What Is Amps?
Amps is the unit of measurement for electrical current. It is a measure of the amount of electrons flowing through a circuit per unit time. In other words, it is a measure of the speed with which electrical charges flow through electrical conductors in a circuit.
Amps, which is the S.I unit of current, is short for amperes. We can also represent it with A.
What Is Watts?
Watts is the unit of measurement for power. More specifically, when it comes to electrical power, watts is a measure of the time rate of energy consumption or production in an electrical system.
Watts, which is the S.I unit of power, can also be represented with W.
Why Convert Amps to Watts?
If you are building or installing a solar system (or any system with limited energy output), knowing the total wattage of the system and all the expected load on the system is vital.
You want to ensure that power source can handle the demands of every appliance you’ll connect to it. Then, if the source falls short of your overall power demand of your appliances, you can upscale it.
Basically, converting amps to watts is important when you want to calculate the wattage of an electrical power source or your appliances.
How to Convert Amps to Watts
Amps to Watts Formula for DC Systems
Converting amps to watts for direct current systems is pretty straightforward. All we have to do is multiply amps by volts:
watts = amps x volts
Amps to Watts Formula for AC Systems
We can calculate watts using the same formula as DC systems. However, we wouldn’t get the most accurate result if we do. For utmost accuracy, we must introduce power factor into our calculation.
What Is Power Factor?
Power factor (pf) is simply the share of the apparent power an electrical system or circuit actually uses. In other words, power factor is the ratio of the real power (the power a circuit actually uses) to apparent power (the power available to the system).
Going by the definition, pf equals:
pf = real power ÷ apparent power
since apparent power = r.m.s current x r.m.s voltage
we can rewrite the formula as:
pf = real power ÷ (amps x volts) eq 1
The formula above applies to a single-phase AC circuit. For a three-phase circuit, when working with line to line rms voltage, the pf is:
pf = real power ÷ (apparent power x √3)
pf = real power ÷ (amps x volts x √3) eq 2
Then when working with line to neutral rms voltage, the power factor is:
pf = real power ÷ (apparent power x 3)
pf = real power ÷ (amps x volts x 3) eq 3
Conversion for Single-Phase AC Circuits
We can get the formula to convert amps to watts for a single-phase AC circuit by making real power (rp) the subject of eq 1:
rp = pf x amps x volts
Conversion for Three-Phase AC Circuits (Line to Line Voltage)
Making real power the subject of eq 2 gives us the formula to convert amps to watts for a three-phase AC circuit when calculating with line to line voltage:
rp = pf x amps x volts x √3
Conversion for Three-Phase AC Circuits (Line to Neutral Voltage)
To get the formula to convert amps to watts for a three-phase AC circuit using line to neutral voltage, we’ll make real power the subject of eq 3:
rp = pf x amps x volts x 3
Amps to Watts Conversion Examples
DC Circuit Example 1
A portable solar charger has a rating of 18 volts and 6.1 amps. How many watts does it give off?
To calculate watts of the portable solar charger, we’ll multiply voltage with amperage since it is a DC circuit:
= 18 x 6.1 = 109.8 watts
DC Circuit Example 2
A 12v solar battery has an amperage of 16 A. How many watts can this battery give off at its peak?
= 16 x 12 = 192 watts
DC Circuit Example 3
A phone charger has an output voltage of 5 volts and output amperage of 2 amps. How many watts does the phone receive from the charger when charging?
= 5 x 2 = 10 watts
AC Circuit Example 1
A single-phase outlet has an output voltage of 240 volts, power factor of 0.82, and amperage of 15 amps. How many watts can it give off?
Converting amps to watts for AC circuits is not as straightforward as DC. But since we have pf, voltage, and amperage, we can solve the question in one step:
for single-phase AC circuits, watts = pf x amps x volts
= 0.82 x 15 x 240 = 2,952 watts
AC Circuit Example 2
How many watts is emitted by a three-phase AC circuit with a line to neutral voltage of 230 volts, current of 30 amps, and pf of 0.85?
watts = pf x amps x volts x 3
= 0.85 x 30 x 230 x 3 = 17,595 watts
AC Circuit Example 3
If the line to line voltage of the circuit in the previous example is 400 volts, how many watts will the circuit give off?
watts = pf x amps x volts x √3
= 0.85 x 30 x 400 x 1.73 = 17, 646 watts
Amps to Watts Conversion Chart
Here’s a quick amps to watts chart at common DC voltages:
Wattage at 12 volts
Wattage at 24 volts
Wattage at 48 volts
This chart should come in handy when an amps to watts calculator is not readily available.
How to Convert Volts to Watts
Using the four formulas we highlighted in the previous sections accordingly, we can convert volts to watts. As long as we know the pf, volts, and amps, the calculation would be straightforward.
If you ever have to calculate amps from watts, you can make amps the subject of those formulas. Then when you want to convert watts to volts, you can also make volts the subject of those formulas.
Volts to Watts Examples
If we have a 24 volts, 20 amps solar panel, and we want to know how many watts it produces, here’s how we’ll do it:
a solar panel is a DC system, so we’ll use this formula: watts = amps x volts
= 20 x 24 = 480 watts
How many watts will a 2.5 amps washing machine connected to a 220 volts single-phase outlet consume if pf is 0.77?
formula for a single-phase circuit: watts = pf x amps x volts
= 0.77 x 2.5 x 220 = 423.5 watts
How Many Watts in 1 Ampere?
As we have shown already, the number of watts generated by a given amount of current is dependent on the voltage.
So, if we have a 1 ampere DC system with a voltage of 20 volts, the number of watts would be:
20 x 1 = 20 watts
Then, if we have a 1 ampere single-phase AC system with a voltage of 120 volts and pf of 0.88, the number of watts would be:
0.88 x 1 x 120 = 105.6 watts
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