Solar power backup is an essential part of a solar power system that’s intended to keep it running no matter what.
Having backup power — even in unexpected or unforeseen circumstances — will ensure you always have a system to provide power for you and your family.
In this blog, we’ll talk about how backup works when you have solar panels.
1. What is solar backup power?
Battery backup solar PV systems work just like normal generator systems.
When your house cannot use power from the grid or your panels, it will use clean, solar energy that has been stored.
2. How does solar backup power work?
Excess solar power is stored in a battery during daylight hours in order to give you energy independence from both the grid and the sun.
This is because the solar inverter — the hardware that converts a solar panel’s DC power output to AC so your home can use it — automatically switches to battery power to run important loads when programmed.
These loads could include the refrigerator, TV, internet, lights, and power outlets regardless of whether it’s day or night.
When you select certain devices to power on backup power, you extend the number of days your battery can power everything.
For the most part, solar systems use backup batteries.
These systems are designed to bypass interruption when grid-connected systems go down.
3. What are the different types of solar battery backup power?
Not all solar batteries are created equal.
Some are designed for grid connectivity while others are not.
The one you choose will depend on your energy and savings goals.
Off-grid DC-coupled batteries: These batteries are often used with both remote properties and recreational vehicles.
They normally come with built-in inverters that convert direct current (DC) to alternating current (AC) power.
Off-grid AC-coupled batteries: These batteries perform the same basic function as their DC counterparts, but the conversion process occurs before reaching the batteries themselves.
Grid-tied AC-coupled batteries: These batteries are the most popular for residential storage needs.
The inverter technology is already built-in, which makes it perfect for both new PV installations and retrofits.
Note that solar permitting and utility approvals are normally required for grid-tied connections.
Grid-tied DC-coupled solar batteries: These batteries use hybrid (or multi-mode) inverters capable of accepting high voltage loads.
These batteries are often compact, which makes them favorable among homeowners.
However, they are not the best option for off-grid applications.
4. What is UPS and what does it do?
UPS stands for uninterrupted power supply, and it’s a system commonly paired with a solar power system.
UPS is designed to keep household appliances running if the power is out.
UPS systems use solar generators to supply hours of backup power for a household.
A power inverter (DC to AC) and a power converter (AC to DC) are used to store power in a battery system to reproduce it when needed.
Homeowners will use their UPS system and pull on the strength of its batteries to power electrical appliances when the grid is down.
5. What is a backup battery and what does it do?
A backup battery is a safeguard for a solar system.
It’s intended to bypass interruption when grid-connected systems aren’t working so that your household and business can continue to run during an outage.
6. What is a backup generator and what does it do?
A backup generator is a more powerful alternative to a backup battery.
Home backup generators are designed to power energy-intensive systems (think heating and air conditioning) even if the grid goes out.
When you have a generator, you have access to a lot more power than a battery system stores.
Batteries typically only store power while generators produce power.
This means that a building or company would have continuous power even while the grid is out.
If you want to use a generator, you simply need to turn it on after a grid outage.
A generator can also be set to automatically turn on, so you don’t experience any interruptions in your devices.
Having a backup generator often provides peace of mind for both residential and commercial customers.
7. Should I opt for battery backup or a generator?
Either option can be the right option depending on your energy goals.
Keep in mind that both applications will be a considerable investment.
That said, if price and payment are your top priorities then battery backup may be the best way to go.
Below, we’ll review everything you need to know about both batteries and generators so you can determine the right route for your situation.
Solar battery backup
A battery is like having an external hard drive that is also ready to go and backed up.
When the grid or your panels are up and running, the battery will act as your “cloud storage.”
It only ever provides you power when you have maxed out your hard drive.
With that, not all solar batteries are intended for grid connectivity.
There are several different configurations and what you choose will ultimately depend on your energy goals as well as your savings goals.
Check out #3 which outlines the different types of batteries (off-grid or grid-tied) that you can use.
Another consideration is the depth of discharge (DoD).
This is the percentage of discharged power relative to the battery’s total storage capacity.
If a battery can hold 10 kilowatt-hours of solar capacity, a DoD of 75 percent means that you can’t reliably draw more than 7.5 kilowatt-hours of clean energy.
You can think about this like a computer as well.
Modern computers will ship with 500 gigabytes of storage.
However, the operating system and pre-installed programs will take up some of that hard drive space already.
A general rule of thumb is that the higher the depth of discharge the more solar power a homeowner can store and use.
We recommend aiming for depths of discharge that are 95 percent or higher.
Generators
If you’re looking at this as a means of backup power, understand that this is not a solar option.
Generators rely on fossil fuels.
They release CO2 and other greenhouse gases during operation.
A generator uses diesel to provide homeowners with emergency backup power during grid outages.
A side effect of this is that they are smelly and noisy even if they’re idle for most of the year.
There are benefits to this.
For one, diesel generators are mature technology.
This means that they are relatively easy to buy, install, service, and repair.
Regardless of weather conditions, you’ll have reliable power.
Additionally, these generators are often portable, which means homeowners can move them whenever and wherever they need emergency backup power.
If you opt for a generator, you’ll need to maintain it with scheduled servicing, trips to the gas station, and frequent top-ups.
This can be a lot of responsibility for a unit that is only used during the occasional blackout.
Many homeowners find their generator to be a frustrating use of space and resources.
You should also note that diesel generators never pay for themselves.
Generators have ongoing costs (both for the owners and the planet) whereas solar batteries recharge themselves with free energy from the sun.
If you opt for a generator, you’re the person who is going to be in charge of constant refueling which can be time-consuming and expensive.
8. What are the advantages of solar backup power?
There are normally several benefits of solar backup power.
Here’s why you might consider adding a backup system to your solar system.
You could save money: Solar backup power systems are typically eligible for federal tax incentives and allow you to avoid peak utility rates by drawing power from batteries during the most expensive times of the day.
You’re also able to store daytime solar electricity for nighttime use, which allows you to reduce your utility bills overall.
You won’t have to do any additional maintenance (lithium-ion batteries): Lithium-ion batteries are safe, reliable, and do not require maintenance.
You’ll always have power: When you use a solar battery, you’ll have access to clean, free solar power even during power outages.
You’ll know how much power you use: You can choose a cloud-based monitoring platform that permits you to track your home’s energy usage and solar production using an intuitive app that can be used on any personal electronic device or home computer.
Keep in mind that most solar backup batteries have a measurable ROI.
This contrasts with diesel generators that technically never pay for themselves.
If you choose to install a battery, you’ll always have the option of using stored solar electricity before taking power from the grid.
9. What are the disadvantages of solar backup power?
While solar backup power offers a lot of pros, they also come with quite a few cons.
Although prices are declining, solar batteries are relatively expensive, which doesn’t make them an accessible option for everyone.
Solar batteries only last an average of 5 to 10 years.
This means that homeowners often have to replace them at some point during the 25-year lifespan of their solar panels.
Solar batteries may seem eco-friendly on the surface.
However, they often use toxic chemicals, precious metals, or a combination of both.
However, this must be balanced against the benefits of using renewable energy as your power source.
Solar backup power can require additional maintenance depending on the battery storage technology that’s being used.
This includes deep-cycle lead-acid batteries, which require frequent topping up with distilled water.
If you want a “set it and forget it” system, then this may be a deterrent for you.
10. How long will my battery system last?
If you rely on solar backup power during an electric grid outage, you may wonder how long that lasts.
The answer is dependent on your home and what it powers.
When you install a battery, the company you work with can help to answer these questions.
Often, they will create a system in which only your essential devices (i.e., your fridge) are powered.
This way, you can extend the useful life of your system to supply power for a longer amount of time.
11. Do you need solar backup power?
No, you do not need solar backup power or a battery of any kind installed at your home or business along with your solar panels.
However, if you do not have solar backup power, then you cannot refuel a battery without sunlight during a grid failure for later use like you can refuel a diesel generator (if you have access to fuel).
Your solar backup power can be charged from either the sun or grid power.
However, if you go the grid power route then you must remember you’re at the mercy of the utility.
Solar power allows you to charge and recharge your battery maintenance-free.
It also works in all locations around the U.S.
You don’t necessarily need to live in a sunny “hotspot” in the U.S.
There are enough quality sun hours to fully charge a battery anywhere in the U.S.
12. How do you find the right solar battery backup option for you?
It can be difficult to find a solar battery option that works best for you because every homeowner and residential property is different.
The criteria that help people identify the optimal battery technology for their needs are below.
Capacity: How much capacity do you need?
Larger batteries can store more solar power; however, they can also be more expensive.
They’re often attractive to homeowners because they allow you to offset a large portion of your energy bills.
Investing in a solar battery can help you save more money in the long term (if you can afford the initial expense).
Cost: Solar batteries have high price tags.
There’s no way around it.
However, the best way to think about it is through the lens of long-term costs and savings.
Batteries deliver returns with predictable payback periods.
Solar-readiness: You need to make sure the battery you’re purchasing will work with your current PV panels.
Some batteries require a lot of expensive modifications while others work on a nearly out-of-the-box basis.
Know what you’re getting yourself into — you don’t want to take on something you can’t handle.
Design: Your battery is an accessory to your home.
Because many consumers think of it as such, manufacturers have started to ship their products in aesthetically pleasing encasements.
This allows them to blend in well with existing homes.
13. What are two solar battery options to consider?
If you’re looking for solar battery backup power options, here are some currently on the market:
Great for homeowners who are searching for a reliable solar-ready storage solution in an aesthetically pleasing design.
The price for this option is normally around $9,000 to $13,000 depending on the vendor.
These lithium-ion battery that can be paired with a solar panel system.
Users can track power consumption, solar production, and battery levels at any time of the day when they pair it with a SolarEdge inverter and optimizers.
During a power outage, this would still allow the typical American household to power essentials like a bathroom, furnace, refrigerator, etc.
Great for homeowners looking for a versatile battery solution to power essential appliances at night, during grid outages, or during peak hours.
The cost for this option is usually between $6,000 and $7,000 per unit.
Keep in mind that you may require 2 or more connected in series to provide sufficient capacity, which could drive up costs.
This option is quickly becoming the standard go-to for both residential and commercial storage needs.
It’s a fully integrated lithium-ion AC battery system.
It’s shipped in an all-weather encasement plus liquid cooling.
It can be installed indoors and outdoors.
Final Thoughts
Both residential and commercial demand for reliable backup power solutions is continuing to grow.
Solar backup power is a great option if you’re looking to keep the lights on during an outage, want to reduce the peak electricity charges from time-of-use rates, and already have an existing solar PV system.
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Disclaimer: we are not lawyers, accountants or financial advisors and the information in this article is for informational purposes only. This article is based on our own research and experience and we do our best to keep it accurate and up-to-date, but it may contain errors. Please be sure to consult a legal or financial professional before making any investment decisions.
Prior to starting Gokce Capital, Erika received a Bachelor of Architecture from the University of Southern California and a graduate degree in Urban Policy from Columbia University. She worked as both an architectural designer and engineer in New York before joining the New York City Department of Housing Preservation and Development.
Erika currently lives in the New York Metropolitan area with her spouse, daughter and cat. She is originally from Chicago and still considers herself a midwesterner at heart.
Erika also loves to read, write and travel (fun fact, she has visited all 50 states and more than 30 countries!). Her new book, Land Investing Mistakes: 11 True Stories You Need To Know Before Buying Land, is now available on Amazon.