Is Rooftop Solar Worth It in Thailand? 5 kW Output, Savings and the 2026 Scheme

How much does a system produce?

The calculator uses:

kWh per day = system size (kWp) × peak sun hours × performance factor

Its defaults are 4.5 peak sun hours and an 80% performance factor, which allows for heat, wiring and inverter losses. On those defaults, 1 kWp produces 3.6 kWh per day.

Many Thai installers quote 4–4.5 kWh per kW per day. These defaults are deliberately more conservative, so the calculator doesn't overstate your savings.

The energy figures use nominal 3, 5 and 10 kWp. Whole 450 W panels instead give 3.15, 5.4 and 10.35 kWp, yielding about 340.2, 583.2 and 1,117.8 kWh/month under the same model. The 2 m² panel area is illustrative (the tool starts at 2.1 m²); allow extra roof space for clearances and shade.

Power you use is worth more than power you sell

There are two values for the electricity a system produces:

Used in your home during the day: under this illustration, each offset unit is valued at about 4.62 THB, the rounded marginal 201–400 kWh tier including the stated Ft and VAT. Your actual avoided charge depends on your bill and tiers.

Exported to the grid: the stated 2.20 THB per unit applies only if the system is accepted into the residential programme and has the required agreement.

Using more production at home during the day can raise its value under these assumptions. Payback also depends on installed cost, system output and the bill actually offset.

Example: 5 kWp

Nominal 5 kWp production: about 540 kWh/month on these defaults. Twelve 450 W panels would instead total 5.4 kWp and have a different modelled yield.

60% used at home: 324 kWh × 4.62 ≈ 1,497 THB

40% exported: 216 kWh × 2.20 ≈ 475 THB

Total: about 1,972 THB per month

This split is only a scenario. If the bill moves into a lower tier, avoided units may be worth less. Solar Size estimates production but not payback; Solar Savings accepts an optional installed cost for simple payback. Get installation quotes before judging the investment.

Key rules of the 2026 residential scheme

As of this guide's review date:

Who's eligible: Type 1 (residential) electricity customers, with panels on the roof or another part of the home. Ground-mounted systems don't qualify.

Buy-back rate: 2.20 THB per unit for exported power, on a 10-year contract.

Export limit: up to 5 kW (AC) per customer. You can install a larger system for your own use.

Quota: 500 MW AC across PEA and MEA areas, first come, first served. The published programme requires commercial operation by the end of 2027; remaining quota must be checked live.

Where to apply: PEA areas through the PPIM system (ppim.pea.co.th), MEA areas through MEA's own system.

Connection inspection fee in PEA areas: 2,000 THB plus VAT.

Equipment: inverters must be on the utility's approved list. Batteries are allowed, provided they meet the utility's engineering standards.

Check the electricity account holder, property rights and any building approvals with the relevant utility and building manager. Condo roofs and rental properties can require permissions beyond a household’s own decision.

Programme terms and available quota may change. Check the current status with PEA or MEA before committing; this guide has not verified remaining places.

Before signing with an installer

Ask the installer for these in writing:

Estimated annual production, and the assumptions behind it.

Shading and roof structure assessment.

Panel and inverter models, with their warranties.

Who handles the utility application and paperwork.

After-sales service terms.

You can check a production estimate yourself with Global Solar Atlas or PVWatts using your home's location.

FAQ

If my panels produce as much as I use, will my bill be zero? No. Daytime production can't cover your night-time use without a battery, and the monthly service charge still applies.