How Many Solar Batteries Do I Need? A Complete Guide

Investing in a solar battery bank can be a great way to gain energy independence and, over time, reduce your utility bills. Whether you’re vaguely familiar with solar power or want to learn more about it, our comprehensive guide can help you get started.

Why Your Home May Need a Solar Battery Bank

Solar battery banks absorb the excess energy generated by solar panels, and store it for use at a later date. This lets you use only what you need in a given moment while replenishing your personal energy stash. These banks offer a versatile energy system that’s completely independent of more traditional power grids and can serve as an excellent main and backup power source.

Solar battery banks can optimize solar panel usage and energy consumption to provide a stable, affordable source of reusable energy year-round. It can also help lower your utility bills and even give you the freedom to go completely off-grid. They’re available in different sizes and capacities to meet a wide range of energy storage needs.

Determining Your Home’s Energy Needs

Before buying solar battery banks in bulk, you’ll need to:

1. Calculate your home’s daily energy consumption
2. Understand how many peak sun hours are in your area
3. Consider days of autonomy

How to Calculate Daily Energy Consumption

To start, make a list of the major appliances you’ll need in a power outage and how many watts they consume. You can usually find this information on the appliance’s label, but, if you’ve misplaced it, the manufacturer’s website may have it listed. You’ll need to multiply the appliance’s watts by the number of hours you plan on using it.

Formula: # of watts X # of hours = # of watt-hours (Wh)

After calculating the kWh for each major appliance, add those totals together to learn your total daily energy consumption. When dealing with larger devices, it’s more practical to use kilowatt-hours (kWh) since one kWH is the same as 1,000 Wh.

To convert between Wh and kWh, add all of the Wh values and divide the sum by 1,000.

Exploring Peak Sun Hours

Peak sun hours are the hours when the sunlight’s intensity reaches an average of 1,000 kilowatts per square meter. Normally, there are five peak sun hours every day, but this number can vary depending on your location. Knowing how many peak sun hours there are in your area can help you estimate how much electricity your solar panels can produce.

Let’s say you have a 500-kilowatt panel but live in an area with only 3 peak sun hours. To determine your kWh, you’ll multiple the watts by hours.

Knowing how many peak sun hours are in your area can determine the size of panels you’ll need, how many you’ll need, and how much energy they produce. For example, if you’re in an area with fewer peak sun hours, having larger or multiple smaller panels can help you better optimize these hours.

Always be mindful of the weather as cloudy, rainy, and stormy days can reduce the number of peak sun hours available.

Estimating Your Days of Autonomy

Days of autonomy is how long your solar battery bank can power your home without needing to be recharged. To calculate this, you should calculate your daily usage in kWh and decide how many days you want energy without sunlight. Multiple the days by your daily usage to determine the storage capacity you’ll need.

Formula: # kWh per day X # days = # kWh of storage required

How Many Batteries Does Your Home Actually Need?

The number of batteries you’ll need to power your home depends on your daily energy use, peak sun hours, days of autonomy, and the kind of battery you choose.

While energy use is typically calculated in kWh, battery capacity is calculated using ampere-hours (Ah) and voltage. To identify the battery capacity in Wh, multiple Ah by V.

Formula: Ah x V = Battery capacity Wh

Convert the battery capacity to kWh by dividing Wh by 1,000 to simplify the math ahead.

When determining how many batteries you’ll need, divide the total storage needed by the battery capacity.

Formula: Storage need kWh ÷ Battery capacity Wh = # of batteries

Let’s say you use 3 kWh each day and want 3 days of autonomy.

3 kWh per day X 3 days = 9 kWh

You need 9 kWh of storage, but the batteries before you have a capacity of 1.1 kWh each.

9 kWh ÷ 1.1 kWh = 8.18 batteries

If the number of batteries isn’t a whole number, round up to ensure you have enough storage space. So, in the above example, we’d need to buy 9 batteries.

Choosing the Right Type of Solar Battery for Your Home

The 4 dominant types of solar battery banks are lead-acid, lithium ion, nickel cadmium, and flow batteries. Since the most efficient batteries for homeowners are lead-acid and lithium ion batteries, we’ll focus solely on those.

Understanding the characteristics of these two battery types can help you choose the best fit for you.

Lead-Acid Batteries

This cost-effective option has been a reliable option for decades. They’re easy to recycle and have a lower upfront cost than other models. Although lead-acid batteries have a shorter lifespan and require regular maintenance, advancements are constantly being made to expand their battery lives.

Lead-acid batteries tend to have a lower depth of discharge (DoD), which requires them to be recharged more frequently. Put another way, once half of the battery’s energy is used, it should be recharged to maintain an optimal lifespan. Using too much energy can cause sulfation inside of the battery, which decreases battery life and performance.

This could cause you to burn through batteries much faster than anticipated, and become costly over time.

Lithium Ion Batteries

These batteries are much smaller, lighter, and efficient than lead-acid batteries. They’re a more modern design that can last up to 10 years, which makes them a more popular option. Although they have a much higher upfront cost than lead-acid batteries, you can go longer periods of time between charges without damaging the battery’s lifespan and compromising performance.

To really make the most of each battery’s lifespan, consider investing in a battery box. This can protect your batteries from environmental damage — like extreme temperatures or humidity — and prevents safety risks should they start to leak.

Cost vs. Benefit: Is a Solar Battery Bank Right for You

Investing in a solar battery bank can have a significant upfront cost, but you do not have to foot the bill alone. Federal, state and local governments offer tax credits, incentives and grants to homeowners interested in switching to solar battery banks. In fact, U.S. homeowners can write off 30% of solar energy installation costs on their taxes under the federal solar tax credit.

If you’re a solar system owner, you can be paid for the excess power you generate through our solar Renewable Energy Credits (SRECs). It’s an automated process that allows you to earn money with no additional effort.

How to Get Started with a Solar Battery Bank

Don’t trust just anyone with your solar battery bank needs. Make sure the installers you’re considering have the proper certifications, experience and a positive reputation. Look for reviews and ask for references to ensure you’re working with a reputable company. Once you create a short list of brands you like, schedule your consultation.

To have a more productive discussion with the installer, here are a few things you can figure out before the meeting:

1. Current energy usage
2. Energy goals
3. Ideal budget (including tax credits)
4. Local regulations

Make a list of questions and concerns you want answered during the consultation, and bring it to the consultation as well. Keep an open mind to the installer’s recommendations, but don’t hesitate to shop around until you find an installer you feel best suits your needs.

Looking for a solar battery bank installer in Maryland? We’ve got you covered. Schedule your free solar estimate today to get started!