As solar panel systems are being embraced and used in more and more homes, the question about how to choose the right size of solar panel is gradually becoming a popular one. This cannot be done without understanding the meaning of several physical quantities as well as the formulas for calculating them. In this article, we will accept the units of measurement of two common physical quantities, amperes and watts, as well as the formulas for converting between the two. This can help you better determine the size of solar panel system you need for your property.

Before learning the formula for converting between the two, we first need to recognize the following physical quantities.

1. What is an ampere (A)?

Ampere is the unit of current (I) in a circuit, abbreviated as ampere and symbolized as A. It is usually used to describe the magnitude of current in a circuit. From a microscopic point of view, it expresses the amount of charge that passes through a section of a circuit in an instant, i.e., the rate at which current passes through a section.

2. What is a watt (W)?

Watt is a unit of power, often used to describe the electrical system to complete a job how much power consumption. The larger the watt value, the more power the appliance consumes, and the smaller the watt value, the less power it consumes.

The watt is a unit of power that is commonly used to measure the power of various small and medium-sized appliances in the home, as well as some of the components in a solar panel system.

3. How do I convert from amperes (A) to watts (W)?

After learning the units of measurement for the physical quantities listed above, we can begin to learn the formula for converting amps to watts. Since the nature of AC circuits and DC circuits are quite different, and the method of converting amperes to watts is not the same, the conversion formulas used in the two different types of circuits are explained separately below.

3.1 DC Circuits

Although amperes and watts are both common units of measurement in electrical knowledge, they do not measure the same physical quantities in a DC circuit: amperes are the unit of measurement for current, while volts-watts are the unit of measurement for power. In order to convert between the two, we need to introduce an intermediate unit of measurement for physical quantities, which is the volt (V). From this, the conversion can be achieved by the following formula:

P (W) = I (A) x V (v)

The p in the above formula is the power in the DC circuit, I is the current in the DC circuit, and V is the voltage in the DC circuit, which is:

Watts = Amps x Volts

To make it easier for you to better understand and grasp the above formula, you will find examples of applications below. When you want to install a solar panel system for your property, and it is known that the household supply voltage is 110v, and your appliances run at a total current of 10A, the solar panels you need to install will generate 10A x 110v = 1100W.

3.2 AC Circuit

First of all, compared to the stable and unchanging current and voltage of a DC circuit, both the current and voltage in an AC circuit continue to change regularly and periodically. As a result, the AC circuit amperage to wattage conversion equation can be more complicated.

After you have understood and mastered the simpler DC circuit formulas above, the AC circuit amperage to watts formulas will be presented below.

Although the formula for DC circuits is simpler to understand, the fact is that AC circuits are used far more frequently than DC circuits in practical applications, and the power supply for the appliances we use in our daily lives is realized through AC circuits. Including by the solar panel system issued by the DC power also need to be converted to AC power through the inverter and then for equipment power supply.

There are two main types of alternating current: single-phase alternating current and three-phase alternating current.

3.21 Single-phase alternating current

Single-phase alternating current (AC) refers to a circuit that has only a single AC voltage, and the current and voltage generated in the circuit change at a specific frequency over time.

For single-phase alternating current, the formula for converting amperes to watts is:

P (W) = PF × I (A) × V (v)

The following will explain the above formula: P refers to the power generated by the electrical system in the above formula, V refers to the RMS voltage, that is, the circuit with the ability to produce the same heating effect of the DC voltage value, the main reason for the existence of AC circuits because of the voltage changes over time, the calculation of the RMS value can be convenient to calculate the I refers to the current of the circuit, and the PF is a single-phase AC circuit of the power factor, namely A value used to measure the phase difference between voltage and current in a circuit. The larger the phase difference between the voltage and current in the circuit, the lower the power factor, the lower the efficiency of the circuit, and the less stable the overall system.

3.22 Three-phase alternating current

Three-phase alternating current is the most commonly used alternating current in practice, which refers to the power system consisting of three alternating current potentials with the same frequency, the same potential amplitude, and a phase difference of 120°.

For three-phase alternating current, there are two ways to calculate the amperage-to-watt conversion formula:

One is to change the RMS voltage to the line-to-line voltage (V L-L) for calculation, and the conversion equation is:

P (W) = √ 3 × PF × I (A) × V L-L(v)

The other is to change the RMS voltage to line-to-neutral voltage (V L-N) for calculation, and the conversion formula is:

P (W) = 3 × PF × I (A) × V L-N(v)

It is worth noting that the symbols in both of the above formulas have the same meaning as in the single-phase alternating current formula.