Until today, I thought the European electricity network was 230 ± 6%. I measured my supply as 250V, which surprised me as that's 6V above 244V.

I checked, and the specification is actually 230 +10% / -6% (so my supply is below the 253V maximum).

However, many of my devices (Laptop Charger, iMac, Phone charger, etc) have a range of 100-240V written on the transformer.

Is any damage to these devices possible?

  • 1
    The listed voltages are nominal. The devices should handle anything within the spec range you mentioned. Variation in line voltage is common almost everywhere.
    – isherwood
    Commented Jul 10, 2018 at 20:08
  • @Tim that quote to isherwood - huh? Typically electronic devices are made for dual voltage operation and you will note many auto switch. The devices are intended to operate across continents utilizing kit of adapters (I am talking plugs) as Manufacturers do not need to make different devices for different markets just because the power systems are different- one size fits all. Economy of Scale. Are you measuring correctly RMS? (UK +10% = 276VAC at that I would be wary) but 240v devices still work there. 250/20 = 12.5V , 250/13 =19V en.wikipedia.org/wiki/Mains_electricity_by_country
    – Ken
    Commented Jul 10, 2018 at 21:13
  • @Ken UK has been nominally 230V for years. In most cases no changes were needed as 240V is within tolerance. Also continuous input is becoming much more common than auto-switching, especially for low powers. The stated range is 100-240, not 100-120 and 220-240 so these devices (unless printed with lies) have a continuous input range
    – Chris H
    Commented Jul 11, 2018 at 9:19
  • the devices you mention all have enough on-board "smarts" to handle the extra ~5%. Some naive appliances, like blenders, fans, vacuums, etc, could slightly overheat on long run times, possibly reducing service life, but only if over-used, for example using a cheap consumer vacuum to clean an entire hotel wing.
    – dandavis
    Commented Jul 11, 2018 at 18:01
  • @ChrisH provide me a link for 'continuous mode power supply'. I am referring to switched mode power supplies often referred to as switching power supplies. They regulate the output voltage/current appropriately. However there are limits on inputs and +10% is 276V in the UK - in the US that is industrial lighting voltage (277V). My comment on the ratio division is to show the result of a non-regulated supply is not out of tolerance for DC devices (< 2V). The op will be fine with his devices, but I would be wary at the top end tolerance of 276V.
    – Ken
    Commented Jul 11, 2018 at 18:53

2 Answers 2


You'll be fine

The voltage rating on mains devices and components is a nominal rating -- tolerances on the mains voltage need not be taken into account here, as it is understood by equipment designers and rating agencies that mains voltages vary slightly for a given nominal voltage.


These devices you mention will be fine. Devices that utilize a direct power transition such as a clothes washer or dishwasher where the AC motor is or you have specific requirements is different.

Your devices utilize what is known as Switching Power Supplies or Switched-Mode power supplies SMPS. They are auto-switching for voltage and auto-regulate. The newest items have an input voltage sensing system as that is a cheaper and more efficient means to regulate than output sensing, however which ever internal sensing technology they use - they work across the globe.

See the below information for more details:

Switched-mode power supply

  • Most of the universal switching type power supplies run fine at 100v up to just over 300v. + for isherwood & 3phase.
    – Ed Beal
    Commented Jul 11, 2018 at 20:03

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