## Update to back of napkin math using first month’s SCE Time of Use Tariff

It’s time for an update.  As a response to my \$0.31 per kWh price for charging my ActiveE on Southern California Edison’s Domestic Tariff, I signed up for Electric Time Of Use (TOU). Now there are TWO flavors of the TOU tariff.  One requires a separate meter, the other does not.  The approximate cost for the separate meter and installation at my house was an additional \$2,000 to \$4,000.  Since, we were not sure if we would be staying on Electric after the two year closed-end lease of the ActiveE, we decided to go with the one offered for customers with a single electric meter.  At this point, barring the lack of good choices after the 2 years, we probably will go ahead and get at least a replacement electric vehicle.

So what did we find out after the first month on the new tariff.  First, let me spell out what assumptions were made to calculate the amount of energy used by the AE.  I could have gotten more detailed (counting ALL the emailed kWh usage identified by my Chargepoint EVSE, but decided that I did not really want to do all the calculations and since most of my charging is done at the super-off peak hours and very few outside of these times, that I would overstate the amount of energy and calculate based on the total super-off peak usage AND 10% of off-peak charging to come up with my model.) but I would’ve run out of room on the back of the napkin.  Bottom line, in the new month, I came up with \$0.12024 per kWh to charge this past month under the winter rates.  This assumption puts me at the cost to fill up at home at \$1.20 per day

So, using the 70 mile number – from my electric cost per mile last month is approximately \$0.01714 per mile.  After two months of driving, I have noticed that my average roundtrip is actually a little higher than the 70 mile number.  Let’s call it 85 miles…  So, using this mileage, I was able to recalculate this cost down to \$0.01412 per mile.

Using the revised mileage numbers, 407 miles is \$5.75 vs. \$60.00 approximately 1/12th the cost of ICE.

Folks with lower kWh pricing obviously come out a lot more.  In fact, it’s practically free for those that are on solar power, though not really free, since installing solar DOES cost money.  Now that BMW got a nice group discount at 35%, but still not “free.”

Of course the subsidized power may disappear as electric cars gain greater traction, but there’s a lot of room to go before it gets close to the same level as an ICE car of a similar caliber.  Additionally, it would seem that my rates are bound to go up when Summer Rates kick in, so I will have another update when those bills come in.