Honestly, that doesn't sound bad at all, given our recent temps here in New Hampshire.
My p52i worked great yesterday during the day, but simply could not keep up with -15 temps overnight. Today it is working great again (it's sunny but very cold -- expected daytime high is 9 degrees, very slightly colder than yesterday) but I expect it will have a hard time overnight, so I will just let it run out of pellets, at which time my oil furnace will kick in (I have it set for 65, which is actually much higher than I like it for overnight -- that is WAY too warm for the master bedroom, so I have had to close the vents). Tonight it is "only" supposed to get down to negative 10, as opposed to negative 15 last night. (Heat wave!
)
(Of course I will leave for work around 4 a.m. Monday, when we will still be in negative numbers -- I hope my car will start! I've gone out and run it a bit today ... hopefully that will help ...)