<prompt> Human: The existing stuff is crappy- energy inefficient, and due to reasons we are missing a patio door glass pane so we need to replace it immediately.Im freaking out because Im the kind of person that takes a really long time to research and plan before making these kinds of decisions, ugh.Anyway, I am wondering if it makes sense to use financing which would be 0 APR for 48 months and spend something like 15K doing it all.Is such an improvement so great for energy costs that I should even consider taking out more debt?I make 120K a year, 1800mo mortgage, finance 2 cars 300mo and 160mo.Thank you.  <response>: Unless youre one of the extremely rare cases where yours are so bad you have 1000 a month heating bills, its extremely unlikely it will pay off. Now saying that, 0 interest, on a small loan, especially given your income isnt too big of a deal. If they make you feel comfortable - not a ton of harm - just dont think of it as an investment. 