Solar vs generator backup power

Pennsylvania is home to nearly 13 million people, making it one of the top five most populous states in the country. Nicknamed the Keystone State, Pennsylvania is known for its rich history, including being the birthplace of the Declaration of Independence and the U.S. Constitution.  With an estimated 3 million people losing power due to winter weather during winter power outages, homeowners in PA and around the nation began questioning where they got their energy from and how they could better prepare themselves for future outages.  

When the grid goes down at such a massive scale, it creates harsh and dangerous conditions. Homeowners who want to get ahead of this have a couple options: they can use a diesel-powered generator or install a solar array with battery storage. We detail the differences of the two in this article so that you can help your solar clients understand which option is best for their needs. 

Energy Automation Solutions  offers design and engineering for solar, battery and generators. 

Comparing generators to batteries is a case of apples and oranges. To make the right decision, your clients must first establish their energy goals. Both applications will be a considerable investment, so if price and payback are their top priorities, a battery might be their best option. Return on investment (ROI) is a common term in renewable energy, and rightfully so.  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.

We like to think of a battery as an “external hard drive” that is always ready to go and keep you backed up. When the grid is up and running, it acts as “cloud storage” providing you power when you have maxed out your “hard drive.” However, not all solar batteries are designed for grid connectivity. There is a range of different configurations. And which to choose depends on your clients’ energy and savings goals:

• Off-grid DC-coupled batteries are often used to power both remote properties and recreational vehicles. They normally come with in-built inverters to convert direct current (DC) to alternating current (AC) power.
• Off-grid AC-coupled batteries perform the same basic function as their DC counterparts – but the conversion process happens prior to reaching the batteries themselves.
• Grid-tied AC-coupled solar batteries are becoming 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 use hybrid (or multi-mode) 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.

Pros

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

• They have access to emergency backup power during outages and other grid failures
• They can avoid peak utility rates by drawing power from their batteries during the most expensive times of day
• They can store daytime solar electricity for nighttime use, allowing them to reduce their utility bills

Because of these savings, most solar backup battery solutions have a measurable ROI. This is in sharp contrast to diesel generators that technically never pay for themselves. With batteries installed, your customers always have the option of using stored solar electricity before taking power from the grid.

Cons

Although solar batteries have many advantages, they’re not without their drawbacks:

• Solar batteries are relatively expensive (although prices keep trending downwards with time)
• They last an average of 5 to 10 years, meaning homeowners will likely need to replace their batteries at some point during the 25 years of their solar panels’ warrantied lifetimes 
• They often use toxic chemicals, precious metals, or a combination of both – which reduces their eco-friendliness. However, this is partially offset when paired with solar PV panels

Moreover, there may be extra maintenance requirements involved – depending on the storage technology being used. Deep cycle lead-acid batteries, for example, need frequent topping up with distilled water.

As with all technologies, diesel generators have their own advantages and disadvantages. And before installing this backup solution for your own clients, it’s important they understand the relative pros and cons of generator technology. 

Pros

Like their battery counterparts, diesel generators provide homeowners with emergency backup power during grid outages. However, they also deliver other important benefits as well:

• Diesel generators are a mature technology, 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

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

• They rely on fossil fuel, which means C02 and other greenhouse gases are released during operation
• In addition to being smelly, diesel generators are also noisy – which is just another kind of pollution
• Diesel 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, diesel generators are not an investment. Whereas solar batteries recharge themselves with free energy from the sun, diesel generators need constant refueling. And this means they never pay for themselves. Instead, generators carry ongoing costs – both for homeowners and for the planet as a whole.

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 diesel 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. As you can see in the image to the side, there are still enough quality sun hours a day to provide anyone in the United States with enough energy to fully charge a battery.

Every homeowner 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:

• 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. However, it’s better to think in terms of long-term costs and savings given that batteries deliver returns with predictable payback periods
• 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

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.

Best for: homeowners in search of a reliable solar-ready storage solution in an aesthetically pleasing design. 

Average cost: it currently retails for approximately $9,000 to $13,000 – depending on the vendor.

This lithium-ion battery is our first choice for a home energy storage solution because it can be paired with a solar panel system. When paired with a SolarEdge inverter and optimizers, users can track their power consumption, solar production, and battery levels at any time of the day. This battery requires a critical panel load to be installed, with a simultaneous 25A capacity. For the typical American home, this would still allow you to power the essentials to get by during an outage (refrigerator, bathroom, furnace, etc.). 

Best for: homeowners looking for a versatile battery solution to power essential appliances at night, during grid outages, or during peak hours.

Average cost: The Tesla Powerwall 2 costs between $6,000 and $7,000 per unit. However, your clients may need 2 or more connected in series to provide sufficient capacity. 

Tesla’s Powerwall 2 is fast-becoming the go-to standard for both residential and commercial storage needs. It ships as a fully-integrated lithium-ion AC battery system that comes in an all-weather encasement plus liquid cooling – allowing it to be installed indoors and outside. In addition to seamless solar PV integration, the Tesla Powerwall 2 can easily be connected in series for greater storage capacity.

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 justify adding PV panels and on-site storage to properties they don’t use frequently – like remote cabins. 

Diesel 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 the pros and cons of solar battery vs generator technology. 

Best for: those who need emergency backup solutions capable of powering their entire homes during grid failures.

Average cost: the Generac or Kohler 20kW 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.