Rinnai gas heater with thermostat set on high ©  2015 Don Boroughs

H is for ‘Hopelessly confused’

You like to cook your egg on a medium stove heat, but to get the pan warmed up you first set the electric hob to high, right?

You arrive at a Kruger Park rondavel on a sweltering day and turn the temperature control knob on the air conditioner thermostat as far as it will go to cool down the room more quickly, right?


You use thermostats every day. Do you understand how they work?

A just-released study of American homeowners reported here found many misuse their heating and cooling thermostats. A third of them seem to not understand how thermostats work at all.

Central heating and air conditioning are much less common in South Africa, but thermostats still govern our stoves, ovens, geysers, portable heaters, and room air conditioners. Use them incorrectly and you could be wasting energy.

I see the confusion in my own home. My Rinnai gas heater has two heating levels—high and low—and a thermostat with temperature settings from 16 to 26. The H setting above 26 means it is kept on high heat even if the room gets hotter than 26 degrees. Since no one really wants to be that hot, I should never find it turned up to H, but that’s frequently where I find it set.

The culprit who set it on high could have chosen 21 instead, for example, and as long as the room was colder than 21 degrees, the thermostat would have kept the burner on high heat, only switching down when the temperature reached 21 degrees.

The gremlins in my house and many other people and confused by the myth that a high setting on a heater, stove or air conditioners will somehow make the appliance work faster. Not so. The element in an electric stove or heater and the compressor on an air conditioner can only be on or off. A low setting on the stove allows your soup to simmer because the thermostat switches it on briefly and repeatedly.

Why does this matter? Because if you walk away or fall asleep with the stove on high and the air conditioner on max, you will waste electricity, burn your pan and shiver all night. Always set a thermostat to the final temperature you would like, then let it do the work of switching on and off. That’s what it’s made to do.