2027 EU Ecodesign Regulation: The Logic Behind Inverter Selection Is Set to Change

The EU has been preparing ecodesign rules for photovoltaic inverters since 2018. While the final regulation has not yet been published, the draft sends a clear message: grid-connected inverters will face mandatory Euro Efficiency thresholds.

What the Draft Says

Grid-tied inverters without energy storage must meet the minimum Euro Efficiency requirements: 94% for Tier 1 and 96% for Tier 2, as tested according to EN 50530.

Euro Efficiency formula:

η_Euro = 0.03×η5% + 0.06×η10% + 0.13×η20% + 0.10×η30% + 0.48×η50% + 0.20×η100%

The 50% load accounts for 48% of the weighting. The test is designed around real-world operating conditions in Central Europe and does not represent nameplate efficiency.

CEC and Euro are not the same thing

The CEC formula assigns a 53% weighting to the 75% load, based on high-irradiance conditions in California. Euro Efficiency places nearly half of the weighting on the 50% load, reflecting the cloudy reality of Central Europe. An inverter optimized for CEC is not the same as a product optimized for Euro.

A Specific Example

A 1 MW commercial and industrial rooftop system in Central and Eastern Europe, with 1,100 hours of annual utilization:

94% efficiency: 1,000 × 1,100 × 0.94 = 1,034,000 kWh/year

97% efficiency: 1,000 × 1,100 × 0.97 = 1,067,000 kWh/year

Difference: 33,000 kWh/year. At €0.15/kWh, that’s €4,950 per year, or €99,000 over twenty years. For a 10 MW portfolio: €990,000.

94% is the legal minimum, not a design target.

Implications for Controller Selection

Nearly half of the weighting in the Euro Efficiency index is at 50% load, indicating that real-world power plants operate at partial load for a significant portion of the time. The MPPT tracking behavior of controllers under low-to-medium irradiance is equally critical. While the EU has not yet established specific performance metrics for controllers, the system efficiency chain will come under closer scrutiny following the tightening of inverter regulations. It is becoming increasingly difficult to justify a datasheet that simply states “MPPT efficiency 99%” without specifying the test conditions.

Procurement Recommendations for 2027

Don’t wait for the final regulations. Start asking suppliers for Euro Efficiency test data now—not peak efficiency, and not CEC efficiency.

94% is the baseline, not the target. High-quality string inverters are already in the 97.5–98.5% range.

For hybrid systems, consider the overall efficiency chain. Pairing a high-efficiency inverter with a low-efficiency controller still results in energy waste.

References:

JRC Preliminary Study: https://susproc.jrc.ec.europa.eu/product-bureau/sites/default/files/2020-12/jrc12431preparatory_study_for_solar_photovoltaic_modules_kj-na-30468-en.pdf

Inmab Inverter Naming Conventions (Tier 1: 94%, Tier 2: 96%):  http://inmab.eu/edu/documents/Naming-rules-for-photovoltaic-inverter-industry_Fri-21-Jan-2022-22429.pdf

ENERGY STAR Scope Report (Euro and CEC Formulas): https://www.energystar.gov/sites/default/files/asset/document/Solar_PV_Inverters_Scoping_Report.pdf

EU Public Procurement Community Presentation: https://public-buyers-community.ec.europa.eu/system/files/2025-01/Presentation%20Ecodesing%20%26%20Energy%20labelling%20requirements%20for%20PV_0.pdf