Battery drain when parked?

[winemart2]

Anyone know how much battery drain occurs when parked? On frosty nights I get 3 places on the windscreen where heat is obviously present. There's a 1" diameter "melt" high up by the rain sensor and 2 more at centre bottom, maybe 2" dia each. You don't get that by just a few milliwatts. I'd guess maybe 5 Watts or so, unused for a week would lose ~80Ah. Or maybe some "smart" stuff thinks "i'd better shut down else he won't start it".