generator vs. battery

Battery backup power vs. generators: which is right for you?

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If you live in an area with frequent power outages, you already know the benefits of having backup power installed at your home. Propane, diesel, and natural gas-powered generators have long been the system of choice for homeowners and businesses that want to ensure that the lights stay on when the power goes out in the neighborhood. Now, an increasing number of people are considering newer, cleaner battery options like the Tesla Powerwall.

Save thousands on a solar and storage installation

Battery backup power offers many of the same backup power functions as conventional generators but without the need for refueling. Read on for a comparison of battery backup options versus conventional generators, including a review of factors like cost, fuel supply, size, and maintenance.

Key takeaways

  • Battery backup power can be an eco-friendly and cost-effective alternative to a gas generator
  • Upfront costs for backup batteries are high, but lifetime savings can offset the upfront payment
  • Start comparing quotes on the EnergySage Marketplace for maximum savings with solar and storage

Comparing battery backup and generator costs

The exact amount that you’ll pay to install backup power at your home or business depends on the amount of power you need and the equipment you choose. There are many standby generator options available in the $3,000 to $5,000 range that can power a standard American home. By comparison, a home backup battery will start at around $6,000 before installation costs, 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. 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 up to a few thousand dollars to your total price tag.

Savings with battery backup power

The upfront price you pay isn’t the only cost to keep in mind. If you install a generator, you also need to buy the fuel to keep it running. Fuel costs can add up if you frequently rely on your generator – this is especially the case if you also need to pay for the delivery of fuel to your home or business.

By comparison, if you install a battery for backup power, you can pair it with a solar energy system to charge it with renewable energy from the sun. This will add to your upfront cost (a smaller-than-average 6-kilowatt solar panel system will cost, on average, $16,860 before incentives), but over time it can save you tens of thousands of dollars on your electric bill.

Even without solar, your battery might be able to save you money on your electric bill. Some utilities have time-of-use (TOU) electric rates, which vary throughout the day. If you have TOU rates, a battery can actually result in lower electric bills by providing an alternative source of electricity when rates are high.

Fuel supply for your backup power

The source of energy for your home backup power system is another consideration when you’re comparing your options.

Generators are usually powered by 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 be connected 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 can be charged either from the grid or from a rooftop 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. (Not all home battery systems can be recharged during power outages, so make sure that your installer knows that this feature is crucial to you.)

Size/power load for backup power options

When you’re comparing your backup power options, think about what you need to keep running when the grid goes down.

If you just want to keep the lights on in a power outage, most batteries will do the job. Many homeowners who choose batteries for backup power are comfortable knowing that “critical loads” like power outlets, lights, and small appliances will be powered in the event of a power outage.

However, not all batteries are capable of quickly discharging 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 that is specifically intended 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 that is sized properly by your installer, you should be able to keep your home or business running without issue, assuming you have adequate fuel onsite.

Operating & maintaining your backup power system

Generators powered by propane or diesel can be hard to ignore when they’re running. One major 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 for the air quality around you.

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

Before you buy, compare solar & batteries to other generator options

Diesel, propane and natural gas-powered generators are relatively inexpensive and easy to size for your property’s power needs, but there are also benefits to installing battery backup power at your home or business. When paired with solar, you can actually save money on your electric bills, and batteries offer clean, quiet power that you can’t get with a conventional generator.

If you’re talking to a contractor about installing a generator, consider getting quotes for solar systems that include batteries on the EnergySage Solar Marketplace. On EnergySage, you can easily compare your solar options, and see both upfront cost and long-term savings information without even having to pick up the phone. When you join, simply note in your property preferences that you’re looking for a system that includes backup power.

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33 thoughts on “Battery backup power vs. generators: which is right for you?

  1. Danny Kindred

    I can get a generator installed for around 5000 to 6500 batteries cost is 10.000 to 15000 how is that saving money if it cost twice as much money for batteries. It doesn’t figure out to save money when you have to pay twice as much. I usually don’t lose power more than 2 or 3 times a year

    Reply
  2. FLS

    Solar doesn’t pay where I live, but I am curious about battery backup during power outages (mostly from snow storms and ice storms in the winter) v having gasoline or propane generator.

    What would it cost to install a battery pack that would support the furnace / blowers (forced air), refrigerator, plus some outlets for lights and charging portable devices. Wouldn’t run the electric oven or any heating coil devices. And how long would it last if the power went out — 1 day, 2 days, 3 days. It would get recharged from the grid when we have power, and I would love to have the option of hooking a portable generator to it to recharge it during an extended outage if need be. If we get a summer outage (thunderstorm), it would run the refrig and some outlets (I assume trying to run central AC would kill it).

    Do such systems exist? Everyone I talk to wants to sell it bundled with solar, and we are too far north for solar to make sense.

    Reply
  3. Greg

    I have been trying to find out if it is possible to somehow use my rooftop solar grid to recharge my back up portable battery box so that I can cycle my refrigerator, freezer sand internet during the night. The closest thing to a no answer is because of the difference between 100 watt solar input for the box and the higher wattage panels on the roof. Isn’t there someway to convert wattages to be compatibility?

    Reply
  4. Patrick Repper

    Keep in mind your grid-tied solar panels pack it in during a power outage. One battery will keep it up.
    Alternately, a generator will keep you solar panels up by telling the inverter the grid is up while cutting power to the grid. The Solar panels will power most of your house with the generator running you AC during the day, then taking over the whole house during the night.

    Reply
  5. Wendy

    Solar seems so expensive. What are you thoughts on using a generator to charge your Tesla power walls instead of solar panels. Would it be possible? Could you do it with a solar powered generator? We Are looking for something more cost effective. Usage is about 1800 KW a month. There were going to be a lot of solar panels. Would this be feasible and cost effective?

    Reply
    1. istvan

      im thinking the same thing. But i would have a portable 4-7kw generator that can be hidden in the garage while not in use, no permit needed, and only need to set up several hours after the power outage starts. Using the partial backup config, seen on tesla powerwall datasheet.

      Reply
    2. Frank

      First if your home is using 1800kwh a month, that is a lot. How old is your home? Do you have energy efficient windows, insulation? Do you have at minimum a 16 seer ac system? Are you using LED lights? In my current home and use about 600 kwh in a 2015 ft home and I have my thermometer set to 75° and at 9pm it goes down to 68°.

      Reply
      1. Florida

        1,800kWh per month isn’t that much depending on where you live. It’s 60kWh per day. They may not have some options that others do. My house, for example, only has electricity as utility. No water (on well and septic) and no gas. Stove, dryer and water heater on electricity adds to power bill where people with gas lines don’t always see that reflection.
        Before I made my house more efficient we were easily using over 60kWh per day in the summer here in Florida. New white metal roof, new multi-zone minisplit AC, new hybrid water heater that’s ducted into the house… power usage was reduced by more than half. Solar and batteries were my choice since we have no gas line and the cost of a whole home generation with large capacity tank would have cost us significantly more in the long run, though slightly less upfront.

      2. John

        That’s unusually low usage to be fair. We also hit 1,800 in the summer months in Vegas – AC is most of that and two separate AC units run, a 3 ton and a 3.5 ton unit, for the 3,600 square foot house. Our house is brand new and state of the art in every respect, every system is smart and every light is LED, no TV older than 2017. In the winter we don’t even run heat most days, we just went 10+ days with 0 hours of heat because the house is so well insulated. But the pool runs on electricity during the spring / fall as well (probably not much in the summer), it’s an electric heat pump, so the cheapest form of heating a pool and the best. The pool system is on its own 100 amp subpanel though and we just upgraded to 400 amp service. With our solar, our electric bills range from zero to $180 in the worst of the summer heat (I love the heat though ha ha). Last month we used 800 Kw so very low, below the average American household despite being much larger, but during the summer it can be more than double that. We also both work from home so there’s no such thing as setting thermostats to 80 or something. I keep it 74 downstairs and 70 upstairs all spring – fall, then winter I turn the upstairs thermostat off entirely and the downstairs to heat to 70, but as I mentioned for the most part it just does nothing since it isn’t needed lol.

  6. Richard

    How do you protect the solar inverter and generator in a grid-tied system without battery from turning on when generator starts automatically?
    Would a contacter relay do the trick, between generator switch and solar inverter? Is that enough?

    Reply
    1. Tony D

      I have a grid tied system 44 200watt panels, 2 inverters. When grid power is lost my 20kw Kohler standby generator turns on “deactivating” two contactor relays that are normally in on position thereby disconnecting the solar. The contactors are wired to the breakers in the panel box. The net effect of generator turning on is the same as turning off the breakers, for the solar, in the panel box. This happens instantly, and reverses when the generator disconnects.

      Reply

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