If someone used a HELOC for a single large transaction taking up most of their credit line, and began paying it off as agreed (but not any earlier), would this be as impactful as having a credit card with a high balance?
I have no idea if a true HELOC (as opposed to home equity loan) appears as revolving during both the draw period AND the repayment period, or if it's classification on CR's changes once the repayment period is entered.
tl;dr - I don't even want to explore this type of product if my scores will suffer the same as if I maxed out a credit card.
Depends on how they code it, lenders are a little awkward on this but most are fine.
HELOCs got excluded around 2008ish from many FICO algorithms, and at least based on some data appears to be one of the maybe 2 times FICO has gone back and changed an existing model where EQ FICO 5 and TU FICO 4 appear to have been updated. FICO 8/9 basically ignore them for balance, it appears to be identified on size and possibly by a real-estate flag which some lenders use as a secondary source.
EX FICO 2 not sure on, unfortunately my own HELOC is from DCU and CU tradelines (specifically ones that use PSCU for servicing) score weirdly to the point of not looking like a valid tradeline on that old FICO model.
This was an old thread I started on my own analysis of my HELOC though I wasn't hip to the CU EX FICO 2 idiosyncracy at that point, maybe is a little more useful: https://ficoforums.myfico.com/t5/Understanding-FICO-Scoring/All-revolvers-zero-testing-HELOC-Amex-ch...
Basically outside of an installment loan, a HELOC is the most consumer friendly debt from a credit scoring perspective you can get, it's just a little awkward in the implementation.