 550 to 600 Wp. 25 kW needs 2,000 to 2,500 sq ft and 42 to 45 panels.

Is there a subsidy for a 20 kW solar system?

A home gets PM Surya Ghar, capped at ₹78,000, plus the ₹22,000 Tamil Nadu top-up if eligible. A business gets no subsidy but claims GST input credit and 40% accelerated depreciation. A housing society gets ₹18,000 per kW for common facilities.

What is the payback period of a 20 kW solar system?

About 3.4 to 3.8 years for a GST-registered showroom on LT commercial tariff using 90% of its solar. A school that exports more and cannot claim GST takes about 4.8 to 5.4 years at 25 kW.

Does a 20 kW system need CEIG approval in Tamil Nadu?

Yes. Every system above 10 kW needs CEIG approval before commissioning and a separate generation meter. We handle both within the price.

What is the TNPDCL registration fee for 20 kW and 25 kW?

₹500 up to 20 kW. A 25 kW system pays ₹600, because the fee rises by ₹100 for each extra 20 kW up to 150 kW.

Get a 20 or 25 kW proposal for your premises

Send your last two electricity bills and tell us how the building is used through the week. We size 20 or 25 kW to your daytime load and send an itemised price with the payback on your tariff.

Blues Renewables installs with its own crews from Guindy, handles CEIG and TNPDCL, and includes two years of maintenance.

Sources

Blues Renewables price bands for Chennai rooftop installations, October 2026: all installed prices on this page.

TNERC Suo-motu Tariff Order No. 6 of 2025, 30 June 2025, effective 1 July 2025: LT V ₹10.45 a unit, LT IIB(2) ₹9.40 a unit, ₹110 per kW fixed charge, time-of-day peak surcharge, and LT network charge of ₹1.60 a unit. TNERC Tariff Order 6/2025

TNERC Order No. 4 of 2026, 27 April 2026, Provisional Tariff Subsidy Order FY 2026-27: state pays half the network charge for LT IIIB (₹0.80 paid). TNERC Order 4/2026

TNERC Grid Interactive Solar PV Energy Generating System Regulations 2021, notified 7 October 2021, and TNERC Order No. 8 of 2021, 22 October 2021: net feed-in for non-domestic consumers, ₹3.37 feed-in tariff for 11 to 150 kW, carry-forward and 31 March settlement, network charge at 75% for domestic above 10 kW, generation meter above 10 kW and check meter above 20 kW, registration fees, feasibility timelines, capacity cap at sanctioned load. TNERC GISS Regulations 2021

Government of Tamil Nadu, G.O. Ms. No. 98, Energy Department, 14 October 2024: Electrical Inspector (CEIG) approval before commissioning any generating unit above 10 kVA.

Ministry of Power, Electricity (Rights of Consumers) Amendment Rules 2024, 22 February 2024: above 10 kW, a feasibility study within 15 days or the proposal is deemed feasible.

CBIC Notification No. 9/2025-Central Tax (Rate), 17 September 2025, in force 22 September 2025: 5% GST on solar power devices; with the 70:30 valuation rule, 8.9% on a turnkey EPC contract.

Income-tax Act 1961, Section 32, and Appendix I to the Income-tax Rules 1962: 40% written-down value depreciation on solar power generating systems.

JMK Research, module prices Q4 2025: non-DCR modules ₹14.32 to ₹14.88 per Wp ex-works. IEEFA, late 2025: DCR modules about ₹23 to ₹26 per W.

Ministry of New and Renewable Energy, PM Surya Ghar: Muft Bijli Yojana: residential subsidy capped at ₹78,000; ₹18,000 per kW for housing society common facilities up to 500 kW, capped at 3 kW per house.

Government of Tamil Nadu, G.O. 102, 19 September 2026: ₹22,000 state top-up for domestic consumers registered on PM Surya Ghar from 5 August 2026, first one lakh consumers.