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.