I Think there is an argument to be made that if it gets so cold outside that the heat pump is basically rendered useless that it's just running and it's not actually providing any type of heat rise across that coil, then it could be argued that that system should turn off just based on efficiency that it's not doing anything anyway. Why would you want to pay for that extra energy? No. I would say in most cases it's not as much energy as say the heat strips anyway, but you could make that argument that it's useless and why are we still running it here? I Will say though, there are certain products on the market that the manufacturers will come out and say that if it gets below a certain temperature that we have a lockout for one reason or another. I Sat through a Class A couple years ago where they said hey, with our product, if the line sets are longer than this particular length and it's below this temperature outside, we want you to lock that unit out because of something to do with the oil or I can actually don't remember what the reason was.