Monday, April 07, 2008

You'll Buy an Electric Car Someday - You'll Charge it!

Has anyone else noticed how expensive gasoline is these days? Ten years ago a gallon of gas could be bought for under $1.00. Gasoline hit the $2.00 mark in 2004, and we were paying $3.00 per gallon in 2006. Now it looks like gas might hit $4.00 per gallon before the end of this year. If this trend continues, we’ll be paying $6.00 per gallon in 2012. Car manufactures are taking notice of this, and several have electric cars in the works.

Since the days of cheap gasoline seem to be gone forever, a sudden shift to electric cars is inevitable. With the automotive industry already working on electric cars, and battery manufacturers competing to see who can make the best batteries, we’re well on our way. The first generation of electric cars will be equipped with a small gasoline engine, included to extend the range of the car. These are called plug-in-hybrid-electric-vehicles, or PHEV’s. And while the PHEV is a great intermediate step, the gasoline engine will eventually be eliminated altogether. Quick charging batteries, and the emergence of battery charging stations, will make that possible.

It looks as if the transition to electric cars will be more of a landslide than a trickle, a scenario that will create some problems. The electric grid, which is already strained in some parts of the country, may not be able to handle the additional load of charging all of these vehicles. Fortunately, most of these electric cars will be charged at night, when other demands on the grid are low. V2G technology (cars that supply power to the grid during the day), will help, but infrastructure upgrades are needed before that can happen. We’ll pay for improvements, and for the upgrades needed for the implementation of V2G technology, through higher electric rates.

Another problem created by a sudden shift to electric cars is that there will be less money available for highway maintenance. Federal and state taxes on gasoline pay for road improvements, bridges, and maintenance. A sudden switch to electric transportation will reduce gasoline tax revenue, and it’s likely that we’ll be required to pay our share of road-usage taxes in some other way. If you use 25 gallons of gas per month, enough to drive about 500 miles, you’re paying about $150.00 per year in road-use taxes. Many of us are paying much more than that. To make up for the loss, we might see additional taxes on our electric bill, but that isn’t the best solution. There is no easy way of determining how much electricity is used for charging our car(s), and how much is ordinary household use. It’s likely that we’ll calculate our share of road-use tax via our state and federal income tax forms. Tax forms will include questions designed to determine how much electricity we use for charging our electric car(s).

The sudden need for more electricity does more than just strain the electrical grid, it means that coal-fired power plants will burn more coal. This will drive up the cost of coal, and you’ll pay for that on your electric bill. Any way you look at it you’re going to have to pay for electricity at an ever-increasing rate, and you’ll soon be taxed for the electricity you use at a much higher rate than you’re paying now. Just as gasoline prices have skyrocketed in recent times, the days of cheap electricity will end as well.

What can you do about it? I’m glad you asked!

Most of the country pays about ten cents per kilowatt hour for electricity now, making it possible to charge an electric vehicle for less than $1.00 per night. You’ll be able to drive 40 miles or more on an overnight charge, instead of burning five to eight dollars worth gasoline at today’s prices. What a deal! But with the likelihood that electric rates will soon mimic the steep increase of gasoline prices, it would be wise to consider other options. For many, a solar electric (PV) system is a great way to deal with the expense of, and problems related to, a sudden switch to electric transportation. It seems that those who already drive electric cars are aware of this, since 50% of them also use solar electric systems.

Off-grid or Grid-tied?

A grid-tied PV system may be the best choice for those served by a robust electrical grid. Electricity is fed into the grid during the day, offsetting electricity pulled from the grid at night. With a large enough system, the user contributes more than he withdraws, and therefore pays nothing for electricity. An off-grid PV system may be the best choice for those with marginal electric service, but system inefficiencies and the added cost of batteries will result in a much higher system cost.

Size matters:

While it’s alright to start out small, it’s going to take a substantial PV system to charge an electric car’s battery bank. GM’s Volt PHEV can be charged via a 110 volt standard home outlet, and a full charge will take 6 ½ hours. I suspect that the charge current will exceed 10 amps, or about 1100 watts, representing a pretty hefty load on a PV system. A 2kw grid-tied system will produce enough electricity (on sunny days) to offset the charging power supplied by the grid at night, but an off-grid system will need to be substantially larger than that in order to compensate for system inefficiencies. If you opt for an off-grid system, and if you’re able to charge your PHEV during the day, you’ll achieve efficiencies similar to those who implement a grid-tied system. An off-grid PV system operates much more efficiently when power flows directly from the solar panels to the load, instead of temporarily storing that power in PV system batteries and retrieving it later. Another thing to consider is that a two-car family will need a PV system twice as large as a one-car family. Still, you can start out with a small system that will generate a portion of your needs, and upgrade later.

PV system cost vs. savings:

As you do your homework you might be shocked by the high cost of a PV system, but don’t forget to do the math. By switching from a gas-powered car to electric, you might be eliminating $3600.00 worth of gasoline per year from your budget. If you apply those savings toward the purchase of a PV system, the payback period will be 2 to 5 years. And better yet, you’ll be driving on FREE power from the sun once your solar equipment is paid for. Any economist, I suspect, would call that a good investment.

Something else to consider:

Once your PV system is in place, you’ll use it as much as possible to charge your PHEV. During times when the sun doesn’t shine, you’ll need to charge your PHEV in some other way. For most people, that other way will be the power grid. This will be the best option as long as electric rates remain reasonable. Charging can be done by wind power, micro hydro, or even a bio-fueled generator after that.

A bonus:

If you don’t drive much on the weekends, you’ll have a surplus of electricity for household use at a time when you’ll need it most.


Like the invention of radio, TV, and the personal computer, the plug-in electric car appears to be the next great invention that will change the way we live. The sudden switch from gas to electricity will trigger an increase in the price we pay for electricity, but those who use PV for some or all of their needs will suffer the least. The surge in the cost of electricity will result in a greater demand for solar panels and equipment, leading to shortages and price increases. To avoid dealing with those shortages and price increases, now is the time to install solar electric panels and systems. And as an added bonus, the massive shift away from internal combustion engines, combined with an increased use of solar panels, will have a positive affect on the quality of our air. You gotta love that!

How will you charge your electric car?

With a credit card of course.



Anonymous said...

Installing PVs on a home is a tragic waste of valuable resources that should be used in building carbon free, efficient cental power stations, which is the only effective means to control energy. Those home systems also use awful lead acid batteries, which are deemed hazardous materials and cannot even be shipped by most carriers.
Electrical geenration is a job for a centralized organization of professionals, and is far more flexible than the systems these amateurs are installing as DIYers.
The idea of recharging a car by using solar panels is totally absurd - most cars don't sit around the house for hours - they go to work or provide transportation during the daylight hours. They also need way too much power to be supplied by a solar panel. Plug-ins that can be charged with 8 kilowattthours will
be supplanted in the not distant future by all electrics, which can need up to 50 or 60 kilowatt hours,
which is way beyond the capabilities of any solar roof - that's approximately 30 days' worth of juice for an entire hours.

d said...

Hi SJ,

Remember that in the UK petrol/gas is already twice what you pay for it, and electricity maybe 3x.

IIRC, my calculations suggest that to fully charge an electric car's ~10kWh battery on a winter's day (assuming that you don't need to actually drive it that day!) would require 10kWp of panels which is a lot. More than I could fit on my roofspace for example...



Solar John said...

Hey Damon,

My thinking was that a 2kw pv array, getting 4 peak hours of sunlight per day, will supply 8kwh to the grid. I've read that the Volt's battery pack will be rated at 16kwh. Assuming that you wouldn't discharge it beyond 50%, you would need to put back no more than 8kwh. It seems that I didn't allow for inefficiencies, but on the other hand, I was talking about a grid-tied system. It still seems to me that a 2.5kw grid-tied system would do the job (at least on sunny days). Am I wrong?

The anonymous commenter makes a good point in saying that electric cars of the future will require much more than 8kwh per night for a charge. Still, I would rather have a PV system that can meet a portion of my needs than to be totally dependant on the utility company.

As for the hazardous materials comment: Don't forget that by producing my own electricity, I'm not using electricity from a coal-fired or nuclear power plant. When my batteries reach the end of their useful life, they'll be recycled properly.

Centralized power generation has it's pro's and con's. There are losses in sending electricity over the wires after all. On the other hand, since I generate so little power with my PV system, I strive to make my system as efficient as possible. I fail to see how I'm wasting valuable resources as the writer claims. sj

d said...

Hi SJ,

Some of the newer EVs have or will have very shortly Lithium-chemistry cells and I'm not aware of a minimum DoD for them cf lead-acid, so the vehicle may be able to use the entire rated capacity. But please tell me if I'm wrong!

My 1kWh/1kWp/day is an average over several days for mid-winter round here with optimally-oriented fixed panels, so yes, on sunny days you'd do better, but you might still have to drive on the others!

BTW, I worked out that if I commuted by road by EV to my main client in London it would require the same energy as the public transport I usually take, ie about 7kWh round-trip. But I usually only go in a couple of days per week. So I'd average 1--2kWh/day charge needs and thus things are plausible with quite a small PV array.



vanessa said...

Reading this article and comments makes one thing clear. Gas or electricity - the future of my credit card isn't bright.

tc worley said...


You seem to attract critics quite well. I'll spare you my negative thoughts and let you know that I appreciate the steps you have taken and are planning to take. Your efforts, while not perfect, are helping offset what so many ignorant people are doing. Good on you. I intend to use your posts and your critics' feedback as a resource. Thanks.

Apolka said...

For miss anonymous: how do i say this politely? you're completely in the wrong on your analysis. Distributed solar power is a definite must for our grid system. For one, you lose a large percentage of centrally generated electricity (be it coal, natural gas, wind or solar driven) and so not having to transmit the power is a great advantage. Second, the idea of recharging your car using solar panels is not absurd at all. You do it at night when the cumulative demand for energy is low. Please read up on base vs. peak load. The Tesla Roadster is the first all electric car in recent years and uses a lithium-ion battery, which is not toxic. Most hybrids use Nickel-Cadmium batteries, not lead acid ones. And while you're correct, most cars don't sit around all day at the house, they do get driven to work. PG&E, a large CA based utility, along with many other startups and more entrenched companies is already working on ways through which these plug in cars can feed energy back into the grid. I hate to bust your bubble, but please be more informed before you write comments that can influence people. The person who wrote this article made a slight error - even when the sun doesn't shine, PV systems gather plenty of light. Please read up on the fact that Germany (not a particularly sunny place) is now the world leader in distributed solar power (PV systems on roofs). Oh, and before you call unleash unnecessary vitriol, I have my MBA and have worked in the energy industry for several years, most recently as a vice president in the solar group of a major bank.

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