I never new pepsi and coke were so useful! They can come in various shapes and sizes, but in all electric boilers, you’ll see water running through the system to be heated by a heating element – similar to the way a kettle works. I'll have to think that one over for awhile a very informative blog, as usual, and voted up! If your appliance is not listed. You don't have to use your energy provider's boiler cover! You could qualify for government.