The first and foremost step in designing environment friendly green energy solution is Energy Assessment. An energy assessment process includes assessing how much energy your building consumes. This helps in evaluating the measures to be taken to make our building more energy efficient and also identify the problems that may, when corrected, save you significant amounts of money over time.
The design of renewable energy systems is not at all difficult if you know what appliances will be used and how long they will operate each day. Consider the case of Solar PV Systems. Because all power must come from solar panels, it is most important that they are large enough to provide the energy needed even on cloudy days. Each household has different set of appliances, their pattern of usage varies and hence the electricity requirement of each house is different. For a solar PV system to work properly, the size of the panels and the battery must be matched with the energy requirements of the appliances.
In the energy assessment process, we need to find out the total power and energy consumption of all loads that needs to be powered by the renewable energy system, in this case, the Solar PV System. For this assessment, we have to gather information regarding the electrical appliances (referred to as load) that will be powered by the new system and estimate how much energy is required for the operation of load. The information to be recorded includes Name of Appliance, Type of Appliance (AC/ DC). Quantity, Power rating and Number of hours the appliance will be used per day. From these data, we can calculate the total power of all connected loads and their daily energy consumption.
To determine the daily energy usage of an appliance, multiply the power rating of the appliance by the number of hours it will operate per day. It is normally expressed in watt hours (Wh) or kilowatt hours (kWh).
Appliances can either be DC or AC. An energy assessment should be undertaken for each type (AC and DC loads) by using the load (Energy) assessment form as shown below.
Load (Energy) Assessment Form 

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2 
3 
4 
5 
6 
7 
Sl. No. 
Name of Appliance 
Power (Watts) 
No. 
Total Watts (W) 
No. of hours of usage/ day (h) 
Energy consumed/ day (Wh) 





















A system designer needs to gather load details from the customer and calculate the electrical energy usage. The problem is that, the customer may not want to spend the time determining their realistic power and energy needs which are required for successful completion of load assessment form. They just want to know only the cost of the new system that is needed to power their lights and TV. A system designer can only design a system to meet the power and energy needs of the customer. In the energy assessment process, the system designer must understand the needs of the customer and at the same time educate him. The load assessment process is always time consuming and it is during this process that you will discuss all the potential sources of energy that can meet their energy needs and you can educate the customer on energy efficiency.
The load assessment form shown above consists of 7 columns.
1) The first one is serial number
2) In the second column, you have to fill the name of appliance e.g. CFL, TV, Fan etc.
3) Column 3 is Power in watts. It should be filled with wattage of the appliance. You can find the wattage of an appliance on the tag or plate located at the bottom or back of the appliances. Or you can refer to the appliance owner’s manual. If an item is rated in amps, multiply amps by operating voltage to find the watts. Normally, the power rating will vary between 5 to 1000 Watt.
4) If there are more appliances of same type, then fill the Fourth column with the total number of that appliance. Thus, if a household is using 5 CFLs of 12W each, then this column is to be filled as 5.
5) In the fifth column, calculate the total wattage of each type of appliance by multiplying the wattage of individual appliance by number of appliance. i.e., multiplying column (3) by column(4). You have to do this for all type of appliances listed in the form. Finally, add up all the values in column 5 to calculate the total power of all appliances connected in the household.
6) Sixth column should be filled with total number of hours for which that appliance will be used in a day. If there are more appliances of same type, but each operating for different hours per day, then take the average of number of hours of operation.
7) Seventh column is for estimating the energy required for each appliance per day. This is obtained by multiplying the total power rating (watts) by No. of hours of operation(h). i.e., multiplying column (5) by column (6). The energy is expressed in Wh.
To find the total energy consumed by the household per day, add all the values of column 7. The monthly energy consumption can be calculated by multiplying the energy consumption per day by the number of days in that particular month.
An example for estimating the energy consumption of AC loads in a household is given in the table below.
Load (Energy) Assessment Form 

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2 
3 
4 
5 
6 
7 
Sl.No. 
Name of Appliance 
Power (Watts) 
No. 
Total Watts (W) 
No.of hours of usage/ day (h) 
Energy consumed/ day (Wh) 

Fan 
60 
2 
60 x 2=120 
8 
120 x 8=960 

CFL 
20 
4 
20 x 4 =80 
8 
80 x 8=640 

Tube light 
40 
2 
40 x 2 = 80 
6 
80 x 6 = 480 

LCD TV 
80 
1 
80 x 1 = 80 
6 
80 x 6 =480 

Total 
360W 

2560Wh 