How to calculate your solar power plant size ?

MNRE has formulated draft Guidelines for Decentralised Solar Power Plants

The most important question, any consumer faces is what is the appropriate size of solar power plant that is required for minimizing the electricity bill. In this post, we shall see, how to calculate the appropriate size of solar plant that is suitable for your house/institution or business.

Step 1: Take out your latest electricity bill and one old bill (5-6 months old)

Step 2: On the bottom right side, you will see month & consumption details. Note down each month electricity unit consumption and add all the units. Collect unit consumption for older months from old bill. Now add all units to see, what is your yearly unit consumption. (Say 5,000 Units)

Step 3: 1 KWp of Solar Power plant produces an average of approximately 4 Units or yearly 1 KWp of Solar Power plant produces approximately 1450 Units.

Step 4: Now divide your yearly consumption (Step2) by 1450 .  In this case, 5,000/1450 = 3.45 or approximately 3.5 KW (Value 1).

Step 5: Now check you sanctioned load & contract demand, whichever is minimum. Say sanctioned load is 10 KW & Contract demand is 6 KW. Then minimum is contract demand and is equal to 6 KW. [Contract demand term may not be mentioned for domestic consumers]

Step 6: Legally, you can install on 80% of the value, you got in step 5. In this case = 6*80% = 4.8 KW (Value 2). Hence, solution we got in step 4 (3.5 KW is still valid). If your solution in step 3 is more than value in step 4, the  either you would have to increase contract demand/sanctioned load or you would have to install a lower power solar plant.

Step 7: Now we shall check for space constraints, 1 KWp of Solar Power plant required a shadow free space of 10*10 feet = 100 Square feet of space. So in this case, for 3.5 KWp of system, you would required 350 Square feet (Value 3). If such space is not available, calculate shadow free space available on your roof and divide by 100 to get maximum size of solar power plant. Let say’ 650 sqfeet is available then plant size is 650/100 = 6.5 KWp

Step 8: To see the size of solar plant that can be installed under present condition, see the minimum of value 1, value 2 and value 3. In this case, minimum of 3.45, 4.8, & 6.5 KWp which is 3.45. Hence, it both legally, space wise and engineering wise,best suitable plant size for your home/institute/business for now.