Rooftop solar in Thailand 2026: payback now the 200,000 tax break exists

The question "does solar pay?" changed its answer in 2569, because a new variable arrived: a tax deduction of up to 200,000 baht on installation cost, which shortens payback by around two and a half years.

But the thing most articles never mention is that the biggest variable is not system size or price — it is what share of your own output you actually use. Two houses with identical systems at identical prices can differ by five years in payback. Here is all of it, calculated.

The three kinds of home solar, and why on-grid nearly always wins

For a city home already on the grid, on-grid is almost always the answer, because the battery is the most expensive and shortest-lived part of the system. Paying extra to store daytime power for the evening usually pushes the break-even point out further than the extra savings bring it in.

⚠️ The trade-off to know: an on-grid system does not supply power during an outage, even in full sun, because the inverter must disconnect itself for the safety of crews working on the lines. Wanting backup power is the one good reason to consider hybrid.

The 200,000 baht deduction — the new term in the equation

A measure enacted on 2 March 2569 lets individuals deduct the equipment and installation cost of rooftop solar on their own home, as actually paid, up to 200,000 baht.

The main conditions:

• system size no larger than 10 kW
• must be your own residence, on a type 1 electricity meter
• claimable once, in the tax year the grid connection completes
• available from 3 March 2569 to 31 December 2571

⚠️ A deduction is not a 200,000 baht refund. It reduces your net income by 200,000, so what actually comes back is 200,000 times your top marginal rate.

Understand this before listening to any sales pitch. Sellers say "deduct 200,000", which is true — but someone in the 5% bracket gets 10,000 back where someone in the 35% bracket gets 70,000: seven times more from the identical measure. To find your own bracket, see our personal income tax guide.

Real 2569 prices and what they generate

Market prices in 2569 for an installed on-grid system (as of September 2026):

Photo: Gray Watson User:E090 — CC BY-SA 3.0 (Wikimedia Commons)

Output is based on the Thai average of 1 kW producing roughly 1,300–1,500 units a year (about 3.6–4.1 a day), since Bangkok gets around 4.7 peak sun hours a day and the northeast has a slight edge at about 5.0–5.1.

The variable that matters most: how much you use during the day

Photo: Benlisquare — CC BY-SA 4.0 (Wikimedia Commons)

Solar generates only during daylight, and an on-grid system has no battery. Power produced while nobody at home is using it flows away without benefiting you — and as the next section shows, exporting it is worth less than half what using it is.

This table is a 5 kW system at 200,000 baht producing 7,000 units a year, costed at a 4.62 baht marginal rate.

Read across and the deduction buys you about 2 to 2.6 years. Read down and your own usage pattern moves the answer by 4.7 years — nearly twice as much.

Which means the first question is not "how many kilowatts should I install" but "is anyone home during the day?"

Homes that use a lot of daytime power

• Someone is home in the day: working from home, retired parents, a carer, small children
• The air conditioning runs during the day, which lines up exactly with peak sun
• A freezer, water pump, aquarium or a small business at home
• Washing machine, dryer or dishwasher that can be timed to run at midday

Homes that should not install

• Out from early morning to late evening with nobody home — almost all the output is wasted
• Bills under roughly 2,000 baht a month, because your marginal unit is cheaper and each unit saved is worth less
• Roofs shaded by buildings or trees for several hours a day
• An old roof near replacement, since taking panels off to repair it is not cheap

You can sell the surplus, but for less than half

The Solar Phak Prachachon (household solar) programme for 2569 opened for applications on 1 July 2569, letting residential customers sell surplus power back to the utility at 2.20 baht per unit on a 10-year contract, capped at 5 kW of export, first-come first-served up to a 500 MW quota.

That figure is the heart of the whole matter:

Using it yourself is worth more than twice as much, because using it means not buying power at the retail price including Ft and VAT, while exporting gets you a wholesale price.

Two consequences:

1. Do not oversize beyond your own daytime usage, because the surplus that spills out is worth less than half, even when you can sell it.
2. Treat export income as a bonus, not the reason. A quotation whose payback figure leans heavily on sales revenue is making the numbers look better than they are.

⚠️ And exporting requires enrolling in the programme, passing inspection and having a suitable meter installed — power does not simply flow back and turn into money by itself.

System size: choose from usage, not from budget

Photo: Downtowngal — CC BY-SA 4.0 (Wikimedia Commons)

The common mistake is going big on the assumption that bigger is better value. It is not:

Notice that 3 kW and 5 kW pay back identically, because price and output both scale together. A bigger system is not inherently better value — it simply saves more in absolute terms, as long as you actually consume everything it makes.

And there is the trap: install 10 kW while using only as much daytime power as a 5 kW system makes, and the extra spend barely returns anything.

⚠️ Also note the 200,000 baht deduction ceiling. A 3–5 kW system uses nearly all or exactly all of it. A 10 kW system at 320,000 can only claim the first 200,000; the remaining 120,000 gets no deduction, so proportionally less of the spend benefits.

To size it roughly: take your monthly units from the bill, estimate what share you use during daylight, and pick a system that generates close to that share — not close to your total consumption.

Comparing it with doing something else with the money

Another useful framing is to convert the annual saving into a return on the capital.

A 5 kW system at 200,000 baht, used at 70%, saves 22,638 baht a year:

Against a fixed deposit at 1–2%, that looks excellent, which is why sellers quote it. Read it with three limits:

• The capital cannot be withdrawn. Unlike a deposit or a fund, if you need money next year, panels on a roof resell for very little.
• It does not yet subtract inverter replacement or panel cleaning, which take several percent over the system's life.
• It is tied to that house. Sell within a few years and you may not recover the value in the price.

Put plainly, solar is not a financial investment. It is paying twenty years of electricity up front at a discount — excellent if you will genuinely still be in that house, and poor value if you are unsure.

Costs people leave out of the calculation

• Inverter replacement, roughly every 10–15 years against panels lasting 20–25 — one replacement within the system's life. Budget for it.
• Cleaning the panels. Dust and grime cut output; once or twice a year, particularly after the dry season.
• Permit paperwork and the meter change. Most installers include it, but ask explicitly.
• Home insurance. Some policies need to be told about the installation.
• Roof structure. An older roof or thin tiles may need reinforcing first.

Before you sign

Check the installer handles the permit paperwork in full. It is not only a legal matter — it is what makes the 200,000 baht deduction claimable at all. Install without approval and that entitlement disappears entirely.

Be sceptical of the payback figure in the quotation. Sellers typically assume maximum self-consumption and the top electricity rate, which is the best case. Ask for the assumptions and compare them with the tables above.

Do not judge on price per watt alone. Inverter quality, warranty and after-sales support vary enormously in the Thai market. A system 20% cheaper with nobody to fix the inverter in year six is not cheaper.

Work out your own marginal rate first. If your household uses under 200 units a month, your marginal unit is 3.38 baht, not 4.84 — which stretches every number in these tables by roughly 30%. How to find yours is in our article on cutting your electricity bill.

Summary: answering "is it worth it" in four steps

1. Open your electricity bill and see the monthly units. Under 300 units, or under about 2,000 baht, park the solar idea and do the faster payback items first — LED bulbs and servicing the AC.
2. Estimate what share you can realistically use during daylight. This moves the answer more than the tax deduction does.
3. Check your tax bracket. The 200,000 deduction returns between 10,000 and 70,000 baht depending on it.
4. Size the system to daytime usage, not to your budget and not to your roof area.

For a home that is genuinely occupied during the day, with a bill over 3,000 baht a month, owned by someone in the 20% bracket or above — 2569 to 2571 is the best window rooftop solar has ever had in Thailand, because this deduction has an expiry date.

Sources

• Sanook Money — 2569 solar prices and how many years to break even
• MEA — Solar Phak Prachachon household programme, 2569
• Thansettakij — 2569 household solar terms, selling back at 2.20 baht
• Sunnergy — solar installation costs 2568–2569
• CapSolar — solar yield and performance ratio in Thailand (kWh/kWp)
• KKP Advice Center — what to know before installing solar for the tax deduction
• Tera Group — conditions for the 200,000 baht solar deduction, 2569–2571
• MEA — current Ft announcement

Installation prices are approximate market rates as of September 2026 and vary by equipment brand, roof difficulty and region. Payback figures use the Thai average output, a 4.62 baht marginal electricity rate and the self-consumption assumptions shown in each row, and exclude inverter replacement and maintenance. They are for comparing options, not a financial offer — ask any installer for a quotation with its assumptions stated before deciding.