Sizing Off Grid Solar Systems

Short on Time? Here’s The Article Summary

The article discusses the trend of off-grid living, where individuals disconnect from utility companies and the electric grid. It highlights that off-grid living is not just for those in remote areas, as people in urban areas are also making the switch, particularly with off-grid solar power. It mentions that 39% of Americans are considering off-grid solar power due to its cost savings and renewable nature.

To calculate the size of an off-grid solar system needed, the article recommends listing all appliances and their wattages, calculating daily energy usage, and understanding peak sun hours for the location to estimate solar energy collection. It suggests purchasing solar panels with sufficient voltage for energy needs and building a battery bank with the capacity to store enough energy for times of reduced sunlight. Lead-acid batteries typically have a 50% Depth of Discharge (DoD), while lithium-ion batteries have 80%-90% DoD, affecting the usable capacity of the battery bank.

Introduction

Off-grid living is no longer defined by self-isolation and foraging for grasshoppers, roots, and wild honey. It's a relationship status. 

You read that correctly. Going off-grid means ending your relationship with utility companies and breaking up with the electric grid and the public water and municipal sewer systems. 

People are leaving the grid in droves. It doesn't matter if you're a country or city mouse. Wherever you're at, it's possible to get off the grid, especially with electricity.

Independent electricity is the most common off-grid utility because there are fewer legal regulations for independent energy than for water or sewage. Off-grid electricity also leads to massive savings because you're consuming renewable resources. That's why 39% of Americans are seriously considering off-grid solar power. 

Stop right there. Before calling your energy company to break up, figure out what size off-grid solar system you need to power your home right. 

How To Calculate Off Grid Solar System Energy

Rising heat levels, natural disasters, and aging grid systems are all causes of the off-grid movement. To be part of it, you must ensure your solar energy system has the capacity to power all your appliances. Thankfully, sizing off-grid solar system panels and batteries is an established process. You just need to know the basics. 

Sizing Off Grid Solar Systems and Estimating Your Energy Needs

First, know what you plan to power. List all the appliances you use regularly. Include air conditioning, refrigerators, ovens, lights, microwaves, electronics, and anything else you rely on to live comfortably. Check the manufacturer stickers and jot down the wattage of each appliance. If it doesn't have a sticker, look up the model on the manufacturer's website.

After gathering your wattage, calculate how many hours you use each appliance daily. From there, you'll obtain an average of watts per day. There are helpful online calculators to help get this number. Or call a professional to conduct an energy audit.

Finally, calculate peak usage hours to find what times of day you use the most electricity.

Learn About Peak Sun Hours

Some locations are better for harvesting sunlight than others. Look at a peak sun-hours map to find the average for your location. A peak sun hour is when solar irradiance measures 1,000 watts per square meter. For U.S. residents, the National Renewable Energy Laboratory is a great place to find your location's peak sun hours. 

Understanding peak sun hours helps you estimate the amount of sun you can collect daily. From there, you can discover exactly how powerful a system you need. And remember that shade impacts performance. So, ideally, panels should be installed in areas where no shade is thrown.

Purchase Panels With Enough Voltage

Panels convert sunlight into electricity. But not all solar panels collect energy with the same efficiency. After estimating daily wattage needs, you can choose panels that are powerful enough for your home. 

Typically, panels are 12V or 24V. If your peak wattage hour is less than 1000V, 12V panels will do. But if it's above 1,000V, consider 24V panels. And if you have usage above 3,000V, consider a 48V system. You can now purchase the right size panel array with enough output to meet your needs. 

Build Your Battery Bank

To go completely off-grid, you'll need a battery bank sizable enough to power you through times of reduced sunlight. Ultimately, you need a battery, or batteries, with enough wattage to meet your peak-hour demands. 

To calculate battery capacity, multiply the battery's voltage by its capacity, measured by amp-hours (Ah). For a 12V battery with 100Ah, you multiply 12 by 100 to get 1,200 watt-hours. But remember that batteries only discharge a portion of their total watt-hours. The type of battery, lead-acid or lithium-ion, determines how many watt-hours the battery discharges. This percentage is known as the Depth of Discharge (DoD).

Lead-acid batteries have around 50% DoD, while lithium-ion batteries have 80%-90% DoD. So if your battery has a 1,200-watt-hour capacity, with an 80% DoD, it can only discharge 960 watt-hours. Always consider this when sizing off-grid solar system battery banks. 

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