I’ve tried boiling water systems and they use a lot of electricity. Primarily because as the humidity starts to drop, they come on to keep the water warm in case you need the humidity. I spent a lot of money warming water. Just switched to DriSteem which also uses a throw away cylinder. Instead of heating the water, it uses electrodes to drive current through the water which instantly boils the water. This is a very energy efficient system. I have two three gallon units and they can raise the humidity 5% in less than an hour, in a 20,000 sqft building.