How to Obtain True Energy Independence - A Battery Sizing Guide
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How to Obtain True Energy Independence – A Battery Sizing Guide

Going off-grid is a great way to meet your energy needs if you live in a remote location, want to be energy independent, save money on monthly utility bills, and live a sustainable lifestyle. The efficiency of the off-grid solar system continues to rise, making off-grid more feasible for more individuals. Choosing the best off-grid solar system is not easy as off-grid systems are many times more complicated than common grid-connected solar systems. In this article, we highlight some of the many considerations which must be taken into account and discuss the various steps in sizing an off-grid system.

The 5 main parts of an off-grid system are battery, solar inverter (AC), battery bank, solar panels and/or a generator. Off-grid systems are built using either AC or DC coupled power sources. AC-coupled storage using these new technologies – high voltage batteries (i.e. > 120V DC) – that can turn any existing system into a “battery ready” system and offer a lower-cost solution. By contrast, DC-coupled storage uses what is commonly referred to as a hybrid inverter, where both the solar and battery are connected to the same inverter.

Most importantly, if you are installing a new solar system but want to wait a few years to install batteries, AC-coupling with High Voltage batteries will allow you to do this at a lower cost in the future compared to choosing a DC-coupled hybrid inverter now and buying batteries later. This is because in the years between installing your battery-ready PV system and buying your batteries, technology would have gotten cheaper for both the inverter and the battery. For example, if you had invested in a hybrid inverter in 2014 and decided to buy batteries in a few years, you would not have been able to take advantage of newer and lower-cost battery solutions.

With AC-coupled storage, you can take advantage of such future developments because the solar and battery systems are independent of each other. AC-coupled storage can allow you to have maximum grid independence compared to a hybrid inverter solution since you are able to supply loads in your home from both the solar and battery simultaneously.

Whether a system is AC or DC coupled, sizing of the system is very important and can significantly affect the system’s performance. In this article, we dive into the step-by-step procedure to size an off-grid system.


Step 1 – Determining the Power Consumption

The primary step is understanding the power consumption of your building. For that, the power each device consumes need to be put together. For example, consider a building having 5x 10 W lightbulbs, a 350 W fridge, 1500 W pump. The total power consumption of the building comes to be 1900 W. We simply added all the equipment together to determine the total power consumption.

Step 2 – Determining the Energy Consumption

Figuring out the wattage is only half of the equation. You will need to think about how long you plan to use each device as well. The formula to calculate this is device wattage x hours of operation (Wh=watt x hours). For example, consider a 500 W equipment on for 5 hours. So total energy consumption is 500 W x 5 which is equal to 2500 Wh. Hence, you will need 2500 Wh of battery capacity to have 5 hours of usage

Step 3 – Finding out the Required Solar Power to Keep Your Batteries Charged

The next step is to determine how often the battery will be in use. The formula is Wh/number of days to find the Wh per day. From there, the wattage of panels required can be calculated by dividing WH per day by the number of hours of sunshine. Say, the energy consumption is 2500 Wh per week. This comes to 357 Wh/day (2500 Wh/7). From there, 357 Wh / 5 hours of sunlight brings us to 71 watts of solar panels requirement

Off-Grid Home Example

Consider a home that uses 10,000 Wh per day (10 kWh). For the home to be grid-independent for 2 days, we multiply the energy consumption by the number of days to get 20 kWh. With a 4000 Wh lithium-ion battery, we’d need 5 batteries to support this system.

Taking the number of hours of sunlight per day as 6, we divide the 2-day energy consumption by this value (20,000 Wh /6 hours) to get 3333.33 W. Utilizing 480 W rated panels, the total number of required panels for this system is 7 (3333.33 W/ 480 W = 7).  Hence this home would need 7 x 480 W panels and 5 x 4000 Wh battery to successfully go off-grid.


Installing an off-grid solar system on your home is a great way to meet your energy needs if you live a remote lifestyle or if you have to be grid-independent. Before you install any solar panels on your roof, make sure you take the time to accurately calculate your energy needs. Once you know how much energy you’re using, you’ll be equipped to build the perfect solar installation for your home.

Our goal at Solar X is to provide you with the information you need to make an informed decision about going solar. Be energy independent, save thousands on energy costs and go green by transitioning to solar today. Use this link to book a complimentary assessment and learn more about the available incentives in Ontario and the value solar can provide to your home!

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