Frequently asked question about how to estimate the power of the Solar PV System for the home or company to eliminate electricity bill ?!

To answer, follow these three steps:

(1) Estimating the amount of energy consumed per day = the number of electrical devices x the electric power of device x daily operating hours

An example house contains:

20 bulbs x 10 watts x 6 hours = 1200 watt hours

 1 TV with Receiver x 100W x 6h = 600Wh

1 electric water heater x 1200 watt x 6 hours = 7200 watt hours

Then, the total energy consumed per day: 1200 + 600 + 7200 = 9000 watts per hour.

(2) Of course, there are energy losses in any electrical system of about 30% due to the conduction, quality of the wires, inverter and the efficiency of the solar panels. Therefore, these losses must be added to the total energy consumed per day by applying the following formula:

Total energy needed = total energy consumed per day x 1.3

To apply it to our example, the electric power to be generated = 9000 x 1.3 = 11700 watt hours

(3) To know the power required for Solar PV System, the energy to be generated must be divided by the Average Hours of Sunlight Per Day for the region in which it will be installed. For example, the northern coast, Average Hours of Sunlight Per Day is 6.3 hrs.

Then, the Power required for Solar PV System = 11700 ÷ 6.3 = 1857 watt i.e. the required power 2kW. 

Important recommendation: Before contracting to install a Solar PV System, firstly confirm that all electrical appliances in the house or company are highly efficient and replace the old ones, as the costs of replacing the old low-efficiency devices with new high-efficiency devices saving more than twice as much spending on the monthly electricity bill as well as purchasing a Solar PV System greater than necessary .. Secondly, check the government approval of the company that will install and the warranty period for each major component and the energy produced annually by the a Solar PV System.. God bless

Dr. Mohamed Gamal Kafafy, PhD., DBA.

Chief Consultant for Energy & Sustainable Development - World Fund for Development and Planning