Generator vs Battery Backup for Home Power Supply

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Battery vs. Generator for Home Power Backup

As larger and more frequent storms become commonplace and with an aging electric grid infrastructure, more homeowners are exploring home power backup to keep their power on during outages. Home battery backup power solutions, especially solar plus battery backup, remain expensive but are becoming more affordable. There are many options to choose from when deciding on a battery or a generator. Request more information about a home power backup solution from Freedom Solar.

If you are considering a whole house battery backup power supply such as the Tesla Powerwall to provide solar backup power for your home, keep in mind that unlike your solar system, there is generally no acceptable financial payback for that investment. However, there are other reasons you may choose to install home battery backup power supply – for example, if you have critical medical or computer equipment running in your home, if you just want the security of knowing that you are not entirely reliant on the grid, or even to help drive the adoption curve to eventually make the technology more affordable for everyone.

Depending on your electricity needs and the reliable availability of grid power, you may find that the best home backup power solution for you is a combination of solar panels for home, batteries, and a generator. To find the best fit for your home, contact us to get a free quote on a solar power backup generator or battery backup power for your home.

There are two main types of home power backup: battery and generator. Batteries store electricity from solar panels from the grid. Generators use liquid fuel that is converted to electricity for use around your home. Each has different features and its own set of advantages and disadvantages.

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Solar Battery Power Backup for Home

There are two main types of batteries used for home power backup:

1. Lithium ion batteries – similar what is in home electronics such as phones and computers

2. Lead acid batteries – similar to a car battery

Lithium ion batteries have a long lifespan, are the most environmentally friendly option for backup power with the smallest carbon footprint. They can generally be connected to smart home software systems that maximizes power usage, minimizes cost, and provides the homeowner with more control. For the home, they are generally installed behind the electrical meter and located in the garage, although they are generally water- and dust-resistant so can be installed outside as well.

Lead acid batteries have been most often used in off-grid solar power systems historically, but lithium ion batteries are becoming more common in that use-case as well. That does not yet apply to the Tesla Powerwall, however, which interfaces with the grid. Tesla is working to develop a battery that is appropriate for off-grid systems, but currently that usage will invalidate your warranty.

Batteries can provide instantaneous power during an outage and are ideal for small loads over a short period (e.g. powering your lights and refrigerator for an outage of a few hours). Compared to generators, they generally have a smaller capacity and are more expensive to install, yet they require little to no maintenance and are also quieter. Moreover, battery costs are likely to decline as adoption of the technology grows (a conservative forecast from GTM Research predicts an eight percent annual decline in the cost of energy storage through 2022). Perhaps most importantly for people who are interested in solar energy, batteries can be charged entirely with renewable energy and do not emit air pollutants when used.

Another unique benefit of a home battery compared to a generator is that it can be programmed to store excess solar during the day to use after the sun sets. That could mean charging an electric vehicle (EV) overnight or offsetting your usage during evening peak demand hours if your utility has a time-of-use plan. The everyday usefulness of batteries could help you save money on your monthly electric bill.

Unlike solar, there is not a financial payback for backup power. If you are calculating the costs of adding battery backup to your home solar power system, keep in mind that you will need to replace your battery multiple times over the length of your solar system’s lifespan. “Most people are still shocked by how expensive batteries are for how little power you get from them,” said Josh Meade, Freedom Solar’s lead designer.

The situations for which we recommend batteries as backup power include:

  • Hurricane prone regions such as Houston – Powerwall could theoretically provide power for a couple of weeks if you minimize your usage and the weather cooperates

  • Small structures in remote areas that are totally off-grid

Common brands of home batteries (all of which are lithium-ion unless otherwise specified) include:

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Tesla Powerwall 2

The American-made Tesla home battery mainly functions as a backup during outages and can only be used with grid-tied solar arrays. It has a capacity of 13.5 kilowatt-hours (kWh). In typical Tesla fashion, it is a high-quality battery, attractive, and popular – so much so that production delays have unfortunately led to long lead times of 6-8 months. It is also an affordable option relative to other batteries, with the cost for a turnkey installation of a single Powerwall2 at $11,985 ($8,390 after the 30% federal tax credit). It has a 10-year warranty on parts and performance (70% energy retention).

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This German-made battery has a reputation for quality and is designed and engineered for full off-grid use. Unlike the Powerwall, the Sonnen battery can’t be stacked or stringed together. The largest battery available, an 16kWh of capacity, costs about $30,000 including installation ($21,000 after the federal investment tax credit). Sonnen offers a 10-year warranty on parts and performance (70% of original storage capacity). Sonnen’s systems come with an industry leading software suite that helps integrate your battery into your lifestyle.

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LG Chem

South Korea-based LG makes a home battery, already in distribution across Australia and Europe, that is becoming available in the U.S. as a solar plus storage solution paired with its NeON panels. Models and pricing are still uncertain, but it is expected to be priced somewhere between the Tesla Powerwall and the sonnenBatterie. LG’s battery is guaranteed with a 10-year warranty on parts and performance (60% of original capacity).

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This Chinese-made AGM battery comes in a range of products that are sealed and designed to be maintenance free; can be strung together to create a larger storage solution and is often used for off-grid solar systems. It comes with a 7-year equipment warranty.


Backup Power Generators for Home

When we talk about generators capable of producing enough power for your home, we are referring to permanent generators that are quieter (but not silent) and larger (generally about the size of an HVAC unit) than portable generators. These generators require professional installation, are designed to be waterproof, and may include an automatic transfer switch that can restore power remotely.

Fuel-powered generators can either be connected to your home’s natural gas (NG) or propane (LPG) line or refilled with gas, propane, or diesel.

A 20-kilowatt (kW) generator is large enough to cover the full load for a home up to 2,500 square feet. The 20 KW model is the most common size that we install at Freedom Solar. About half of our customers choose a gas-line-connected generator, with the other half installing a standalone propane tank.

Products that are sometimes referred to as solar generators, such as the Goal Zero Yeti portable generator, are simply batteries with built-in inverters.

A generator can handle larger inrush current, so it is ideal for larger loads or to maintain power for longer periods of time. However, generators must be replaced about twice as often as lithium ion batteries.

Situations in which we recommend a generator include:

  • When backup power is required for critical loads (e.g. hospital or valuable items in home like servers for cryptocurrency) because batteries don’t handle heating and cooling loads
  • Where reliability is important and larger loads need to be covered

Common brands of generators include:

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KOHLER is a Wisconsin-based manufacturer best known for its bath and kitchen fixtures, which began making generators in 1920. Their home generators are known for their premium quality as they are designed for durability in harsh conditions. These generators are duel-fuel rated, available in a range of capacities, and carry a 5-year

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Founded in 1959 and built in Wisconsin, Generac is the leading generator brand with a 3 capacity options. The company offers a 7-year warranty on its generators.

Summary of the differences between a home battery and a generator




Size measurement


Power rating




Environmental impact

Depends on charging source

Uses fossil fuels and produce exhaust

Internet connected/controlled



Activation time following outage

Nearly instantaneous (no noticeable power loss)

10-30 seconds (devices will lose and then regain power)

Installed cost for the equivalent of 20kW system



Eligible for federal tax credit?



Replacement lifespan

10 years for lithium ion and 5 years for lead acid

5 years



Replacement fuel costs; or oil change every thousand hours (at least once a year) for line-connected generators

Recommended usage

Emergency backup, smaller loads, off grid

Critical loads that require a reliable source of large amounts of power

Ready to get a home battery backup?

To calculate the appropriate size of a solar battery system for your home and electricity usage, check out this handy solar plus storage calculator from SunPower.

Freedom Solar is a certified installer for the Tesla Powerwall battery, sonnenBatterie home battery, and KOHLERgenerator. We can also create a custom battery closet solution for you by piecing together other batteries and equipment, typically housed in a storage closet. This can be a lower cost solution but will not have the same warranties as the name-brand batteries such as Tesla and Sonnen.

Call 877-969-1946 or submit this form to request a quote for your home today!