How to calculate electricity cost?

This part is important to us when suddenly our electricity cost is higher than normal usage.We can determine the figure from electrical supplier is correct or not

We also can calculated a electricity cost  for estimated our new electrical design such as install new motor,compressor,furnace or others equipment.With this calculation we can know the estimated of cost and can make a decision for that installation either it reasonable or not.

This calculation is simple and all of you can do it by your self to check and compare our electricity cost by monthly period and we can plan the next step for improvement or reduce electricity cost.

Calculation for electricity cost

You can calculate the approximate electricity cost of each different appliance if you know these:

i. Power rating of the appliance (usually found on a nameplate or etched on the appliance) and its efficiency;
ii. Number of hours you use the appliance
iii. The electricity tariff per kilowatt-hour ($/kWh).

Firstly, calculate the energy consumption in kWh :-

kWh = Power (in Watts) x Hours of operation/1000


kWh – unit of measurement for electricity consumption
k – 1000W = 1 kW
W – Watt, the unit of measurement for the load (i.e. how much power is drawn)
h – hour, the unit for usage duration

Secondly, calculate the cost of energy

Energy Cost = Energy (kWh) x Electricity Tariff ($/kWh)


Example for calculation

A nominal “1 Horse power” air conditioner (A/C) has an electrical load of about 850 to 950 watt. The cost of using a 950 watt air-conditioner unit for five (5) hours daily is derived as follows:

1) Firstly, calculate the energy consumption in kWh
kWh = 950 W x 5 h = 4.75 kWh/1000

2) Secondly, calculate the cost of energy per day (refer for domestic electricity tariff)
Energy Cost = 4.75 kWh x $ 0.25 = $1.19

Assuming that the usage is constant, the cost for using the air conditioner for a month (assume 30 days) would be:
= $1.19  x 30 days = $35.70

Why electricity bill increase?

Monthly electricity bills usually increase over time due to the increased use of electricity. Increased consumption of electricity can be caused by:

• Additional or new appliances
• Longer duration of usage of appliances.
• During festival periods when additional decorative lighting and other appliances are used.
• Replacement of older,smaller appliances with larger units for a growing family.
• Faulty appliances e.g. a refrigerator with faulty thermostat, shortage of refrigerant or defective door gasket will result in having the refrigerator working continuously thereby wasting electricity for longer period.

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