Standby Power and the ErP Directive: What the Numbers Mean

A power supply that is feeding nothing still draws something. Multiply that by every adaptor left plugged in across a country and it becomes worth regulating — which is what the ErP (Energy-related Products) Directive exists to do.

What is actually regulated

ErP is a framework; the detail sits in product-specific regulations underneath it. For external power supplies the current one is Regulation (EU) 2019/1782, in force since April 2020. Great Britain applies equivalent requirements through its own ecodesign regulations, so a compliant unit will generally carry both CE and UKCA marks.

It pins down two figures:

• No-load power — what the unit draws with nothing connected. For a standard mains adaptor the limit is a fraction of a watt: broadly 0.10 W up to 49 W of rated output, and 0.21 W from there up to 250 W.
• Average active efficiency — the mean of the efficiency measured at 25, 50, 75 and 100 % of rated load. Averaging across the range stops a supply passing by being efficient at one convenient point and poor everywhere else.

Reading it off a datasheet

Look for a no-load figure quoted in watts or milliwatts, and for a named compliance level rather than a bare claim of efficiency. CoC Tier 2 — the EU Code of Conduct, voluntary and stricter than the legal minimum — and the US DoE Level VI are the two you will meet most often, and a supply that meets either clears ErP comfortably.

Why it still matters for built-in supplies

Component and built-in supplies sold for integration sit outside the external-supply regulation. The finished equipment they go into may well fall under an ErP measure of its own, though, so standby draw is a number worth having at design time rather than after the enclosure is closed.

Browse the AC/DC range or ask us for the standby figures on anything in the catalogue.