What is a volt watt

Einstein Online - watts your volt - electricity terms finally understandable

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Every electrical device consumes energy - from the bedside lamp to the refrigerator to the laptop. If we want to save energy, it helps to know how much electricity which device uses. But does it take watts, volts or kilowatt hours? A brief overview.

Watt - the unit of power

What horsepower is in a car, watts are in our electrical devices - the indication of power. And just as the horsepower is indicated with every car purchase, the wattage is also noted on every electrical device.

This number indicates the maximum performance of the device, so you can compare them wonderfully. A 40-watt light bulb, for example, has twice as much power as a 20-watt bulb - and of course it also uses twice as much electricity.

But wait: why is everything on the electricity bill in kilowatt hours?

Kilowatt hour - measurement of electricity consumption

Quite simply: the energy consumption is calculated in kilowatt hours. That is the energy that a device with an output of one kilowatt - that's 1000 watts - converts in one hour. They are used to calculate what an electrical appliance consumes per year. This is the only way to make a comparison, because most devices are not in constant use.

Kilowatt hours can be calculated very easily: Power (watts) x time (hours) = energy consumption in watt hours. To convert the watt-hours into kilowatt-hours, divide by 1000. For example, a hair dryer that says "2000 watts" has an energy consumption of 2000 watt hours in one hour, which is - divided by 1000 - 2 kilowatt hours (kWh) .

Conversely, you can calculate that a 20 watt energy-saving lamp that lights up for one hour consumes 20 watt hours (0.02 kWh). So it can burn for 50 hours until it has consumed one kilowatt hour of electricity. A 40 watt lamp consumes the same energy in 25 hours, i.e. twice as fast!

Recently, however, not only the wattage but also the lumens is given for incandescent lamps ...

Lumens - the brightness

Lumen describes the brightness of a lamp - it is the unit for the light intensity. It has been on every packaging since the end of the classic light bulb. Roughly you can say: If you multiply the wattage of the light bulb by 10, you get roughly the lumens (see box).

LED lamps, for example, get much more brightness out of one watt than a light bulb. Many only need 10 watts for 600 lumens, while light bulbs need 60 watts. The comparison of the wattage of two lamps does not necessarily say anything about the brightness, but certainly something about the amount of energy consumption.

Volts - the electrical voltage

Often there are other physical units on electrical devices that can cause confusion. For example volts. Volt is the unit for electrical voltage, so to speak the pressure with which the current is «pressed» through the cable. This variable does not say anything about the performance or energy consumption of a device, only the electrical voltage with which it works.

Constant 230 volts come from our sockets. Lamps, computers or hairdryers work with this voltage; the oven uses a voltage of 400 volts and needs an extra socket.

But be careful when buying lightbulbs: Some packages say 12 or 24 volts - but that says nothing about their energy consumption. These bulbs are only intended for devices that work with this voltage. A 40-watt halogen lamp that works on 12 volts uses just as much energy when connected to a normal 230-volt socket as a 40-watt lamp.

Amps - the strength of the current

For the sake of completeness, don't forget amps. This unit measures amperage - the amount of current that flows through a line. The higher the voltage (volts) and the more current flows (amperes), the more power (watts) is made available. There is a formula for this which is: Watt = ampere times volts.

It can also be used to easily calculate the current strength: If the 2000 watt hair dryer is connected to a 230 volt socket, it is around 8.7 amps (Amps = watts through volts).

A normal socket can run around 10 amps. If the amperage increases - because the 800 watt vacuum cleaner (3.5 amps) is connected to the same socket in addition to the hairdryer - the fuse blows. This protective mechanism ensures that the power lines do not overheat.

Conversion of watts into lumens

Open the box Close the box
• 25 watts: 180 to 200 lumens
• 40 watts: 350 to 390 lumens
• 60 watts: 590 to 650 lumens
• 75 watts: 800 to 890 lumens
• 100 watts: 1150 to 1270 lumens

Source: www.test.de

Corinna Daus

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• Commentary by Monika Hofmann, Brütten
Very good and logically explanatory, complete article. Thanks.
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• Comment from Martin Stucki, 8212 Neuhausen am Rheinfall
Dear Ms. Daus The value "30 VA" is written on the transformer of my model railway. What does this value mean that I have not met anywhere else? And what does it do when the VA number is higher? Kind regards Martin Stucki
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1. answer from Corinna Daus (SRF)
The 30 volt amperes (VA) denote the so-called apparent power of your transformer, while 30 watt denotes the effectively transported power - the real power. It makes no difference with small devices, it only becomes important with large ones. Technicians use the term volt-amps because it is more accurate than watts.
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