I converted my home charging service to Eversource Time of Use (TOU) rates just about a year ago, so I thought I would report my experience over this first year.
I have a separate electric service for charging my car so all the power on the meter is for car charging, except for a small amount used for a security lamp.
With just about 11,000 miles driven in the past year, I have used a total of 4,501 kWh from Eversource in that time. My total cost of electricity was $809.82, which includes the energy cost, plus the delivery cost, plus the monthly fee ($9.99/month). That is an average cost of 17.99 cents/kWh. The TOU rate affects only the delivery portion of the bill. Compared to what I would have paid if the service had been on normal residential rates, I saved $96.15 or 10.6% of my total bill. More meaningful is that the savings is 20.5% of the delivery portion of the bill (i.e., including the monthly service fee but excluding energy). So, the savings is small, but it did not cost anything to switch to TOU rates, so I am glad I did it.
Although I tried hard to do most charging during the nighttime off-peak hours, I did use some peak period power during the year. In most cases this was for preheating or precooling the car. I used 159 kWh of peak energy, which is about 3.5% of the total power used. The penalty for using that power was $16.76 for the year – in other words, that is how much extra I paid to buy that power in peak period versus in the off-peak period.
My total savings would have been higher if I had driven more miles, of course. And my percentage savings would have been higher, because the fixed monthly fee would become a smaller part of each kWh’s cost. The monthly service fee is higher for TOU ($9.99/month) than for normal residential service ($6.43).
One other relevant point is that Eversource changed the TOU rates on January 1, 2017. The savings was much more under the 2016 rates than it is now. In my first month of TOU in late 2016, I saved more than 4 cents/kWh, while I saved an average of only 2.1 cents/kWh with the new rates. Savings are somewhat higher in the summer than in the winter, which is helpful since we are likely to drive more in the summer, and I am more likely to use peak period preheating in the winter.
Besides charging at home, we used Superchargers for trips away from home. According to my notes, we used just about 400 kWh of energy from Superchargers over the year, plus a small amount from Level 2 chargers here and there (not tracked). It is an amusing coincidence that our Supercharger energy use during the year was almost exactly the amount (400 kWh) being provided free by Tesla to cars that do not have free Supercharging.
I have a separate electric service for charging my car so all the power on the meter is for car charging, except for a small amount used for a security lamp.
With just about 11,000 miles driven in the past year, I have used a total of 4,501 kWh from Eversource in that time. My total cost of electricity was $809.82, which includes the energy cost, plus the delivery cost, plus the monthly fee ($9.99/month). That is an average cost of 17.99 cents/kWh. The TOU rate affects only the delivery portion of the bill. Compared to what I would have paid if the service had been on normal residential rates, I saved $96.15 or 10.6% of my total bill. More meaningful is that the savings is 20.5% of the delivery portion of the bill (i.e., including the monthly service fee but excluding energy). So, the savings is small, but it did not cost anything to switch to TOU rates, so I am glad I did it.
Although I tried hard to do most charging during the nighttime off-peak hours, I did use some peak period power during the year. In most cases this was for preheating or precooling the car. I used 159 kWh of peak energy, which is about 3.5% of the total power used. The penalty for using that power was $16.76 for the year – in other words, that is how much extra I paid to buy that power in peak period versus in the off-peak period.
My total savings would have been higher if I had driven more miles, of course. And my percentage savings would have been higher, because the fixed monthly fee would become a smaller part of each kWh’s cost. The monthly service fee is higher for TOU ($9.99/month) than for normal residential service ($6.43).
One other relevant point is that Eversource changed the TOU rates on January 1, 2017. The savings was much more under the 2016 rates than it is now. In my first month of TOU in late 2016, I saved more than 4 cents/kWh, while I saved an average of only 2.1 cents/kWh with the new rates. Savings are somewhat higher in the summer than in the winter, which is helpful since we are likely to drive more in the summer, and I am more likely to use peak period preheating in the winter.
Besides charging at home, we used Superchargers for trips away from home. According to my notes, we used just about 400 kWh of energy from Superchargers over the year, plus a small amount from Level 2 chargers here and there (not tracked). It is an amusing coincidence that our Supercharger energy use during the year was almost exactly the amount (400 kWh) being provided free by Tesla to cars that do not have free Supercharging.
