GST on Solar Installation Services in India

Most EPC businesses in India price their projects accurately enough on the hardware side, panels, inverters, mounting. Where they consistently get into trouble is the installation service component. Charge 12% when 18% applies, and you have under-declared tax. Charge 18% when 12% is correct, and you have overcharged your customer and hurt your competitiveness. Get the pure service vs works contract distinction wrong, and you may be facing a GST notice under Section 73 for a short payment.

This guide resolves that confusion for Indian solar EPCs in 2026. It covers the correct SAC code for solar installation services (SAC 9954), when the rate is 12% vs 18%, the difference between a pure service and a composite supply, government project exemptions, Reverse Charge Mechanism (RCM) applicability, Input Tax Credit (ITC) reversal rules, and the invoicing structure for residential vs commercial projects, with real ₹ examples.

For the hardware side of your solar invoice, panels at 12% under HSN 8541 43, inverters at 12% under HSN 850440, see the complete GST guide for solar systems in India and the detailed GST rate guide for solar inverters. This post focuses exclusively on the service component: the installation labour, commissioning, and related services your EPC provides.

What SAC 9954 means for solar EPCs

SAC (Services Accounting Code) 9954 covers "Construction Services" under the GST classification system. Solar installation, being a construction-type activity (mounting, wiring, commissioning, grid synchronisation), falls under this broad heading.

Within SAC 9954, the sub-classifications that matter for EPCs are:

• 9954 10, Services involving construction of buildings and other structures (relevant for building-integrated solar)
• 9954 20, Services involving general construction for civil engineering works
• 9954 40, Installation services, electrical and similar (the primary code for solar installation)
• 9954 90, Other construction and related services (catch-all for specialised solar commissioning)

The Central Board of Indirect Taxes and Customs (CBIC) has consistently classified rooftop solar installation under SAC 9954 40 in its advance rulings database. However, the applicable rate (12% or 18%) depends on several factors, which the next section explains in full.

Pure service vs composite supply vs works contract, the three categories

Before you can apply the correct GST rate to your solar installation, you need to identify which category your supply falls into. The GST law distinguishes three types of supply relevant to EPCs.

Pure service (labour only)

If you supply only labour, your electricians install a system that the customer has procured independently, this is a pure service. No materials pass from you to the customer. GST rate: 18% under SAC 9954. This is less common in practice because most EPC contracts include both materials and installation.

Composite supply (goods are the principal supply)

If the supply of goods (panels, inverter, mounting) is the dominant element and installation is merely incidental, for example, a distributor who sells equipment and offers free installation as a sweetener, the entire supply is taxed at the rate of the principal supply. Since the goods (solar equipment) are at 12%, the composite supply is also at 12%. The key test is whether the installation can be "naturally bundled" with the goods in the ordinary course of business.

Works contract (the standard for most EPC projects)

A works contract is defined under Section 2(119) of the CGST Act as a contract involving the transfer of property in goods (as goods or in some other form) in the execution of a works contract, including building construction, fabrication, erection, installation, fitting out, improvement, modification, repair, maintenance, renovation, or alteration. Solar installation, which involves both material supply and installation labour, almost always qualifies as a works contract.

Works contracts have their own GST rate schedule under Notification 11/2017-CT(Rate) and its amendments. The rate depends on the nature of the work, residential vs commercial vs government.

GST rates by project type, the definitive table

The residential vs commercial distinction, why it matters so much

The 6% difference between 12% and 18% may not sound dramatic, but on a large project it is significant. Consider a 100 kW commercial rooftop for a Bengaluru-based factory where BESCOM (Bengaluru Electricity Supply Company) is the DISCOM:

The test for "residential" is whether the end-use is a dwelling unit. The Ministry of New and Renewable Energy defines residential rooftop solar as systems installed on individual dwelling units or residential housing societies. Commercial buildings, offices, factories, warehouses, retail establishments, hospitals (unless specifically under government exemptions), do not qualify for the residential works contract rate.

EPCs sometimes try to argue that a housing society with a few offices is "residential." The tax authority looks at the primary use of the structure and the proportion of floor area. When in doubt, charge 18% and let your customer claim ITC, a commercial customer recovers the 18% GST through ITC anyway, so they do not bear the cost.

Government project exemptions and special rates

Solar installations for government bodies have their own GST treatment under Notification 11/2017-CT(Rate) Entry 3(vi): works contract services supplied to the Central Government, State Governments, Union Territories, or Local Authorities for construction of civil structures or historical monuments attract 12% GST.

However, "government body" has a precise legal definition in GST law, it includes ministries, departments, statutory bodies, and local authorities, but not all public sector enterprises. A DISCOM (Distribution Company) that is a government company but operates commercially may not qualify for the 12% government works contract rate. Always verify your customer's legal status.

For PM Surya Ghar empanelled vendors, the scheme involves both residential customers (who get subsidy) and the government portal PM Surya Ghar National Portal coordinating reimbursement. GST is charged on the full pre-subsidy invoice value, the subsidy is not deducted before calculating GST. Your invoice to the residential customer should show the full system price with 12% works contract GST, and separately indicate the PM Surya Ghar subsidy as a receivable from the government.

RCM, when your EPC faces Reverse Charge Mechanism

Reverse Charge Mechanism (RCM) under Section 9(3) of the CGST Act makes the recipient of a service liable to pay GST instead of the supplier. For solar EPCs, RCM is relevant in two situations:

Situation 1: Sub-contracting to unregistered workers. If your EPC engages unregistered electricians or sub-contractors to do installation work, and the total value of such services from a single unregistered supplier exceeds the prescribed threshold in a financial year, RCM applies. Your EPC must pay 18% GST on the value of those services received, and then claim ITC on it (subject to the usual ITC conditions).

Situation 2: Services from a specified category under Section 9(3). The government has notified certain specific categories of services where RCM applies regardless of the supplier's registration status. Check the latest Schedule IV of CGST Notifications to verify whether your sub-contracting arrangement falls under any listed category.

For most small and mid-size EPCs in India, the most common RCM exposure is hiring local electricians for installation. Keep a register of all labour contractors, registered and unregistered, and compute RCM liability monthly. According to the GST Portal guidelines, RCM-based tax must be paid in cash, you cannot use ITC balance to discharge RCM liability.

ITC rules for EPCs, what you can and cannot claim

The ITC rules for solar installation service are where most mid-size EPCs have compliance gaps. Here is the framework, drawn from Sections 16–17 of the CGST Act.

ITC on inputs for residential projects

If your EPC primarily supplies to residential customers (PM Surya Ghar, MSEDCL-subsidised rooftop in Pune, DGVCL-scheme installs in Gujarat), and the residential supply is exempt or zero-rated, your ITC on inputs (panels, inverters, mounting, cables) must be reversed in proportion to the exempt supply.

Rule 42 of the CGST Rules prescribes the formula:

ITC to reverse = (Value of exempt/zero-rated supply ÷ Total outward supply) × Total common ITC

If 70% of your business is residential (where ITC chain ends at EPC) and 30% is commercial (where ITC flows), you must reverse 70% of your common input ITC every month. Most EPCs ignore this and carry the full ITC forward, which shows up as excess ITC in your credit ledger and can trigger reconciliation demands.

ITC on inputs for commercial projects

Commercial solar installation is a taxable outward supply. You can claim full ITC on inputs used exclusively for commercial projects. The 18% GST collected from your commercial customer is offset by the ITC on panels (12%), inverters (12%), mounting (18%), and cables (18%), your net GST outflow is significantly lower than the headline rate suggests.

ITC on capital goods (tools, equipment, vehicles)

ITC on capital goods used for solar installation, scaffolding, power tools, service vehicles, can be claimed over 5 years (60 months) at 5% per year, provided the goods are used in taxable supplies. If your installation van is also used for personal purposes, you must restrict ITC to the business-use proportion.

The Works Contract Compliance Stack, a framework for EPC ops teams

If you are Priya managing compliance for a 40-person Pune EPC with MSEDCL as your primary DISCOM for commercial projects, you need a consistent process across your project managers, billing team, and CA. Here is the Works Contract Compliance Stack, four layers that must align for every project invoice.

1. 1

   Classify the project at intake

   Mark every new lead as Residential / Commercial / Government at the CRM stage. This classification drives the GST rate on the eventual invoice. If it changes during the project (e.g., a residential compound that turns out to be a commercial building), update it before the first milestone invoice is raised.

2. 2

   Split goods and services on every proposal

   Never quote a single blended price. Every proposal should have separate line items for hardware (12% GST with HSN codes) and installation service (12% or 18% with SAC 9954). This gives your billing team a clean basis for the tax invoice and reduces amendment risk.

3. 3

   Compute ITC reversal monthly, not at year-end

   Rule 42 reversal must happen in the same tax period as the exempt supply, not at year-end. Most EPCs push this to March and then scramble with their CA. Monthly computation is far easier and avoids interest liability on the delayed reversal.

4. 4

   Register sub-contractors and account for RCM

   Maintain a register of all installation sub-contractors with their GSTIN status. For unregistered contractors, compute RCM monthly and pay it in cash. Your CA should include this in the monthly GSTR-3B filing before the 20th of the following month.

Practical invoice examples

Example 1: 5 kW residential installation (Surat, DGVCL)

This is a PM Surya Ghar eligible installation. The EPC (Rohit's business in Surat) supplies and installs a 5 kW on-grid rooftop system for a household customer. The total works contract value including all materials and installation is ₹2,80,000 before GST.

Tax invoice structure:

Line	Description	HSN / SAC	Value	GST %	GST Amt
1	Solar Modules 5kW (13 × 400Wp)	854143	₹1,88,500	12%	₹22,620
2	String Inverter 5kW	850440	₹28,000	12%	₹3,360
3	Mounting Structure	7610	₹12,000	18%	₹2,160
4	Cables, ACDB, DCDB	8544	₹11,500	18%	₹2,070
5	Installation Service (works contract)	995440	₹40,000	12%	₹4,800
Total			₹2,80,000		₹35,010

Total invoice value: ₹3,15,010. PM Surya Ghar subsidy (for 3 kW eligible portion): ₹78,000 receivable from PM Surya Ghar National Portal. Customer's net outlay: ₹2,37,010.

Example 2: 100 kW commercial installation (Pune, MSEDCL)

A factory in Pune's Pimpri-Chinchwad MIDC area installs a 100 kW rooftop system. The EPC quotes a works contract at ₹35 lakh (goods + installation). Since this is a commercial installation, the GST rate is 18%.

Summary tax invoice:

Description	Value	GST %	GST Amt
Solar Modules 100kWp (250 × 400Wp)	₹14,50,000	12%	₹1,74,000
String Inverters (10 × 10kW)	₹4,20,000	12%	₹50,400
Mounting Structure	₹2,80,000	18%	₹50,400
Cables, BOS, Protection Devices	₹3,50,000	18%	₹63,000
Installation & Commissioning Service	₹10,00,000	18%	₹1,80,000
Total	₹35,00,000		₹5,17,800

The commercial customer claims full ITC of ₹5,17,800 from their GST credit ledger, making the effective cost ₹35 lakh. From the CBIC's perspective, your EPC has correctly charged 12% on goods and 18% on the installation service, two separate SAC/HSN line items, two different rates, clearly distinguishable in GSTR-1.

Common GST mistakes EPCs make on installation service invoices

These are the errors that show up most frequently in GST scrutiny of solar EPCs, drawn from advance ruling orders and departmental audit reports:

GST notices EPCs receive, and how to defend against them

The three most common GST notices solar EPCs receive relating to installation services are:

ASMT-10 (Scrutiny of Returns): The system flags a mismatch between GSTR-1 (sales) and GSTR-3B (tax paid). Typically triggered by: claiming ITC that should have been reversed for residential projects, or showing 12% GST on what the department classifies as commercial supply. Respond with documentary evidence, contract, commissioning certificate, building use certificate from the local municipality.

DRC-01 (Demand and Recovery): Formal demand for tax shortfall. This comes after failed scrutiny response or after audit. For installation service disputes, the key document you need is the advance ruling from your state AAR or a similar ruling from another state that supports your classification. Gujarat AAR, Karnataka AAR, and Maharashtra AAR have all issued rulings on solar works contract classification.

DRC-03 (Voluntary Payment): If you discover a classification error in your own audit, voluntarily pay the differential tax using DRC-03 before a notice arrives. This reduces your interest exposure and demonstrates good faith, which matters in penalty determination under Section 73 vs Section 74 (negligence vs fraud).

For a deeper understanding of the capital and compliance structure your EPC needs, see the guide on how much capital to start a solar business in India.

How QuickEstimate fits into GST-compliant solar proposals

Most GST errors in solar EPCs originate not in the accounting system but in the proposal stage. When a sales rep quotes a blended price with no goods/service split, the billing team tries to reconstruct the split later, and gets it wrong. Rohit's EPC in Surat faced exactly this problem: 23 proposals in one quarter had no separate installation line item, and the billing team was guessing the split.

QuickEstimate solves this upstream, at the proposal generation stage, before a customer signs anything.

• Proposal Generator, creates branded PDF proposals with separate line items for solar hardware (HSN codes, 12% GST) and installation service (SAC 9954, 12% or 18% depending on project type), so your invoice is clean from day one.
• Quotation System, pre-loaded with correct HSN/SAC codes for every solar component, including the residential vs commercial rate toggle for installation services. Your sales team selects "Residential" or "Commercial" and the right GST rate applies automatically.
• Pipeline Management, flags each deal with its project type (residential/commercial/government) from lead intake, so the billing team always has the classification before they raise an invoice.
• WhatsApp Follow-up, sends the proposal to the customer via WhatsApp with read-receipt tracking, so you know the moment they have reviewed the GST-compliant quote, and can follow up before they go to a competitor who is quoting incorrectly at a lower apparent price.

The solar sales pipeline in India moves fast. An EPC that loses a deal because a competitor undercut by ₹20,000, but did so by charging the wrong GST rate, has not actually lost on price. They have lost on perceived price. The solar sales funnel guide for India covers how to present GST correctly in your sales conversations so customers understand total cost, not just base price.

What to do this week, for your EPC compliance

Three actions your EPC can take in the next five working days to reduce GST risk on installation services:

1. 1

   Classify every open project in your CRM as R/C/G

   Go through every active deal and tag it Residential, Commercial, or Government. This should take your ops team 30–60 minutes. Once tagged, verify that the tax rate on any pending invoices matches the classification. Fix any mismatches before invoicing.

2. 2

   Ask your CA to run a Rule 42 ITC reversal audit for the last 6 months

   If your business is more than 50% residential projects and you have not been reversing ITC monthly, you likely have an excess ITC carry-forward. Your CA should calculate the reversal and file an amendment in GSTR-3B. This is far less painful now than responding to a demand notice later.

3. 3

   Update your proposal template to show separate HSN/SAC line items

   If your current proposal template shows a single "Solar System Installation" line at one blended rate, update it this week. Hardware items need HSN codes and 12% GST. Installation service needs SAC 995440 and 12% (residential) or 18% (commercial). This is the change that prevents 90% of GST invoice disputes before they start. Book a demo of QuickEstimate to see how this is pre-configured in the system.

For the companion guide on GST on solar inverters specifically, including how to classify hybrid inverters and handle ITC on imports, see the complete GST guide for solar inverters. For the broader picture of GST on your entire solar system supply, the GST on solar systems in India guide is your reference. When you are ready to think about whether a CRM tool makes sense for your compliance workflows, the when to buy a solar CRM guide has a clear decision framework.

Frequently asked questions

What is the GST rate on solar installation service in India?

Solar installation service in India is taxed under SAC 9954 (construction services). The rate depends on the project type: residential solar installation as a works contract attracts 12% GST under CBIC Notification 11/2017-CT(Rate) Entry 3(v). Commercial and industrial solar installation as a works contract attracts 18% GST under Entry 3(xii) of the same notification. Pure labour service without material supply attracts 18% GST regardless of the property type.

What is the SAC code for solar installation in India?

The SAC code for solar installation services is 9954, specifically 995440 (installation services, electrical and similar). This 6-digit SAC code should appear on every service invoice for solar installation. For businesses with annual turnover above ₹5 lakh per invoice or specific thresholds, the 6-digit SAC is mandatory. SAC 9954 covers both the installation labour and the commissioning activity as part of the works contract.

Is solar installation a works contract or a pure service?

Solar installation by an EPC that supplies both materials (panels, inverters, mounting) and installation labour is a works contract under Section 2(119) of the CGST Act. Works contracts have specific GST rates (12% residential, 18% commercial) under Notification 11/2017-CT(Rate). Pure labour-only service, where the customer supplies all materials and you only provide workers, is a pure service taxed at 18%. Most EPC projects in India qualify as works contracts.

Can a solar EPC claim ITC on installation costs for residential projects?

EPCs cannot retain ITC on inputs used for residential solar installation if the residential supply is exempt or zero-rated. Under Rule 42 of the CGST Rules, ITC must be reversed proportionally for exempt outward supplies. If your EPC does 70% residential projects and 30% commercial, you must reverse 70% of your common input ITC every month. Failure to do so results in excess ITC carry-forward, which is recoverable with interest by the GST department.

Does Reverse Charge Mechanism apply to solar installation services?

RCM under Section 9(3) of the CGST Act applies when an EPC receives services from unregistered sub-contractors or labour contractors whose supply falls under the notified categories for reverse charge. The recipient EPC must pay GST at 18% on the value of unregistered sub-contractor services and can then claim ITC on it (subject to conditions). RCM liability must be discharged in cash, it cannot be paid from the ITC credit ledger.

How does PM Surya Ghar subsidy affect GST calculation?

The PM Surya Ghar subsidy does not reduce the GST base. GST is charged on the full pre-subsidy invoice value. For a 5 kW residential system valued at ₹2,80,000 before GST, the EPC charges 12% works contract GST on ₹2,80,000, regardless of the ₹78,000 subsidy the customer receives from the government. The subsidy is a separate government-to-customer or government-to-EPC transaction and does not affect your GST liability.

What GST rate applies when an EPC sub-contracts solar installation?

Sub-contractors providing works contract services to the main EPC contractor always pay 18% GST on their supply, even if the main contractor is charging 12% to the residential end customer. This rule is explicitly stated in the CGST works contract provisions, the concessional 12% rate for residential works contracts does not pass through to sub-contractors. Sub-contractors should invoice at 18% SAC 9954, and the main EPC can claim ITC on that 18% to set off against their outward GST.

What documents do I need to defend my GST classification if challenged?

For residential works contract at 12%: the contract specifying the property as a residential dwelling, the DISCOM net-metering application confirming residential connection, and the customer's Aadhaar/property document. For commercial at 18%: the commercial property registration or factory licence. For government projects: the government department's letter of award and their legal entity type. State AAR orders on solar works contract classification are also admissible as precedent, though not binding across states.