Every inverter that can run in parallel with a public electricity network must satisfy the rules of the country it lands in — and those rules are not one standard but a family: a European baseline, national add-ons layered on top, a North American framework built around a listing mark, and, in Great Britain, engineering recommendations run through the distribution network operators. For a buyer or importer the real question is not "is it CE marked?" but "will the network operator accept this exact model?" Here is how the four rulebooks differ, and the evidence that decides acceptance.
Why a safety mark is not a grid approval
A CE mark is a manufacturer's declaration that a product meets the applicable EU directives — for inverters, the low-voltage and electromagnetic-compatibility requirements that sit in the EN 62109 safety family. It does not by itself prove that the grid-support behaviour a distribution network operator (DSO) will ask for has been independently verified. North America works the other way round: a base UL 1741 listing is fundamentally a safety listing, while what most utilities require for interconnection is the Supplement B revision. In both regions the grid layer is separate, testable and decisive.
The four rulebooks you will meet
1. Great Britain — EREC G98 and EREC G99
In Great Britain the Energy Networks Association's Engineering Recommendations sit under the Distribution Code. EREC G98 covers Fully Type Tested micro-generators up to and including 16 A per phase — about 3.68 kW single-phase and 11.04 kW three-phase, counted as the aggregate capacity at the premises rather than per device. It is a "fit and inform" route: commission, then notify the DNO within 28 days. Anything above that threshold, or any unit that is not fully type tested, falls under EREC G99, which needs DNO approval before connection. Both replaced G83 and G59 for generation connected from 27 April 2019, and qualifying equipment is listed on the ENA's public Type Test Verification Report Register.
2. Europe — EN 50549-1/-2 plus national add-ons
EN 50549 sets the European baseline for generating units in parallel with public distribution networks — Part 1 for low voltage, Part 2 for medium voltage. The 2019 edition superseded the earlier technical specification and EN 50438, so a supplier quoting only those old numbers is describing a replaced file. EN 50549 defines voltage and frequency response, reactive-power capability and interface protection. Countries then layer national rules on top: Germany's VDE-AR-N 4105 adds stricter ride-through, start-up and reactive-power behaviour for low-voltage units, with power-factor ranges that tighten as unit size grows, while VDE-AR-N 4110 does the same at medium and high voltage.
3. North America — UL 1741 SB and IEEE 1547-2018
In the United States the framework is IEEE 1547-2018, tested under IEEE 1547.1-2020, with equipment listed to UL 1741 Supplement SB. Supplement SA introduced the first "smart inverter" functions; Supplement B aligns them with the 2018 edition — voltage and frequency ride-through, volt-VAR and volt-watt control, frequency-watt response, and standardised communication such as SunSpec Modbus. Several states require it as a condition of interconnection, and a base-listed unit may not receive permission to operate.
The four frameworks at a glance
| Region | Governing document | Applies to | What the buyer must show |
|---|---|---|---|
| Great Britain | EREC G98 | Fully Type Tested micro-generation up to 16 A per phase (≈3.68 kW single-phase / 11.04 kW three-phase, aggregated) | Type-test report and listing on the ENA verification register |
| Great Britain | EREC G99 | Above 16 A per phase, or any equipment that is not fully type tested | DNO application and written approval before connection |
| Europe | EN 50549-1 / -2, plus national rules such as VDE-AR-N 4105 | Generating units in parallel with low-voltage and medium-voltage networks | Conformity declaration and a type-test report naming the exact model |
| North America | UL 1741 Supplement SB (IEEE 1547-2018) | Inverters and distributed-energy interconnection equipment | Independent listing to Supplement B, covering the required grid-support functions |
The three tests that decide acceptance
- Anti-islanding. IEC 62116 is the reference procedure; the unit should stop energising the line within roughly two seconds of losing the mains, protecting line workers and preventing out-of-phase reconnection.
- Ride-through. Instead of tripping at the first disturbance, the inverter stays connected through defined voltage and frequency excursions — the feature that separates a basic grid-tie unit from a grid-supporting one.
- Power quality and control. Limits on harmonic current, DC injection and flicker, plus the ability to adjust reactive power on command rather than only at unity power factor.
Key takeaways
- A safety mark is not a grid approval — two different layers of evidence.
- Great Britain splits at 16 A per phase (≈3.68 kW): G98 is fit-and-inform, G99 needs prior approval.
- In Germany, EN 50549 is the baseline and VDE-AR-N 4105 is the national requirement on top.
- In the US, ask specifically for Supplement B — the base UL 1741 listing may not be enough.
- A listing covers a tested configuration, not a name.
A five-point document checklist before you buy
- Ask for the type-test or conformity report itself — not a marketing statement — and confirm the model number on it matches the unit you are ordering.
- Check the model appears on the relevant national register, where one exists.
- Compare the rated AC output with the local power ceiling, remembering that thresholds usually count the total at the premises.
- Confirm the as-shipped configuration includes the correct country grid settings and local-language documentation.
- Plan for re-testing if you change hardware or grid firmware beyond the certified scope — a listing covers the tested configuration, not the brand on the box.
Frequently asked questions
Does a CE mark mean my inverter can be connected to the grid in Europe?
Not on its own. A CE mark is a manufacturer's declaration that the product meets the applicable EU directives, but the grid connection itself is governed by EN 50549-1 and by any national requirement layered on top, such as VDE-AR-N 4105 in Germany. A distribution network operator may still ask for a type-test report naming the exact model and firmware configuration.
What is the difference between UL 1741 SA and UL 1741 SB?
Supplement SA introduced the first generation of smart-inverter functions. Supplement B aligns the listing with IEEE 1547-2018 and IEEE 1547.1-2020, adding voltage and frequency ride-through, volt-VAR and volt-watt control, frequency-watt response and standardised communication. Many utilities now require Supplement B as a condition of interconnection.
Is a 3.68 kW system in Great Britain covered by G98 or G99?
16 A per phase works out at about 3.68 kW on a single-phase supply and 11.04 kW on three-phase, counting the aggregate capacity at the premises. A fully type tested system at or below that figure can use the G98 fit-and-inform route, notifying the network operator within 28 days. Go above it, or use equipment that is not fully type tested, and EREC G99 prior approval applies.
Can one type test cover several inverter models?
Only the configuration that was tested. A listing describes a defined hardware and settings scope, so changing components, power stages or grid-country firmware beyond that scope normally requires a new test or a formal extension of the existing report — a rebadged unit is not automatically covered.
Sources & further reading
- Energy Networks Association — Engineering Recommendations G98/G99 and Type Test Verification Report Register — energynetworks.org
- UK legislation portal — Electricity Safety, Quality and Continuity Regulations 2002 — legislation.gov.uk
- UK Government — Department for Energy Security and Net Zero — gov.uk
- International Electrotechnical Commission — IEC 62116 (anti-islanding) and IEC 62109 (PV inverter safety) — iec.ch
- National Renewable Energy Laboratory — distributed energy resource interconnection research — nrel.gov
中文摘要
并网逆变器进入不同市场，需要面对各自独立的并网规范：英国以 ENA 的 EREC G98/G99 为界，16 A/相（单相约 3.68 kW、三相约 11.04 kW，按同一场所总量计）以下且整机完成型式试验可"装后告知"，超限或未做型式试验则须 G99 事先报批；欧洲以 EN 50549-1/-2 为基准，德国另叠加 VDE-AR-N 4105；北美则以 IEEE 1547-2018 为准，设备侧关键是 UL 1741 Supplement SB 认证。CE 与基础 UL 认证仅为安全层面，不等于并网许可。采购前务必核对型式试验报告上的具体型号、国家级名录列名与随货的参数配置。