Multiple Charging Sources

Multiple Charging Sources

So, I pulled the trigger (thanks everyone for the help in making an informed purchase), not time to prep the garage.

I ended ordering a 85kWh battery and the HPWC and dual chargers.

I mostly work from home, but have to drive Sacramento to San Jose (220 miles round trip) about once a week, but sometimes more often and on consecutive days.

I have a 4.9kW solar system on my roof (thank you Solar City) with the idea that I would use that for daytime charging of my Model S. At the same time, the local utility offers a dedicated ToU meter with a special rate for EVs thats about $0.03kWh cheaper off-peak.

My concern is for days when I have back-to-back trips, I want to minimize my costs for charging off the grid. I am wondering if it makes sense to have my utility add the dedicated ToU feed and have a switchbox or the like installed so I can flip over to the cheaper ToU power at night.

Any thoughts on this? I kinda think this might be over-complicated to save $0.03 cents/hr.


therealmach3 | June 20, 2013

Yeah, seems like the economics are hard to make work. If you assume 350 watts/mi, then a 220 mile charge is 77 kWh or savings of about $2.31. If you'd really only be able to take advantage of it on the back to back trips, then I guess it just depends on how many of those trips you make.

Is the Supercharger in Folsom far out of your way? That would be free charging anytime you want it.

create | June 20, 2013

Not sure that is necessary. Supposedly the HPWC charges at 20kW but from what others are saying it is not quite there yet and it is really more like 15kW. Even at that rate it would take you less that 6 hours to completely charge the 85kWh battery from 0. You should be fine just charging at night with the lower rates and effectively get 2 or 3 to one kWh from your solar system (utilities offset the electricity based on $ not kWh). | June 20, 2013

Thanks for the comments. BTW, the Folsom SC is north of me, so the wrong direction. :)