Apartment and freezing weather

For anyone living here, there is a lease stipulation I am looking at that says something along the lines of - Residents agree during times of freezing weather to maintain apartment to atleast 50F to prevent broken pipes and will be subjected to pay for damages if not”

Now these apartments are controlled by dual ac/heat units that run on electric which after my first time having it, its really not bad. But in any case, is this legal? During freezing weather I have to keep the heat going all day in hopes the pipes dont burst while im at work? Electric bill will be insane. Anyone gone through this? Appreciate feedback, thanks!