Is the storage room for your exclusive use? If not, I doubt your fellow tenants would appreciate you pushing up the common electricity bill, and you also risk others having the odd joyride on your treadmill. If it's all yours, you will ultimately pay the (trivial) power bill through the annual adjustment to your Nebenkosten.
What do you mean by "cold storage room"? Is it refrigerated, or just unheated?
As for being wary of treadmills that speak in tongues, it can't possibly be that difficult. How many terms would you have to learn to adjust the speed, incline and a few pre-set programs? In any case, I wouldn't mind betting that most treadmills would come programmed with multiple languages, to reduce the manufacturer's selling and marketing costs. Just check the range at whichever sports store you want to buy from. (Look at Migros Sport XX, Dosenbach, etc., as well as Athleticum.)