Induction cooking is very efficient. The problem is that most home units have an output designed for home cooking. As far as boiling liquids is concerned, 4-8 quarts of water for pasta is about it, not really gonna cut it for brewing. When I started brewing, I was doing extract batches indoors on our propane cooktop, and the highest output burners are only @7500 btu. Not that great for full boils, waiting for the wort to come to a boil was a lot of downtime. I got some automotive firewall insulation from JC Whitney (along with the foil tape for the outside and a heat-resistant glue to stick it to the pot), installed it, and the situation improved markedly. For the past two years, I've been doing AG boils outside in the garage on a propane burner, not looking back.
“Malt does more than Milton can / To justify God’s ways to man”
-A. E. Housman (1859–1936). A Shropshire Lad , 1896.