Roman numeral on a power supply (efficiency level, e.g. VI)
The minimum energy-efficiency level the external power supply meets, both when it is in use and when it is plugged in with nothing attached (no-load), on a scale from I (least efficient) to VII. The maker gives the highest numeral whose requirements are met in both cases. In the US, direct-operation external power supplies made on or after 10 February 2016 must meet Level VI and be marked under the protocol.
A mark tells you what the maker declares, never that the product is safe.
- What it looks like
- A Roman numeral from I to VII, often VI, on the power supply label, sometimes after the words “EFFICIENCY LEVEL”. Plain serif type is preferred. It is not in any box or logo.
- Who may apply it
- The power-supply manufacturer, following the International Efficiency Marking Protocol for External Power Supplies, now published by the US Department of Energy.
- Where it goes
- On the power supply’s nameplate; the exact spot is up to the manufacturer.
What it does not promise
It is about wasted energy, not safety. The original protocol says the mark is not a consumer information label. A VI shows the supply meets the US federal minimum for efficiency, not that it is a suitable or safe charger for your device.
Other marks with the same shapes
Sources
Each page below was fetched and read on the date shown. Where a symbol’s IEC 60417 or ISO 7000 number is given, a public page listing that number is among them.
- ENERGY STAR (US EPA): The External Power Supply International Efficiency Marking Protocol (the original 2005 version, PDF) — The mark “consists of a Roman numeral (I – VII)” printed on the nameplate, I least efficient and VII most efficient; choose the highest numeral meeting BOTH the Active and No-Load requirements; “This mark does not serve as a consumer information label”. This 2005 version still listed VI as reserved for the future. Checked 2026-09-24.
- eCFR (US Government): 10 CFR 430.32(w) — energy conservation standards for external power supplies (current text read via the eCFR versioner API) — 430.32(w)(1)(iii): external power supplies manufactured on or after February 10, 2016 — direct operation EPS: Level VI; (w)(4): EPS subject to the standards “shall be clearly and permanently marked in accordance with the International Efficiency Marking Protocol for External Power Supplies”, published by the US Department of Energy. Checked 2026-09-24.
Written in our own words; quotations are the sources’ wording.