Sunday, March 18, 2012

Eleven Months in Our Nissan LEAF and the End to Our Solar Net Metering Year





We're entering our twelfth month with our Nissan LEAF and still purring along with zero problems and a lot of quiet, smooth, enjoyable miles.  Our LEAF now has 10,217 perfectly reliable miles and no sign of a problem yet.  The car is a real pleasure to own and to drive, and the spaciousness and flexibility of its interior make it useful for every kind of driving that we need it to do.  That includes family pleasure trips, going out to dinner with four adults and a baby aboard, ferrying elderly parents to appointments, grocery trips, and pleasure driving, and even moving small furniture and boxes.


Speaking of pleasure driving, I want to go into the question of performance driving, or as I like to say, "are we having FUN yet?"  Months ago in this blog, I described myself as a "car guy", and I really do enjoy driving sports sedans and coupes with good performance, steering and handling.  Coming from a BMW 3 Series coupe before the LEAF, I do know what a good handling car feels like, and the LEAF, not surprisingly, doesn't really measure up by comparison.  Being a front wheel drive car, lacking an independent rear suspension and performance wheels and tires, and being a heavier car, the LEAF isn't intended to perform like a sports sedan.  And the higher seating position than in an average sports sedan due to the battery placement below the seats doesn't contribute to a sporty feel.  






That said, though, the LEAF has a low center of gravity due to the placement of the batteries below the floor, a pretty even front/rear weight distribution, and good power at moderate speeds.  So it really can be fun to drive.  Due to the impressive torque of the electric motor being available at low rpm, it spurts ahead at traffic lights if you want to pass other cars to change lanes.  It has a smooth flow of power up through highway speeds, and the lack of gear changes makes the power flow even more satisfying.  The quiet operation and the lack of engine clatter make the power delivery even more impressive, and you just "whoosh" along.  


I did take the LEAF to my favorite piece of twisty road and I did enjoy the instant torque in the corners.  But the higher seating position, the light, uncommunicative steering feel, the eco-centric tires and a fair amount of body lean reminded me that this was no BMW.  So I've come to enjoy driving the LEAF in the way it was designed to excel, smoothly and rather economically.  As someone said on the MyNissanLEAF forum last year, the LEAF encourages one to drive more "Zen-like". In fact, I've found that my driving economy has increased over the months that I've been driving the LEAF, mostly because I've begun to enjoy driving smoothly and braking gently to regenerate as much energy as I can.  I will say that it is fun to arrive at the top of a long hill and coast down the other side and actually gain energy back in the process.  For me, that is the way to enjoy driving the LEAF; to experience the pleasure of smooth driving that is so different from the vibrating, noisy gasoline engine, and to enjoy the power and the torque of the electric motor whenever I need it.  I have to say that the electric drive experience is something that I've become addicted to, and I won't willingly go back to the inefficiency and fuss that are essential parts of driving a car with a gasoline engine.   LEAF owners often feel that we are driving a well-kept secret, and that when others drive an EV for the first time, they too realize how great it is to drive electric.


Net Metering Year End Billing:  
Our solar power net metering year ended with the meter reading on March 7.  I was pleased to see that our February bill was only $49.65 and that after subtracting the $43.14 credit balance that still remained from the sunnier months of the year, our final actual bill for the twelve months was only $6.51 even though we used almost 3,000 kWh MORE than our solar power system generated!  Yes, amazing as it sounds, this bill is the year's total for all of our household power use AND charging our LEAF for 10,217 miles!  This demonstrates the beauty of the combination of solar PV power and time-of-use rates.   We generate solar power mostly during the Peak hours when rates are highest and we get full retail credit for those kWh against the power that we use.  This is especially valuable during the summer months, when we get credit for some of our solar power generated at 54 cents/kWh, while paying an average of only 13 cents/kWh for LEAF charging after midnight.


Notice the negative dollar amounts due to the net solar power flowing back to the utility.  This adds up to a savings of about  $37 on this bill alone.  The savings are much more pronounced in summer months.  Note that we do not use air conditioning in the home.

This final bill is the outcome that I have been very interested in seeing for the past 15 months or so, since I decided that the single meter time-of-use TOU-D-TEV rate plan would suit our needs best.  I created a lot of spreadsheets and at one point I concluded that we could drive about 14,000 miles per year without paying anything in electric power costs for our household use and LEAF charging.  I can now confirm that that number should be at least 17,000 miles at the current average efficiency of our LEAF of 3.2 miles/kWh.


During the year, though, something changed in our household power use.  We had three family members move in with us in July, as part of their transition to living nearby.  I calculate that we used 2,262 kWh of our total power use of 11,408 kWh in the year because of the extra residents.   I calculated this by comparing each month's usage with the same month in the previous year.   






Since the additional family living with us is a temporary thing, I conclude that the extra kWh that we used due to their presence caused our year's bill to be more than zero, and that it wasn't due to the kWh used to charge the LEAF, so our LEAF charging costs were zero.  Had we not had the extra residents, our total net usage for the year would have been only about 700 kWh and we would have had a total bill of zero.   If you want to argue that all of our usage should be counted equally, then you could assign that $6.51 total year's bill equally against our total usage of 11,408 kWh for the year, for a cost per kWh of $0.00057 or about six one hundredths of a cent, and charging the LEAF at home cost us $1.72 for the whole year!  This is obviously ridiculous, and I will conclude that our total power cost was essentially zero.  As full disclosure, I haven't included the dollar or so that we are charged per month for billing costs, just to be SCE customers.


Of course, besides the major benefit of special TOU EV charging rates from our utility, this power is "free" to us only because we spent about $25,000 out of pocket five years ago to install the solar PV system.  At the time we installed the PV system, the payback time penciled out to 12 or 13 years.  But now that we can replace the cost of expensive gasoline, the payback period is closer to 7 years.  Since we've had the system installed for five years, we'll have paid off our solar system in just a few more years.  At that point in time, our cost for electricity to power our home and for about 17,000 miles of driving per year truly will be zero!


The Numbers:
2011 Nissan LEAF SL Placed in Service: March 30, 2011
All Home Charging Done Using: 220 Volt Aerovironment/Nissan Level 2 EVSE
Home Solar PV System: 24 Sunpower 215W panels totaling 5.16 kW DC mounted on a 20 degree South facing roof.
Total Solar PV Power Generated for Net Metering Year Ended February 2012:  8,568 kWh
Total Net Power Use for Net Metering Year Ended: 2,949 kWh (This is total household and Leaf charging usage minus solar power generation.)
Total Electricity Costs for the Net Metering Year Ended: $6.51  (see text)


Month:  February 2012
Total Miles at Month End: 10,217 
miles
Miles Driven in Month:  944 miles
Electric Power Used for Charging in Month: 291.2 kWh (measured at wall power source, includes public charging)
Public Charging in Month, Power Use:
 36.5 kWh 

Charging at Home in Month, Power Use: 254.7 kWh
Energy Efficiency, Month of February 3.24 miles/kWh (wall to wheels)

Total Charging Energy Used, Lifetime, and Net Metering Year Ended: 3,199.3 kWh (Includes public charging)
Energy Efficiency, Lifetime:  3.19 miles/kWh (wall to wheels)
Energy Efficiency, Lifetime:  31.35 kWh/100 mi (wall to wheels)
Number of Home Charging Days in Month: 19
Most Electric Energy Used for Charging in a Day in February:  28.0 kWh  (7.6 charging hours, includes 6.9 kWh of public charging)
Most Electric Energy Used at Home for Charging in a Day in February: 21.3 kWh (5.8 charging hours)
Least Electric Energy Used at Home for Charging in a Charging Day in  February : 8.4 kWh  (2.3 charging hours)
Average Electric Energy Used for Home Charging in a Charging Day in 
 February :  13.4 kWh  (3.6 charging hours)
Household Power Used for Month:  787 kWh (without car charging)
Total Power Used for Month:  1,042 kWh (includes car charging)
Solar PV Power Generated for Month:  616 kWh
Net Power Used or Sent to Grid for Month:  426 kWh net used
February Electric Bill, So Cal Edison, Schedule TOU-D-TEV:  $49.65 
 (A charge in this amount will be added to our net metering total charge for the year.)
Solar Net Metering Year Total Cumulative kWh Used at Month #12:  2,949 kWh (Total kWh net used for the net metering year. This is total household and EV charging usage minus solar PV generation.)

Solar Net Metering Year Total Cumulative Cost at Month #12:  $6.51 (Total energy and delivery costs for all power usage for the net metering year.  See text.)
Cost for Charging Car in February:  $0.00 (see text)
Cost per Mile:  $0.00  (see text)
Cost for Charging Car, Lifetime: $0.00  (see text)
Cost per Mile, Lifetime: $0.00  (see text)

(If We Didn't Have Solar Power, Est Cost for Charging Car in February: $33.11)
(If We Didn't Have Solar Power, Est Cost per Mile in February: $0.035) 
Average (Mean) Miles per Driving Day in February:  38.5 miles

Average (Median) Miles per Driving Day in February:  40 miles
Longest Day's Driving in February:  74 miles (no charging mid-trip)
Shortest Day's Driving in February:  15 miles
Number of Times we Took the Prius Instead of the LEAF Due to Low Charge: 3
Unexpected Low Charge and Unable to Reach Destination:  Never





Saturday, March 3, 2012

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