Net Billing in Thailand: How It Works in Practice

As in many countries, owners of solar installations in Thailand can sell their surplus electricity to the state. Residential systems fall under a net billing model: power drawn from the public grid is billed at the utility’s standard rate, while exported solar energy is bought back at a separate rate. As of late 2026, that rate is 2.20 THB/kWh, well below the retail price.

What happens to the energy a home is not using at a given moment depends on how the system is set up. A standard grid-tied inverter delivers all the power the panels produce. If consumption is lower and there is no battery, the surplus flows through the connection point into the distribution grid. Under the net billing program, this export is recorded by a bidirectional meter and paid for. Without a contract with the utility, however, feeding power into the grid is not allowed, so PEA and MEA usually require such systems to have reverse power flow protection (zero export). A current sensor or meter at the home’s service entrance continuously monitors which way power is flowing. As soon as energy starts flowing out to the grid, the inverter cuts its output to match the home’s current consumption. At those moments the panels run below full capacity, and some of their potential output is simply never generated. If the system has a battery, the surplus goes to charging it first.

In Thailand, this is the more common setup in practice. Few owners sign a contract to sell their surplus: in the first five years of the net billing program, about 51 MW of residential capacity was connected to it, which amounts to a few thousand homes nationwide. Most systems run on self-consumption alone.

That said, the quota for buying surplus power from households was recently expanded, and this may affect the popularity of net billing. If your panels produce well beyond your home’s daytime consumption and you have no battery, it makes sense to sign a contract with PEA or MEA. Income from selling electricity adds to the project’s overall cash flow and shortens the system’s payback period. But since the selling price is lower than the purchase price, the most profitable use of the energy you generate is self-consumption.

Below, we take a closer look at how net billing works in Thailand.

Net metering vs. net billing

Net metering

Net metering is another scheme for selling surplus generation. Under this model, exported and imported energy offset each other: every kilowatt-hour sent to the grid during the day, when solar output exceeds demand, cancels out a kilowatt-hour drawn in the evening. In effect, exported energy is worth exactly as much as purchased energy.

Historically, net metering was the dominant model in countries where residential solar took off in the 2000s and 2010s. Today, however, countries around the world are gradually moving away from it.

Net billing

With net billing, imports and exports are counted separately. Energy drawn from the grid is paid for at the retail rate, while energy exported to the grid is sold to the utility at a separate rate below retail. A kilowatt-hour you consume yourself is almost always worth more than one you export.

Why the export rate is lower than the retail rate

Why don’t utilities simply buy energy at the same price they sell it for? Because the retail rate covers more than the cost of the energy itself. An electricity bill in Thailand, for example, has several components:

·         Base rate

·         Variable fuel adjustment charge (Ft)

·         Service charge

·         VAT

When consumers buy electricity from the grid, they pay not only for generation but also for the delivery infrastructure, system costs, grid maintenance and regulatory charges. If they sold energy back at the same price, they would effectively stop paying for that infrastructure while continuing to use it (especially in the evening).

Solar generation peaks at midday, while much of a household’s load comes in the evening, when the owners get home and the panels are no longer producing. This means the grid still has to keep reserve capacity on hand, maintain the transmission and distribution infrastructure, and cover evening demand.

That is why Thailand’s net billing is designed to encourage self-consumption first and foremost, rather than sales to the grid.

How exported energy is calculated

Three quantities matter for a home solar system:

1.      PV generation – how much the panels produce.

2.      Self-consumption – the share of generation the property uses itself.

3.      Grid export – the surplus the property did not need at the moment it was generated, which went into the grid.

The relationship is simple: Generation = Self-consumption + Export

If a home needs 3 kW at noon and the solar system is producing 5 kW, 3 kW goes to the home’s own load and the remaining 2 kW flows into the grid.
If this continues for an hour, 2 kWh of electricity will be exported, and that is the amount counted under net billing. In zero export mode, the inverter would throttle its output to 3 kW in the same situation, and the remaining 2 kW would never be generated at all.

How this shows up on your electricity bill

With net billing in place, the bill effectively has two separate parts:

1. Charges for grid imports: the household pays for all the electricity it actually drew from the grid at the standard retail rate for its category.

2. A separate settlement for exports: exported energy is metered separately and paid for at the set buyback rate.

Economically, these are two different transactions: buying electricity from the grid and selling surplus power back to it. This is why the owner can see two separate items on the bill: the reduction from self-consumption and the income from exports.

Key tariff benchmarks

In other words, for a household using more than 400 kWh a month, the marginal saving from each kWh of solar power consumed on site is roughly 4.52 THB/kWh before VAT, while exporting it earns 2.20 THB/kWh. That is almost a twofold difference.

Worked example

Take a typical villa with both daytime and evening loads.

·         System size: 8 kW

·         Monthly generation: 960 kWh

·         Self-consumption: 60%

·         Export: 40%

·         The household pays the progressive residential rate

·         For simplicity, we assume that the grid electricity being replaced falls mostly in the above-400 kWh block.

Energy breakdown

Financial impact

How net billing shapes system design

When designing a home solar system in Thailand, an engineer has to weigh several practical considerations:

·         An oversized system increases the volume of low-value exports or, with zero export, the amount of generation lost to curtailment

·         A system that better matches the property’s daytime load usually pays for itself faster

·         Managing loads during the day increases the share of self-consumption

·         A battery can be useful for shifting your own solar energy to the evening hours, if its cost and operating mode justify it

To raise the share of energy used on site, the engineer studies the load profile closely. Consumption is often uneven: some residents may be out during the day, while in the evening the load jumps as air conditioners, lighting, the kitchen and household appliances come on. Some of the load from energy-intensive appliances can be shifted to the sunny hours.

The goal of the design is to strike a sensible balance between available roof space, daytime and evening load, evening demand, the share of exports, and equipment cost.

How to sign up for net billing in Thailand

The key element is a contract with the utility: PEA (Provincial Electricity Authority) in most regions, and MEA (Metropolitan Electricity Authority) in Bangkok and the surrounding area.

You can sell no more than 5 kW per meter, contracts run for 10 years, and only rooftop systems are eligible. A larger system can still be connected, but it needs an export limiter. This is the same mechanism as zero export, only with the threshold set at 5 kW. In September 2026, the National Energy Policy Council approved expanding the program to 10,000 MW and extending contracts to 20 years, including those already signed. Before any of this takes effect, the regulator has to update the program rules.

The process involves several steps:

1. Online application (PEA’s PPIM system or MEA’s MyEnergy)
2. Document review and quota allocation
3. Signing the power purchase agreement
4. System inspection and installation of a bidirectional meter

The application requires the following documents:

• ID of the meter owner (only the meter owner can apply)
• Technical specifications of the solar system
• Electrical connection diagram signed by a licensed electrical engineer
• Installed capacity details
• Bank account details for payments

Once the project is approved, the utility confirms that the system can be connected and installs a bidirectional meter, which records imports and exports separately.

The contractor’s role

In practice, most homeowners do not file the paperwork themselves. It is usually handled by the contractor installing the solar system. Siriteja Energy, for example, submits the application to the utility, manages the project approval process and coordinates installation of the bidirectional meter. For the client, this means that signing up for net billing becomes part of the solar installation project.

Legally, however, the contract is still concluded between the electricity account holder and the utility, so the owner has to sign some of the documents personally.

Conclusion

Net billing in Thailand is a model in which electricity imports and exports are settled separately. A household buys grid power at the standard retail rate and sells its surplus solar generation at a separate, lower rate.

Three key conclusions follow from this.

1.      Self-consumption is more profitable than exporting

2.      System size affects the share of exported energy and, therefore, the payback period

3.      The economics of a home solar system depend not only on annual generation but also on how well generation matches the load profile

That is why, under Thailand’s net billing model, a well-designed solar system is one in which as much of the energy produced as possible is used on site.

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