How to Choose the Correct Size of Home Battery for Your Solar System
Published on: 07/08/2023 · 6 min read
Home batteries are an essential part of any solar system, as they allow you to store excess solar energy to use when the sun is not shining. However, not all batteries are created equal, and the size of the home battery you need will depend on a number of factors.
In this article, we will discuss how to choose the correct size home battery for your solar system. We will cover the following topics:
- The factors that affect the size of your home battery
- How to calculate the size of your home battery
- Examples of home battery sizes for different solar systems
- Tips for choosing the right home battery size
Factors that Affect Home Battery Size
The size of your home battery will depend on several factors, including:
- Your solar panel system's capacity: The larger your solar panel system, the more energy it will generate, and the larger home battery you will need to store that energy.
- Your daily energy usage: Analyzing your daily energy consumption during the day and night in kilowatt-hours (kWh) will help in sizing the home battery.
- The depth of discharge (DoD) of your home battery: The DoD is the percentage of the home battery's capacity that you can use before it needs to be recharged. Understanding both DoD and home battery efficiency is crucial.
The capacity of your solar panel system is the amount of energy it can generate in a day. The larger your solar panel system, the more energy it will produce. For example, if you have a 5 kW solar panel system in Belgium, with an average of 4 hours full sunlight , your system will produce approximately 20 kWh per day.
The amount of energy you use on a daily basis will also affect the size of the home battery you need. A typical Belgian household might consume around 10 kWh per day.
If you want your system to provide energy during cloudy days or unexpected outages, consider how many days of backup you need. For 2 days of backup for a home consuming 10 kWh per day, you would need a 20 kWh home battery, considering the efficiency and DoD.
The DoD and home battery efficiency are essential factors. A home battery with 90% efficiency and 80% DoD will provide 72% of its rated energy (90% efficiency * 80% DoD). For a 12 kWh home battery, this means the effective energy available would be 8.64 kWh.
If you want to reduce energy bills and avoid selling during the day at cheap prices and buying at high prices from the grid during the night, we can size the home battery differently. For instance, if your solar system produces 8 kWh of excess energy during the day and you typically consume 5 kWh at night, a 5 kWh home battery would be an ideal choice. This way, you can store the excess energy generated during daylight hours for use at night, aligning your energy consumption with solar production and avoiding higher grid costs. This tailored approach to home battery sizing ensures you maximize savings and efficiency in your solar system.
Calculating the Size of Your home battery
Calculating the correct size of your home battery is a multi-faceted process that depends on your particular needs. Here's how to approach it for two common purposes:
For Backup: Calculate the size based on the daily energy usage multiplied by the number of days you want backup power, considering the home battery's efficiency and Depth of Discharge (DoD).
Formula: Home Battery Size (kWh) = Daily Energy Usage (kWh) * Number of Days of Backup Power * Efficiency * DoD
To Reduce Energy Bills: Consider how much excess energy is generated during the day that you would like to store for nighttime usage. The home battery size should match this excess generation.
Formula: Home Battery Size (kWh) = Excess Energy Generated (kWh)
Examples of home battery Sizes for Different Solar Systems
The following examples demonstrate how home battery sizing varies based on your solar system's capacity and daily energy consumption:
A 5 kW solar system with a daily energy usage of 4 kWh needing 2 days of backup would need a home battery with a size of 10 kWh (considering efficiency and DoD).
A 10 kW solar system with a daily energy usage of 8 kWh needing 2 days of backup would need a home battery with a size of 20 kWh (considering efficiency and DoD).
A 15 kW solar system with a daily energy usage of 12 kWh needing 2 days of backup would need a home battery with a size of 25 kWh (considering efficiency and DoD).
To Reduce Energy Bills:
If a 5 kW solar system produces 4 kWh of excess energy during the day and you consume 4 kWh at night, a 4 kWh home battery would be suitable.
If a 10 kW solar system produces 8 kWh of excess energy during the day and you consume 8 kWh at night, an 8 kWh home battery would be suitable.
If a 15 kW solar system produces 12 kWh of excess energy during the day and you consume 12 kWh at night, a 12 kWh home battery would be suitable.
These examples illustrate the importance of defining the purpose of your home battery when determining the correct size. Whether for backup or reducing energy bills, understanding your specific needs and daily consumption patterns is key to selecting the right home battery for your solar system.
Tips for Choosing the Right Home Battery Size
- Oversizing your home battery is not always a good idea, as it will increase the cost of your system.
- If you are not sure how to calculate the size of your home battery, you can consult with a solar installer or a trusted provider like EmaxSolar.
- Consider the DoD of your home battery when choosing a size, and also assess compatibility with the existing inverter in your home.
EmaxSolar offers top-of-the-line batteries from industry leaders such as Huawei, Pylontech, SolarEdge and BYD. Price fluctuates a lot and it varies with the size and type of batteries. Here's a table for your reference:
|Huawei ||5 - 25 kWh ||Starting at €5,000 ||5-6 years|
|Pylontech ||3.55 - 21.3 kWh ||Starting at €3,500 ||5-6 years|
|SolarEdge ||3.8 - 15.2 kWh ||Starting at €3,800 ||6-7 years|
|BYD ||10.24 - 22.08 kWh ||Starting at €7,000 ||5-6 years|
The choice of a home battery must be compatible with the existing inverter in your home. Here's why:
- Matching Specifications:The home battery voltage and capacity must match the inverter's specifications to ensure efficient energy conversion.
- Brand Compatibility:Certain inverters may have better compatibility with specific brands like Huawei, SMA, SolarEdge, Solis, Enphase, Goodwe or Growatt. EmaxSolar’s experts can guide you in making the best match.
- Hybrid Options:Considering a hybrid inverter that combines a solar inverter and home battery inverter can be an efficient choice for new installations.
Choosing the correct size home battery for your solar system is an important decision. By considering the factors that affect home battery size and following the tips above, you can choose a home battery that will meet your needs and provide you with reliable power for years to come. Partnering with EmaxSolar, a leading name in solar panel and home battery installation in Belgium, ensures that you make an informed choice. Whether investing in a home battery right away or later, our expert team is here to guide you every step of the way. Contact us today to take the first step towards a sustainable future with a tailor-made solution!