plug in cooler, 60W, ok to use in Prius?

Congrats on the prize. If you plug it into the accessory socket, 60 W will almost certainly not blow the fuse, so OK so far. That power load is insignif to the 12 V system while in ready. So are 100 w of headlights. When you turn Prius off any and all accesory sockets become de-powered. This I would think is the only issue you should consider. The cool box will slowly warm while you are parked. If this matters to you, it would not be hard to hot-wire an accesory socket. In that case, your 60 w load will discharge the 12 v battery in 5 hrs. Perhaps quite a bit quicker. You should not do that.

 

Tochatihu is right, the electrical system will cope no sweat when in ready mode, when the system is powered down the cooler will be like an esky or ice box. It will keep the contents cool but for only as long as the insulation and outside temperature allow. This should be fine for day trips but not good to keep your seafood fresh on a camping trip. If you want to run the cooler while the car isn't powered up get a portable battery pack to run it from, if it goes flat that isn't going to leave you stuck.

 

I second that, good suggestion.

Locally, Canadian Tire has an assortment of battery boxes, some are meant to jump start the car, some provide power for accessories. Some even have inverters to run small 120 vac items

They range in price from $35-$299, depending on how fancy you want to go, and how much capacity you need. Their largest one is actually a cart on wheels, with an inverter

Considering how intolerant the little 12 vdc Prius battery is of abuse and chronic discharge, it's cheaper to use a dedicated 12 vdc source

 

I use a 45W cooler for camping and
carrying frozen goods from stores
but it only operates when the car is
operating and the lighter plug is
activated which is a good thing
because it would run down the
little 12V computer battery fast.
Bud