Transformers also step up or down the voltage, but they are more expensive than converters and are used with “electronic” products. Electronic products have a chip or circuit. Transformers can also be used with electric appliances and may be operated continually for many days. The advantage of converters, however, is that they are lighter and less expensive.
Computers are electronic devices and therefore they must be used with a transformer, unless they are dual voltage. Fortunately, nowadays all laptop, tablet and phone chargers are dual voltage, so they can be used with only a travel adapter.
Transformers are sold in various sizes based on how much wattage they can support. Therefore you must pay careful attention to the wattage ratings of the appliances to be plugged into a transformer. The wattage rating of the transformer should always be larger than the wattage rating of the appliance to be plugged into it (plus a 25% buffer to allow for heat build-up in the transformer or converter). When plugging multiple items into a power strip, then into the transformer, you have to calculate the combined wattage of all appliances and the power strip, then add an additional 25% to that total.
The appliance’s voltage and wattage requirements are listed on the manufacturer’s label located on the back or at the bottom of the appliance. In some cases, the voltage and amperage will be listed, but not the wattage. If this is the case, simply multiply the voltage by the amperage rating to find the wattage rating (e.g. 230 V * 2 A = 460 W).
Below is a list that gives an idea what the wattage of common appliances is. Use this as a guide only. Always check your appliance first!
- 100 watts (or less): small, low-wattage appliances such as small fans, printers and desktop computers.
- 300 watts: most TVs, electric blankets and refrigerators.
- 500 watts: blenders, projectors and home cinema systems.
- 1000 watts: small heaters and stand mixers.
- 1600 – 2000 watts: hair dryers, dishwashers, washing machines, vacuum cleaners, most appliances that have heating elements such as convector heaters, toasters, deep-frying pans, irons, grills and coffee makers.
- 3000 watts: tumble dryers and big air conditioners.
Transformers and converters only convert the voltage, not the frequency. The difference in cycles may cause the motor in a 50 Hz appliance to operate slightly faster when used on 60 Hz electricity. This cycle difference will cause electric clocks and timing circuits to keep incorrect time: European alarm clocks will run faster on 60 Hz electricity and American clocks will lose some 10 minutes every hour when used in Europe. However, most modern electronic equipment like phone chargers, laptops, printers, etc. are usually not affected by the difference in cycles and adjust themselves automatically.