Over the years I have installed five Hydrosil heaters. I have installed both the 110 and 220 versions. Each person I have installed them for has had nothing but good things to say about the heaters. Since I run a seperate circuit and conduit for each heater, I prefer the 220 version better. Make sure you buy the wall mounted thermostat that they offer. It is very user friendly and then you don't need to have a dial on the heater. I am unsure about how much they cost to run because none of my clients have ever complained about the bill.
If you have a hot water heater system in your house and need additional heaters in a kitchen or bathroom look at the Myson heater.
I will do some searching around for how much the heaters cost to run and get back to you guy's.
If you are installing any electric heaters in a bathroom, kitchen, or anywhere water could be present make sure you have that heater circuit GFCI protected.
Take care,
Rob C.