Solar Power: Basic Knowledge of Electricity

Điện mặt trời: Kiến thức cơ bản về điện

Before officially starting with solar power, you need to understand basic knowledge about electricity, electrical concepts and quantities, voltage, current, resistance, capacity…

Mastering these concepts and quantities, you will better understand the solar power system, helping you be more confident in the field of solar power:

  • How to calculate energy
  • Install solar power system

Summary of basic electrical knowledge

When talking about solar power , what do you think it is? Is it a battery system that stores electricity ? Rooftop solar power system produces electricity? Or home solar power system ?

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The term “electricity” covers a wide range of physical knowledge, all related but always distinct. Some key quantities include charge, current, voltage, and electrons:

  • Charge is the accumulation of electrical energy, the unit of measurement is coulomb. In nature, you can charge in the form of static electricity or lightning. Batteries store electric charge.
  • Electric current is the flow of electrical charges, for example through a wire, the unit of measurement is ampere.
  • Voltage is the difference in electrical energy between two points, such as between the positive and negative terminals of a battery. Electric potential (also called voltage), is measured in units of volts.
  • Electromagnetism is the relationship between electricity and magnetism, allowing the generation of electricity from mechanical energy (such as a generator) and the generation of mechanical energy from electricity, such as an electric motor.

Basic quantities related to solar power

  • Voltage is often understood as the potential difference between two points. For example, AA batteries: voltage is the potential difference between the positive and negative terminals of the battery. The unit of voltage measurement is volt and has the symbol “ V ”.
  • Current is the flow of electricity (electrons) in an electrical circuit; Current intensity has the symbol “ ” and the unit is ampere A ). If you check the power supply, the current is usually written on it.
  • Resistance is the resistance to electric current in a material through which electric current passes. Resistance has the symbol ” ” and the unit of measurement is ohm .
  • Power is measured according to the energy conversion rate, the unit is watt (W) and the symbol is “P”. Capacity in watts is often clearly stated on electronic devices (irons, electric stoves, air conditioners…). 
  • Energy is considered the ability to do work: power multiplied by time. Energy is denoted “ E ”, measured in joules (one equal to one watt-second) , but electricity is often calculated in watt-hours (Wh) or kilowatt-hours (kWh), with 1 kWh = 1000 Wh .

Relationships between measuring quantities


Current x resistance = voltage

I x R = V

Voltage is equal to current multiplied by resistance. This formula is the expression of Ohm’s Law. Similar to power calculations, you can express this formula in many ways. If you know the voltage and current, you can calculate the resistance. If you know the voltage and resistance, you will easily calculate the current.

Voltage/resistance = current

V / R = I


Voltage x current = power

V x I = P

Power is measured in watts, which is voltage multiplied by current. A 12-V circuit with 4 amp current has 48 watts (12 x 4 = 48).

Based on this formula, you can calculate the voltage if you know the power and current; and calculate the current, if voltage and power are known.

Power/current = voltage

P / I = V

For example: A 48W motor with 4A current will require 12V voltage.

48W / 4A = 12V

Current = Power / Voltage

I = P / V

For example: A 48W motor with 12V power will consume 4A current.

48W / 12V = 4A

Power is also calculated by the square of the current multiplied by the resistance:

Square of current x resistance

I2 x R = P


Energy is a measure of power over time, writing the amount of power consumed or produced by a device, over a period of time, usually one hour. In solar power systems , energy is measured in watt-hours (Wh) or kilowatt-hours (kWh).

The device uses a capacity of 50W, will have an energy demand of 50Wh in one hour. The latest technology solar battery will generate 450W in one hour, capable of providing 450Wh of energy.

However, solar power will depend on variations in time, temperature, and weather conditions during the day. A specialized quantity is needed for solar power systems: watt-peak ratio (Wp).

So what is Wp rate?

Wp rate

The Wp rate represents the power that the solar battery can produce, the Wp rate of that panel. This is to emphasize the energy value a solar panel can produce and remind consumers that a panel with a 450W rating does not produce 450Wh of power at all times of the day.

The above content provides you with basic knowledge about electricity. If you want to add more knowledge about solar power systems or learn about the process of implementing solar power projects , you can learn more:

  • How to design a solar power system for a project
  • How to install solar power system
  • Solar power system maintenance process

Receiving a minimally effective electronic device

Or if, you only plan to install solar power at home , you need to pay attention to regulations on standards, technical specifications, and electrical safety. You can consult professional issues with VREnergy’s technical support team so we can give you useful advice.