The sparky has looked at my place and also been out to visit Tesla. He tells me that it will cost around $3k to go 3 phase, but needs to put a quote together. Meanwhile he suggested that I make a list of all of the outlets etc in the house to calculate what the real load would be. I've done that and created a google calc sheet for it. On the sheet I also looked at the current switchboard and did a worst case and sensible load calc. In the worst case I'd be at home on a cold night with the air conditioning pumping heat, with the dishwasher running and cooking dinner in the electric oven, making coffee using the machine and the microwave, the stereo playing a movie on my plasma while the off peak hot water kicks in. This is pretty unlikely, but adds up to 77.5A. A more realistic estimate would be around 40A, for a short time, say making coffees with the movie playing, air-co pumping warm air and the off peak hot water heating up. This is telling me that I might be able to get away with a single phase 32A in the garage without having to go 3 phase. I'll have the dual chargers for travel, but probably won't need the HPWC installed at home. You can look at my calcs at Google Sheets - create and edit spreadsheets online, for free. Either way, it'll be interesting to see what the sparky comes back with.