What electrical goods can I bring from the States, and how can I use them?

Question

I hope to move from a 110-volt area (the U.S.A.) to a 220-volt area. I am interested in bringing electrical devices with me but am concerned because my understanding is that some stateside devices cannot be used at all under 220 volts, some can but only with a transformer, and some can with just a plug adapter — but which are which? (Ideally, I'd also like to know why.)

Answer 1

If you're lucky, all of your devices will have a label stating what electrical conditions they work under. Your big care is voltage. (I can't speak so much to frequency.) Here are a few real labels to give you an idea of what you might encounter:

Examples

1. Input: 110V ~60Hz 7W : Won't work in the 220V area.
2. Input: 220V ~50Hz 7W : Will work in the 220V, but you can't take it home to the 110V area.
3. AC Input: 115/230V 8A/4A 50/60Hz : Works in both areas, but you probably need to flip a switch to change modes. If there's a brown out and the power sags to, say 160V, it won't work. This is from the label on a desktop power source.
4. Input: 100-240VAC 50/60Hz : Works in both areas and continues working if there's a voltage drop. This is from the label on a desktop power source.
5. Input: AC 100-240V, 0.27A 50-60Hz : Works in both areas even with voltage drop. This is the label from the a USB cell phone charger.

Rules of Thumb

There are two generalizations we can use to guess if a device will work on both even if we haven't looked at the label.

1. Anything with an electric motor or heating element can't switch over. This includes mixers, blenders, fridges, corded drills, massagers, electronic razors, toasters, panini presses, rice cookers. Most appliances will not work in both places. By their very nature, these devices are calibrated to take in a specific sinusoidal wave to function correctly. If they get anything different, their sensitive insides will probably melt and never work again.
2. Anything with that just needs DC current should be able to work with multiple voltages. This includes almost anything with a wall wart, power brick or batteries: cell or computer chargers, LED lights, most computer equipment, cordless drill. These devices need a built-in transformer to convert AC to DC, and, as a manufacturer, it's pretty easy to take multiple AC voltages while they're at it. But be careful: some electronics manufacturers will take the cheap route and put in transformers that only accept one voltage.

Check the label. These are only for guessing.

Accidents Destroy Devices

You may need an adapter to physically plug your devices into the new outlets (depending on the region), or you may find yourself in a place where every outlet accepts basically any plug. If you accidentally plug your incompatible device into the wrong voltage outlet, you will likely destroy it. Take steps to keep yourself from having to think too hard. Save your heartache by pre-labeling all your devices and outlets with color in three categories:

1. Works in both purple
2. 110-120V only red
3. 200-240V only blue

Many expats have sad tales of ruining an irreplaceable device by plugging when they were tired or thought a regular adapter was actually a transformer. (Transformers tend to be huge, heavy efficiency sappers.)

Update

Generally, when I say "it works," I mean that the device will operate well once you plug it in. (Caveat: sometimes it requires an adapter to make the wires fit right, but that's not the same as needing a transformer.) For most devices, even if I don't grant one "it works" status, it will work with the right transformer. (E.g., if you're in a 220V region with a 110V device, you'll need a transformer that takes in 220V and outputs 110V---and can handle the wattage, but that's for another post). There do exist devices that depend on specific frequencies (e.g., 50 or 60Hz), a problem that most transformers won't address, but I don't have experience with them. One thing I can say, though, is that if the device's frequency matches the region's frequency, you should be fine!

As for evidence, let the votes speak for themselves. That's what this style of Q&A is for. I have coursework in electrical engineering and worked as a system administrator for an American NGO in Cameroon, West Africa. We dealt with this issue every day.

Answer 2

Just the "why": Some equipment uses the voltage supplied directly, like a light bulb, washing machine, lawn mower. To run properly, you need Watts. And Watt = Volt times Ampere. To get the same number of Watts with half the Volts, US devices are designed to use twice the current (Ampere) of a European device. Plug that kind of 110 Volt device into 220 Volt, and it still takes twice the Ampere, which means twice the power it is designed for. Which is unhealthy for the device and possibly for you. The other way round is mostly harmless, a European light bulb would just be very dim in the USA, your water heater would take ages to heat the water.

Other equipment has to reduce the voltage to something much lower that it can use. Typically computers, mobile phones, etc. Your computer will have a transformer that reduces 110 Volt to say 12 Volt. Many such transformers work purely electronically and automatically take just as much voltage as they need, no matter how much you put in (within reason). Since the voltage has to be reduced anyway, it's not difficult to design this in a way that a wide range of voltages can be used. And that means the manufacturer doesn't need two designs for different areas of the world.

Transformers that reduce 220 Volt to 110 Volt are big, ugly, and expensive. Some devices "just work". Some devices that come with cheap external transformers may need a new transformer which you get in a decent electronic shop or on eBay. For other items (say a coffee machine), buying a transformer is probably much too expensive. It would likely be better to sell things and buy new in the new country, especially if you consider transport cost.

You may need some new plugs; you can probably do with travel adapters. They are designed to use with a 1000 Watt hair dryer, so you should have no problems there. Consider bringing some power strips with you, so all you need to change is one plug and then you can plug in four or six devices from your home country. (And I actually found a US power strip on eBay UK for £12).

Answer 3

I must disagree with gnasher729's answer but this is too big for a comment:

As he says, power = volts * amps. However, in dealing with simple devices amps = volts / resistance. Thus power is volts * volts / resistance. Note that volts appears twice--when you plug a 110V device into a 220V circuit it doesn't draw twice as much power, but rather four times as much. The device isn't designed for this kind of power, it almost certainly melts quite quickly.

Complex devices capable of regulating their own power draw will do fine so long as the extra voltage doesn't exceed the breakdown voltage of some part of the device.