Is it safe to run arduino uno 24/7 with usb as power to cellphone charger?

wildbill:
Robin2 - what does your fridge controller do for you?

I'm running the fridge from a quasi-sine-wave inverter and the regular thermostat misbehaves so my Arduino takes its place. I just turn the regular thermostat to max cold and let the Arduino turn the power on and off. It measures the temperature with an LM335.

...R