Generally most houses have effectively 2 phase which is two legs of 110-120V ~ 220V you mentioned. Though those are not necessarily on different phases. Go out on a major street and if they still have overhead lines, you'll genearlly see 3 lines. Those three lines are all AC (sinusodal) but are being transmitted in phase shifts. i.e. the peaks and troughs of the sinusodal wave hit such that they are offset when compared to one another. More powerful motors generally run more efficently on 3phase power than single phase. The cost to run a 5hp motor on single phase power is significantly higher than one ran in 3 phase. I can almost guarantee that the place in question does have 3 phase power.
220V in your house really only works in heat applications such as your hottub,water heater, range, or dryer.
Thanks for sharing your temp situations. You said it's 74 outside... what is the temp of the tank room/house? Is the tank running that hot from the sunlight's input? I discovered a simple $7 walmart fan on a temp controller keeps my tank's chiller from operating but maybe once or twice a week. And that's with my house maxing out at 82-84F.
Though I can see renting for quite a while unless something else changes in my future so LED will be my choice until I can build my own house and something like you've done! So I'd be interested in all this type of information as you go along.