All right, it is an overstatement. The correct title should be: a new study claims that free ad-supported apps use about 75% of their total energy consumption to power the advertisement displayed in the app. Most energy is being spent during multiple connections to the server to download fresh ads.
Indeed, the cost of this electricity waste does not offset a dollar or two the consumer would have to pay for an ad-free version of the app. However, it is not hard costs, it is an inconvenience of killing the battery while one is killing time.
Needless to say, MobileNoter for both Android and iOS doesn’t carry any ads and no, it’s not free.
Interestingly enough, Microsoft released a light ad-supported version of its Office suite for PCs some time ago and may decide to roll out the same thing for mobile platforms.