What the numbers mean
Global horizontal irradiation (GHI) is the solar energy that falls on one square metre of flat ground, measured in kWh/m²/day (or per year). A value of 5.0 kWh/m²/day is the same as five hours of full 1,000 W/m² sunshine, which is why installers call it peak sun hours.
GHI is the starting point for every solar yield estimate. The table below gives it for all 77 provinces, plus the energy one kilowatt-peak (kWp) of panels produces in a year at each location.
Where the data comes from. These are the provincial averages LEONICS engineers use in Solar Insight Pro, compiled from the Department of Alternative Energy Development and Efficiency (DEDE) Solar Map 2017 and the Global Solar Atlas. Districts inherit their province's value, so we list provinces only.
Thailand at a glance
- National average: 4.99 kWh/m²/day (about 1,822 kWh/m²/year).
- Highest: Ubon Ratchathani 5.35, Amnat Charoen 5.32, Nakhon Ratchasima 5.30, Sisaket 5.30, Yasothon 5.30.
- Lowest: Ranong 4.55, Phang Nga 4.60, Satun 4.60, Narathiwat 4.60, Mae Hong Son 4.65.
- Spread: the sunniest province receives only about 18% more than the least sunny one. Solar works in every province; location changes the payback period, not whether solar makes sense.
| Region | Provinces | Average GHI (kWh/m²/day) | Est. yield (kWh/kWp/year) |
|---|---|---|---|
| North | 16 | 4.89 | 1,425 |
| Northeast | 20 | 5.23 | 1,525 |
| Central | 16 | 5.04 | 1,470 |
| East | 7 | 4.99 | 1,455 |
| West | 4 | 5.09 | 1,485 |
| South | 14 | 4.69 | 1,370 |
How much electricity does 1 kWp produce?
A simple, widely used estimate is:
Annual yield (kWh/kWp) ≈ GHI (kWh/m²/day) × 365 × PR
PR (performance ratio) covers every real-world loss: panel heating, dust, wiring, inverter efficiency and shading. A well-installed system in Thailand typically lands between 0.75 and 0.85. Panels lose output as they get hot, so rooftops in the Thai sun tend towards the lower end. The table uses 0.80.
Example — a 5 kWp home system:
| Location | GHI | Est. yield per year |
|---|---|---|
| Bangkok | 4.95 | ≈ 7,225 kWh |
| Ubon Ratchathani | 5.35 | ≈ 7,800 kWh |
| Ranong | 4.55 | ≈ 6,650 kWh |
Solar irradiation by province (all 77 provinces)
Sorted by region, then alphabetically. Yield column = GHI × 365 × 0.80, rounded to the nearest 5 kWh.
| Province | Thai name | Region | GHI (kWh/m²/day) | GHI (kWh/m²/year) | Est. yield (kWh/kWp/year) |
|---|---|---|---|---|---|
| Chiang Mai | เชียงใหม่ | North | 4.70 | 1,716 | 1,370 |
| Chiang Rai | เชียงราย | North | 4.75 | 1,734 | 1,385 |
| Kamphaeng Phet | กำแพงเพชร | North | 5.00 | 1,825 | 1,460 |
| Lampang | ลำปาง | North | 4.80 | 1,752 | 1,400 |
| Lamphun | ลำพูน | North | 4.72 | 1,723 | 1,380 |
| Mae Hong Son | แม่ฮ่องสอน | North | 4.65 | 1,697 | 1,360 |
| Nakhon Sawan | นครสวรรค์ | North | 5.10 | 1,861 | 1,490 |
| Nan | น่าน | North | 4.85 | 1,770 | 1,415 |
| Phayao | พะเยา | North | 4.80 | 1,752 | 1,400 |
| Phichit | พิจิตร | North | 5.05 | 1,843 | 1,475 |
| Phitsanulok | พิษณุโลก | North | 5.00 | 1,825 | 1,460 |
| Phrae | แพร่ | North | 4.82 | 1,759 | 1,405 |
| Sukhothai | สุโขทัย | North | 4.95 | 1,807 | 1,445 |
| Tak | ตาก | North | 5.05 | 1,843 | 1,475 |
| Uthai Thani | อุทัยธานี | North | 5.08 | 1,854 | 1,485 |
| Uttaradit | อุตรดิตถ์ | North | 4.88 | 1,781 | 1,425 |
| Amnat Charoen | อำนาจเจริญ | Northeast | 5.32 | 1,942 | 1,555 |
| Bueng Kan | บึงกาฬ | Northeast | 5.15 | 1,880 | 1,505 |
| Buri Ram | บุรีรัมย์ | Northeast | 5.25 | 1,916 | 1,535 |
| Chaiyaphum | ชัยภูมิ | Northeast | 5.22 | 1,905 | 1,525 |
| Kalasin | กาฬสินธุ์ | Northeast | 5.22 | 1,905 | 1,525 |
| Khon Kaen | ขอนแก่น | Northeast | 5.25 | 1,916 | 1,535 |
| Loei | เลย | Northeast | 5.05 | 1,843 | 1,475 |
| Maha Sarakham | มหาสารคาม | Northeast | 5.25 | 1,916 | 1,535 |
| Mukdahan | มุกดาหาร | Northeast | 5.25 | 1,916 | 1,535 |
| Nakhon Phanom | นครพนม | Northeast | 5.18 | 1,891 | 1,515 |
| Nakhon Ratchasima | นครราชสีมา | Northeast | 5.30 | 1,934 | 1,550 |
| Nong Bua Lam Phu | หนองบัวลำภู | Northeast | 5.18 | 1,891 | 1,515 |
| Nong Khai | หนองคาย | Northeast | 5.12 | 1,869 | 1,495 |
| Roi Et | ร้อยเอ็ด | Northeast | 5.28 | 1,927 | 1,540 |
| Sakon Nakhon | สกลนคร | Northeast | 5.15 | 1,880 | 1,505 |
| Sisaket | ศรีสะเกษ | Northeast | 5.30 | 1,934 | 1,550 |
| Surin | สุรินทร์ | Northeast | 5.28 | 1,927 | 1,540 |
| Ubon Ratchathani | อุบลราชธานี | Northeast | 5.35 | 1,953 | 1,560 |
| Udon Thani | อุดรธานี | Northeast | 5.20 | 1,898 | 1,520 |
| Yasothon | ยโสธร | Northeast | 5.30 | 1,934 | 1,550 |
| Ang Thong | อ่างทอง | Central | 5.08 | 1,854 | 1,485 |
| Bangkok | กรุงเทพมหานคร | Central | 4.95 | 1,807 | 1,445 |
| Chai Nat | ชัยนาท | Central | 5.12 | 1,869 | 1,495 |
| Lopburi | ลพบุรี | Central | 5.25 | 1,916 | 1,535 |
| Nakhon Nayok | นครนายก | Central | 5.00 | 1,825 | 1,460 |
| Nakhon Pathom | นครปฐม | Central | 5.00 | 1,825 | 1,460 |
| Nonthaburi | นนทบุรี | Central | 4.95 | 1,807 | 1,445 |
| Pathum Thani | ปทุมธานี | Central | 4.98 | 1,818 | 1,455 |
| Phetchabun | เพชรบูรณ์ | Central | 5.05 | 1,843 | 1,475 |
| Phra Nakhon Si Ayutthaya | พระนครศรีอยุธยา | Central | 5.05 | 1,843 | 1,475 |
| Samut Prakan | สมุทรปราการ | Central | 4.92 | 1,796 | 1,435 |
| Samut Sakhon | สมุทรสาคร | Central | 4.95 | 1,807 | 1,445 |
| Samut Songkhram | สมุทรสงคราม | Central | 4.95 | 1,807 | 1,445 |
| Saraburi | สระบุรี | Central | 5.20 | 1,898 | 1,520 |
| Sing Buri | สิงห์บุรี | Central | 5.10 | 1,861 | 1,490 |
| Suphan Buri | สุพรรณบุรี | Central | 5.10 | 1,861 | 1,490 |
| Chachoengsao | ฉะเชิงเทรา | East | 5.08 | 1,854 | 1,485 |
| Chanthaburi | จันทบุรี | East | 4.80 | 1,752 | 1,400 |
| Chonburi | ชลบุรี | East | 5.10 | 1,861 | 1,490 |
| Prachinburi | ปราจีนบุรี | East | 5.05 | 1,843 | 1,475 |
| Rayong | ระยอง | East | 5.05 | 1,843 | 1,475 |
| Sa Kaeo | สระแก้ว | East | 5.15 | 1,880 | 1,505 |
| Trat | ตราด | East | 4.70 | 1,716 | 1,370 |
| Kanchanaburi | กาญจนบุรี | West | 5.15 | 1,880 | 1,505 |
| Phetchaburi | เพชรบุรี | West | 5.05 | 1,843 | 1,475 |
| Prachuap Khiri Khan | ประจวบคีรีขันธ์ | West | 5.05 | 1,843 | 1,475 |
| Ratchaburi | ราชบุรี | West | 5.10 | 1,861 | 1,490 |
| Chumphon | ชุมพร | South | 4.85 | 1,770 | 1,415 |
| Krabi | กระบี่ | South | 4.70 | 1,716 | 1,370 |
| Nakhon Si Thammarat | นครศรีธรรมราช | South | 4.80 | 1,752 | 1,400 |
| Narathiwat | นราธิวาส | South | 4.60 | 1,679 | 1,345 |
| Pattani | ปัตตานี | South | 4.70 | 1,716 | 1,370 |
| Phang Nga | พังงา | South | 4.60 | 1,679 | 1,345 |
| Phatthalung | พัทลุง | South | 4.75 | 1,734 | 1,385 |
| Phuket | ภูเก็ต | South | 4.65 | 1,697 | 1,360 |
| Ranong | ระนอง | South | 4.55 | 1,661 | 1,330 |
| Satun | สตูล | South | 4.60 | 1,679 | 1,345 |
| Songkhla | สงขลา | South | 4.75 | 1,734 | 1,385 |
| Surat Thani | สุราษฎร์ธานี | South | 4.85 | 1,770 | 1,415 |
| Trang | ตรัง | South | 4.65 | 1,697 | 1,360 |
| Yala | ยะลา | South | 4.65 | 1,697 | 1,360 |
Using these numbers correctly
- For a quick home estimate, multiply the yield figure by the system size and compare it with your annual consumption. The free Solar Insight tool does this with your province and bill.
- For a factory or building, annual kWh is not enough. What you save depends on when you use electricity. Solar offsets on-peak units and can cut the demand charge only if the peak falls in daylight — see Thai electricity tariffs, TOU and demand charges.
- Monthly output varies. The hot season (March–May) is sunniest; the rainy season has more cloud. Annual averages already include both.
- Shading and roof direction matter more than province. A roof shaded for two hours a day loses more than the difference between the sunniest and the cloudiest province.
FAQ
Which province in Thailand gets the most sunlight?
Ubon Ratchathani has the highest average GHI at 5.35 kWh/m²/day, followed by Amnat Charoen (5.32) and Nakhon Ratchasima (5.30). The Northeast is the sunniest region, averaging 5.23 kWh/m²/day.How much electricity does 1 kWp of solar produce in Thailand?
About 1,330–1,560 kWh per year depending on the province, using a performance ratio of 0.80. In Bangkok the estimate is about 1,445 kWh per kWp per year.What are peak sun hours?
Peak sun hours equal the daily GHI in kWh/m². A location with 5.0 kWh/m²/day receives the same energy as five hours of 1,000 W/m² sunshine. Thailand averages about 5.0 peak sun hours a day.Is solar worth installing in southern Thailand?
Yes. The least sunny province, Ranong, still receives 4.55 kWh/m²/day, only about 18% less than the sunniest. The payback period is somewhat longer, but the difference is smaller than the effect of shading, roof orientation or how much of the solar power the building uses itself.Why do district values equal the provincial value?
The source data is published at provincial level. Local terrain and microclimate can change irradiation within a province, so for a large project the engineering study should use site coordinates.Where does this data come from?
From the DEDE Solar Map 2017 and the Global Solar Atlas, compiled by LEONICS for its Solar Insight Pro design software.Summary
Thailand receives 4.99 kWh/m²/day of solar energy on average, and every province is within about 18% of the best one. One kWp of panels produces roughly 1,330–1,560 kWh a year. Use the table for a first estimate; for an investment decision, model the site with its real load and tariff.