BOI backs Solar Factory investment 2026 — what you still get, and what's been dropped

For industrial factory owners, "electricity" is often one of the biggest production costs eating into profit. With the Ft charge fluctuating in 2026, factory solar has become unavoidable — and the good news is you may not have to pay the full installation cost

Many people have heard that "install solar, get BOI support and cut costs by 50%." How true is it, what conditions are hidden, and what has changed this year? This article lays out the numbers to show how much the "real price" after incentives speeds up a factory's payback

Does the BOI really pay 50%?

First, understand that "cut costs by 50%" in BOI terms doesn't mean the government hands back half in cash the moment you buy. It comes as a "Corporate Income Tax Exemption"

Under the measure to upgrade industry for energy savings, the BOI lets factories that install solar for self-consumption deduct the investment from their taxes, subject to these main conditions

• Benefit: 3-year corporate income tax exemption
• Exemption cap: up to 50% of the investment (excluding land and working capital)
• Key 2026 condition: since mid-2025 the BOI has become stricter, favoring projects that use advanced technology or are installed with energy storage (BESS) or smart energy management, in line with Grid Modernization

In short

Suppose your factory already pays tax on its profits every year. Instead of paying the full amount to the Revenue Department, you can use that money to "pay yourself back" for the solar installation — effectively the government covers 50% of the installation through the tax system

The numbers: factory solar with BOI vs. without BOI

To make it as clear as possible, let's compare a mid-sized factory installing a 500 kWp system, assuming:

• Installation investment: 12,000,000 baht (hypothetical figure for the calculation)
• Electricity savings: 2,400,000 baht/year
• The factory has enough net profit to owe more tax than the exemption cap

Insight: with BOI support, payback drops to just 2–3 years — a better investment than almost any other machinery in the factory

Which factories can apply for BOI solar support?

Not every factory qualifies right away. You must meet these basic criteria:

• Your business is a BOI-promoted activity, which covers almost all manufacturing and some services
• It must be an existing, operating project, since this measure is an "Improvement"
• Investment of at least 1 million baht (500,000 baht minimum for SMEs)
• Installation must be completed within 3 years of receiving the promotion certificate

How to apply for BOI solar support in 2026

The process is straightforward if your documents are complete, and almost all of it is now done online (e-Investment)

1. Submission

Submit an application through the e-Investment Promotion system, choose the "Efficiency Improvement measure" and specify your plan, the equipment used (panels, inverter) and projected energy savings

2. Project presentation

BOI officers will schedule an interview (usually online) to go over the project. Have your engineering team or consultant ready with the technical details

3. Approval and acceptance

Once approved you'll receive a resolution letter, which you must accept within 1 month

4. Certificate issuance

Submit documents to have the promotion certificate issued — your key to claiming the benefits

5. Implementation

Install the solar system, import equipment (if any) and connect to the grid

6. Tax incentive claim

After installation, a credible third party (such as an energy institute or university) must assess the energy savings, and the resulting certificate is used to claim the tax exemption with the Revenue Department

Latest BOI conditions for 2026 (watch out)

The latest BOI announcement (effective since mid-2025) includes important changes factory owners need to know

• BESS condition: a self-consumption Solar Rooftop project on its own may not qualify for the tax exemption. In some cases the BOI encourages installing it together with energy storage (BESS) for grid stability
• Technology: solar panels and inverters must be new machinery — no second-hand equipment

Tip: before signing an installation contract, consult a company experienced with the BOI to check that your specs and project format still meet the latest 2026 criteria

Tax deductions of up to 200,000 baht for homeowners and businesses

Beyond factories, the government has also introduced incentives for households. On 25 November 2025, the Cabinet approved in principle a draft Royal Decree under the Revenue Code granting tax exemptions to encourage people to switch to solar energy

The key point is the "solar installation tax deduction" measure: individuals can deduct up to 200,000 baht from personal income, under Revenue Department Notification No. 3/2026

Why did the government introduce this measure?

The country's big goals are Carbon Neutrality and Net Zero greenhouse gas emissions. The Revenue Department estimates this tax measure will cut national electricity use by up to 25,545 million units a year and reduce LNG imports for power generation by more than 88,300 million baht

Measure for individuals (household Solar Rooftop)

Personal income taxpayers can deduct the actual "equipment and installation costs" of a Solar Rooftop system, up to a total of 200,000 baht

• Solar costing 150,000 baht: deduct the full 150,000 baht
• A larger system costing 300,000 baht: deduct up to the 200,000-baht cap

Who is eligible

• Individuals only (excluding ordinary partnerships and non-juristic bodies of persons)
• Homeowners installing on the roof, rooftop or any part of their residential building
• Using a Type 1 electricity meter, the standard residential meter

Technical requirements

• Must be a grid-connected (On-Grid) system connected to the Metropolitan Electricity Authority (MEA) or Provincial Electricity Authority (PEA)
• Hybrid systems qualify if connected to the grid, but Off-Grid systems (not connected to the utility) do not
• Total installed capacity of no more than 10 kWp per home, in line with residential connection rules

Timing and claiming

• Program period: from the day after the law is published in the Royal Gazette until 31 December 2028
• Tax year to claim: the tax year in which the "grid connection is completed," not the year you paid (e.g. paid in 2026 but connected in 2027 — claim in the 2027 tax year)
• One claim, for one system only, for the entire program period

Documents for the Revenue Department

• A full electronic tax invoice (e-Tax Invoice) is required
• Payment must be made to a VAT-registered business

Measure for companies and business owners

Beyond homes, the Cabinet also approved a measure to reduce business costs under the "tax measure to promote high-efficiency machinery, equipment and energy conservation materials"

Benefit: 1.5× deduction

• Individuals with income under Section 40(5)–(8), such as dormitory owners, medical clinics, architects and contractors, can deduct 1.5× their investment
• Companies and partnerships can expense 1.5× the investment, e.g. invest 1 million baht and book 1.5 million baht as a tax expense — worth roughly 50% of the investment in tax savings

Equipment conditions and restrictions

• Must be energy conservation machinery/equipment/materials with a 5-star energy efficiency label from the Department of Alternative Energy Development and Efficiency (DEDE)
• Must be new, never used, and located in Thailand
• Cannot be claimed in addition to BOI or EEC privileges
• Requires an e-Tax Invoice, as with the household measure

Home vs. business entitlements

5-step checklist to secure your entitlement

• Check readiness: make sure the meter owner's name matches the person claiming, and that the roof structure can take the system
• Choose a professional installer: a VAT-registered company that can issue e-Tax Invoices
• Install and get approval: install the Solar Rooftop (homes up to 10 kW) and apply for grid connection with the utility (MEA/PEA) — the law counts the "date of successful connection" as the claim date
• Handover and paperwork: confirm the system is generating, receive the e-Tax Invoice and keep the utility's approval documents
• File your taxes: enter the deduction on Form P.N.D. 90/91 for the tax year in which the connection was completed

The math: how much do you gain by installing this year?

Installing in 2026–2028 is good timing because you gain twice

Combining both, payback for a home drops to just 3–5 years

Frequently asked questions (FAQ)

Q: I installed solar earlier. Can I claim retroactively?

A: No. The law requires the expense and installation to occur from the day after the law is published in the Royal Gazette

Q: My home has several meters. Can I combine the claims?

A: Only 1 person / 1 system, and it must be a residence (Type 1 meter). If you have several homes, family members who separately own the property and the meter may each claim for a different home

Q: Can I claim if I buy the equipment and install it myself (DIY)?

A: You risk losing the entitlement, because the law requires a grid-connected (On-Grid) system that passes the utility's standards inspection and an e-Tax Invoice from a registered business — DIY installations often can't provide complete documents and approvals

Summary

The BOI helps factory solar pay off faster — from 5 years down to 2–3 years — but it requires planning from the start: system design (especially Solar + BESS), document preparation and tax planning

The EV Power Energy team can help from site assessment and Solar + BESS design matched to your factory's usage through to preparing the information for your incentive application, so you get the highest return on your investment

Note: the information above is a general overview for educational purposes and the calculations are hypothetical. Official conditions and benefits may change, so check the latest BOI and Revenue Department announcements or consult an expert before proceeding