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Solar Load Calcs: Definitions & Examples Provided

Dive into the world of solar load calculations, crucial for efficient solar system design. This blog post explores different types and provides practical examples for each.

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    When planning a residential solar project, a crucial part of the process is understanding and correctly calculating your energy needs. These calculations, known as solar load calculations or better known as just “load calcs” are fundamental to designing an efficient and effective solar system as well as better permit submittals. This blog post will delve into different types of load calculations and provide examples for each:

    General Load Calculation

    General Load Calculation involves computing the total energy consumption of a home or building. It encompasses all power-consuming components such as electrical appliances, HVAC systems, and lighting.

    Example: If a home has 10 light bulbs each using 60W for 5 hours daily, 1 refrigerator using 150W constantly, and an HVAC system using 3kW for 4 hours daily, the total daily energy consumption would be:

    (10 bulbs x 60W x 5 hours) + (1 refrigerator x 150W x 24 hours) + (1 HVAC system x 3kW x 4 hours)
    = 3000Wh + 3600Wh + 12000Wh = 18,600Wh or 18.6kWh

    Peak Load Calculation

    Peak Load Calculation estimates the maximum load at any given time. It’s key for determining the required peak power output of your solar system to meet demand during periods of highest usage.

    Example: If all appliances in a house are simultaneously turned on and consume a total of 6kW, then the peak load is 6kW.

    Seasonal Load Calculation

    Seasonal load calculation accounts for varying power demands throughout different seasons of the year. Solar output can vary depending on the season, so this is crucial for your solar panel system design.

    Example: If a home uses 30kWh daily during summer (due to air conditioning) and 20kWh during winter, a solar system should be designed to meet the higher summer load.

    Future Load Calculation

    If you’re planning to add more appliances or electrical systems to your home or foresee an increase in your electricity usage, you should account for your future load calculations.

    Example: If you plan to purchase an electric vehicle that requires 10kWh per day for charging, add this amount to your current daily energy consumption.

    Backup Power Load Calculation

    If you’re installing a battery backup with your solar panel system, do the backup power load calculation that you want the backup system to support in case of a power outage.

    Example: If your critical loads (e.g., refrigerator, lighting, and HVAC system) consume 3kW, then your backup system should be designed to supply at least 3kW.

    Solar System Sizing Calculation

    Based on your load calculations and factors like the amount of sunlight your location receives, you can determine the solar system sizing calculation and number of solar panels needed to meet your energy needs.

    Example: If your total daily energy consumption is 18.6kWh, and you receive 5 hours of peak sunlight daily, you would need a solar system with a capacity of:

    18.6kWh / 5 hours = 3.72kW


    The tilt and orientation of your solar panels can significantly impact their output. Calculating the optimal angle and direction (usually towards true south in the Northern Hemisphere) maximizes the panels’ exposure to sunlight.

    Example: If you live at a latitude of 40 degrees in the Northern Hemisphere, a good starting point for the tilt of your solar panels would be 40 degrees.

    Solar Irradiance Calculation

    The solar irradiance calculation involves calculating the average amount of solar radiation that hits your geographical location. This data allows for a more accurate estimation of the potential energy generation of your solar system.

    Example: If your location receives an average solar irradiance of

    5 kWh/m2/day, and your solar panel’s area is 2 m2, then the potential energy generation is:

    5 kWh/m2/day x 2 m2 = 10 kWh/day

    Battery Sizing Calculation

    If you’re incorporating battery storage into your solar system, the battery sizing calculation is required to store the necessary amount of energy. This usually depends on your energy usage during peak and off-peak hours, and the amount of backup power you want in case of a power outage.

    Example: If you need 10kWh of energy storage for nighttime use, and you’re using a battery with a Depth of Discharge (DoD) of 80%, the required battery capacity would be:

    10kWh / 0.80 = 12.5kWh

    Understanding these load calculations is essential for creating an efficient, cost-effective, and sustainable solar panel system. It’s recommended to work with a professional solar planner or use specialized solar design software to ensure accuracy.

    Let SolarPlanSets Handle Your Plan Sets

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