Electric Car + Solar Panels: Are They Right For You?

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House with 5.3 kW Solar PV, courtesy of SolarEcity, Rocklin, CA.

House with 5.3 kW Solar PV, courtesy of SolarEcity, Rocklin, CA.

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When it comes to service costs and fuel, everyone knows that electric cars are far cheaper to run than gasoline cars. 

Even with a plug-in car, however, you still have to pay your local utility company for the electricity used to charge it. 

Like gas prices, electricity prices are on a steady, upward rise in many places, meaning the cost of charging your electric car will gradually go up. 

But what if you could charge your car from photovoltaic solar panels fitted to the roof of your home? 

Investing in solar panels on the roof of your home isn’t cheap, but now a new online tool from WattPeople (via GreenCarCongress) aims to promote its series of specialist electric car and photovoltaic finance packages--and to highlight the claimed cost savings of its products over a conventional gasoline car. 

Launched at last week’s SxSW Eco, the app offers a year by year financial breakdown of the costs involved in investing in home solar panels and an electric car.

It also details all of the usual finance package information you’d expect with any loan, such as loan interest rates, monthly payments, and installation costs. 

It also predicts how much money you can save in the future.

Although the tool itself has been built to provide WattPeople a sales window for its specialist loans, it has enough functionality to provide at least a basic idea of cost breakdown for anyone considering a bank loan to buy an electric car and solar panels. 

Robert Llewellyn Nissan Leaf Solar Panels

Robert Llewellyn Nissan Leaf Solar Panels

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As those with solar panels and electric cars testify, the cost of driving is dramatically reduced once the initial outlay has been recouped.  And having a solar panel in combination with an electric car can decrease the amount of time before a return on investment is guaranteed. 

“After almost three years with a full solar array of both photovoltaic (5.1 kW) and solar hot water, and two years with both the Volt and Leaf feeding off that solar PV, we are most happy with the bottom line,” said George Parrott, GreenCarReports contributor. 

“Before going solar PV, our monthly electric bills in a new house in West Sacramento never were lower than $250 and touched as high as $400,” he explained. “Our cars, prior to the Volt and Leaf were both Toyota Hybrids, and even with those frugal gas-sippers, we were still paying about $2,800 per year in fuel and upkeep costs.”

As Parrott explains however, the costs of running both the Volt and the Leaf--as well as home electricity costs--have dropped dramatically since making the switch. 

“Since going solar and electric motive transport, our monthly electricity cost has average only $13, as this is the basic connect fee that PG&E charges to be on the grid,” he continued. 

Thanks to clever use of time of use metering, Parrott says the home’s solar array feeds power to the grid during the day, while cheaper night-time electricity charges the family cars. 

“Our solar array totally wipes out all of our actual home electricity costs AND with “time of use” metering for charging the cars at specific off-peak times, we have Zero energy costs for powering the cars,” he proclaimed. 

With the costs of solar panels coming down, and gas and electricity prices rising, there’s never a better time to think about investing in solar panels and an electric car. 

As with any financial commitment, you should seek professional financial advice before signing any installation or loan contracts, be sure you can cope with the financial investment, and shop around first to make sure you have the best deal. 


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Comments (27)
  1. Your lead picture is the Parrott/Iwahashi house here in West Sacramento, with the picture from our solar PV installation company after they installed the final 1.4 kW of the total 5.1kW system.

  2. I really like the way the owner chose to increase his overhang to provide shading for the windows in the summertime. It's a shame there are so many roof penetrations scattered across the roof that forced the remaining panels to be distributed the way they are laid out.

  3. I brought in 12 solar PV contractors for possible installation bids, BUT only 3 would even give me a bid because of my demand for the "awning installation." The upper panels were installed a year later in anticipation of going to two EVs instead of our previous hybrids.

  4. I have a 5.2k PV System and a 2012 Volt and estimate I am saving at least $300/month over no solar and my previous 25mpg car. I did the solar myself at a cost of $7000 after rebates, so a 2 year payback!

  5. I have seen that the costs of the PV panels have dropped by more than 50% since we installed first in 2008. In California, as I understand it, the state based part of the potential rebate only comes if a licensed contractor installs the panels. BUT a $7000 total after rebates (which rebates?) is wonderful!!!!! At that price, we would have had a ONE YEAR payback!!!!

  6. nice calculator. I would have removed the cost of the ev from the loan. That way it's just energy vs. energy.

    Most in California will find a 6-9 year payback vs. utility cost, 2-3 year payback vs. gasoline and a 4-5 payoff if you are doing both.

    We did 7.5kw 6 years ago and it's paid for already. Home, Honda Fit EV @ 12,000 miles and BMW ActiveE @ 20,000 miles, all for about $500 a year total cost. Prior energy cost with utility and two gas cars was $10,500.

  7. In California, any state benefit at this point is zero/negligible, so it doesn't much matter. The rebates phased out with installed capacity and we are now in the final tier in all parts of the state.

  8. Wow, how did you get a 5.2KW System for $7k?

    21 panels for $7k + inverters are cheap. That is $300 per panel! $1.35 per W installation.

  9. Actually, the up-front cost of a home PV system can now be zero.

    Under a PPA (Power Purchase Agreement) companies like Solar City (whose chairman happens to be Elon Musk) will actually install a PV system on your roof for free. You then contract to buy your power from Solar City at a fixed rate that is typically a lot less than power company rates.

    The payback period is about one millisecond. You literally save money from the moment you flip the switch on.

  10. If you can afford to purchase the solar array, rather than getting into some finance agreement, it's an even better deal.
    Based on my installation in December 2011, and with time of use array, I'm getting a 15% return on my solar panels in savings on gasoline and electricity. Tax free. Hedged against inflation. Lifetime.

  11. And the value of my home increased, so I really just moved money from one asset class to another asset.

  12. Thanks for posting that Gus. Solar City is great for people without any cash to spare or an inability to use home equity/mortgage financing. For other folks, self-financing is better. Any leasing plan with absolutely cap the return the system generates >below< what a self-financed system will do. We installed in February 2006 and generate a return of north of 8% -- even using the much higher prices paid back then. If I recalculate based on current electric rates, it's possible we're approaching 10% now.

  13. PPA don't cap the system. Of course, they don't "install" excessive capacity either..

    Under PPA, you get to keep the extra generation beyond what you agree to pay for... Especially in those up front PPA plans.

    The best thing about PPA plan is the fact you don't have to worry about Inverter and Panel warranties and insurance. (Also, no service worry either) And it is cheaper upfront with less cash. You also have the right to buy it with a pre-set or FMV price as well...

  14. Got a Volt his July and putting in PV this November. 8.16KW using USA-made parts. We're looking forward to slightly-better sustainable future but it'll take millions more of us doing this to make a big impact.

  15. 8.16KW would be about 33 panels. Wow!

    You must have a large sunny roof. :)

  16. I'm working the other way around, but the basic plan is the same: PV + EV. We're in the process of wiring our new 6.81 KW array. Will be leasing an EV in the not too distant future {I do not qualify for the full $7500 tax credit, but the lease company will, so I plan to buy it after I finish the lease.} It makes my family far more secure in the long run than putting the money in a 401k or IRA where scams abound.

  17. Solar is great. I have signed up with Solar City's PPA plan. I am basicially paying Solar City $0.093/KWh to either power the grid or my Volt.

    The only down side is that the max size that solar city is willing to put on my roof is 3.3KW due to my weird shape roof AND the roof facing location. (And the Petaluma city ordinance where it has to leave fire access lanes around the edge of the roof)

    So, in general if it works for you, you should at least check out the solar and various PPA plans.

  18. PPA's are great up front. But with rates so low now, if you have the credit you can do better mid and long term configuring your own system how you like it and getting financing yourself. If you can get zer0 down or nearly or nearly no cost down you can beat the PPA's on nearly every dimension.

    Though some PPA's allow you to buy the system outright at a low cost basis, after a few years. You'd have to pencil out what works best in your situation. And don't sign the 1st contract offered just because it pays for your power and is convenient.

    "Even with a plug-in car, however, you still have to pay your local utility company for the electricity used to charge it."

    For $25 (15.49 GBP) a month? Not the $100 a month gains of no petrol!

  19. I agree. I looked at both. The financing is not the issue with me. Instead, it is the warranty, service and insurance for me. If I buy it, all those factors fall on me. Warranties are provided by the manufacturer. What if they are out of business in 5 years? Service? I have to hire people to fix issues if parts are broken. Plus, I have to insure the extra value of panels and inverters. In PPA plan, all those are Leasing company's issue. Plus, I don't have to file any of the Tax Credits or dealing with drop in efficiency over the years. I have the right to buy starting in yr 5 and it is pretty good deal. And that price combined with my current upfront PPA price is about the same as if I bought it myself (net).

  20. Oh, 1 big issue with PPA vs buying is the fact that NO Solar company will lease you a larger system than your roof is best fit for than you could with your own system.

    So, for example, if you want a 5KW system and your roof only has 100% for about 3KW of it and additional panels will only generate in partial rate. No PPA company will sell you a 5KW system. However, with your purchasing, you can choose to "eat the cost" and install a 5KW system anyway, but end up getting probably only 5KW about half of the time...

  21. Hmmm, functions similar to the PV ROI calculator I created 2 years ago. I need to add a few cars to my calculator though... especially since I own a Volt now: http://www.empulsebuyer.com/pvCalculator.php

  22. I was inspired to put a 6.5kw solar array on my roof after buying my Nissan Leaf in January. I just commissioned the array three weeks ago. Now, all of my electricity for the Leaf for a month of driving is made on just four sunny days!

  23. Home solar + electric car = Best decision I ever made. What other home improvement actually pays you back from day 1?

  24. Yep, 1) look for energy savings at home, 2) consider putting the home (and car) on solar.

  25. Indeed. My simple comparison is between my 25 mpg Subaru and my 2011 LEAF plus rooftop solar. Each year, just one panel on my roof makes the equivalent of 44 gallons of gas for the Subaru. 12 panels = free gas for life.

  26. I have solar on my house for three years now and an EV (Fluence ZE) for 9 months. I produce onj average 20 KwH per day whiuch is good for 80 miles of EV driving

  27. Had my solar / electric car combo for one year now. The solar was DIY, costing about 22K. Am saving about $2500 a year on gas and electric. The system has exceeded my expectations, so far. The panels on my roof provide all this electric - amazing!

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