Over the years, natural gas was cheaper to run than electric.
However, recently with prices of gas, both natural and cng on the rise, the difference is marginal at best. The variables are, what will it cost for you to run the electricity to the unit, or the cost to run a gas line, the cost of or rate you pay for both gas and electric, and where you live (can you run the electric exhaust into your house to offset the cost of your furnace)...and so on.
I have had both, and after trying to figure it all out, my head hurt.
Gas driers still use electric to roll the drum, and set off the buzzer
You should never exhaust the gas dryer into the house but you can humidify your home air in winter with an electric unit.
Anyone who buys one or the other trying to save money because....just didn't do the math because they are very close when you enter all t he factors including how much you use it....which affects the life of the unit, and repair costs.
In the end, I have decided that I like electric because it is a bit safer to use.
Otherwise, flip a coin.
I know, that folks swear by one or the other but in reality, it all comes down to what you want to use. Cost saving really doesn't enter into it....and if you really want to save a nickle...drive right past the beer store on friday nite and you will save the difference either way.