When I was buying my Model S I decided that I didn’t need the High Power Wall Charger (HPWC), but I did decide to go with the dual chargers. At home I regularly charge on a NEMA 14-50 which gives me about 28 miles/hour of charge but with dual chargers its possible to charge even faster. My office is across the street from the Tesla store in Natick, MA and they have free charging available in 6 parking spots with a couple HPWCs a short walk away. The other day I skipped my nightly charge and parked in one of the HPWC spots at the mall for a charge the next morning.

The HPWC

With the HPWC you don’t need any adapters or cables — you just plug it into your Model S. This is especially helpful in Natick as the outlets there have been a bit messed up otherwise for regular charging.

The HPWC’s can charge at up to 80A if you have dual chargers (which I do). Don’t worry though, if you only have a single charger the HPWC still works with your car. One of the magical things about the Model S is that if things fit with the adapters provided by Tesla then it will charge and you don’t have to worry about scary things like voltages, amperages and watts.

Charging

SuperChargers use DC to charge your Model S and bypass the chargers to deliver their magical charge rates. The HPWC uses a more traditional AC approach, just with a very high current.

Right now, pretty much the only way to verify you have dual chargers installed and working in your Model S after taking delivery is to find a HPWC — there are very few public chargers out there that can charge at over 40A, and the ones that do you probably don’t have an adapter for (CHAdeMO).

HPWC is the only way to verify dual chargers are installed and working

When charging you can set your rate of charge. The rate is limited by both your car’s ability (40A or 80A for single or dual chargers respectively) and then the maximum rate provided by your source. So when you plug into a HPWC, make sure your charge rate is set to the max to get the best charge time. Remember that the Model S does remember charge settings based on your GPS location, but I’ve never had to adjust my settings and the Model S has always just used the max rate possible.

Charge Rate

After I started charging, I let it go for a while to ramp up while I walked to my office. I used the iOS app to check on the charging and it reported the charge rate to be about 50 miles/hour, 208v at 81A confirming my dual chargers were working and I was charging faster than I can at home at about 28 miles/hour.

To confirm the rate of charge I timed the charge and recorded the reported rated range. I started charging at 8:30am and stopped at 11:07 AM (a 90% charge limit was set). I went from 106 miles of rated range to 240 miles of rated range. So I added 134 miles in 2.6 hours for an actual charge rate of 51.2 miles/hour.

I’ve heard about charge rates tapering off as your near the limit of your charge but in this case after the short ramp time it charged at the same rate all the way to a 90% limit. I’m assuming that the charge rate may decline after the 90% mark, but I didn’t have a chance to test that this time.

It charged at the same rate all the way to a 90% limit

 Summary

After I got my Model S I wanted to check out all the features I had carefully selected and test each out. Dual chargers were a bit tricky but I wanted to see them in action and to know they’re there and ready for fast charging on the road if I should ever need it. They worked great and the charge rate was very reasonable and a lot higher than my home NEMA 14-50 can provide. I still don’t need a HPWC at home, but its great to know there are a couple close by my office in a pinch. It’s amazing that Tesla lets you us the HPWC’s and outlets whenever you need to and they gave me 134 miles of extra range that day for free.

They gave me 134 miles of extra range that day for free.

This post first appeared on Teslarati.