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Backup battery vs generator: which backup power source is right 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 back-up power systems on the market, but each of them serves the same primary purpose: to keep your lights and appliances on when your power goes out.

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

Although they serve the same function, battery backups and generators are very different devices. Each has a particular set of pros and cons, which we’ll cover in the following comparison guide. Read on to learn about the main differences between battery backups and generators, and to decide which option is best for you.

Back-up batteries

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

Separately, if you have an electricity plan according to the time of use, 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 the energy from your battery backup to power your home. During off-peak hours, you can use your electricity normally (but at a lower rate).


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On the other hand, back-up generators connect to your home’s electrical panel and turn on automatically when the power goes out. Generators run on fuel to maintain your electricity during an outage – typically natural gas, liquid propane, or diesel. Other generators have a “dual fuel” function, 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 is no need to refill them manually. However, diesel generators will need to be recharged to continue operating.

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 be spending more over time to maintain a constant supply of fuel.

With back-up batteries, you will have to pay for the back-up battery system up front, along with the installation costs (each in 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 home battery backup system to operate between $ 10,000 and $ 20,000.

For generators, the initial costs are slightly lower. On average, the cost of purchasing and installing a standby generator can range from $ 7,000 to $ 15,000. However, keep in mind that generators require fuel to run, which will increase your operating expenses. The 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.


Backup batteries gain a slight advantage 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, both of 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.


Back-up batteries are clear winners in this category. They are quiet, operate independently, produce no emissions and require no ongoing maintenance.

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

Keeping Your Home Powered

When it comes to how long they can keep your home powered, backup generators easily outperform backup 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 can supply power for a few hours on its own. 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 life and guaranteed

In most cases, back-up batteries come with longer warranties than back-up 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 index, which measures how efficiently a battery will hold a charge at the end of its warranty period. In Tesla’s case, the company guarantees that the Powerwall battery is expected to retain 70% of its capacity by the end of its 10-year warranty.

Some back-up battery manufacturers also offer a “throughput” guarantee. It is the number of cycles, hours or energy efficiency (called “throughput”) that a company guarantees on its battery.

With back-up generators, it is easier to estimate the lifespan. Good quality generators can run for 3,000 hours, provided they are properly maintained. Therefore, if you run your generator for 150 hours a year, it should last around 20 years.

Which one is right 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. In addition, they have longer warranties than standby generators.

That said, traditional generators can be a good option in some cases. Unlike back-up batteries, you only need one generator to restore power in the event of an outage, reducing up-front costs. Additionally, backup generators can outlast single-session battery backup systems. As a result, they will be a safer bet if the power is cut for days at a time.

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