Well, I'm still trying to figure out which electric rate plan to go with from SCE, so I spent about two hours today really diving into the numbers based on my historical usage (from SCE.com), and some assumptions, which I will detail below. I thought this might be useful for someone who is considering a Leaf, or for those that already have them as a comparison.
Some important initial information:
I do not have solar.
Numbers are based on the following:
13,000 miles per year (35.6164 miles per day) at an average of 4.8 miles per KWH (which is what I've maintained for 800 miles so far).
All EV charging done at the least expensive time of day each rate plan allows.
Let's start with the bottom line:
Based on my usage patterns, 'fueling' the Leaf will cost me:
Residential Rate Plan: $804/yr.
TOU-D-TEV Rate Plan: $792/yr.
TOU-EV-1 Rate Plan: $324/yr.
Cost of fuel for the ICE vehicle the Leaf replaced: $2,304 per year.
That is based on the same 13,000 miles per year, average fuel economy of 22 mpg, and gas at average of $3.90 per gallon. I kept meticulous fuel records on my previous vehicle, tracking every tank's number of miles driven and number of gallons added, so 22 mpg is the actual fuel economy I had for the entire time I owned the vehicle. I was always careful to try and drive as efficiently as possible.
Conclusions:
What I found very interesting is that based on my predicted usage patterns, the residential rate and the TOU-D-TEV rate are pretty much the same. However, I have the added inconvenience of having to pay very close attention to when I use electricity throughout the day. So, there is no real incentive for me to use that TOU-D-TEV rate. The one rate that would save me a signficant amount of money is the TOU-EV-1 rate, however I have yet to determine how much the electrical work will cost to get that second meter installed. If it is more than about $1,000, I don't think it would be worth it.
I'm really glad I did the analysis, as I now have a lot more information to make an informed decision.
So, let's dig into some details of my methodology.
My sample was based on three months of electricity usage data - a high summer month, a high winter month, and a month that I typically use little or no climate control. Based on what I saw in my SCE data, I generally have 2 high summer months, 2 high winter months, and 8 months where I use little or no climate control. With that in mind, I extrapolated the year based on those assumptions.
Based on 13,000 miles per year, and an average of 4.8 miles per KWH, I calculated that I would be adding approximately 225 KWH to each month's usage.
For the residential rate, I added that 225 KWH to actual usage in the months I sampled, and determined the resulting power usage in each of the five tiers according to SCE's standard tier structure (detailed on each bill), and calculated accordingly. For example, in the high summer month I sampled, I detemrined that adding 225 KWH would have pushed me into Tier 5, and that would have resulted in an overall bill of $273.00.
For the TOU-D-TEV rate, I assumed the monthly 225 KWH to charge the Leaf would be Super Off Peak, that there would be 100 KHW per month that would be at Peak usage rates (which is in line with how much I consume now if I don't run climate control between 10 and 6, as shown in SCE data), and the my actual usage in the sample months minus 100 (counted in Peak usage) is what I used to calculate Off-Peak usage.
To determine how much the new monthly bill would be after adding 225 KWH in Super Off Peak, I first had to determine how many KWH would be counted as Tier 1 under the TOU-D-TEV plan in each of the sample months. To do this, I used the actual usage in KWH on the Residential Rate Plan Tiers 1 and 2 for those months from my bills to determine the number of KWH that would be counted as Tier 1 in each month on the TOU-D-TEV plan. Tiers 1 plus 2 on the Residential Rate Plan is equal to Tier 1 on the TOU-D-TEV plan.
Then, based on how many KWH of total usage I had allocated to each time period (SOP, OP and P) using the method described above, I calculated what percentage of the total KWH for the month each time frame represented. For example, in my high summer sample month, I found that of the 1,272 KWH (1,047 KWH from my actual bill, plus 225 KWH to charge the Leaf), 17.7% of that would be SOP (225/1272), 7.9% would be Peak (100/1272) and 74.4% would be off peak (947/1272).
Using those percentages, I determined how many KWH of the Tier 1 allowance would be allocated to each time period. For example, in the high summer month, I found that I had a Tier 1 allowance of 524 KWH (based on Tier 1 plus Tier 2 on my bill which is on the Residential rate plan). So, I found that of the 524 KWH that would be billed at the Tier 1 Summer rate, 92.75 of those would be billed at SOP (524 x .177), 41.4 KWH would be billed at Peak (524 x .079), and 389.86 KWH would be billed at OP (524 x .744).
I then used the current rates for Summer Tier 1 SOP (.11 per KWH), Peak (.19 per KWH) and OP (.14 per KWH) on the TOU-D-TEV rate plan to calculate how much I would be billed for Tier 1 usage in that month - a total of $72.65.
Finally, I took the total number of KWH allocated to each time frame, and subtracted the number of KWH that would be billed in Tier 1 for each time frame to determine how many KWH I would be billed for in each time frame in Tier 2 for the month. For example, in the high summer month I sampled, I determined earlier that 225 KWH would be at SOP, and that 92.75 of those SOP KWH would be billed at Tier 1, so that means that 132.25 KWH of that SOP usage would be billed at Tier 2 (225 - 92.75). Using the same method, I determined that 58.6 KWH in Peak would be billed in Tier 2 that month, and 557.14 KWH in OP would be billed in Tier 2 that month. I then simply calculated how much the Tier 2 usage would be billed at based on the rate chart for TOU-D-TEV (.20 per KWH in SOP, .70 per KWH in Peak and .31 per KWH in OP). That total was $240.18.
I then added Tier 1 usage to Tier 2 usage to come up with a total bill of $312.83 for that month, if I had been charging the Leaf that month, and on the TOU-D-TEV plan.
For the TOU-EV-1 calculations, I simply took the overall bill from that month, and added 225 KWH x .12 per KWH (which is the Off Peak TOU-EV-1 rate) to the bill. For example for the high summer month, my actual bill was $206.57. I added another $27 for Leaf charging, and that resulted in a bill of $233.57 if I had charged the Leaf that month.
I used the same mehodology as described above to calculate the Residential, TOU-D-TEV and TOU-EV-1 rates for the high winter usage month, and the low usage month where I use no climate control. I then used the factors I mentioned in the very beginning of this post (2 months high summer usage in a year, 2 months high winter usage in a year, and 8 months of no climate control in a year) to extrapolate the annual cost for electricity for a year. Those figures are:
Residential: $2,031
TOU-D-TEV: $2019
TOU-EV-1: $1551
To determine annual cost to 'fuel' the Leaf, I calculated an annual average for electricty before the Leaf by taking my high summer usage month, my high winter usage month, and my low usage month and extrapolating based on 2 months of high summer usage, 2 months of high winter usage, and 8 months of low usage. I could have just added up all of my bills, but I wanted to compare 'apples to apples' based on my earlier calculations to get a better sense for it.
Then, I took the difference between that annual usage before adding the Leaf ($1,227) and the total energy usage with the Leaf shown above to determine the annual cost to 'fuel' the Leaf.
Some important initial information:
I do not have solar.
Numbers are based on the following:
13,000 miles per year (35.6164 miles per day) at an average of 4.8 miles per KWH (which is what I've maintained for 800 miles so far).
All EV charging done at the least expensive time of day each rate plan allows.
Let's start with the bottom line:
Based on my usage patterns, 'fueling' the Leaf will cost me:
Residential Rate Plan: $804/yr.
TOU-D-TEV Rate Plan: $792/yr.
TOU-EV-1 Rate Plan: $324/yr.
Cost of fuel for the ICE vehicle the Leaf replaced: $2,304 per year.
That is based on the same 13,000 miles per year, average fuel economy of 22 mpg, and gas at average of $3.90 per gallon. I kept meticulous fuel records on my previous vehicle, tracking every tank's number of miles driven and number of gallons added, so 22 mpg is the actual fuel economy I had for the entire time I owned the vehicle. I was always careful to try and drive as efficiently as possible.
Conclusions:
What I found very interesting is that based on my predicted usage patterns, the residential rate and the TOU-D-TEV rate are pretty much the same. However, I have the added inconvenience of having to pay very close attention to when I use electricity throughout the day. So, there is no real incentive for me to use that TOU-D-TEV rate. The one rate that would save me a signficant amount of money is the TOU-EV-1 rate, however I have yet to determine how much the electrical work will cost to get that second meter installed. If it is more than about $1,000, I don't think it would be worth it.
I'm really glad I did the analysis, as I now have a lot more information to make an informed decision.
So, let's dig into some details of my methodology.
My sample was based on three months of electricity usage data - a high summer month, a high winter month, and a month that I typically use little or no climate control. Based on what I saw in my SCE data, I generally have 2 high summer months, 2 high winter months, and 8 months where I use little or no climate control. With that in mind, I extrapolated the year based on those assumptions.
Based on 13,000 miles per year, and an average of 4.8 miles per KWH, I calculated that I would be adding approximately 225 KWH to each month's usage.
For the residential rate, I added that 225 KWH to actual usage in the months I sampled, and determined the resulting power usage in each of the five tiers according to SCE's standard tier structure (detailed on each bill), and calculated accordingly. For example, in the high summer month I sampled, I detemrined that adding 225 KWH would have pushed me into Tier 5, and that would have resulted in an overall bill of $273.00.
For the TOU-D-TEV rate, I assumed the monthly 225 KWH to charge the Leaf would be Super Off Peak, that there would be 100 KHW per month that would be at Peak usage rates (which is in line with how much I consume now if I don't run climate control between 10 and 6, as shown in SCE data), and the my actual usage in the sample months minus 100 (counted in Peak usage) is what I used to calculate Off-Peak usage.
To determine how much the new monthly bill would be after adding 225 KWH in Super Off Peak, I first had to determine how many KWH would be counted as Tier 1 under the TOU-D-TEV plan in each of the sample months. To do this, I used the actual usage in KWH on the Residential Rate Plan Tiers 1 and 2 for those months from my bills to determine the number of KWH that would be counted as Tier 1 in each month on the TOU-D-TEV plan. Tiers 1 plus 2 on the Residential Rate Plan is equal to Tier 1 on the TOU-D-TEV plan.
Then, based on how many KWH of total usage I had allocated to each time period (SOP, OP and P) using the method described above, I calculated what percentage of the total KWH for the month each time frame represented. For example, in my high summer sample month, I found that of the 1,272 KWH (1,047 KWH from my actual bill, plus 225 KWH to charge the Leaf), 17.7% of that would be SOP (225/1272), 7.9% would be Peak (100/1272) and 74.4% would be off peak (947/1272).
Using those percentages, I determined how many KWH of the Tier 1 allowance would be allocated to each time period. For example, in the high summer month, I found that I had a Tier 1 allowance of 524 KWH (based on Tier 1 plus Tier 2 on my bill which is on the Residential rate plan). So, I found that of the 524 KWH that would be billed at the Tier 1 Summer rate, 92.75 of those would be billed at SOP (524 x .177), 41.4 KWH would be billed at Peak (524 x .079), and 389.86 KWH would be billed at OP (524 x .744).
I then used the current rates for Summer Tier 1 SOP (.11 per KWH), Peak (.19 per KWH) and OP (.14 per KWH) on the TOU-D-TEV rate plan to calculate how much I would be billed for Tier 1 usage in that month - a total of $72.65.
Finally, I took the total number of KWH allocated to each time frame, and subtracted the number of KWH that would be billed in Tier 1 for each time frame to determine how many KWH I would be billed for in each time frame in Tier 2 for the month. For example, in the high summer month I sampled, I determined earlier that 225 KWH would be at SOP, and that 92.75 of those SOP KWH would be billed at Tier 1, so that means that 132.25 KWH of that SOP usage would be billed at Tier 2 (225 - 92.75). Using the same method, I determined that 58.6 KWH in Peak would be billed in Tier 2 that month, and 557.14 KWH in OP would be billed in Tier 2 that month. I then simply calculated how much the Tier 2 usage would be billed at based on the rate chart for TOU-D-TEV (.20 per KWH in SOP, .70 per KWH in Peak and .31 per KWH in OP). That total was $240.18.
I then added Tier 1 usage to Tier 2 usage to come up with a total bill of $312.83 for that month, if I had been charging the Leaf that month, and on the TOU-D-TEV plan.
For the TOU-EV-1 calculations, I simply took the overall bill from that month, and added 225 KWH x .12 per KWH (which is the Off Peak TOU-EV-1 rate) to the bill. For example for the high summer month, my actual bill was $206.57. I added another $27 for Leaf charging, and that resulted in a bill of $233.57 if I had charged the Leaf that month.
I used the same mehodology as described above to calculate the Residential, TOU-D-TEV and TOU-EV-1 rates for the high winter usage month, and the low usage month where I use no climate control. I then used the factors I mentioned in the very beginning of this post (2 months high summer usage in a year, 2 months high winter usage in a year, and 8 months of no climate control in a year) to extrapolate the annual cost for electricity for a year. Those figures are:
Residential: $2,031
TOU-D-TEV: $2019
TOU-EV-1: $1551
To determine annual cost to 'fuel' the Leaf, I calculated an annual average for electricty before the Leaf by taking my high summer usage month, my high winter usage month, and my low usage month and extrapolating based on 2 months of high summer usage, 2 months of high winter usage, and 8 months of low usage. I could have just added up all of my bills, but I wanted to compare 'apples to apples' based on my earlier calculations to get a better sense for it.
Then, I took the difference between that annual usage before adding the Leaf ($1,227) and the total energy usage with the Leaf shown above to determine the annual cost to 'fuel' the Leaf.
