Comparing A Solar Battery System To A Home Generator
Updated: Feb 8
Originally published: June 24, 2021
Updated: February 7, 2023
When the grid experiences a massive 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 solar array with a battery backup.
As an installer, it’s important to know the pros and cons of both in terms of necessary equipment, cost, reliability, capacity, and more.
We’ll explore the difference between the solar batteries and generators below, and highlight some of the top performers in both categories on the market today.
Comparing A Solar Battery System To A Home Generator
Comparing generators to solar batteries is a case of apples and oranges. 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 be 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 for both batteries and generators to help you determine what’s best for your client’s situation.
Solar Battery Backup System
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 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 these 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 that 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.
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
Although 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
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.
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, you can charge and recharge, maintenance-free. There is a common misconception that solar only works in the 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.
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. But if you need help choosing a storage technology for your own clients, here are some of our top picks.
Tesla Powerwall 2
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 storage needs. It offers a 10-year performance warranty and can qualify for 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.
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 their microinverter technology. Enphase is known for their high-quality inverters; they claim their microinverter-based storage system is safer and more reliable than other systems on the market. One downside to these 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.
Despite the growing popularity of solar batteries, there may be situations in which a generator is more suitable. For example, many homeowners have a hard time justifying adding PV panels and on-site 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 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
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.
Best for: homeowners who want reliable backup power with minimal setup and maintenance.
Average cost: This model 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.
Adding backup power to your list of installation services is essential for long-term growth in the solar energy sector. Understanding the differences, benefits and drawbacks to both solar battery systems and generators can provide your clients the necessary information to make the best decision.
GreenLancer offers design and engineering for solar, battery and generators. Installers can sign up for free and shop a catalog of fast-turnaround, on-demand, standardized services.