Does hubitat have enough power to run a raspberry pi off the USB port power. Going to setup assistant relay and thought I could just hang out off the hubitat.
Which Pi are you talking about? A 3B, 3B+, 4B or a Zero/ZeroW?
Zero.
You probably won't have a problem with a zero running off the USB port. I run my zero off of the USB port on my Lutron Pro Bridge. You might run into a problem getting AR to run on a zero though. It is only Arm6 Architecture and I think the Google Assistant SDK requires Arm7 minimum. Haven't tried it in a while.
I wouldn't chance it. Hubitat sized their power supply to run their hub + a USB Z-Wave/Zigbee stick. A RPi can pull quite a bit of current. Per the RPi FAQ below, a 5V/1.2A power supply is recommended for a Pi Zero W.
That's not a realistic estimate for a zero with no peripherals running on it. I use a supply that provides only 500mA and it never has a problem. You'll only need 1.2 A if you are using a camera module or a HAT, or PHAT or Bonnet.
You don't say whether your hub is a C4 or C5 or what region you're in 1 USB stick or 2 or 0.
If you are running a C4 hub, you're already powering one device of the USB port, so a Zero might put you over for total usage. If your router has a USB port for attaching an external hard drive, use that instead. Or buy a cheap 1A phone charger.
Why risk it? These things always have a way of biting us in the ass by manifesting themselves as odd and difficult to troubleshoot problems.
I wouldn't take the risk. BTW a rpi draws as much power as needed for all the hardware it has and the way it is used. So you'll have to measure it yourself at the moment of running the most consuming task. My rpi3b+ runs on 14mA Kodi, when idle. But when I start to play a movie it goes up to about 2.2 amps if 1080p and full audio decoding.
I ran my homebridge pi on the router USB power for a bit, worked, until the router had to be reboot and made things go haywire for the pi. In my experience, I would have the devices on separate power supplies as this prevents issues with one if the other needs a reboot or troubleshooting.
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