What Does It Really Cost to Humidify a House?

Humidifying a house takes energy, no matter which type of system does the work. A recent discussion looked at the two common approaches: steam humidifiers and evaporative humidifiers. Both turn liquid water into vapor, but they pull the energy needed for that change from different sources, which affects what it costs to run them.

The basic physics: turning water into vapor takes a fixed amount of energy, roughly 8,090 Btu per gallon once the water is already at its boiling point. If you start with cold tap water instead, you need extra energy first just to heat the water up to boiling before it can turn to vapor. That first step is called sensible heat (raising temperature without changing the water's form), and the second step is latent heat (the energy used to change the water from liquid to vapor). Steam humidifiers generally supply both kinds of heat directly with electricity, while evaporative humidifiers rely more on your home's existing heated air to do the evaporating.

For a homeowner, the practical point is that the type of humidifier you run can change your energy bill, since one method may pull more directly from your electric bill while the other leans on heat your furnace or heat pump is already producing. Specific cost comparisons and dollar figures for each type weren't detailed here, but if you're weighing a humidifier purchase, it's worth asking how each option gets its energy and how that fits with your home's existing heating system.