I dunno about the electricity claims for practical purposes— where I live, that’d be roughly 128 hours of 600W. I suppose the real question is, would it take 128 hours ($11) of power to generate 720 hours of TTS content assuming a good enough model was available?
On Android I’d imagine, big emphasis on imagine since I don’t use it, you could probably script something up and use a phone with an audio jack to record it. Theoretically hitting that maximum of 720 hours of content per month, but I’d imagine at some point they’d find it peculiar you’re listening to content 24/7.
Even with a local model and hardware you already own, you're not beating that on electricity costs.