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Solar Battery Backup Vs. Generators

Updated: Apr 30

solar battery backup

When the grid experiences a massive power outage, it can create dangerous conditions for everyone in the area. Home and business owners looking for more reliable power even during an outage event might look into diesel or propane-powered generators or installing a PV system with solar battery backup.

As an installer, it’s important to know the pros and cons of a generator vs solar panels in terms of necessary equipment, cost, reliability, capacity, and more. We’ll explore the difference between a solar battery backup and a generator and highlight some of the top performers in both categories on the market today.

Solar Panels Vs. Generator

Comparing generators to solar batteries is a case of apples and oranges. Solar panel installers can help clients understand the differences between the two options and, by examining the clients’ energy usage, can recommend which, if any, option makes sense for them.

Both applications will require a considerable investment, so installers should be prepared to discuss the payback period and costs associated with each option. In this section, we’ll review the pros and cons of both batteries and generators to help you determine what’s best for your client’s situation.

Solar Battery Backup

Solar systems equipped with solar battery storage make it possible for clients to store excess energy generated during the day and draw on it during nighttime or during an outage. Solar batteries store and discharge energy generated by a solar installation.

Some batteries are not built for grid connectivity, however, and may only be appropriate for completely off-grid installations. Installers can assess a client’s energy needs and savings goals to help determine the best configuration.

Some common options for solar battery backup include:

  • Off-grid DC-coupled batteries: This type of system is often used to power both remote properties and recreational vehicles. They normally come with built-in inverters to convert direct current (DC) to alternating current (AC) power.

  • Off-grid AC-coupled batteries: These systems perform the same basic function as their DC counterparts – but the conversion process happens prior to reaching the batteries themselves.

  • Grid-tied AC-coupled batteries: This arrangement is more popular for residential storage needs. The inverter technology is already built-in, making this ideal for both new PV installations and retrofits. Just keep in mind that for grid-tied connections, solar permitting and utility approvals are usually required.

  • Grid-tied DC-coupled solar batteries: These batteries use inverters capable of accepting high-voltage loads. Although poorly suited for off-grid applications, their compact size makes them a favorite among homeowners.

Another important consideration is the depth of discharge (DoD), which 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% means you can’t reliably draw more than 7.5 kilowatt-hours of clean energy. It’s similar to how modern computers ship with “500 gigs” of storage even though the operating system and pre-installed programs take up some of that hard drive space.

As a general rule, the higher the depth of discharge, the more solar power a homeowner can store and use. So aim for DoDs that are 95% or higher.

Pros of Generators

Below are just some of the core benefits your residential clients can enjoy when combining solar battery backup technology with their PV panels:

  • Generators have been around for a while, making them relatively easy to buy, install, service, and repair

  • They’re dependable, able to provide reliable power day or night – regardless of weather conditions

  • Many generators are “portable,” allowing homeowners to move them whenever and wherever they need emergency backup power

Cons of Generators

Although backup generators have their plus sides, they also have many drawbacks:

  • They rely on fossil fuel, which means C02 and other greenhouse gasses are released during operation

  • Using a generator safely is crucial to prevent potential hazards such as carbon monoxide poisoning, electrical shocks, and fires.

  • In addition to being smelly, generators are also noisy – which is just another kind of pollution

  • Generators remain idle for most of the year – only being used during the occasional blackout. And for many homeowners, this is a poor use of space and resources

  • Generators have substantial maintenance requirements, complete with scheduled servicing, trips to the gas station, and frequent top-ups

Last but not least, a typical generator is not an investment. Whereas solar batteries recharge themselves with free energy from the sun, gas generators need constant refueling. And this means they never pay for themselves. Instead, generators carry ongoing costs – both for homeowners and the planet as a whole.

Home Generator Vs. Backup Generator

A home generator and a portable generator serve different purposes and have distinct characteristics.

Home Generator

  • Purpose: Designed for whole-home backup during power outages, providing continuous electricity to essential appliances and systems.

  • Fuel Source: Typically runs on natural gas, propane, or diesel and is often connected directly to the home's utility lines.

  • Installation: Permanently installed on or near the property and wired into the home's electrical system.

  • Capacity: Higher capacity to support the entire home's electrical needs.

  • Automation: Equipped with an automatic transfer switch to start automatically when grid power fails.

Portable Backup Generator

  • Purpose: Offers temporary and mobile power for various applications, such as camping, outdoor events, or providing backup for specific appliances.

  • Fuel Source: Runs on gasoline, propane, or diesel and requires manual refueling.

  • Installation: Portable and can be moved to different locations as needed; no permanent installation is required.

  • Capacity: Limited capacity suitable for running specific appliances or devices.

  • Automation: Requires manual startup and connection to appliances using extension cords.

The choice between a home generator and a portable generator depends on specific needs, such as the scale of power requirements, mobility, and the duration of backup power needed. Home generators are ideal for prolonged outages and whole-home backup, while portable generators offer flexibility and convenience for temporary or smaller-scale power needs.

How Long Do Solar Batteries Last?

Lithium-ion batteries are commonly used in solar energy storage systems due to their higher energy density and longer lifespan. High-quality lithium-ion batteries can last anywhere from 10 to 20 years or more. The exact lifespan depends on factors like the specific lithium-ion chemistry, energy storage usage patterns, and environmental conditions.

Among lithium-ion solar battery chemistries, lithium iron phosphate (LiFePO4) is known for its longevity. LiFePO4 batteries have a higher cycle life, often exceeding 10,000 charge-discharge cycles, making them suitable for long-term use in solar energy storage systems. Their stable chemistry and thermal performance contribute to extended battery lifespan, providing reliable and efficient energy storage for solar applications.

It's important to note that the term "lifespan" in the context of solar battery backup often refers to the period during which the battery can retain a certain percentage of its original capacity. For example, a battery may be considered at the end of its lifespan when it retains only 80% of its initial capacity. However, even a solar battery that has 80% of its original capacity may still provide a lot of value.

What is a Solar Backup Generator?

A solar backup generator or solar battery backup is a system that combines solar panels with an energy storage solution, typically batteries, to provide a reliable source of power during grid outages. It captures and stores solar energy when the grid is active, allowing homeowners or businesses to use stored energy when needed, ensuring uninterrupted power supply and enhancing resilience to power disruptions.

Do You Need Solar Panels To Have A Battery?

Solar energy is not required to install a battery at your home. The key difference is that you cannot “refuel” a battery without sunlight during a grid failure like you can refuel a gas generator (assuming you have access to fuel). A battery can be charged from grid power, but you are always at the mercy of your utility pricing by going this route.

With solar battery backup, you can charge and recharge, maintenance-free. There is a common misconception that solar only works in sunny “hotspots” in the United States. However, there are enough quality sun hours a day to provide a large portion of households in the United States with enough energy to fully charge a battery.

solar battery backup vs generator

Best Solar Battery Backup Recommendations

Every homeowner is different, and residential property is different, meaning there is no universal solar battery solution that is ideally suited for all situations. However, you can help your clients determine the optimal battery technology for their own needs based on things like:

  • Configuration: batteries can be AC- or DC-coupled; what’s needed will depend on the installation

  • Capacity: larger batteries are able to store more solar power – allowing homeowners to offset a larger portion of their energy bills

  • Cost: because of their high price tags, this is a common concern. Consider what’s going to give your client the most bang for their buck

  • Solar-readiness: most storage technologies can be paired with solar PV panels. But some batteries need a lot of expensive modifications, while others work almost out-of-the-box

  • Design: in response to changing consumer preferences, many battery manufacturers now ship their products in aesthetically pleasing encasements that blend well with existing homes

  • Warranty: look at battery warranties to understand DoD, production capacity, etc. to get a good idea of the lifespan and confidence in the technology

Fortunately, there is no shortage of solar battery solutions out there. Some of the most popular solar batteries on the market are the Tesla Powerwall 2, LG Chem RESU, Sonnen Eco, Panasonic EverVolt, and Enphase IQ. But if you need help choosing a storage technology for your own clients, here are a couple of our top picks.

Tesla Powerwall 2 Solar Battery

Best for: Homeowners looking for a battery solution with a high DoD and standard 10-year warranty

Average cost: The Tesla Powerwall 2 costs between $8,500 and $10,000 per unit. However, your clients may need 2 or more connected in series to provide sufficient capacity.

Tesla’s Powerwall 2 is a well-known, well-reviewed product for both residential and commercial solar battery backup. It offers a 10-year performance warranty and can qualify for solar battery rebates and incentives. It ships as a fully integrated lithium-ion AC-coupled battery system that comes in an all-weather encasement plus liquid cooling – allowing it to be installed indoors or outside.

In addition to seamless solar PV integration, the Tesla Powerwall 2 can easily be connected in series for greater storage capacity. Installers should keep in mind that these only come in one size, so it could be difficult to customize for client energy needs.

Enphase IQ Solar Battery

Best for: Customizable configurations between the different models (IQ 3, IQ 3T, IQ 10, and IQ 10T)

Average cost: Depending on the model, costs can range from $3,000 to $9,000

The Enphase IQ comes in four different models with different capacities and designs, depending on client preference and space. These are all AC-coupled models, like the Tesla Powerwall 2, but what sets Enphase IQ apart is its microinverter technology. Enphase is known for its high-quality solar inverters, and it claims its microinverter-based storage system is safer and more reliable than other systems on the market.

One downside to these solar backup batteries, though, is that they will only work with systems that use an Enphase inverter. While there’s not a ton of flexibility to pair with different solar installation configurations, Enphase IQ does offer a 10-year warranty with the option to add a 5-year extension.

Best Home Generator Recommendations

Despite the growing popularity of solar batteries, there may be situations in which a backup or home generator is more suitable. For example, many homeowners have a hard time justifying adding PV panels and on-site energy storage to properties they don’t use frequently – like remote cabins. Generators are sometimes better equipped to provide on-demand power for occasional needs. In addition, many backup generators are portable – allowing users to relocate them as required.

You might not specialize in generator installation, but knowing some of the top brands allows you to talk competently about your client’s options.

Generac 20kW 6244 Home Generator

Best for: Those who need emergency backup solutions capable of powering their entire homes during power outages

Average cost: The Generac 20kW 6244 currently retails for $5,000 to $7,000.

This whole house generator has an air-cooled aluminum enclosure along with technology that allows it to safely and efficiently power any household item. A 200A auto transfer switch provides you with the ability to power an entire home, as opposed to only critical loads as a battery would.

Westinghouse WGen7500 Generator

Best for: Homeowners who want reliable backup power with minimal setup and maintenance.

Average cost: The Westinghouse WGen7500 retails for just under $1,000 on Amazon and other retailers.

This electric start generator scores points on its portability and ease of use. With minimal assembly, it delivers 7,500 W of reliable power at the push of a button. The WGen7500 comes with 6.6 gallons of fuel capacity and can run continuously for up to 11 hours on a full tank.

Choosing Between a Generator Vs Solar Panels

Solar battery backup has skyrocketed in popularity in recent years. Understanding the differences, benefits, and drawbacks of both solar battery systems and various types of generators can provide your clients with the necessary information to make the best decision.

GreenLancer offers design and engineering for solar battery backup and generators. Installers can sign up for free and shop an online catalog with fast turnaround, on-demand, standardized services.


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