Estimating the solar system size you need isn’t a herculean task anymore. It mainly depends on how much energy you use every day to power your equipment. System requirements for each house will be different based on their electricity usage. Following are the steps to estimate the PV solar system size:
- Figure out your electricity usage rate:
- Calculate the array size:
Before getting into sizing the system, it’d be advisable to go through your past electricity utility bills in order to get an idea of your average electricity consumption. Note your average monthly kWh (kilowatt hour) usage and your electricity bills. Also note your annual energy consumption in kWh. You can simply check with your utility service provider regarding this.
In order to calculate for yourself as to what exactly is the array size you need in kW, use the below formula:
In the above formula, GPK denotes the generation per kW. This is the number of kWh generated by 1 kW of solar PV panels in your region. The GPK varies from region from region, and mainly depends on the solar radiation in your region. For a region with excellent solar radiation, the GPK could be as high as 5 kWh per kW per day. For regions with poor solar radiation, it could be as low as 2.5 kWh per kW per day.
As a thumb rule, you can take GPK to be 4 if your region has average-good sunshine. If you consider your region to have excellent sunshine, you can consider GPK to be 4.5; on the other hand, if yours is a cold region with sunshine, consider GPK to be 3, or check with your local solar installer for the right amount.
The Array Size in the formula is above the solar system size that you require to meet all your electricity requirements.Note however that meeting all your electricity requirements through rooftop solar PV panels alone will in most cases require the use of batteries, for the simple reason that the sun doesn’t shine at night.