Sizing Your Off-Grid Solar System: Step-by-Step Guide
How much power do you need? Take stock of your daily energy usage. The more you use, the bigger your system needs to be. Where will the panels go? Find the sunniest spot
Now that you know your daily energy use and sun hours, it's time to calculate how large your solar array needs to be. Formula: Total Daily Use (Wh) ÷ Sun Hours × 1.25 = Solar Array Size (W) The “× 1.25” accounts for system inefficiencies (inverter losses, shading, panel age, etc.) Example: 1,460 ÷ 5 × 1.25 = 365W
This isn't our first rodeo - we have a similar install video of our much larger, more complicated DIY solar system - it has 10kw of solar, 28kwh of lithium battery storage, and 5000w of 120V AC power. We'll be referring to this project a lot as it informed a lot of the decisions we've made for this system.
This will decide everything about your PV setup, from the inverter down to the solar panels you buy. Small systems, such as those on an RV or boat, should use 12V systems, while larger solar arrays do best with 24V. A good rule of thumb is that if your energy needs are less than 1,000 watts, go for a 12V system.
Formula: Total Daily Use (Wh) ÷ Sun Hours × 1.25 = Solar Array Size (W) The “× 1.25” accounts for system inefficiencies (inverter losses, shading, panel age, etc.) Example: 1,460 ÷ 5 × 1.25 = 365W That means you need a solar array rated at around 365 watts to meet your needs reliably. Next, choose your panel type.
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