I left food in the microwave as shabbos started. Which is worse ?
1) Leave it there & bal tashchis
2) open the door & the light goes on
3) unplug it & the digital numbers go off
First off, there is no Issur of Baal Tashchis at all if it is for a good purpose, even if it is only Assur mishum minhag and certainly if it is an issur gamur (whether D'oraysah or D'rabanan)
Now, when it comes to the other 2 (in certain situations of a choleh or the like), if the light is incandescent/halogen, that is the worse issur. If not, they would be equal, BUT PLEASE ASK YOUR LOR IF IT'S L'MAASEH