When you say it uses "a lot more power" are we talking running the battery down in an hour, a few hours, by the end of the day?
Given how I choose to tour, I usually have access to power once a day (at night, on most occasions). If the higher power option meant I'd be out of power at the end of every day, then I wouldn't care. If it runs the phone down in a hour, then I'm not interested.
By the way, when I am riding through remote areas, I do what those above said, which is to turn off the cellphone as searching for signal also runs down the battery (as does leaving the Wi-Fi setting on).
So, if your less power option requires keeping the cellphone on, I'm not so sure it is the "lower power" answer.
Why not offer both?