How to calculate electrical load in a house?

how to calculate total electrical connected load in a house or office or industry?

This question comes across often if you an engineer, an electrician, or even a common man, sometimes, there is situation comes in our life where we have to find our electrical connected load in our house, office, or industry.

If you are an electrical engineer, electrician then you have to do it so many times in different situations. However, today we are going to provide you an easy way understanding to understand this concept.

In an electrical system, finding out the total connected load (TCL) is very important. Because on the basis of this, you assess the requirement of cable size, size of the circuit breakers, and getting approval of accurate sanctioned load from the utility service provider. This article covers how to calculate electrical load in a house or office etc.

What is Electrical Load?

Every device which require a certain amount of electrical energy to operate which is represented in Watts (W) or KiloWatts (KW) is called Electrical Load. It could be small or large, depends upon the size, nature of application. In general we use term “electrical load” for the total sum of electrical energy for all appliances which are installed in home or offices or shops etc.

However, from microelectronic devices, which takes very tiny amount of energy, to large size of motors of cranes, elevators, industries requires huge amount of power to operate.

What is total connected load? And How to calculate electrical load in a house?

The sum of power rating of all devices or accessories which are installed or connected in the system are called total connected load

Example:

In below table, you can find a sample of random appliances and their power rating along with calculation.

S.No Appliances Wattage Qunatity Total Power
1 Fan 80W 4 320W
1 LED Lights 15W 20 300W
2 1 HP Motor 746W 1 746W
3 Iron 1500W 1 1500W
4 Inverter AC 1200W 2 2400W
5 An Oven 3000W 1 3000W
Total Connected Load 8.268KW

On the basis of this load, a consumer applies for its electricity connection from a utility company. Once it is approved by the utility company it is considered as a Sanctioned Load.

A consumer is bound to use electricity within their limit of sanctioned load. In order to increase his sanctioned load limit, a person has to apply again to increase his load from a utility company like K-Electric in Karachi, Pakistan.

How to Calculate Ampere rating of electrical load?

Once we know our total load now we have to calculate the total ampacity of the load. Because without knowing the value of current we are unable to know the size of cable and breaker. However, calculation of current depends upon many factors; whether it is a single-phase load or a three-phase load. Both have different methods to calculate the total current.

so this is an easy way to understand this concept. if you have more appliances, you can add their power rating in this so you can find out the electrical load of your own house.

Let’s move to the calculation of the electrical current

How to find electrical current of the load?

Current is one of the important parameters to take different decisions regarding protection devices like Circuit Breaker, Fuses, Relays, and sizing of the cable as well.

First of all, we should know that whether we need a single-phase connection or a three-phase connection from the utility company. If your sanctioned load is more than 5KW then the three-phase connection is recommended. Otherwise, a single-phase connection would be enough to bear this load.

Calculation for a Single-Phase Load:

For a Single-Phase load, we use simple formula of Ohm’s Law.

V=IR

where V is voltage, I is the current and R stands for resistance of the circuit. That is so simple, which we study during our graduation and diploma courses. Here we can rearrange the above equation to find current in this way.

I=V/R

Let’s move to the next page for next Page Calculation of Three-Phase Load.