Electrical energy supposes the flow of electrons within a conductor. Energy can be understood as the capacity of doing work. Electrical energy comes from the conversion of other forms of energies; a diesel generator for example convert mechanical energy into electrical energy.

kWh, the product of power expressed in kW and time expressed in hours, is used to measure electrical energy. Therefore, electrical energy is electrical power over time. In our every day life, KWh is what we pay power companies for.

Electric power in watt is obtained by multiplying voltage expressed in volts and current expressed in amps. Power is defined as the rate at which energy is supplied to a circuit or a load; it is energy over an instant.

But, what is voltage and what is current? First, electricity is defined as the flow of electrons within a circuit and the current the amount of electrons passing in a single point of the circuit.

Making an analogy with a water hose, current could be compared with the quantity of water and voltage with the force or pressure that is necessary to move water.

Just like in a water hose, if we increase the voltage, or the pressure, then the current or the water flow will increase.

Resistance refers to the resistance to the flow of electricity through a conductor. It is measured in ohm. Resistance reduces the voltage. Referring again to a water hose An increase in the pressure causes the flow to increase, but getting a kink in the hose, increasing the resistance, will cause the flow to decrease.

Voltage drop in a circuit is calculated by multiplying current and resistance. The relationship between voltage, current, and resistance is described by Ohm's law.

Together, a power source, conductors and loads make an electric circuit.

Electric circuits can be configured in series or in parallel to power several loads, such as light bulbs, TVs, washing machines and others. In a series circuit made of load 1 and load 2, the negative of the load 1 is connected to the positive of the load 2.

Current is constant in a series circuit and voltage ads.

In a parallel circuit, the negative of the loads 1 and 2 are connected together and the positives, separate from the negatives are also connected together.

In a parallel circuit current ads and voltage remains constant.

Solar panels are DC sources. DC referring to direct current. In DC electrical systems, the charge carriers' flow or movement stays the same at all times.

Alternating current or AC refers to electrical systems where the electric charge carriers periodically reverse their moving direction.

Diesel generators for example are AC sources.