Prius Home Generator

My original home generator system consisted of a 7000w power generator hooked up to a manual transfer switch which would power ten circuits in my house.  It was a perfectly fine setup, but once I started researching other alternative options, I knew I had to change my approach.

After doing a LOT of research, I was able to find examples of how I can have my Prius power my house.  What’s unique about my setup is that it takes the 110v that the Prius generates and transfers it into the 220v manual transfer switch.  The flow is: Prius -> Inverter -> 15amp plug -> 30amp plug -> 10 circuit manual transfer switch.

The four main components of the system are:

Lets go into detail on some of the items:

 

Inverter:  The inverter I chose can generate 1000w of electricity and peak at 2000w.  After doing several tests, I knew that I didn’t need any more than 800w so a 1000w inverter would be more than sufficient.  Additionally, I opted for a more expensive Pure Sine Wave inverter because I wanted to be able to to power electronics such as the TV, cable box, cable modem and routers.  I also wanted a quick an easy way to connect the inverter to the Prius.  You could go with alligator clips similar to how you would jump start a car, but after finding Woodman’s setup, I knew this is how I would need to set it up.  I have more info in the video, but here is the parts list:

I won’t repeat Woodman’s instructions, but do watch my video for a few tips on actually putting the cables together.  Also, the crimping can take some practice, but this crimping video should help.

Manual Transfer Switch:  Even though I didn’t have a lot of circuits to power at one time, I did have at LEAST six circuits I wanted to power.  You can find 4 circuit transfer switches which are made to work with 110 volt cables, but it doesn’t seem like they make 6 circuit’s anymore.  My setup allows you to power ten different circuits using a 120volt input

Custom Cable:  They do not sell 15a to 30a power cords.  If you want to mimic this setup, you’ll have to create your own.  I followed the great instructions provided by hazardjk.  In my video I talk a little bit about it, but there are a few things you should note:

During the installation of my manual transfer switch, my electrician found some serious issues with my subpanel.  I had double tapped breakers, no grounding to the main panel, neutral and ground bars mixed up and multiple MBWC.  I actually paid him to rewire the subpanel to sort out those issues which needed to be fixed regardless of generator setup.

Watch the two videos which show how I setup everything:

Through my research I found many folks who thought that using a Prius as a generator was not worth risking the car’s durability.  Here are my thoughts:

  • Why would you risk your $30k+ as a generator when you can buy one for 500?  For me, it was a fun project and I wanted to be able to user my existing car as a way to power my house.  The cool factor for me outweighed any potential risk I was putting on my car.  If I think about how often I have lost power in the last 10 years it’s probably been only ten days total.  To be able to use the Prius in-case-of-emergency is not going to put a burden on the car or the traction battery for the few times that it would be needed.  Also, I can always switch to portable generator like a Honda EU2000is in the future if I sell my Prius or don’t have a hybrid car in the future
  • The Prius is not an efficient generator.  Actually it is!  I can’t find the link on Priuschat.com at the moment, but from the spreadsheets that I saw, it was as efficient as a conventional generator (non inverter type).  This means that with a full tank of gas in the Prius, I should be able to power the house for a few days.
  • The Prius can’t generator enough power for the home.  That’s simply untrue and really depends on how much power you need to generate.  While there aren’t a lot of videos on Prius’ powering the home, a lot of people have successful powered their homes with small Honda generators:  BillyNewport powers his Home with a 2000w Generator (and subzero fridge!), Honda EU2000is connected to a home, Another Honda powering a home,

So now I wait for the first power outage and we’ll see how my setup performs in a real life situation.  I tested the setup a few times and everything worked flawlessly so I’m excited to try it out.  However, if I never have to use it, that’s ok too, at least I’m prepared.

 

 

14 thoughts on “Prius Home Generator

  1. Bob

    Thanks for doing these videos. One question, any problem using a slightly larger inverter or is 1000 watts the max for hooking up to the 12 volt battery?

    Reply
    1. Bryan

      Great write up! I will be doing the exact same thing to my 2012 (non plug in) Prius. Planning to use this for camping and an emergency generator for my home / coral reef tank!

      I had a similar question re. A larger inverter..

      I’ve read elsewhere that the 12V battery has around 100 amps available as a draw from the traction battery. So that is about 1000W that can be safely drawn down via the small 12V battery. If you pull more than 1000W then the remainder will have to come from the 12V battery itself. Which might be OK for appliance start ups but not for anything continuous, since the 12V is so small.

      I am considering a 2000W inverter only for the extra AC output amps.
      My fridge needs 11.2 amps for startup, but the 1000W inverters I’ve looked at (xantrex prowatt 1000) only can give 9.6.

      I need to read a bit more on this, but I am hoping I could safely start up the fridge, and then draw well below the 1000W limit of the traction->12V step down limit.

      Reply
      1. Frank PerkinsFrank Perkins Post author

        Sounds like you might have to purchase the inverter and test it to see if it will work. If you buy from Amazon, you should be able to return it pretty easily if it doesn’t work out for you. Good luck and let us know how you make out!

        Reply
    2. Tom Norman

      I too want to know what are the risks? How can you find out, instead of the vague “Why would I risk my 13000$ used prius for a $500 gas generator?

      There has to be some reason for the concerns if there are. What are they? How can we find out from the Toyota engineers?

      Is my greatest risk the little startup battery having to be replaced?

      Reply
  2. Crystal

    Hi Frank:

    Setting up my Prius as a generator has been on my list of things to do for about 2 years now…and I’m just getting motivated to do it. I’d be using your set up to get the inverter ready, then just use an extension cord to the house in emergencies.

    I am very intimidated, though, by the wiring: i.e., the red and black wires, the fuse, the anderson connector…Is there ANY chance, if I bought all the materials and shipped them to you, you’d be willing to put that together for me? I’d pay for your time!

    I’m sure it’s easy and I’m just chicken, but I don’t want to screw that part up.

    Just email me back if you’d consider it. Thanks!

    Reply
    1. Frank PerkinsFrank Perkins Post author

      You can do something more simpler like using alligator clips (like when yo jump start a car). I’m sorry, but I don’t have the time to assemble this stuff 🙂

      Reply
  3. rj

    Yes, very nice setup indeed. I was wondering why did you choose the Power Bright 1000w invertor over some of the others? There wasn’t very many reviews on Amazon as compared to the others, this one had only 11 comments. Also, would it be ok to use the suggestion from someone else by using a 45 amp inline fuse instead of the 80 amp? One last question, are you still satisfied with your original setup or would you change anything?

    Reply
    1. Frank PerkinsFrank Perkins Post author

      * At the time, that seemed to be the right inverter for the price.
      * I don’t see why using a 45amp fuse wouldn’t work. The most important thing is to ensure it’s below 100 so it blows before the Prius fuse
      * Unfortunately, as luck would have it, I haven’t had a power outage so I haven’t had to use it during a real storm event. If/When I do need it in a power outage, Ill be sure to updated the post to include my learnings!

      Reply
      1. Tom Norman

        I did the calculation from the simple formula: Power or WATTS = Volts X Amps…

        The power out of the inverter should be just a little less than the power into the inverter.
        So I came up with this:
        Watts Volts Amps
        960 12 80
        960 120 8

        Which says you can get 8 amps of 120 volt AC out before it will blow.

        I want to use a 2200 watt inverter.
        SO HERE IS THE REAL QUESTION:

        When the starter battery drops, it is charged up by the system.
        So why should it be limited to 100 amps… since the PRIUS generates 42,000 WATTS of power.

        And when parked there is no usage to speak of by the drive train to power the generator in reverse to drive the car.?

        So as long as the voltage is being generated by the PRIUS GENERATOR to keep the PRIUS’ little starter battery above 10.5 volts… then two questions:

        ONE: Why should it matter if there is a larger capacity inverter connected… as long as the fuse to the invertor trips before the fuse from the PRIUS GENERATOR to PRIUS starter BATTERY trips.

        TWO: Why can’t I go directly to the drive train Generator and be a load on it without effecting the smaller battery circuit or the other invertors…. since they are all pulling power from the generator… and none of them are pushing power into the 42,000 watt or 42K watt PRIUS drive train generator?

        My question then is how to not “tag” the inverter down stream from the center distribution point out of the generator… with a branch that is limited to 100 amps.

        So I will cut this off with this lead to explore the first question asked in this blog: Why not branch the inverter into the drive train circuit, instead of into one of its sub circuits?

        I then look at the “jumping instructions” in the PRIUS OWNERS manual. It said, don’t connect the jump to the battery terminals directly, but in the driver’s side of the front hood, there is a black covered electrical hub. It says take the power off of the copper connector. And ground it to the auto body…. for the instruction for the two jumper cables being hooked up.

        Therefore it seems to me, that is where to connect the invertor… because there the subcircuits going to power brake inverter etc… are isolated APPARENTLY. It would be good to know from a TOYOTA tech. And I see no warning that says, DO NO CONNECT INVERTERS to the GENERATOR of your PRIUS.

        So I take that as either great NEGLENCE on the part of the brilliant TOYOTA engineers… who are among the best in the world apparently vis a vis automobile and specifically hybrids auto generators.

        … or PERMISSION to connect to their PRIUS there, since they don’t say no… and THEY don’t want their cars to fail… and have their customers not be forewarned… i.e. gross negligence on the part of the engineers and quality oversight would be the charge to TOYOTA.

        So why can’t we get the straight story from TOYOTA. I have gone to the most successful dealer in the area, and they don’t want to have any part in installing the inverter.

        That is not engineering. That is dissappointing.

        Can you, Frank, shed light on this. Surely you have considered this. I am tempted to hook the inverter up to the Jump Point under the hood and leave the battery alone. I could do that with a shield grounded power cord leading from the inverter with a 400 amp protection :

        watts volts amps watts vp;ts amps

        2200 12 184 4000 12 334

        Reply
        1. Tom Norman

          continuing… since I inadvertently hit the send button before stating why the 400 amp trip fuse connecting between the GENERATOR / battery jump point [presumably well ahead of the 100 amp inline fuse protection to the startup battery at the rear]…

          so the 400 amp to protect the PRIUS and the inverter from power demands put across the 2200 watt [4000 watt transient peak].

          Here are my calculations using Watts = Volts time AMPS simple formula…[ as long as capacitance and inductance by our loads don’t get into the circuit and cause a greater power factor than the “True straight up North” of resistance don’t distort]:

          watts vp;ts amps watts vp;ts amps

          2200 12 183.3333333 4000 12 333.3333333
          2200 120 18.33333333 4000 120 33.33333333

          And for FRANK’s 1000 Watt usage protected by 80 AMP fuse:
          960watts = 12 volts times 80 amps

          when converted to 120 volts AC through the inverter
          960 watts = 120 volts times 8 amps

          And that fuse is really not necessary unless one is plugging to appliances without protection for the output of the 120 volt inverter . If there is an appliance short or too much load put on the inverter, that is a problem for the PRIUS, I presume.

          It is a problem for the PRIUS for the same reason that they put a 100 amp fuse in the branch that goes to the starter battery in the rear.

          So there needs to be circuit breaker protection then for the PRIUS at two points. One is the branch circuits or plug ins to the 120 volt AC inverter. That first protetion is for both the inverter and the prius Generator circuits upstream from the inverter to the Generator.

          That is my point, above.. TOYOTA has protected I am certain all of the possible sensitive PRIUS computer and power circuits by providing the copper alligator jumper connection under the hood infront of the driver.

          So the system is not vulnerable at that point… It is the point for the alien intruders to come in and zap the ‘heart’ to start the PRIUS. However, to be safe, the second fuse then would be placed after the inverter at the 12 VDC input side that it hooks up to the PRIUS.

          In this way, a melt down by the inverter itself would be limited and not have a fire hazzard, and the PRIUS “DRIVE TRAIN GENERATOR” Motor wiring would not be ‘cookable’.

          Surely however there are high amp protection at that point.

          I reason this way from the 42K or 42,000 watt generator which I have read is the spec for the PRIUS generator that goes to the drive train motor. [The nuclear submarines for instance are not driven by nuclear power, but by electric motor generators. That was my first job after graduation that gave me a draft deferI ment to work as an electrical engineer in the electrical design department of San Francisco’s and Vallejo, CA nuclear shipyard.

          I didn’t know much, but I shuffled plans and redid drawings as I was instructed having to do with the electrcially powered motor generators on the Nuclear Submarines that came through the yard. The power was generated by Steam. and the steam came from the heat of the Nuclear reactor.

          So the PRIUS has a gas driven generator, and another feed… a regenerative braking system driving the generators to generate electricity and store it then in the battery.

          The battery then gets the message from the boss, the computer, to turn the generator into an electric motor to propel the drive train… which it shares with the gas engine.

          So there is the gas engine which the “boss” tells to generate electricity to have it stored in the very large capacity batteries for future use… or to uncouple from the generator and couple the gas engine power to the drive train to propel the PRIUS.

          So all of that circiutry is certainly isolated from the generators output as a generator, or input from the batteries as a motor .

          It is there then that we should want to know that we can tap into power WHEN the PRIUS is not moving, and power or house.

          Otherwise it is like what happened when my grandfather got his first Model T. They told him how to start it but not how to stop it. So the story was, my grandmother would throw him a hamburger every time he circled the house until the gas was all used up.

          THEREFORE SURELY somebody can give us guidance as to what is permissible and what is forbidden in the “BLACK BOX of CIRCUITRY” which protects and drives forward the PRIUS and continually keeps its battery levels appropriate for its generator and internally driven DC rectified circuits for its computers and other VDC components.

          It may be they can’t say unless they test it, and then there will be people wanting to push the envelop. And more, they want to just move cars and not power houses.

          However there is a big market as well for that, and there will probably be the time that they will want to structure a 2200 watt or a 5000 watt feed for its consumers… when the drive train is not engaged.

          So, please tell me. I have a 2200 inverter… Is my thinking sound. Dare I connected under the hood with two “01” guage wires to the inverter, and a third one to the auto body?

          And protect the upstream from the inverter and the downstream into the inverter with a 300 to 330amp or 400 amp circuit breaker… so that I can use the 2200 watts for power circuits and starting up motors and microwaves which use two and three times the power to get them going?

          If anyone knows answers, please let me know.
          If, Frank, you have not gone beyond the 1000 or 960 watt point that your 80 amp breaker gives you because you have thought about this and concluded… don’t risk anymore than causing a 80 amp power pull should your inverter or branch circuits fail and short?

          I hope I hear from someone, or we could hear from a sober technician at TOYOTA, that anonymously wouldn’t cause TOYOTA liability issues, and so give us direction.

          In the meantime, it is too late to reread and correct the typos [and the hypos], so I send this without further ado or apology.

          Reply
  4. priyan

    Just wondering, why did you use a 80 amp fuse? I saw in prius chat someone used a 15 amp fuse to connect to the traction battery.

    Reply
  5. John Allred

    I didn’t see where you used any 220V ac circuits. I your dryer electric? I thought that was why you would use a 220 V plug. I’m confused.

    Reply
  6. Dee

    Still no power outage? Just curious if you have used your system yet or have anything that you would change if you was going to build it again?

    Reply
  7. Chris

    I’ve used my ’02 Prius for 14 years in a similar setup to power selected circuits of my home.
    This year I pressed my ’14 Leaf (new to me in ’16) for the same duty. I ran it continuously for 3 days, stopping twice to run out to the Chademo to refill; the Prius filled in during those breaks.

    Reply

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