Home battery backup power vs. generators: Which is right for you?

More and more homeowners are looking for ways to improve the resilience of their home's electricity systems. Historically, most people who invested in a backup power supply for their homes in the event of an emergency (think natural disasters and other blackout events) looked to propane, diesel, and natural gas-powered home generators for that resilience. But, these days, homeowners are increasingly choosing a cleaner alternative for that peace of mind: home backup batteries.

Solar battery storage systems offer many of the same backup power functions as conventional generators but can run on clean energy instead of fossil fuels. We compare the costs, fuel sources, size, and maintenance requirements of battery backup options compared to conventional generators.

There are two primary reasons that homeowners have historically opted for generators as a backup solution. First, they cost less upfront. Second, in the past, generators have been easy to find and set up at your home. You can frequently buy backup generators at home improvement stores, and some might not even need to be installed by an electrician. 

However, backup generators come with several downsides. For one, you'll have to ensure you have the fossil fuel they require, which can be problematic during unexpected outages. Next, backup generators are large, loud machines that shouldn't run every day and require regular maintenance, meaning you only benefit from having them in the event of an outage. Finally, and perhaps most importantly, backup generators cause significant local pollution by burning fossil fuels, not the least of which is carbon monoxide, which has become a considerable safety risk with fossil fuel-powered backup generators. 

On the other hand, batteries are more expensive upfront and require an electrician to install, but they solve most of the issues that can sometimes plague backup generators. When you pair batteries with solar panels, the sun powers them, keeping them charged as long as the sun keeps shining. Also, batteries are eligible for incentives like tax credits and rebates, which can significantly lower those upfront costs. Finally, there are no local emission concerns with solar & storage installations – they run entirely on clean, renewable solar power.

The amount you'll pay to get backup power at your home or business depends on the power you need and your chosen equipment. Many standby generator options in the $2,000 to $7,000 range can power a standard American home, but the average generator cost, including installation, is $9,000. 

By comparison, a 10 kilowatt-hour (kWh) home backup battery will start at around $13,000, and in many cases, you'll require multiple batteries to provide whole-home power. Altogether, you can expect to pay anywhere from $10,000 to $20,000 to install a battery backup system depending on your energy needs. If you use more energy than your neighbors, you'll need to buy a bigger generator or more batteries, and you can expect the installation cost to add thousands more to your total price tag.

The average net upfront cost of a solar-plus-storage system is around $31,150, based on the following calculation:

$29,500 (solar panels) - $8,850 (solar tax credit) + $15,000 (batteries) - $4,500 (battery tax credit)

Total cost over 20 years: solar + storage vs. natural gas generator

Table sources: EnergySage, U.S. Energy Information Administration, Forbes

The upfront price you pay isn't the only cost to consider. If you install a generator, you must buy fuel to keep it running. Fuel costs can add up if you frequently rely on your generator – especially if you must also pay for fuel delivery to your home or business. Not to mention, you need to store the fuel somewhere in your home.

By comparison, if you install a battery for backup power in your home, you can pair it with a solar energy system to charge it with renewable energy from the sun. A battery will add to your upfront cost (on average, a 10-kilowatt solar panel system will cost $20,650 after the federal solar tax credit), but over time it can save you tens of thousands of dollars on your electric bill.

Even without solar, your battery can save you money on your electric bill while increasing your energy independence. Some utilities have time-of-use (TOU) electric rates, which vary throughout the day. If you have TOU rates, a battery can lower electric bills by providing an alternative power source when utility electricity rates are high.

We typically power generators with diesel, liquid propane, or natural gas. Your generator can continue to run as long as you have the fuel to supply your generator, and some generators can even connect to an existing natural gas line. If you don't have access to a natural gas line, you should expect to refill your generator as needed.

By comparison, a home battery backup system runs on electricity, and you can charge it either from the grid or a home solar panel system. If you design a solar-plus-storage system for off-grid backup power, you can recharge when the grid goes down, adding an extra layer of security for situations where you might be worried about having access to fuel for a generator. However, you can't recharge all home battery systems during power outages, so make sure your installer knows this feature is crucial to you.

What appliances do you need to run when the electrical grid goes down? Most batteries will keep the lights on in a power outage. As a backup energy source, batteries can power "critical loads" like power outlets, lights, and small appliances in an outage.

However, not all batteries can quickly discharge enough electricity to get energy-intensive equipment up and running. If your home relies on a sump pump, well pump, or other equipment that uses a lot of power to start up, you'll need to install a battery intended explicitly for backup power.

If you install a conventional generator, you won't have to worry about critical loads. As long as you choose a generator sized properly by your installer, you should be able to keep your home or business running without issue, assuming you have adequate fuel onsite.

Generators powered by propane or diesel can be hard to ignore when running. One significant advantage of a battery backup system is that it operates quietly and doesn't burn any fuel, unlike a conventional gas-powered generator. As a result, you don't have to deal with exhaust fumes or other polluting emissions – a win for the environment and your home's air quality.

Generators powered by fossil fuels like natural gas or diesel can also have higher maintenance requirements than battery backup options. In addition to refueling, you'll need to run and regularly test some generators to ensure they operate when you need them most.

Overall, the best batteries for your home are options that provide scalability, reliability, and durability. Learn more about available home batteries below:

Enphase IQ Battery

The Enphase IQ Battery comes in two sizes and is advantageous for people who experience regular power outages. Unlike many other solar batteries, the IQ Battery doesn't require an external transfer switch to facilitate backup power. Instead, the IQ Battery works with the IQ System Controller 2 to automatically provide power when the grid goes down.

Read our full review of the Enphase IQ Battery.

The Tesla Powerwall

The Tesla Powerwall can easily integrate with any home and has a 10-year warranty. It comes with an app that allows you to wirelessly control your energy usage patterns, which can be especially beneficial in places where variable electric rates change the price you pay for electricity depending on the time of day.

Read our full review of the Tesla Powerwall. 

LG Chem RESU

The LG Chem RESU home battery boasts a 94.5% round-trip efficiency, meaning that 94.5% of its stored electricity will convert to usable energy. It's also one of the most compact home batteries available, making it a popular choice for those with space constraints. 

Read our full review of the LG Chem RESU.

Generac PWRcell

The PWRcell's best feature is its ability to provide an instantaneous power surge to appliances faster than most home batteries. Its high power surge comes in handy when you need to power appliances that need instant and quick power to start up rather than continuous power. 

Generac also offers a generator, PWRgenerator, designed specifically to recharge home batteries directly and efficiently. The PWRgenerator integrates with Generac's PWRcell batteries to keep them charged during an outage, even when the sun isn't shining. 

Read our full review of the Generac PWRCell.

How long do home batteries last?

Depending on your energy needs and how conservative you can be with the energy you store, a home battery backup can usually last a day or two during an outage. For optimal energy storage and output, you should pair the battery with a solar panel system to create a closed system that produces and stores energy while powering your home. 

How much battery backup do I need for my house?

For the average American household that requires power for up to three days while off-grid, a battery bank backup must supply over 100 kWh of energy. Again, battery backup needs vary depending on energy usage and other factors. 

How long can a Tesla Powerwall power a home?

The average American home uses about 30 kWh of electricity daily, meaning a 13.5 kWh Tesla Powerwall can power an entire house for about 10-11 hours. However, if you have multiple Powerwalls and use a solar panel system to charge them, you can feasibly power your home for days on stored electricity.

Interested in backup power or in reducing how much you pay for electricity? Get started comparing solar-plus-storage quotes from vetted installers on the EnergySage Marketplace today. Our expert team of independent Energy Advisors can guide you through the entire process so you can go solar with confidence. The best part: EnergySage is free, and signing up takes just a few minutes!