Can I calculate string sizing based on daily energy consumption?

Calculating Daily Energy Consumption

To calculate string sizing, start by determining your daily energy consumption in watt-hours (Wh). This can usually be found on your energy bill or by monitoring your usage with a smart meter. For example, let’s say you have a household with a daily energy consumption of 20 kWh (enough for a refrigerator, lights, and some appliances).

Determining Peak Sun Hours

Next, you’ll need to determine your peak sun hours (PSH) per day, which is the number of hours the sun shines brightly on your solar array. This value varies by location and time of year, but a typical range is between 4 and 7 hours. In this example, let’s assume you live in a region with 5 PSH.

Sizing Your Solar Array

Now that you have your daily energy consumption and peak sun hours, you can calculate the required solar array size. Divide your daily energy consumption by the number of peak sun hours to determine the required array size in watts. For this example, 20 kWh / 5 PSH = 4 kW. To ensure safe and efficient operation, you’ll want to add a 25% margin for voltage drop and other losses, making the required array size around 5 kW.

Understanding System Voltage and String Sizing

When sizing your solar array, it’s essential to consider your system voltage and string configuration. Most residential solar systems operate at 240 or 480 volts. A general rule of thumb is to limit your string current to around 12 amps for 240-volt systems and 24 amps for 480-volt systems. For a 5 kW array, you might consider splitting it into two or three strings, depending on your available roof space and desired string voltage.