Energy Products

Powerwalls or Generator?

I wanted to get some feedback as far as choosing a generator or Powerwalls for back up for power outages. My housing development here in NJ tends to lose power quite often. It's not fun sitting in your house with no AC no lights no internet, TV, hot water etc especially when its 90 degrees outside and 90% humidity.

I have a 12.6K solar array and we have a 1:1 net metering so TOU is not an advantage of choosing battery back up. However, it would be nice to use the PV panels during an outage. I know on the surface, the generator makes more fiscal sense as I can get a 20Kwh Generator installed for about half the cost of 3-4 Powerwalls and the generator can run my entire household load.

But.......I find the idea of battery back up a much more elegant solution. The Powerwalls could be installed in my basement out of the weather unlike the generator. There's no noise (and man those generators are loud) or maintenance with the Powerwalls. I am pretty handy and have worked on engines, changing oil tune ups etc. But at this stage of my life, I rather not be bothered with ICE maintenance. I spoke to a friend that has a generator, while it has come in handy for him, he has had issues with it from time to time and it consumes a lot of fuel. I also spoke to others that have complained that break downs are inevitable, and generally poor customer support from generator companies. But the Powerwalls are a lot more expensive.

When trying to calculate loads I have some things in my favor when considering Powerwalls, I have a gas cooktop, gas dryer, and gas water heater and a high efficiency refrigerator. I could also load shed a few things like the electric wall oven, bar refrigerator and pool pumps.

However, I have a 5 ton Geothermal heat pump with a LRA of 118. But it does have a hard start on it. In the winter the Geo also makes heat down to 40 degrees outside and then, below 40 degrees a gas furnace kicks in, as its actually more cost efficient to run the gas furnace when its below 40 degree outside. So it would draw some juice in the winter, but I could always switch to the gas furnace during an outage to draw less on the batteries. This was set up by my Geo installer and its worked out great.

When trying to determine a back up solution I really want to include my AC as it get unbearable here in the Northeast with the humidity in the summer. Per the Tesla calculator 3 Powerwalls should do it with some load shedding. But for how many hours would they last? I was thinking of buying a 4th Powerwall if I go battery, since the ITC is still available. With 4 Powerwalls I probably should be able to power everything via the main panel with shedding a few minor things like the bar frig, pool pump and wall oven.

Would the cost savings of not having to install a critical loads panel offset some of the cost the 4th Powerwall? Doesn't the Powerwall Gateway offer a way to load shed a few items already from its panel? If so, I might be able to justify buying a fourth Powerwall.

I know the logical answer is the generator, but I am curious to know your thoughts.

Comments

  • The majority of deaths in the latest hurricane were due to generators and CO poisoning. You sound like you could manage those issues, but it should factor into your decision regardless. Moving parts, fuel, exhaust, maintenance are all negative contributors to the generator.
    You already have the solar - Powerwalls allow you to maximize that investment. I have a 10kW array and 2 PW. It is just enough to run a 5 ton AC - but barely. After dark, when there is not the additional solar, the PW are right at the limit. They have never failed, but there is trepidation in that mode. 3 PW would have ben a better choice, but I was a bit naive at that point. The critical outage issue it seems you would need to deal with would be solar output in the winter - is it enough to run the house during the day *AND* recharge the batteries for the next night. 4 PW would be even better - but then again, do you have enough solar output during winter to recharge them ? And of course - with 4 PW, you could go just a bit further between good solar days.
    Another issue would be the switchover at the point of grid failure. With the generator, I would presume a significant time delay to restore power. With PW - you don't even know it has happened unless (like me) you have a neighbor show up at your front door with an extension cord asking to borrow a cup of electrons.
  • If you like to reduce hassle, go with the PWs. They're seamless. In fact, you might not even realize that your neighbors are without power.

    Do understand that your AC units will probably need a soft-start device added to them. Inrush currents on inductive loads like large AC compressor motors are horrific. This could cause PWs, or even generators, to go bonkers at AC start-up, without inrush limiters. They're not cheap, so factor that into your analyses.
  • you can get an installed generator for the cost of 1 pw or install it yourself for 1/2 the cost of a pw. why not go with 2-3 pw's & a generator. pw's should cover 97% of outages but for those really long term outages the generator can kick in. the pw's can integrate with the generator.

    i just had 3 pw's with a generac 22kw propane unit installed. when utility fails the tesla gateway(transfer switch) switches to solar/battery power & when the sun is gone & batteries depleted the generac transfer switch automatically starts up the generator
  • I'd opt to have a professional do the integration of a generator with PV and PWs. Done incorrectly, you can easily fry the generator's power outputs, and maybe destroy the TEG and Powerwalls. There's a reason that cities require permits, with licensed and bonded professionals, to do these things. It's to protect your neighbors from you burning your house down...along with theirs.
  • I have a 16.4 kW Tesla solar system and two PW2 units for 27 kWh of storage.

    Big Florida house, two AC units, electric water heater, electric cooking, electric pool heating for hot tub, no natural gas in my neighborhood.

    We are doing fine with just two Powerwalls. According to my backup history, we have had a few outages where the Powerwalls took over the load for a few minutes. I never even noticed till after it was all over.

    One neighborhood outage did last 4 hours. Car accident nearby required shutdown and repair of some equipment. I noticed that because we were the only house with lights.

    27 kWH of battery backup is a lot and can get most houses thru the night till the sun comes up the next day. In the winter with no AC running, it would be easy. During the summer, I might turn off one AC unit (and water heater) and everyone sleeps downstairs that night. But during the day, we would run AC normally, even if power outage was happening.

    I think two Powerwalls would be enough for anyone. Maybe keep a small generator for additional backup just in case.

    It really depends on how long your outages are. Mine have been only a few hours max. But with knowledge of our electric consumption, I could go off grid indefinitely as long as it is sunny the next day.
  • Yup. During a grid emergency, the prudent thing to do is shut down all non-essential electrical loads. It is an *emergency* after all.

    Critics of battery backup often use *average* energy consumption figures to exclaim that batteries don't have the capacity to back up an entire house-worth of loads for very long in an emergency. They either don't understand the concept of "emergency", or want to sell you a generator...
  • Also, based on what I am reading about integration between Solar, Powerwall and the charging unit to Tesla cars, it is obvious that the Tesla cars are becoming part of the home/grid power in the future. The Tesla cars being produced today have bi-directional energy already built-in.

    That means everything necessary is already there for your Tesla car battery to be used as a Powerwall.

    https://thedriven.io/2020/05/20/teslas-switch-on-vehicle-to-grid-technology-is-big-news-for-clean-energy-shift/
  • The two questions you need to deal with are: Does the solar panels produce more power than your daily (low power) usage? What is your access to a fuel source for a generator?

    If your solar panels are producing more power than you are able to use, capturing that excess that you have been sending to the grid and instead keeping it local sounds like a good idea. If you are not able to produce enough power during bad outages (winter) then Powerwalls may not be a good idea or you need to add more panels at the same time.

    If you have access to natural gas or have a large propane tank, having a generator is an option. If you have a propane tank, you have to account for how long can you run your generator based off of the amount of fuel you have on hand. If you have enough fuel to power a generator for 30 hours but you typically have outages for over 72 hours, things start to get complicated. Also keep in mind that the fuel still has a cost and you will be paying for it with every power outage. On the flip side, since you use a generator, your solar panels are essentially doing nothing for you.

    I also live in NJ and deal with the same outages. I went with a 16.3 kWh solar install and 4 Powerwalls. My house hemorrhages power due to my well pump and two HVAC units but the Powerwalls have enough capacity to handle one full day of power for my house. My solar install is able to charge the Powerwalls completely during the day while also powering the house with a little extra sent to the grid. This only works when there is no snow on the solar panels and there are no clouds in the sky.
  • I went with Powerwalls vs generator and regret the decision because of Tesla's lack of flexibility in how the system functions. I live in Florida and experience frequent power outages but regardless of how low my batteries get, they will only recharge from solar even when power comes back up. Storm watch seems like a great idea but again poorly implemented. I have lost power 4 times in the last 3 weeks yet Storm Watch has never kicked in (I guess it takes a direct hit from a hurricane). Lastly, my solar system is down due to a bad inverter and my PW's have slowly dropped to 0% because the will not charge off the grid. If I had them installed without solar they would charge off the grid but Tesla decided to lock out that capability because they know better. Generator gives the owner complete control of when it operates and for how long, the same can't be said about Powerwalls.
  • > @sigfreund said:
    > I went with Powerwalls vs generator and regret the decision because of Tesla's lack of flexibility in how the system functions. I live in Florida and experience frequent power outages but regardless of how low my batteries get, they will only recharge from solar even when power comes back up. Storm watch seems like a great idea but again poorly implemented. I have lost power 4 times in the last 3 weeks yet Storm Watch has never kicked in (I guess it takes a direct hit from a hurricane). Lastly, my solar system is down due to a bad inverter and my PW's have slowly dropped to 0% because the will not charge off the grid. If I had them installed without solar they would charge off the grid but Tesla decided to lock out that capability because they know better. Generator gives the owner complete control of when it operates and for how long, the same can't be said about Powerwalls.

    Actually, its because of the ITC. Per the IRS you can take the credit as long as the Powerwalls are only charged from Solar. That way its considered part of the solar equipment requirement. I think it was something the power companies lobbied for when the credit was being implemented. Technically Tesla could connect you to the grid to charge the Powerwalls but not if you are taking the ITC. If you had get Powerwalls and don't have solar you can charge form the grid or when its in Storm Watch as an emergency. But if Storm watch doesn't work then yes I see it being a big headache.
  • Oh well.............So I finally decided to go for it and order 4 Powerwalls. My decision was based partly of a Tesla rep saying that there was an 80% chance of getting them installed by the end of the year.

    So.....I filled out all of the info, paid my deposit, took a bunch of pics of my solar and power equipment, and uploaded my electric bill as instructed.

    When I got the copy of the contract with the cost breakdown on it, I noticed they charged me sales tax. In NJ there is no sales tax on solar equipment including battery storage. I called Tesla and got connected with a Project coordinator. She said they can get the contract corrected and take off the sales tax. Then she said "by the way....., you wont be able to get them installed until sometime in the first half of 2021". I was furious! I told her I was told by a different Tesla rep that I had an 80% chance of getting installed by the end of the year and I would be good to go to qualify for the 26% ITC. The Project Coordinator is saying there is no way that is going to happen. when I ordered the Powerwalls on their site, it said 1 week to 90 days for installation which would put me within 2020 to qualify for the credit.

    Does Tesla know what they are doing with their messaging? I want to get the 26% ITC credit that is available this year. Its the only reason I decided to order them. If I have to wait until 2021 I lose $1,160 when the credit drops to 22%.

    At this point, if I have to wait until 2021, I should just cancel my order now and get my deposit back. I can just reorder in 2021 or not. I figure I have a better shot at one of the following possibilities in the mean time:

    1. A new administration gets in power and increases the ITC.
    2. Tesla comes out with a new version of the Powerwall thats more cost effective.
    3. Tesla lowers their price of Powerwalls like they did when the ITC on their cars phased out.
    4. Just buy a generator and deal with the maintenance etc.
  • It's not necessary to spam multiple threads with the same post.
  • Powerwalls definitely!
    Why would you stink up your yard/garage with fossil fuel and inhale carcinogen vapours?
    Why would you spend that money on something that you may need to use once in a blue moon? Powerwall system, gets charged overnight and stays charged until you need the power...no stink, no vapours, much safer too.
    Reduce your carbon footprint, make it your contribution to a healthier world.
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