Update August, 2020: We finally had a long term power outage where I could test the Prius generator system. What I observed is that the plugin battery slowly discharged as I drew power from the traction battery hookup. I estimate I can get an hour of electricity for every mile of EV range. This means that the battery was essentially drained after about 9 hours and then the engine would kick on to recharge the system. While it was running, I kept checking the various plugs and cords and nothing was warm. When the main battery was drained, I would disconnect, go to one of the public chargers in town that had electricity. Everything worked as expected with no issues except for the fridge. My subzero needs more than 1000w to startup and would trigger the inverter’s load sensor. While I could reset the inverter and try again to keep the fridge running, it seemed to be only partially running. Perhaps on only one compressor as I believe I have a 2 compressor fridge.
Even though it worked well, I was somewhat nervous of overloading the systems within the Prius. After a few days of driving, everything is working exactly as normal with no issues so I think the setup is safe and works pretty well. Because of the fridge needing more power, I since purchased a Honda EU2200i generator as my primary standby. I can still use the same transfer cable, but can now power the fridge.
Original Post: 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:
- Prius. I have a 2012 Advanced Plug in Prius, but a normal Prius works fine too. ($30k+)
- An Inverter. I went with a Power Bright 1000w Pure SineWave Inverter ($280)
- Manual Transfer Switch. I had my electrician install a Reliance Controls 31410CRK 30AMP manual transfer switch. It allows me to pick ten circuits to power (not all at once!) ($350) + 800 labor
- Custom built 120v to 240v (15a to 30a) power cord.
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:
- 2 awg copper ring terminals
- Hammer Crimper Tool
- 80amp ANL Fuses
- 80amp Fuse Holder
- 2 AWG cables
- Heat Shrink tubing
- 2 Anderson Battery Charging Connector Cables
Instructions for building the cable can be found here, but included in my video are a few tips on actually putting the cable 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 here. In my video I talk a little bit about it, but there are a few things you should note:
- This is not a suicide cable. A suicide cable has two male ends.
- You have to be careful your breaker panel doesn’t have any Multibranch Wired Circuits. Here are some discussions on the topic: Thread 1 and My own Thread
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.