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Battery Backup or Generator: Which Backup Power Source is Best for You?

Andrew Francis Wallace/Toronto Star

When you live somewhere with extreme weather conditions or regular power outages, it’s a good idea to have a backup power source for your home. There are different types of backup power systems on the market, but each of them has the same main purpose: to keep your lights and appliances on when your power goes out.

In the past, fuel-powered standby generators (also known as whole-house generators) dominated the standby power supply market, but reports of the risk of carbon monoxide poisoning have led many people to seek alternatives. Backup batteries have become a greener and potentially safer option than conventional generators.

Although they perform the same function, backup batteries and generators are very different devices. Each has a particular set of pros and cons, which we’ll cover in the following comparison guide. Keep reading to learn the main differences between backup batteries and generators and decide which option is right for you.

Backup batteries

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Home battery backup systems (such as the Tesla Powerwall or LG Chem RESU) store energy, which you can use to power your home in the event of an outage. Backup batteries run on electricity, either from your home solar system or from the power grid. As a result, they are much better for the environment than gasoline generators. They are also better for your wallet.

Separately, if you have a utility use plan, you can use a battery backup system to save money on your energy bills. Instead of paying high electricity rates during peak hours, you can use your backup battery power to power your home. In off-peak hours, you can use your electricity normally (but at a cheaper rate).


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Standby generators, on the other hand, plug into your home’s electrical panel and turn on automatically in the event of a power outage. Generators run on fuel to keep your electricity going during an outage – usually natural gas, liquid propane, or diesel. Other generators have a “bi-fuel” feature, which means they can run on natural gas or liquid propane.

Some natural gas and propane generators can connect to your home’s gas line or propane tank, so there’s no need to manually fill them. Diesel generators, however, will need to be recharged to keep running.

Battery Backup vs Generator: How Do They Compare?


In terms of cost, backup batteries are the most expensive option initially. But generators need fuel to run, which means you’ll spend more over time to maintain a stable fuel supply.

With battery backups, you’ll need to pay for the battery backup system up front, along with installation costs (each running into the thousands). The exact price will vary depending on the battery model you choose and how many you need to power your home. However, it is common for an average sized home battery backup system to cost between $10,000 and $20,000.

For generators, the initial costs are slightly lower. On average, the price to purchase and install a standby generator can range from $7,000 to $15,000. However, remember that generators need fuel to run, which will increase your operating expenses. Specific costs will depend on a few factors, including the size of your generator, the type of fuel it uses, and the amount of fuel used to run it.


Battery backups gain a slight edge in this category as they can be wall or floor mounted, while generator installations require a bit of extra work. Either way, you’ll need to hire a professional for either type of installation, which will take a full day’s work and can cost several thousand dollars.

Besides setting up the device itself, installing a generator also requires pouring a concrete slab, connecting the generator to a dedicated fuel source, and installing a transfer switch.


Backup batteries are the clear winners in this category. They are quiet, operate independently, produce zero emissions and require no ongoing maintenance.

On the other hand, generators can be quite loud and disruptive when in use. They also emit exhaust gases or fumes, depending on the type of fuel they use to operate, which can irritate you or your neighbors.

Keep your home powered

When it comes to how long they can power your home, standby generators easily outperform standby batteries. As long as you have enough fuel, the generators can run continuously for up to three weeks at a time (if needed).

This is simply not the case with backup batteries. Take the example of the Tesla Powerwall. He has 13.5 kilowatt hours of storage capacity, which alone can supply energy for a few hours. You can get extra power from them if they are part of a solar panel system or if you use multiple batteries in one system.

Expected and guaranteed life

In most cases, standby batteries come with longer warranties than standby generators. However, these guarantees are measured in different ways.

Over time, battery backup systems lose their ability to hold a charge, much like phones and laptops. For this reason, backup batteries include an end-of-warranty capacity rating, which measures how well a battery will hold a charge at the end of its warranty period. In the case of Tesla, the company guarantees that the Powerwall battery will retain 70% of its capacity by the end of its 10-year warranty.

Some backup battery manufacturers also offer a “throughput” warranty. It is the number of cycles, hours, or power output (known as “throughput”) that a company guarantees on its battery.

With standby generators, it is easier to estimate lifespan. Good quality generators can run for 3,000 hours, as long as they are well maintained. Therefore, if you run your generator 150 hours per year, it should last around 20 years.

Which is good for you?

In most categories, battery backup systems come out on top. In short, they’re better for the environment, easier to install, and cheaper to run in the long run. Plus, they have longer warranties than standby generators.

That said, traditional generators can be a good option in some cases. Unlike battery backups, you only need one generator to restore power in the event of a power outage, reducing upfront costs. Additionally, standby generators can last longer than single-session battery backup systems. As a result, they’ll be a safer bet if the power is out for days at a time.

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