Be aware there is nothing magical about them... they heat a room up the same amount as any other electrical heater of the same wattage. And they are only "money saving" in the sense that (like any portable electrical heater) they allow you to run the furnace thermostat way down and then just use the electrical heater in the room you're in. This works fine if you spend long periods of time in one room and if freezing pipes is not an issue. But, that is the ONLY way the "save money" -- by letting you keep most of your house colder.
If that suits you, they are neither better nor worse than any other electrical heater of the same wattage as your eden pure model.