Denmark’s power is 230 Volts and 50 Hz, which means that if you are traveling from a country with another power specification (like the United States, at 110 Volts and 60 Hz) you have some considerations to make.
Last year when I was there for the VMworld conference I had my Dell laptop, my iPad, my iPhone, and my Nikon D80 digital SLR camera. I left my electric razor at home; devices with motors in them need step-down transformers so they don’t catch fire. Step-down transformers are heavy and annoying and have fuses that blow. I can shave with a disposable razor for a week, no big deal.
I planned to charge my iPhone off my laptop’s USB, thereby saving an adapter & some weight. I checked the labels on the rest of my adapters to see if they are autoswitching. This particular adapter, for my laptop, says that it can handle up to 240 Volts and down to 50 Hz, so I’m set:
My Nikon battery charger says something similar. My iPad charger, being a white block of plastic with a USB connector on it, says nothing about anything. However, the Macintouch folks say it’s autoswitching, and I can confirm that mine didn’t catch fire & melt.
If a device of yours does not indicate that it switches then you will need to get a transformer for it (or the international adapter from the manufacturer). Look at the label on the device to see what the power draw is, and make sure the transformer is big enough to handle it. The laptop label above says that the maximum power output is 90 Watts, so a 200 Watt transformer would likely work fine for it (if it were needed). If it doesn’t state a maximum you can calculate a worst-case value by multiplying the input amperage by the voltage to get the wattage. 1.5 A * 110 V = 165 Watts in this case.
A simple search tells me that Denmark uses standard European “C” and “K” style outlets with a twist: they’re deeper than most typical European outlets. But… I also know that a “C” style standard Europlug adapter will fit in the thing. Cool.
I ended up using a universal travel power adapter I bought from my local Walgreens for $7. It doesn’t have surge suppression but I decided I’d risk it. If you do want surge suppression there appear to be versions of that adapter that offer it for the appropriate voltages, for $20ish. I also picked up a short US extension cord that has three outlets, which was very handy both in my hotel room, as there was only one power outlet available, and at the conference where the power strips were big jumbles of adapters. I plugged the adapter into the wall, the extension cord into the adapter, and all my stuff into the outlets.
Another option might be some smaller, Europe-only adapters. Amazon stocks a six-pack for $4 plus shipping, they’re small and light.
Oh, P.S., European hotel rooms have a master power switch in them that is actuated by the room key. Bring an old drivers license, Costco membership card, or other plastic card to stick in there to keep your room powered on while you run down to the hotel bar. :)