For those who want a thermos to keep the coolant warm, there is this solution BlueHeat® FAQ It runs off the 12V battery to pre-heat the coolant and circulate it around the engine. The problem? well it's a hefty price over an engine block heater.
WOW !! $1,700 for a device that drains the battery AND the fuel tank, in order to warm the car. It's GOT to be a gag, right?
OOo webasto.. that runs on fuel to and 12volt battery ---------- Once activated, BlueHeat® Coolant Heater draws power from the vehicle's battery and fuel from the vehicle's fuel tank. BlueHeat® burns the fuel to create heat. Circulating the engine's coolant, ----------
Yes, you are using the fuel. But usually those little heaters are much more efficient in terms of providing the heat compared to the internal combustion engine running. So for heating up the car and not freezing your butt off during winter, it makes sense. Regarding fuel economy, it does not necessarily as the little heater consumes around deciliter or two fuel for heating up the car. ICE consumption will of course be lower due to it being heated up already, but overall fuel consumption will still probably be higher. It depends on your expectations ... Some of those can also be started by timer or even radio operated remote control.
Some people do not have access to electricity plug with their Prius for EBH to work. Also fuel heaters make heat while on the road even for those having a possibility to "plug in" but do not have extension cord long enough for EBH to work while on the road. In Europe most people who have installed additional heater in the car, usually install a fuel powered one. Some newer cars, mostly diesel, already come with additional heater pre-installed as diesels are more difficult to heat up and more susceptible to cold at same time. Including Toyotas.
I wonder where they would install it on a Prius, but I assume they can't install it on small cars. Their application list on the website pretty much only lists large trucks