Based on data on electricity consumption, they solve household and professional problems. The unit of power is Watt. Studying the information presented below will help you correctly compare the efficiency and functional parameters of different models of equipment, and create reliable lines for connecting power supplies. This information will be useful at the selection stage and during the operation of the equipment.
To measure power consumption, special equipment is used
History of appearance
How many watts are in a kilowatt
For many millennia, humanity has used horse-drawn vehicles to perform heavy work tasks. At the end of the 19th century, for example, public transport in the United States operated on the basis of this traditional technology. The total length of railways for the corresponding purpose was approximately 8.9 thousand km.
It was during this time period that new energy sources began to be actively introduced: steam and electric machines. At the same time, a need arose for more accurate power measurement. A new unit of power was defined within the framework of a scientific congress (Great Britain, 1882). After this, for a long time an alternative designation was used - horsepower (hp). It was only in 1960 that the Watt (watt) was officially approved along with other SI units as an international standard. Watt abbreviation – W.
Learn more about value ratios
Watts are derived units. This means that values are expressed using basic system units. One W is the power of one joule per second. So the power looks like this:
In addition, watts can be expressed in terms of joules and newtons.
People use prefixes to indicate that a value is a multiple of ten of its original value. Kilo is a common prefix, translated from Greek it means 1000.
If this prefix is used, it means that the indicator has been increased tenfold.
The formula for converting Watts to kilowatts will look like this:
Kilowatts refers to the power of many electrical appliances that we use every day.
These include vacuum cleaners, microwave ovens, and many other devices. Engines in cars are also calculated by this value, although in cars this value can also be represented in horsepower.
But horsepower is outside the system, and has been used since the moment when the power of a machine was calculated by the number of horses it could withstand. The kW value is quite easy to convert into them:
Thus, as can be understood from the above, 1 kW equals a thousand watts. Compared to the first formula (1), the second will look like this:
To convert W to kW, you need to increase the W value tenfold.
To obtain Watts from kW, you need to perform the reverse operation accordingly and divide the kW value by ten to the minus third power.
There are tables that can make the calculation much easier. For example:
Who came up with the idea of using watts?
Current unit
A specific name was given to this unit of measurement after the name of the Scottish inventor D. Watt. It was he who first proposed the use of a standardized amount of power - horsepower. This approach became the basis for standardizing this most important parameter, the main assessment of the energy potential of power units.
Drawing of the steam engine improved by James Watt
For your information. One horsepower is equivalent to the power required to lift a 75 kg object to a height of 1 meter per second (≈734 W).
Power formula
Illuminance unit
By basic definition, from the horsepower example discussed above, the principle of calculating energy consumption is clear. Power ( P ) can be measured in terms of work (A) done in a certain time interval ( t ) as follows:
P=A/t.
Inverse proportionality emphasizes the relative increase in energy expenditure to quickly perform a specific action.
F applied to the object and the speed of movement ( V ):
P = F * V.
The direct dependence of power on the two components from the second part of the formula is clear without detailed explanation. If the speed is expressed in terms of the distance traveled (D) in a certain time (V = D/t), after a simple mathematical transformation we can obtain the following result:
P = (F * D)/t.
Formula for the relationship between power, voltage and current
To derive dependencies between the parameters under consideration, you can return to the definition with work. In this case, the movement of charge (Q) over a given distance is considered. When moving from point F1 to F2, work (A) will be performed equal to the change in potential or voltage. The basic formula is easy to transform:
P=A/t = (U/t)*Q.
The current strength is determined by the amount of charge that moves during the control time (I = Q/t). After combining the marked dependencies, the following result will be obtained:
P = U * I.
“Related” parameters have been removed from this expression. Typical electrical quantities are left. If we add the well-known formula of Ohm's law, we can establish working relationships for calculations taking into account electrical resistance:
P = U2/ R = I2 * R.
Basic formulas for calculation
For your information. The presented dependencies allow you to obtain accurate calculation results when working with a direct current source. However, in a standard household network, single-phase 220 V power is used. The signal amplitude changes with a normalized frequency of 50 Hz, so it is necessary to take into account the peculiarities of energy consumption by different types of loads.
If a classic incandescent lamp or a boiler with a heating element is connected to heat water, it is permissible to use the formulas discussed above. However, the simple technology is not suitable when dealing with load reactance. Inductive and capacitive components form an oscillating circuit. The process of accumulation and exchange of energy with the power source is activated. During such cycles, part of the power is wasted, so for an accurate assessment the active component is isolated:
Pact = U * I * cos ϕ.
The additional multiplier in the formula characterizes the losses in a certain load. The cos ϕ value is indicated on the nameplates of electric motors, in the accompanying documentation for machines, transformers, and generators.
Experts advise not to forget about “useless” reactive power (Preact = U * I * sin ϕ). The passage of current through a circuit in any direction increases the energy potential of the molecular lattice of the conductor. This process is accompanied by heating. If you exclude this component from the calculations, the risk of breakdowns and emergency situations increases. The total power watt can be calculated using the formula:
Ptotal = √((Pact)2 + (Preact)2).
Special equipment is used to check operating circuits, repair and configure. You can measure power with a wattmeter. For constant online monitoring, such a unit can be installed in the electrical panel. Products in this category are equipped with indications. Some models are capable of transmitting information over a local network and via the Internet.
In the mobile version, the wattmeter is used to clarify the electricity consumption of devices connected to the outlet
Instead of specialized equipment, you can use a standard universal multimeter. To measure current, the device is connected to an electrical circuit in series with the load. Parallel connection will help you find out the voltage. Next, using the formulas presented above, calculate how much power watts a TV or other equipment consumes.
Sub-unit W
Having found out what is measured in watts, you can move on to the nuances that are important for practice. In some situations, the base units are too large to estimate performance parameters. Thus, some sensors (heat, light) consume a minimum of electricity. The power of a suitable power supply can be determined after performing the calculation. For convenience, instead of 1 watt, fractional values are used:
- 10-3 – mW, milliwatt;
- 10-6 – µW, microwatt;
- 10-9 – nvt, nanowatt.
Zeptowatts (10-21) and other smallest units have no practical significance in everyday life. These values are used in theoretical calculations of various physical processes.
Unicode characters [edit | edit code ]
| Unicode symbols. [4] | ||
| Symbol | Name | Unicode number |
| ㎺ | Picowatt (Square PW) | U+33BA |
| ㎻ | Nanowatt (Square NW) | U+33BB |
| ㎼ | Microwatt (Square Mu W) | U+33BC |
| ㎽ | Milliwatt (Square MW) | U+33BD |
| ㎾ | Kilowatt (Square KW) | U+33BE |
| ㎿ | Megawatt (Square MW MEGA) | U+33BF |
Multiple units of W
The basic value (1 W) is too small for assessing household needs. For a clear example, you can study the operation of a modern washing machine. The total power of the equipment is determined by the operating parameters:
- an electric motor that rotates the drum;
- heating element (heating element);
- pump for forced drainage of liquid;
- control and monitoring unit.
The following factors influence actual energy consumption:
- working temperature;
- duration and other features of individual modes;
- rotational speed;
- loading volume.
The information provided demonstrates the impossibility of obtaining correct results using measurements. For the convenience of buyers, energy efficiency standards have been established at the selection stage. Modern models are marked with the Latin letter “A” with the addition of “pluses”. The higher the final designation, the lower the bill for consumed electricity will be.
Using the accompanying documentation, you can clarify the parameters officially indicated by the manufacturer. An example of a modern model for energy consumption (Samsung WF60):
- class – A+++;
- for one standard operating cycle –860 W;
- per year - 175,000 W.
To simplify the assessment of such consumers, it is convenient to use the designation kilowatt - 103 (watt, kW). By applying this dimension, you can get the following result instead of the data given in the previous list:
- per cycle consumption will be 0.86 kW;
- per year - 175 kW.
From this example it is clear that the watt designation is suitable for power levels from 0.1 to 999.
In distribution and transmission networks, as well as in production processes, they operate with significantly larger quantities. The watt unit of measurement is not appropriate. To perform calculations, a multiple of 106 is used (megawatt abbreviation MW). The capital "M" is used to avoid confusion with mW. This addition, if necessary, will indicate a fraction of a watt (0.03 W = 30 mW).
Watts and watt-hours
What is wat is clear. However, when studying documentation and reference information, watt-hours are often mentioned. This term refers to the energy consumption for the corresponding period of time (60 minutes).
The following example explains what a W*hour is in practice. If a 900 W heater ran for 180 minutes to raise the temperature in a room, that means 2.7 kWh of electricity was consumed. By choosing the 1,800 W model, you can reduce the procedure time to 90 minutes. However, energy costs will remain unchanged:
1,800 *1.5 = 2,700 = 2.7 kWh.
Not to be confused with kilowatt hour
Probably everyone has heard at least once in their life about such a unit as a kilowatt-hour (kWh). This unit measures the work done by the device per unit of time. In order to understand its difference from a kilowatt, let’s take the example of a home TV with a power consumption of 250 W. If you connect it to an electric meter and turn it on, then exactly an hour later the meter will show that the TV has consumed 0.25 kW of electricity. That is, the TV consumption is 0.25 kWh. A device with such a consumption value, left on for 4 hours, will “burn”, respectively, 1 kW of energy. The daily consumption of a particular device depends on the features of its design, and sometimes it may turn out that the devices that seem the least “gluttonous” to us actually make up a larger share of the total electricity costs. So, for example, a regular TV has 4 times lower consumption compared to a 100 W incandescent lamp. In turn, an electric kettle “burns” three times more light than such a light bulb. The average daily energy consumption of a personal computer is about 14 kW, and that of a refrigerator is up to 1.5 kW.
Examples in nature and technology
From the following list you can understand what watts and derivative power consumption in the surrounding world are:
- laser range meter – 4 µW;
- smartphone in talk mode – from 0.8 to 1.2 W;
- heat fan – 1.2 kW;
- passenger car with a 140 hp gasoline engine. – 103 kW;
- modern electric train – 1.3*107 W;
- lightning – 1012 W.
- the flux of solar radiation falling on the Earth's surface is 1.7*1017 W.
Power of different models of household wind generators
To correctly assess energy parameters, it is necessary to jointly take into account the power and time of the working process. When working with technical documentation, conversion is carried out into the same units of measurement for ease of calculation.
Watts, kilowatts and megawatts
Having dealt with submultiples, it is worth considering multiple units of watts. These are exactly what every person encounters quite often when heating water in an electric kettle, charging a mobile phone or performing other daily “rituals”.
In total, today scientists have identified about a dozen such units, but only two of them are widely known - kilowatts (kW - kW) and megawatts (MW, MW - in this case the capital letter "m" is used so as not to confuse this unit with milliwatts - mW).
One kilowatt is equal to a thousand watts (103 W), and one megawatt is equal to a million watts (106 W).
As in the case of fractional units, among the multiples there are special ones that are used only in narrow-profile enterprises. Thus, power plants sometimes use GW (gigawatts - 109) and TVW (terawatts - 1012).
In addition to the above, petawatts (PW - 1015), exawatts (EVt - 1018), zettawatts (ZW - 1021) and iotawatts (IWt - 1024) are distinguished. Like especially small submultiples, large multiples are used mainly in theoretical calculations.
