Tuesday, October 5, 2010

Electrical Charging Costs and Special Utility Time of Use Programs



Costs of Driving an EV Compared with Driving a Internal Combustion Engine (ICE) car:
Nissan says that average electrical rates in the United States are about 11 cents per kilowatt hour (kWh).  EVs can drive about 4 miles per kWh of power from their batteries. So it costs an average of 2.75 cents per mile for power, or $2.75 for 100 miles of driving.

The Toyota Prius averages 50 mpg.  At $3 per gallon, that would be $6 per 100 miles.

A great many cars on the road today average 20 mpg combined. At $3 per gallon, that would be $15 per 100 miles.

If a family drives an EV an average 12,000 miles per year, they would save $390 per year over driving a Prius, and they would save $1,470 over driving an average 20 mpg ICE car.  As gas prices rise, these savings will become more dramatic.  For homes like ours with excess solar power available, the electricity costs can be considered zero for the miles driven on excess solar power, so again, the savings would be greater.

Maintenance costs for an EV will likely be less than for an ICE.  These include oil and filter changes, belt and timing chain adjustments, and maintenance on the cooling, exhaust, transmission and ignition systems. Except for the systems for cooling the batteries and inverter, EVs usually lack these systems, so maintenance should be far less expensive.

Systems that are common between EVs and ICE cars include tires, brakes and instrumentation systems, though the brakes on an EV will wear more slowly than those on an ICE car because of the EV's regenerative braking system.

Battery replacement costs may be a major expense for EVs kept for longer than their battery warranty periods, which are 8 years for the Leaf and the Volt.  These batteries may cost thousands of dollars and more, though prices may drop a lot in the next decade.  Battery life is still an unknown for the new crop of BEVs and much will be learned on this topic over the next decade, as the performance of the batteries in the hands of consumers is revealed.





Special Utility Time of Use Rates:
Public utilities are interested in encouraging the adoption of EVs for several reasons.  Governments are incentivizing them to make EV adoption more attractive to consumers.  The utilities will be able to sell more electrical power (realize that the utilities will replace the oil companies as energy suppliers for these cars).  If EV drivers charge their cars late at night, the utilities will be able to better balance the use of their power plants.  Most power plants are not efficient to ramp up and down between high and low usage times of the day.  So it is to the utilities' advantage to have power usage increase at night, while not increasing during the daytime peak use times.  It has been calculated that we can add four million EVs in California without building any new power plants IF the EVs are charged at night.

Off-peak charging times are usually any time other than noon to 6 pm.  Some utilities offer so called Super Off-Peak rates for charging between midnight and 5 am.  High power (Level 2) charging at home can reduce overall charging time, and thereby make it easier to charge during the off-peak times.  The EVs' onboard computers and the EVSE systems provide charging timers to that you can program the charging times easily.

For these reasons, utilities are making available special Time Of Use (TOU) rate schedules.  Rates vary widely around the country, but rates as low as 4 cents per kWh are available in some areas.   In my area of Southern California, rates as low as 8 or 9 cents per kWh are available at night as compared with 15 cents for regular daytime use.  That difference could translate to a savings of $210 per year.

To be able to use these TOU rates to charge an EV during off-peak times, a homeowner needs to obtain a special electric meter that can record the times and amounts of power usage.  These TOU meters are usually  available at no extra charge from the utility, and technicians will install them for you.  Some utilities are installing so-called "Smart Meters" that are computerized and can communicate with the utility wirelessly.

In my next blog post:  Where Are We Now in the Introduction Timeline for the New EVs?