5 kWp Solar in Chiang Dao: 4-Year Performance and Cost Reality

TL;DR: Bjørn Nyland installed a 5 kWp rooftop solar power system in Chiang Dao, North Thailand in early 2022 for 217,000 THB. After four years, annual production runs 6.5–7 MWh, generating about 24,000 THB in savings per year. At that rate, full payback takes roughly 11 years — longer than ideal, partly because of a 7° roof that’s too flat for northern Thailand’s winter sun angle, and a near-year-long wait before the grid feed-in permit came through.

A Real System With Four Years of Real Numbers

Most solar content falls into two camps: sales pitches with optimistic projections, or first-year owners who don’t have enough data yet. Bjørn Nyland’s December 2025 video is neither. By late 2025 his Chiang Dao installation had four full years of production logs, electricity bills, and hard-won lessons about what makes northern Thailand a different solar environment from what most installers describe.

The system sits on a family house in Chiang Dao, a small town in Chiang Mai Province at roughly 19°N latitude. Bjørn uses the property seasonally — mostly the cooler months from November to February — which means long stretches when electricity demand is low and most solar production flows back to the grid. That usage pattern shapes the financial story in ways that don’t show up in typical ROI calculators.

The installer was EV Power Energy, and the final cost came to 217,000 THB after a 10% discount. About a year after installation, Bjørn added three more 450W panels for an estimated 16,000 THB, bringing total capital invested to approximately 233,000 THB.

Technical Specs: What’s on the Roof

The original build used 11 Longi LR4 450W mono PERC half-cell panels paired with a Huawei SUN2000 5 kW 3-phase inverter. Longi backs the panels with a 25-year linear performance warranty — guaranteed output of at least 84.8% of rated capacity at year 25, with annual degradation capped at ≤0.55% after the first year. The inverter carries a 10-year warranty, shorter than the panels because power electronics wear faster than glass and silicon.

Component	Details
Panels (original)	11 × Longi 450W mono PERC half-cell
Panels (expansion)	3 × Longi 450W (~16,000 THB)
Total capacity	~6.45 kWp
Inverter	Huawei SUN2000 5 kW, 3-phase
Inverter warranty	10 years
Panel warranty	25-year linear performance (≥84.8% at year 25)
Roof tilt	7° fixed (cannot be adjusted)
Grid connection	On-grid with PEA feed-in
Installer	EV Power Energy
Total investment	~233,000 THB

One detail stands out immediately: a 5 kWp nameplate system that peaks at around 4 kW in winter. The culprit is roof angle. The house sits on a natural 7° slope and the existing roof tile structure couldn’t support tilted mounting. Optimal tilt for Chiang Dao’s latitude across the dry season — November through April, when Bjørn is actually there — would be roughly 15–20°. At 7°, the panels face the winter sun at a poor angle and lose significant output during the months they matter most.

EV Power Energy confirmed the fix isn’t possible without replacing the roof. Bjørn estimates that correcting the angle alone might eliminate the need for extra panels — but that ship has sailed. It’s useful information for anyone building in northern Thailand: specify your panel tilt angle before the roof goes on, not after.

What Four Years of Production Data Shows

Annual production sits at 6.5–7 MWh once the system was fully operational. On the best days — clear October sun — the system generates 24 kWh in a single day. Typical cloudy days drop that to 11 kWh. Winter peak output runs around 4 kW; summer can hit 4.5 kW or above, though Bjørn is rarely in Chiang Dao during the hot months.

The financial calculation uses two rates. Bjørn pays approximately 3.30 THB/kWh for the first 150 kWh he imports each month and around 4.40 THB/kWh for the 151–400 kWh band. He earns 2.20 THB/kWh for electricity exported to the PEA grid — the standard residential feed-in tariff rate under a 10-year Power Purchase Agreement.

Over four years, roughly 15 MWh went back to the grid, generating about 33,000 THB in export revenue. The remaining production was consumed on-site, saving approximately 71,000 THB in avoided electricity purchases. Combined total: around 104,000 THB in financial benefit against 233,000 THB invested. Annual ongoing gain runs about 24,000 THB per year.

The simple payback period works out to roughly 11 years from installation — though Bjørn notes that the first year was largely “wasted” because the grid feed-in permit took nearly a year to approve.* Without that delay, and with an optimally angled roof, he estimates payback could realistically fall to 7–8 years.

*(according to my sources, the government has recently enacted a speedy application process that is nearly instant [March 2026]).

Why Northern Thailand Is Harder Than the Brochure Suggests

Chiang Dao sits in a valley ringed by mountains. Solar irradiance for the broader Chiang Mai area runs approximately 4.5–5.5 kWh/m²/day — comparable to good European locations, though below Thailand’s central plains. The valley setting adds penalties that irradiance maps won’t show you.

First, valley fog. From November through February, cool-air fog builds in the valley floor most mornings and often doesn’t clear until 9:00–10:00 AM. Since early-morning sun angles are already low in winter, this timing stacks losses: poor geometry on top of atmospheric scatter. Bjørn estimates losing roughly one hour of productive morning sun to fog on many winter days.

Second, mountain shading. Hills to the east and west shorten the effective solar day on both ends. The effect is largest in winter when the sun’s arc stays low. By December, afternoon shading from teak trees on the property becomes visible in the Huawei app data as a sudden production drop around 2 PM — even on otherwise clear days.

Third, panel degradation may be quietly starting. Bjørn notes that the peak output he recorded a couple of years ago (4.3 kW in winter) is now gone. He isn’t certain whether trees are responsible or if the panels have degraded slightly. At the Longi warranted degradation rate of ≤0.55% per year, a 5 kWp system should retain at least 97.8% of rated output at year four — so if there’s a measurable drop, tree shading is the more likely culprit.

None of these factors are unique to Chiang Dao, but together they explain why blanket solar yield estimates for “Thailand” overstate what a north-facing, valley-sited, seasonal home will actually see in November through February.

The Battery Question: Probably Not Yet

EV Power Energy quoted a 7 kWh battery at an estimated 75,000 THB installed (including VAT). Is it worth it? Bjørn ran the numbers and found it marginal.

Because most of the household’s surplus goes back to the grid at 2.20 THB/kWh rather than being stored and reused, the arbitrage gain from a battery is only 2 THB per kWh — the difference between the import price (averaging around 4 THB/kWh across typical consumption) and the export price. With roughly 5 MWh flowing to the grid each year, intercepting it with a battery could save about 10,000 THB annually. That gives a payback of roughly 8 years on the 75,000 THB unit.

The chart above explains the core battery logic. Every kWh you self-consume saves 3.30–4.40 THB; every kWh you export earns 2.20 THB. That 2× difference is the arbitrage a battery captures. For households that are home during peak solar hours and consuming heavily — running an EV, operating a business appliance — a battery sharpens that arithmetic. For low-occupancy seasonal properties, the math is marginal.

Bjørn’s view: wait. Battery prices continue declining while panel prices have stabilized. Buying the same capacity in two or three years will likely cost less and perform better. The exception would be a specific use case that needs overnight power — like the family’s banana-drying business, which runs dehumidifier ovens that draw around 5 kW into the evening after solar ends. For that specific load, a battery makes practical sense even if the pure financial case is thin.

Thai Regulatory Context: What Has Changed Since 2022

When Bjørn installed in early 2022, getting grid feed-in approval meant navigating an older PEA application process — and then waiting nearly a year before the Power Purchase Agreement was signed. That delay cost him roughly one full year of export revenue at 2.20 THB/kWh.

The regulatory landscape has since shifted. In December 2024, Thailand’s cabinet removed the requirement for a factory license (Ror. Ngor. 4) for residential rooftop solar installations. Panels below the relevant threshold are no longer classified as industrial facilities, which simplifies the installation permit process (source: PVKnowhow, December 2024).

However, there’s a critical caveat for new installations: the residential rooftop feed-in tariff quota of 90 MW was fully subscribed in 2024. New applicants can install and self-consume freely, but currently have no path to receiving payment for electricity exported to the grid under the existing scheme. A new Community Solar program offering 2.25 THB/kWh is pending final regulations from the Energy Regulatory Commission (ERC), but no launch date is confirmed as of early 2026.

This changes the ROI math for anyone calculating today. A system that earns 2.20 THB/kWh for surplus export, like Bjørn’s, is on a 10-year PPA signed before the quota closed. A new system in 2025–2026 earns zero on export until a new program opens. For the Chiang Dao scenario — low on-site consumption, lots of surplus — that difference is significant. For a family home with EVs and high daytime usage, self-consumption alone may still justify the investment.

For PEA-area installations (Provincial Electricity Authority, which covers Chiang Dao), a system of ≤10 kWp qualifies for the simplified residential track. Permitting timelines under the new rules should be shorter than Bjørn experienced, but interconnection agreements for future feed-in programs will depend on when — and whether — new quotas open.

Key Takeaways

• 4-year ROI trajectory: ~11 years. 233,000 THB invested, generating about 24,000 THB per year. Without the feed-in delay and with better roof angle, Bjørn estimates 7–8 years is achievable.
• Roof angle matters more than panel count. A 7° tilt in Chiang Dao consistently underperforms the nameplate 5 kWp in winter. Design for 15–20° if you’re building in northern Thailand, and agree on the tilt before the roof goes on.
• Low-occupancy homes earn less from solar. When most production goes back to the grid at 2.20 THB/kWh, you capture roughly half the value of self-consumed electricity at 3.30–4.40 THB/kWh. Families who are home during peak hours benefit significantly more.
• The residential feed-in quota is currently closed. New installations can’t receive PEA payment for surplus export under the existing scheme. Factor zero export income into your ROI unless a new program is confirmed.
• Batteries are marginal for low-usage seasonal homes. At 75,000 THB for 7 kWh with a 2 THB/kWh arbitrage gain, payback is roughly 8 years. Households with EVs and high daytime loads see better battery economics.
• Trim your trees. Bjørn’s production data shows visible afternoon drops from teak tree shading in winter months. A few thousand baht for an annual trim is a high-return maintenance investment.

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