SI Prefixes: How Many Watts in a Kilowatt and Kilowatts in a Megawatt
SI prefixes are very important in electrical engineering but also in everyday life. Their use is relatively easy, but it can also cause many problems when done incorrectly.
Watts to kilowatts, kilowatts to megawatts, and other conversions are very important when electric energy and power of electric motors, pumps, winches, inverters, batteries, and other devices are being calculated, planned, transferred, or being used. SI prefixes help significantly, especially when dealing with very large or very small values.
Standard SI Prefixes
SI prefixes are used in order to write down a very large or very small numbers - after all, it is much easier to write, for example, 25 kW than 25000 watts. But, it is also much easier to write 25 MW than 25000 kW or 25000000 watts.
The following chart lists the International System of Units (SI) official prefixes:
| Prefix | Base 10 | Decimal | English Word | ||
| Name | Symbol | Short Scale | Long Scale | ||
| yotta | Y | 1024 | 1 000 000 000 000 000 000 000 000 | septillion | quadrillion |
| zetta | Z | 1021 | 1 000 000 000 000 000 000 000 | sextillion | trilliard |
| exa | E | 1018 | 1 000 000 000 000 000 000 | quintillion | trillion |
| peta | P | 1015 | 1 000 000 000 000 000 | quadrillion | billiard |
| tera | T | 1012 | 1 000 000 000 000 | trillion | billion |
| giga | G | 109 | 1 000 000 000 | billion | milliard |
| mega | M | 106 | 1 000 000 | million | |
| kilo | k | 103 | 1 000 | thousand | |
| hecto | h | 102 | 100 | hundred | |
| deca | da | 101 | 10 | ten | |
| - | - | 100 | 1 | one | |
| deci | d | 10-1 | 0.1 | tenth | |
| centi | c | 10-2 | 0.01 | hundredth | |
| milli | m | 10-3 | 0.001 | thousandth | |
| micro | μ | 10-6 | 0.000 001 | millionth | |
| nano | n | 10-9 | 0.000 000 001 | billionth | milliardth |
| pico | p | 10-12 | 0.000 000 000 001 | trillionth | billionth |
| femto | f | 10-15 | 0.000 000 000 000 001 | quadrillionth | billiardth |
| atto | a | 10-18 | 0.000 000 000 000 000 001 | quintillionth | trillionth |
| zepto | z | 10-21 | 0.000 000 000 000 000 000 001 | sextillionth | trilliardth |
| yocto | y | 10-24 | 0.000 000 000 000 000 000 000 001 | septillionth | quadrillionth |
Note: the 'Short Scale' is in use in, for example, the United States, while the 'Long Scale' is in use in, for example, Europe.
How Many Watts in a Kilowatt
If you wonder how many watts (W) are there in a kilowatt (kW), just check the chart:
1 kW = 1 000 W
This is a strictly mathematical 'issue' and can be even continued:
1 kW = 1 000 W = 1 000 000 mW (milliwatt) = 106 mW = 1 000 000 000 μW (microwatt) = 109 μW
It may look confusing, but multiplying large numbers using SI proxies is very simple:
1 kW = 103 W = 103 * 103 mW = 103+3 mW = 106 mW
Or, just use a good calculator and be careful with typing the decimals.
How Many Kilowatts in a Megawatt
Similarly, if you want to know how many kilowatts (kW) are there in a megawatt (MW), just check the chart:
1 MW = 1 000 kW = 103 kW = 103 * 103 W = 103+3 W = 106 W = 1 000 000 W
One kilowatt is a thousand watts, one megawatt is a thousand kilowatts and/or a million watts.
If You want, You can easily express yottawatts using yoctowatts:
1 YW = 1024 W = 1024 * 1024 yW = 1024+24 yW = 1048 yW
Why would anybody in a real-life electrical engineering use such large or small units, I don't know, but it is a good way of showing the actual scale from one end to another of the SI prefixes chart.
Long Story Short: Unit conversions, including W to kW to MW and back, are easy, just be sure to remember right formulas:
1 MW = 1 000 kW = 1 000 000 W
And don't forget to use the calculator, especially for very large or very small values.