Solar panels without batteries are a flash in the pan. They can only supply power until solar rays approach them. During the night or on cloudy days, you will need a reliable power backup that can fulfill your power needs. That is where solar batteries come into the scene.
But how many solar batteries are needed to power a house? The answer to this question involves a multi-pronged strategy. For a basic understanding, this depends on your energy needs. However, additional factors like the availability of peak sun hours and your goal for the solar system could also come into play.
To help you understand everything, this piece will comprehensively discuss solar batteries, their types, what will be suitable for you, how many batteries you will need, and how you can maximize your savings through solar batteries.
What Is a Solar Battery?
Simply put, solar batteries are a crucial component of a solar installation that ensures a reliable power supply. These devices are paired with solar panels to store any extra power they produce.
This stored power is used later, at night or during periods of low solar radiation, when your solar panels' ability to generate electricity diminishes.
Their fundamental purpose is to help you reap the maximum from your solar setup. Without them, your system will be half a loaf. This means your panels are generating power, but because you don't have any storage options, this will eventually be wasted.
Types of Solar Battery
Since the invention of the battery, dozens of its variables have surfaced in the market, each with specific pros and cons. However, in today’s scenario, four battery types are commonly used.
Below is their brief discussion, that will help you differentiate among them and choose what aligns best with your needs.
Lead Acid
These were once the most commonly used battery types in industrial and automotive installations. Their use shrunk due to their low power storage capacity, added by their short life spans. However, technological advancements have improved their shelf life.
Lead acid batteries are good to go for individuals with limited budgets as they are cost-effective.
Lithium-ion
These are modern derivatives of batteries, with multiple benefits and limited disadvantages. They are used everywhere, from small gadgets like mobiles and laptops to the heavy-duty automobile industry.
Along with other benefits, what makes them exceptional is their high discharge rates. This means you can utilize most of the stored energy before recharging. However, their high price tags could be a concern for individuals.
Nickel-cadmium
Nickel-cadmium batteries are highly durable, require very little maintenance, and can function effortlessly at extreme temperatures.
However, due to the high toxicity associated with cadmium, their use is rare in common households. Their applications are more suitable for industrial installations, specifically in airlines.
Flow batteries
As their name indicates, flow batteries involve the use of an electrolyte liquid that flows between its two chambers. Compared to their other counterparts, their efficiency is exceptional as they offer 100% discharge depth.
However their low energy density is a barrier to their widespread use. Further, their high costs rendered them unsuitable for household usage.
What Type of Solar Battery Should I Choose?
Lithium-ion or LiFePO4 batteries are more recommended to be used for a solar setup. This is due to their fast charging, extended battery life, and high power storage capacity.
Lithium batteries, especially those offered by BLUETTI, recharge in two stages. These include fast charge and trickle charge. In the fast charge phase, the battery quicky recharges from 0 to 80%, then starts the trickle phase, which is relatively slow and includes recharging from 80 to 100%.
In the case of BLUETTI LiFePO4 battery, the first stage took around 1 to 2.5 hours. This means, that even if you have very low peak sun hours, your battery will charge enough to fulfill your power needs.
Additionally, the recharging process for these batteries is simple. You can recharge them without 100% emptying the battery, and one charge cycle will count only when you use 100% of the battery, even at different intervals, like 60% at one time and 40% at another time.
Further, their high discharge depth offers you access to more of your stored energy, making them a highly suitable option for solar installations.
How Many Solar Batteries Are Needed to Power a House?
Calculating how many batteries are required to power a house could not be acquired through any mathematical calculations. This is because the power usage varies from house to house. Additionally, it depends on your solar setup preference. You could use it as a backup option or completely live off-grid.
Below is a comprehensive discussion of various factors that can help you with your estimates.
Your goal for solar installation
Individual’s choices for their solar setup vary from person to person. You can go completely off-grid, use it for energy bill cost cuttings, or ensure a power backup in case of outages. In all these cases, the battery requirement would be different from that of others.
If you are going completely off-grid, you will need a strong power backup to ensure a reliable power supply for all your home appliances. In other cases, your use cases are temporary for some hours thus a small number of batteries could also serve the purpose.
Battery specifications
The power required by the appliance is measured in watt-hours or kilowatt-hours. In contrast, the battery current supply is usually given in amps and Voltages. In such a scenario, matching your appliance's compatibility with the battery’s output capacity could be daunting.
So, to make things easy, you can convert amps and Voltages into watt-hours by multiplying them. No, you can arrange your battery according to your appliance's wattage requirements.
Amps X Volts = Watts
Watts / 1000 = Kilowatts
How Many Batteries Do You Need For Your Home Solar System?
There are different sizes of solar systems available, varying in output capacity. Usually, for a common household, it ranges between 3kWh and 15kWh. Before we calculate batteries for your home solar system, below explained are some important terms regarding this.
- Discharge depth: DoD, or Depth of discharge, is the maximum power you can use from your battery. It’s different for every battery type. and lithium-ion batteries are the most commonly used home solar setup batteries, with DoDs of 50% and 90%, respectively.
- Efficiency ratings: There is a loss of current while charging and discharging. Thus, the actual power available for use is the battery efficiency. A battery that has less energy lost during its operations will have a higher efficiency rating.
Now, below are step-by-step details for calculating how many batteries you will need for your home solar system.
Understand your energy requirements
This is the most crucial requirement while calculating the number of batteries for your solar setup. The more your power needs are, the more batteries should fulfill them.
A home's electricity requirement is measured in kWh. You can evaluate your energy consumption by checking your monthly bills. Look for the total monthly power consumed in kWh, divide it by 30, and you will get your daily electricity requirements.
Which battery type you are going to use
Each battery has a different DoD and efficiency, so it's necessary to opt for a battery typer prior to checking their compatibility with your solar system. Below are details for the two most commonly used batteries for home solar setups.
- Lead-acid: These batteries' Dod is around 50%, and because around 40% of their energy is lost during operations, the efficiency factor we use for them is 1.2.
- Lithium Ion: They come with a DOD of around 80% or more and their efficiency factor is around 1.2 as only 20% of power is lost during their operations.
Calculating the batteries
According to some stats, the average American household consumes 30kWh of power daily. Based on that number, we can calculate the batteries required using the equation below.
Battery capacity required = Dalily power usage X DoD X efficiency ratings
Using a lead acid battery
Battery capacity required = 30kWh X 2 (For 50% DoD) X 1.2 (efficiency ratings)
Battery capacity required = 72kWh
Here are the calculations for the battery size in Ampere hours.
Battery capacity required = 72/12 X 1000 = 6000 Ah
Using a lithium-ion battery
Battery capacity required = 30kWh X 1.2 (80 % DoD) X 1.05 (efficiency ratings)
Battery capacity required = 37.8 kWh
After conversions into Ah
Battery capacity required = 37.8 /12 X 1000 = 3150 Ah
So, for a 30kWh solar system, you will need 30, 200Ah lead-acid batteries and 16 lithium-ion batteries. It's important to note that the above calculations are average figures based on total off-grid living. The battery requirement will be lower for a grid-tied system.
How Can I Maximize My Savings with Solar Batteries?
Solar batteries require significant upfront costs. Thus, it's crucial that you get the most out of your investments. However, it requires a prudent approach. Here are some steps you can follow to maximize your savings with solar batteries.
Ensure their usage time
The fundamental purpose of solar batteries is to store energy that can be later used during non-sun hours. Ensure that, in the daytime, you are using power directly produced by solar panels and that your batteries are charging at their maximum potential.
Leveraging the peak bill hours
If your solar setup is grid-tied, take advantage of peak billing hours. Most power supplies bill depending on electricity use during different times of the day. This means they charge more rates when the demand for electricity is higher, which is usually between 8-10 AM in the the morning and 6-10 PM at night.
Do not use grid power and rely solely on your batteries during this time. This could help you cut significant amounts on your energy bills.
Selling energy back to the grid
You can also earn money by selling electricity back to the grid. Use energy-efficient products like LED bulbs and smart appliances that save electricity. This will yield extra power that could eventually be sold back to grid stations.
Best BLUETTI Solar Batteries Recommend
Choosing a battery that is efficient, compatible, and can help cut the cost of your overall solar setup is difficult. So, to help you out with this, below are recommendations for our two variables. They are most recommended for medium to large home solar setups.
BLUETTI EP800+B500 Home Battery Backup
This LiFePO4 unit has an immense power storage capacity of 9920Wh. To ensure it goes a long way with you, it offers 4000+ charge cycles. This means, that with one charge cycle per day, it has a shelf life of more than 11 years.
With its 7600W output, it ensures reliable power for almost all your home devices. With its 9000W solar input, you do not have to worry about the charging running out. Additionally, you can also charge it through a traditional AC port during non-peak hours.
While price is a fundamental concern, purchasing this unit will give you a 30% Federal Tax Credit, which is a savings of around 2500$. For safety, you can rely on its Battery Management System (BMS), which offers smooth operations during high and low temperatures.
BLUETTI EP900 + B500 Home Battery Backup
Imagine you buy a product and later find the same spec product at a low cost. You complain to your product brand, and they return the extra cost. This is true with EP900 + B500, as this unit has a price match guarantee.
Its built-in storage capacity is 9920Wh, which can be expanded up to 19840 Wh. The unit is compatible with all your appliances, whether 120V or 240V. Do you have a limited indoor installation space? Don’t worry. We have also you covered here. You can install this system even outside. With IP65 water resistance, it is totally safe both indoors and outdoors.
10-year overall warranty to secure your investment, Battery Management system for safety, smooth operations through the BLUETTI smart app and Bluetooth, and compatibility with your new and existing solar setups. Indeed, this unit is a go-to choice for all your power backup needs.
Final Thoughts
Solar batteries are a no-skip part of any solar installation. They make your solar setup reliable and ensure a continuous household power supply. However, to decide how many batteries would be perfect for your home, it is crucial to set your goals right.
While these power backups have high initial costs, it's important to make wise and careful decisions when opting for them. BLUETTI batteries, with their strong reputation across three continents, are not only reliable and efficient but could also help you save a significant amount on your upfront costs.
