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Published on September 17th, 2011 | by Zachary Shahan


Combining Solar Power and Your Electric Vehicle — Too Practical to Pass Up (Reader Comment)

September 17th, 2011 by  


We recently got the following reader comment on a post of Andrew’s on electric vehicles, the smart grid, and residential solar power. It’s a great one, so I thought I’d highlight it further with a quick repost here. Check it out:

May I please emphasize this?

“A small, 1.2-kilowatt solar system priced at around $4,000 will cover charging costs for an electric vehicle for up to 40 years.”

For $4,000 you can buy your ‘gas’ for the next 40 years.

For the next forty years you will be producing the power for your EV for $8.33 a month. Those are fixed dollars, not dollars that will rise with inflation, the $8.33 per month is locked in.

The $185 per month that ICEV owners will be paying for gas? In forty years, based on past inflation, will cost you $1,027.

Let’s use historical inflation rates to look forward to forty years from now…

Price for gas now = $185.
Price for electricity now = $8.33.

Price for gas forty years from now $1,027.
Price for electricity forty years from now $8.33.

Forty years from now $8.33 will have the buying power of $1.44 in today’s dollars. For less than the price of a latte, you charge your EV for a month.

On an annual basis, $12,324 for gas, $100 for electricity.

What’s not to love about that?

(Yes, curmudgeons, there may be some inverter repair necessary along the way, and a tree might need to be trimmed back. Thank you in advance for grousing.)

Image Credit: SunPower


About the Author

Zach is tryin' to help society help itself (and other species) with the power of the word. He spends most of his time here on CleanTechnica as its director and chief editor, but he's also the president of Important Media and the director/founder of EV Obsession and Solar Love. Zach is recognized globally as a solar energy, electric car, and energy storage expert. He has presented about cleantech at conferences in India, the UAE, Ukraine, Poland, Germany, the Netherlands, the USA, and Canada. Zach has long-term investments in TSLA, FSLR, SPWR, SEDG, & ABB — after years of covering solar and EVs, he simply has a lot of faith in these particular companies and feels like they are good cleantech companies to invest in. But he offers no professional investment advice and would rather not be responsible for you losing money, so don't jump to conclusions.

  • Robert Pollock

    You are so right, America has untold, almost uncountable wealth available, it’s just that a few privileged power brokers control almost all of it, and our plan for the future, is much different than theirs. Also, the trillion for IRAQ hasn’t been paid yet, only borrowed so the contractors could be paid in cash out of the American taxpayers creditworthiness.

  • Robert Pollock

    Zach missed one critical and expensive component, the other battery. Not the 21 kw battery in my Spark EV, the one in the ‘off-grid” system I’d need to be able to charge it at home. Southern California Edison has a ‘special’ plan for EV owners, allowing them to charge their cars after midnight for 11c/kwh, which is very cheap. It’s so cheap, solar doesn’t pay but that doesn’t matter because for allowing you that, they also limit the power your whole house uses during peak hours and make you pay a premium/penalty by knocking you up into the highest tiers for all the other electricity you use. Suncity (Musk joined the board) is working on re-cycling li-ion batteries, they’ve seen the need to just ‘break away’ from the utilities.
    Decentralization of everything appears to be the universal solution. Even the one sewage treatment plant in Palm Springs has to be made into two, or three, or five or six. Instead they’ve just approved another 117 unit “mixed-residential” project on probably the most important piece of real estate left in the city, that will bring traffic, noise, pollution and another 200 or so toilets. Our city leaders have less vision for the future and wisdom to interpret and apply critical information than my dog. Augie has a lot of common sense.
    To be fair, you can ‘net-meter’ (sell back to Edison) the 8 or so kwh per day the 1.2 kwh system will produce at whatever rate Edison is charging you for electricity at that moment, which is an exceptional rule because most utilities pay they’re net metering bills with the lowest rate charged to them from the wholesalers. None the less, the 8kwh isn’t going to offset the $.33/kwh (average of tier 3, 4 and 5) that they’ll charge you for most of the other electricity you use to run your house.
    The best answer is also the most expensive upfront: Build a 5kwh system and go off grid. Then all your energy costs will be fixed during retirement.
    Don’t get me started on reducing use: Why aren’t the swimming pools insulated if they’re heated!?!? Doesn’t anyone know about geo-thermal? It will reduce AirCond costs by more than 50%. And most importantly, losing the stick-frame building code, along with Leed and the rest of it. Thermal mass is required to moderate temperature extremes. Concrete, insulated on the warm side which is outside, not inside. Rigid insulation can bring colder ground temperatures near the surface, solar furnace-towers, can instigate natural ventilation that will increase as it gets hotter. No moving parts.

  • Pingback: The Green Life: Top 5 Green Life Ingredients | Planetsave()

  • A 1.2 kW hour system will produce on average about 6 kilowatt-hours of electricity per day over the course of the year. This will vary by region. That might be enough to drive 25 miles per day or a little over 9,000 miles per year. If you have a car that gets 25 mpg then you save the cost of a gallon of gas per day, or around $110/month, not $185. But forget about those gas savings. This 6 kilowatt-hours of electricity would have cost you around 60 cents a day or $20 a month if you purchased it from the grid. So the person with the PV system saves $110/month and the person who charges his EV off the grid saves $90/month. So you’re saving an additional $20/month by installing a PV system. Even if the price of gas goes up the savings is still only $20 over what charging from the grid would have saved you. Of course grid electricity will become more expensive and at that point a PV system will make more sense.

    • Anonymous

      Tom, apparently the program allows the owner of the 1.2kW system to sell their power to the utility and then get back more kWhs that they put in.

      From the original article…

      “San Diego Gas & Electric (SG&E) has equipped area homes with smart grid-based demand response capabilities that enable customers with residential solar power systems to sell electricity to the grid operator according to a rate schedule that pays them more to do so during the day when electric power demand is high than at night, when demand is low.

      Electric vehicle owners, on the other hand, pay lower rates to recharge their vehicles overnight during off-peak hours. The particulars wind up meaning that home solar power and EV owners “only need a solar system that creates half the electricity required by their vehicle to offset its total charging cost….”

      Source: Clean Technica (http://s.tt/13eyl)

  • Anonymous

    I’m shocked that you are saying EVs aren’t an option for average people. There were EV adds during the Super Bowl — why do you think? Because they are available to average folks now.

    • Colin Mckinney

      Existing is not the same as affordable and available. And at $33 – $46K, not really an option for an average wage earner when 40+ MPG vehicles are available for $16K.
      And if you discount price as a reason, I would bet you can not give me a phone number for any dealer in all states but CA that has a Volt or Leaf for sale, call around – I put money down last week, MAY get my car in December.

      I am EV and solar proponent – but reality is price and availability HAS to come down or you will have < 1% of early adopters enjoyning them.

  • Anonymous

    You may be able to ditch the inverter if you’re DC to DC.

    • Anonymous

      Is anyone DC to DC? All the people who are off the grid gave up
      DC a long time ago once inverters improved.

      About the only people I can think that are DC are folks in undeveloped countries who are running a couple of lights and charging their cell phones.

      And don’t forget, with DC to DC you’re still going to need to do voltage matching….

  • Anonymous

    I agree, but I also try to think in terms of what is possible.

    Right now energy efficiency and renewable energy have political enemies. The Republican base has declared war on anything “hippie”.

    If we took the ~$2 billion dollars we spend per day on importing foreign oil and “defending our oil supply” we could rapidly get ourselves off of oil for personal transportation. A trillion dollars a year spent to subsidize EV/PHEV purchases and providing low interest rate loans for renewable energy could get us where we need to go in a hurry. And create a lot of US jobs.

    But that will not happen. At least not unless we give President Obama a Congress which will work with him to make changes on a grand scale.

    I think we’re going to need to be creative in order to get the job done. Let’s consider some low cost ideas….

    1) Use limited monies to finance longer terms for EVs, reducing the monthly out-of-pocket to that of a modest priced ICEV.

    2) Create cheap loans for ICEV->EV conversions. Lots of limited income people could make do with an EV that had only 30 – 40 miles range. Let them take their tired-motor Civic/whatever to a conversion shop and drive off with a EV they could plug in. Make the payoff such that they would end up with a few extra dollars in their pocket each month.

    (That would also create a bunch of conversion shop jobs.)

    3) Let building/parking lot owners write off 100%+ (something more than the actual cost) of installing outlets for EVs. Work out a system where the building/lot owner would be close to zero dollars out of pocket for the installation and could make some modest money for maintaining the outlet. Charge points at work/school would make limited range EVs more usable.

    4) Make low interest loans available for homeowner rooftop solar. Pay the utility company small money to collect the monthly payment as part of their regular bill. Tie collection to property tax systems and default would not be an issue. Upon sale taxes are subtracted before owners get any money out.

    5) Create low interest rate loans for putting solar canopies over parking lots as long as EV charge points are installed.

    6) Extend subsidies for smaller sized battery pack EVs. Lots of people could do quite well with an EV ‘sports car’ – two passenger with limited cargo room. Make them small and light and they require less batteries which saves both cost and weight.

  • euroflycars

    May I draw your attention to the oddness of some of the names given by the major automakers to their EVs — just to give you a clue about the seriousness of their announced marketing intents.

    – Nissan-Renault’s iMiev contains the root of the french word mièvre, meaning mickery, whereas the Germans would pronouce it like mief = filthy.

    – Citroëns C-zéro sounds exactly like “c’est zéro” = it’s nuts, nil, worth nothing.

    – Audi’s e-tron sounds like the french “étron”, designing a lump of solid poop…

    – VWs Nils means what it sounds to you, and

    – BMW’s i3 is easily confused with the number 13 (especially when spelled in capitals) carrying bad luck for most of us, whereas the i8 sounds close to “I hate”…

    I’d be glad to be informed on any more odd names I might have left out (by the way, the videos on the i3 and the i8 are utterly boring — have a look at them!

    It’s not the automaker’s bad intent, Sonny, it’s Big Oil’s!

    • Anonymous

      There’s the Chevy Nova of a few years back…

  • Anonymous

    Let’s consider another way to make EVs more “affordable” in terms of purchase price. Assume that EV/battery prices won’t drop (IMO, an unrealistic assumption, but just in case).

    A 2012 Nissan Leaf sells for $35,200 without subsidies. One could purchase a perfectly adequate gas-fueled vehicle (let’s call it a Smith) for $20,000. (Less is possible, but let’s try to keep from comparing the Leaf to an econobox.)

    A buyer with no trade in would be looking at $648 in monthly payments for the Leaf vs. $368 for the Smith. (That’s using 4% finance charges and a five year term.)

    The Leaf buyer would be spending $35/mo for electricity and the Smith buyer would be spending $143/mo for fuel. (12,000 miles per year, $0.10/kWh, $4/gallon.)

    That makes the Leaf $683/mo for payment and electricity and the Smith $511/mo for payment and fuel. The extra $182/mo can be off-putting. Of course after five years the EV becomes much cheaper to drive, but many people are likely to be more influenced by cash out of pocket up front rather than savings some time in the future.

    What if we offered 7 year financing for EVs? That would drop the Leaf payment to $481/mo and the payment plus electricity about the same as the payment plus fuel cost of the Smith. The difference, Leaf buyers would have to wait two additional years to gain the big savings of not buying fuel, but at least they might be more willing to take that route.

  • Wild_Goose_52

    Guys, a reality check please. My current car (Nissan X-Trail) has a 100 kW diesel engine. Even a small run-around will need about 30 kW. To charge my car to run to half it’s capacity for one hour would therefore require your solar array to run for approx 40 hours at 100% of it design performance. This is equivalent to a week in the Sahara or Arizona deserts. And that just gets me to work for one day, I still need to get home.
    C’mon people, at least do the math before you publish stuff like this. And I am in favour of solar energy by the way

    • Anonymous

      I think you’re missing the point that the 1.2kW array covers the cost, not the total amount of power required. Apparently the utility company is paying back more kWhs of off peak power than they are buying in peak kWhs.

      I don’t really follow your argument based on a diesel engine. Your engine is wasting a tremendous amount of the energy in a gallon of fuel, tossing it off as unused heat.

      A Nissan Leaf uses 0.35kWh per mile. A small one or two person commuter vehicle could use as little as 1/3rd that amount.

      12,000 miles per year, 33 miles per day, 0.35kWh per mile would take 11.5kWh per day. In a place that gets 5.5 hours per day of good sun that would require a 2.1 kW array. (Plus a little for system inefficiencies.)

      A light weight ‘zipper’ might need only a 700 watt array.

    • Karmann Eclectric

      Wild Goose is comparing apples and oranges. His 100 kW diesel is a peak rating, not what it actually produces 99% of the time. My 2800 lb EV conversion consumes 12 kW while cruising on the highway, but I have 170 kW on tap for whenever I want to ‘smoke a gasser’. All told, my efficiency is better than 0.33 kwh/mile, EVen though I drive like I stole it. Bob’s theoretical array would serve my 32 miles/day of driving quite nicely. Who needs a reality check?

      • Anonymous

        Thanks for the info!

  • This is sort of a “holy grail” of energy for Americans. Our whole society is based on land transportation, mostly built since the advent of the gasoline-powered car. The easiest way to reduce transportation fuel cost is to conserve. But I see so many people driving huge vehicles, usually alone. Since price is the easiest way to encourage conservation, one idea would be to raise the weight required for commercial qualification. (didn’t Bush Jr. lower it so salespeople could drive Hummers and write it all off?) Another justifiable price or tax hike would be to pay for the Iraq war, and the Navy in the Persian Gulf, with fuel tax. We all saw what a “global” recession did to the price of crude. Somewhere between extravagance and hardship, is a happy medium that reduces the debt of our children, and still provides for a middle-class standard of living. I’m all in favor of keeping the devils vomit under the ground. This poor planet is getting a fever, and everyone, and everything, is going to be affected by it. Alternative, carbon neutral fuels could also sure use a price stabilization boost from the only player big enough to deal with big oil.

    • Anonymous

      Totally agree.

      A better gas tax, like the carbon tax, is sorely needed (to pay for the health and national security costs not included in the price today). But, unfortunately, the majority of the public doesn’t get that yet and doesn’t seem to care that much about future generations.

    • Anonymous

      I agree with all the ideas about conserving, walking, biking, using public transportation, etc. but I also try to consider “human nature”.

      People really want to get in their personal car, all by themselves, and drive where they want to, when they want to. People, I suspect, only give up their personal car when the problems of parking/stop and go traffic make that more difficult in dense parts of cities.

      If we try to force people to conserve by artificially racking up fuel prices via taxes we’re likely to see political push back and, likely, failure.

      We can make it easier for people to get around without personal cars by improving bike lanes, sidewalks, public transportation, etc. but that will only chew a bit off the edges.

      I suspect we will be more successful in cutting our oil use by focusing on a laser beam on creating affordable, fun to drive electric-powered vehicles (or any better technology which might emerge).

      Battery cost and weight is the current problem with EVs. So how about some light weight, shorter range EVs for “students” and commuting shorter distances? We’re seeing prototypes for tandem seating two passenger vehicles which are capable of highway speeds. Make them very safe via crash cages, air bags and collision-avoidance radar systems.

      Here’s a small car prototype, only a single seater but stuff can be stretched. It’s got only a 40 mile range but it can hit 80MPG so one isn’t barred from highways.


      Here’s the sort of ‘car smarts’ that could be very popular – an autopilot system for stop and go traffic. Takes the stress of that sorts of driving away, leaving the driver free to do something else and insures that your car won’t rear-end the one in front.

      (Monitor the car behind you and flash some very bright lights toward them if they are closing too fast.)


      Small and short range can make EVs affordable for a good part of the population. Make them with reusable and sustainable materials, power them with electricity and we could avoid a lot of oil use while not having to force people to do so.

      • Anonymous

        BTW, the VW Nils concept linked above weights less than 1/3rd as much as the Nissan Leaf. The Leaf ‘burns’ about 0.35kWh/mile. The Nils projects to use 0.13kWh/mile.

        That means that one could charge up their “Nils” fairly quickly at a Level 3 rapid charge outlet, which makes the Nils more practical for the occasional trip greater than its 40 mile range. Charging in while at work/school would double the effective range.

        You could buy the solar panel ‘fuel’ for your Nils for 1/3rd the cost of the Leaf (above).

        This could be some very cheap riding, get a lot of us off oil, and reduce our impact on the environment to an acceptable level.

        Make ’em safe and fun to drive.

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