Zero Export Solar Explained: When You Need It, How It Works

Zero export means a solar system runs in parallel with the grid but sends no power back to it. Everything it generates is used in the building or stored, and any extra output is held back. You need it when the utility will not accept export from your connection, or when exported power earns nothing and you would rather store it. It works by measuring power at the grid connection. As soon as export starts, the controller turns the inverter down or sends the surplus to a battery. A zero-export system is still grid-connected, so in most countries it still needs the utility's approval.

Zero export, export limit, off-grid: the difference

These terms are often used loosely, but they mean different things.

Zero export is simply an export limit set to zero. The same control does both: measure at the grid point, compare with the limit, and reduce generation when the limit is reached.

An off-grid system has no grid connection, so there is nothing to export to and no parallel operation. By contrast, a grid-connected system with zero export still synchronises with the grid, still needs anti-islanding protection in the inverter, and still falls under the utility's connection rules.

When you need zero export or an export limit

There are three common situations.

The utility does not allow export. In some markets, or on parts of the network, customers may use solar for their own consumption but may not send power back. Thailand is a common example: homes and businesses that do not join a programme to sell power to the grid install systems for self-consumption, and the utility expects a device that stops reverse power flow. Businesses with high daytime demand often choose this route, because they use most of what they generate on site anyway.

The network sets a limit. Network operators set export limits where the local network cannot take more. In Australia, distribution network service providers set export limits for many new connections, usually a fixed value of a few kilowatts per home, and in some areas limits that change with network conditions. In Germany, under the Solarspitzengesetz of 2025, most new PV systems without a smart meter may feed in no more than 60% of their module power at the grid connection.

Export is worth little. Where exported energy earns little or nothing, it makes more sense to use the surplus at home: charge a battery or an EV, or run a water heater or air conditioning in the afternoon. Export control then becomes part of energy management, not just compliance.

How zero export works

A zero-export system has three parts: a measuring point, a controller and at least one device the controller can command.

1. Measure at the grid connection. A current transformer (CT) is clipped around the incoming conductor, between the grid and the first branch circuit, so that it sees the net flow for the whole building. The controller also measures voltage, which tells it the direction of the power flow: import or export.
2. Decide. The controller compares the measured export with the limit. Below the limit, nothing changes. As soon as export rises above it, the controller acts.
3. Act. It reduces the inverter's output, charges a battery, starts an EV charger, or does all three in order of priority. When the building's load rises again, it allows generation to increase.

The CT position matters most. If the CT sits downstream of a branch circuit that has its own loads or its own inverter, the controller sees only part of the picture and cannot hold the limit at the true grid point. On three-phase supplies, each phase needs its own CT, and the utility may require zero export on each phase rather than on the total.

Control is continuous, not instant. When a large load switches off, PV output stays high until the controller reacts, so very short excursions around the set value can occur. Strict utilities sometimes require a reverse power relay as a backup; it disconnects the system if export continues. Ask your utility which method it accepts.

Zero export in Thailand: what to check

Thailand has two distribution utilities: the Metropolitan Electricity Authority (MEA) for Bangkok, Nonthaburi and Samut Prakan, and the Provincial Electricity Authority (PEA) for the rest of the country. Their procedures differ, and requirements also depend on system size and connection voltage. The general points are:

• Approval is still needed. A zero-export system still runs in parallel with the grid, so it needs the utility's approval like any other grid-connected system. Zero export changes the technical review, not the need to apply.
• The device may have to be on a list. MEA publishes a list of zero-export controllers that have passed its checks and a list of inverters accepted on its network; PEA publishes its own inverter list. Where a listed controller is required, the application usually includes the controller and CT datasheets.
• ERC exemption. Small rooftop systems are generally exempt from an ERC licence but are notified to the Energy Regulatory Commission. Larger systems involve additional steps with other agencies.
• Building rules. Rooftop installations may need a permit from the local authority or a certificate from a structural engineer.

Because lists and forms are updated often, get the current versions from your MEA or PEA office before you choose equipment.

Checklist before installing zero export

1. Confirm the requirement. Zero export, a fixed export limit, or per-phase limits? Ask the utility in writing.
2. Check accepted devices. If the utility keeps a list of accepted inverters or controllers, check that the exact models are on the current version.
3. Place the CT correctly. On the grid side of every load and every generator, one CT per phase, with the arrow in the right direction.
4. Match the controller to the inverter. The controller must be able to command the inverter. A meter that only measures cannot limit export.
5. Plan for the surplus. Without storage, zero export wastes the midday surplus. A battery, an EV charger or a scheduled load turns it into savings.
6. Test before handover. Switch off large loads with the PV at full output and check that export stays at the set value. Record the result for the utility inspection.
7. Decide what happens offline. Check how the system behaves if the local network or the internet connection fails. Local control should not depend on the cloud.

How EnergyPilot does it

EnergyPilot is VaySunic's local energy management (EMS) controller. It mounts on a 35 mm DIN rail in the distribution board, measures at the grid connection with clip-on CTs, and keeps feed-in at zero or at a set limit.

• Two models. VDG-EM-1 for single-phase supplies (220/230 V, one CT) and VDG-EM-3 for three-phase supplies (3 × 230/400 V, three CTs, or three separate single-phase measuring points). The CTs are rated 100 A and clip around the conductor, so the main cable does not need to be cut.
• Measures what matters. It measures voltage, current, power, frequency, and import and export energy, with ±1% accuracy for voltage, current, power and energy. EnergyPilot measures for control and monitoring; it is not a billing meter.
• Decides on site. The control logic runs on the device itself, inside the home network. If the internet connection drops, export limitation carries on. The VIP Cloud app is used for monitoring, history and remote settings.
• Uses the surplus. Before limiting solar, it can send surplus to a PowerCube or SolarHub battery or to a ChargeFlow EV charger.

There are two limitations. First, EnergyPilot controls VaySunic devices (SolarCore, SolarHub, PowerCube and ChargeFlow). It can monitor the output of an existing inverter of another brand through the spare CTs of the VDG-EM-3, but it cannot control it, so it cannot provide zero export for a third-party inverter. Second, feed-in is regulated continuously, so short fluctuations around the set value can occur when the load or PV output changes quickly.

Installation must be carried out by a qualified electrician. Where your utility requires a controller from its accepted list, check the current list before you quote.

How VaySunic can help

For self-consumption systems, we supply the complete chain: SolarCore microinverters, SolarHub hybrid microinverters and PowerCube storage, with EnergyPilot keeping feed-in at zero or at the limit your connection allows. See our on-grid solutions for typical configurations, or contact us with your utility's requirements and we will propose a system that meets them. Installers and distributors can find terms and support in our distributor programme.

Sources

• MEA, documents for generator parallel connection, including the Zero Export Controller notification form
• PEA, Regulation on grid connection requirements (2016) (PDF)
• pv magazine Deutschland, Solarspitzen-Gesetz vom Bundestag angenommen (January 2025)
• Solaris Green Energy, overview of the MEA and PEA approval lists (inverters and zero export controllers)