How Many Solar Batteries Do I Need?

How many solar batteries are needed to power a house

Determining the number of home batteries you need can be a daunting task. If the battery capacity isn’t sufficient for your home, you risk running out of power. But getting too many batteries is not much better either, as it adds unnecessary costs and maintenance to your solar system. 

However difficult it may seem, sizing your solar battery storage is an essential part of planning your off-grid solar system. Fortunately, you can rely on the leading solar panel installers in Mira Mesa, CA and its surroundings to help you determine the right number of solar batteries for your home. Read on. 

How many solar batteries are needed to power a house?

The size and capacity of your solar battery storage will depend on several factors specific to your particular situation. These are: 

1. Your energy consumption 

The energy consumption of your household is generally measured in kilowatt hours. In order to calculate the total consumption, you can either calculate the energy usage of all appliances in your household and add them up, or look at your electricity bills from the previous months to estimate your daily consumption. 

2. Days without sunshine 

The number of days your solar system will have to run without sunlight is a crucial factor in properly sizing your battery storage. For instance, if you live in a rainy or cloudy area, you will have to purchase a battery that has sufficient capacity to power your panels until the clouds clear away. 

This is known as days of autonomy: if your battery has two days of autonomy, that means that it can power your panels continuously for two days on a single charge. Most solar batteries fall into the 2-5 days of autonomy range. 

3. The battery you choose  

Different types of solar batteries have different characteristics and sizing requirements. In most cases, homeowners choose between lead acid and lithium-ion batteries. For the most part, lithium batteries tend to be more efficient and have a greater DoD (depth of discharge). 

This means that lithium batteries waste less power and allow you to use more of your battery’s capacity. For example, most lead acid batteries have a DoD of only 50% whereas a lithium-ion battery can boast a DoD of as much as 95%. 

How do you calculate solar battery capacityHow do you calculate solar battery capacity?

In order to properly size your battery, you will need the following information:  

  • How much energy you need on a daily basis 
  • How many days of autonomy the battery has to have 
  • The maximum battery power (DoD) 
  • The inefficiency factor 

Let’s say you want your 80% DoD battery to last for 3 days without charging and your daily energy consumption is 10 kWh. The calculation should go like this: 

  • 10 x 3 x 1.2 (80% DoD) x 1.05 (inefficiency factor) = 37.9 kWh 

This number represents the amount of energy you’ll need from your solar batteries. You can then divide this amount in watt hours with your system’s voltage (12, 24, or 48V) to get the amp hours (AH). Dividing this number by your battery’s rating will give you the number of batteries you should get for your home. 

Let skilled solar panel installers design your off-grid system in Mira Mesa, CA 

Why deal with all the tedious battery sizing calculations when you can leave the whole process to professionals? Whether you want to know how many batteries you need or wonder if you can use car batteries for solar, don’t hesitate to reach out to Action Solar. 

We are a long-standing solar company serving Mira Mesa and the rest of San Diego County. If you are ready to go off-grid and gain energy independence with the help of skilled professionals, reach out to us today!