solar electric vehicle

Purchased a home and want to add solar panels? Five considerations to ponder

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This week, we have been engaged by three new homeowners to help them evaluate solar. Thereby, we begin with a simple, open-ended question: Why solar, why now? Responses vary, but generally their motive is twofold: Why not, since I just bought my home; and, PG&E’s rates are only going to go up. While we agree with the latter, we believe the former warrants consideration.

Before adding solar to your recently purchased home, here are five considerations:

1. The condition of your roof. Since new homebuyers have recently had their roof inspected, they have an objective evaluation regarding the condition and remaining life of their roof. In simple terms, if your roof has less than 10 years of remaining/warrantied life, you do not want to install solar (on such roof planes); if your roof has 10+ years, you’re in good shape.

2. Historical/future electricity use. Since new homeowners have limited (or zero) electricity use data, we recommend one of four approaches (to forecast future use and accurately size and model their prospective solar system):

  • Live in your home for 12 months and, thereby, quantify how much electricity you will use.

  • Wait until you have occupied your home for six months -- particularly 1-2 months of summer use, when electricity demand peaks. (Thereby, we can model 12 months of electricity demand based on your use pattern and comparable homes).

  • Employ comparable homes’ electricity use (based on their vintage, neighborhood, size, occupancy, etcetera) to model your home’s future electricity use. Fortunately, we have several hundred data sets — electricity use patterns for homes in all neighborhoods in our community — to approximate future use.

  • If it’s not too late, request 12 months of PG&E data from the home seller. Oftentimes, this is a futile effort, but it’s worth trying.

3. Home improvements. Stating the obvious: Many new homeowners improve their homes. Adding a pool and/or hot tub will increase your electricity use, as would replacing your furnace with an electric heat pump (an increasingly common practice for Repower homeowners). Conversely, replacing windows, adding insulation, or installing a variable speed pool pump reduces your electricity use. In all cases, we model the impact vis-a-vis solar system sizing.

4. Electric vehicle. If you own — or intend to purchase, in the next 12-24 months — an eV, you’d  want to factor future charging of your car into the sizing of your solar system. We find that eVs travel 4 miles per kWh of electricity. The math is simple: Take the number of miles/year you anticipate driving and multiply it by the percentage of charging you believe will be done at home (versus your workplace, public chargers, etc.). Then, divide the number by 4 to quantify additional electricity use (in kWh). For example, if you intend to drive 10,000 miles per year and charge your car 80% of the time at home (fueling 8,000 miles), you will consume 2,000 kWh of electricity.

5. Your electrical panel. Though adding solar does not increase your electrical demand, we need to ensure your electrical panel has sufficient capacity (or space) to accommodate the solar inverter. Furthermore, we will evaluate non-solar changes to your electrical demand — car charger, spa, swimming pool, heat pump, etcetera — to determine your panel’s amenability. (We perform load calculations and review your future electricity use with the city or county to ensure solar will work.)

 Net-net, going solar is simple, but there are a few nuances worthy of consideration … particularly if you recently purchased a home. Feel free to contact us to learn more and receive a free solar assessment.

50,000 Model 3s in 90 Days: Tesla is Tipping the World


Tesla reported earnings yesterday. To the surprise of most experts (!), Elon crushed it. In three months, Tesla sold more than 80,000 electric vehicles, including 52,339 Model 3 sedans. And, they made money, registering a $312 million profit and generating more than $800 million in free cash flow. Well done.

We tweeted last month about Tesla’s extraordinary business model and outcomes:

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Further amplifying the above, from yesterday’s Wired story:

At the end of the quarter, Tesla actually welcomed existing customers as volunteers to help deliver cars, as that became the new bottleneck. “I’ve never heard of a case where customers volunteered their time to help a company succeed,” said Musk. “That’s amazing. It chokes me up actually.”

Great news for Tesla, but more important, for the future of electric vehicles (and, thereby, our planet) … an American auto manufacturer is making money selling all-electric cars. Amen.

We have had the fortune of helping more than 60 electric vehicle owners (including ~15 Tesla owners) go solar. The economics of solar are good; solar + electric vehicles are outstanding.

A few anecdotes:

  • Increasingly, we are installing 240A eV outlets in concert with solar systems, in advent of a future/soon-to-come electric vehicle (and its charger). Very simple, efficient and inexpensive process, particularly when bundled with the solar engineering and permit. (And, you get the 30% tax credit on your additional electrical work.)

  • Refresher on the math for increasing your solar system’s size to accommodate eV charging: Simply take the total number of miles/year you anticipate driving (e.g., 12,000), multiply by the percentage of time you will charge at home (e.g., 75%), and divide the number of at-home miles by 4 (e.g., 9,000/4) to calculate the additional electricity load in kWh (in this scenario, 2,250 kWh).

  • The amortized cost to generate solar electricity is ~$0.08 per kWh. Hence, your cost to drive electric is about two cents per mile. (Add in the fact that there’s no maintenance and the picture’s even rosier.)

  • All electric vehicle owners should switch to PG&E’s “EV” rate schedule … the benefits are amplified if you have solar. (We model multiple PG&E rate schedules for Repower homeowners … in most all cases, switching to “EV” is the best case.)

  • We’re working with a number of churches in the community, helping them go solar and install eV chargers … all churches see it as a community benefit, and thus public availability of chargers is going to increase significantly — via churches, local governments, businesses, apartments, hotels, et al — in the near future.

Want to learn more? Feel free to contact us and/or attend a Davis Electric Vehicle Association (DEVA) meeting at our office.

I am going solar. Now.



We have the fortune of exploring solar with dozens of homeowners each month. No two conversations are the same, but common themes prevail. We normally commence with a simple question: Why solar, why now (in terms of the homeowner’s interest)?

Solar is not a panacea and it does not make sense for all homeowners. Further, there is no single, silver bullet that prompts people to pull the trigger; here are a selection of “why solar, why now” anecdotes from homeowners:

1. PG&E: Opinions sway from virtual venom to distrust to steady rate inflation to I’m sick of paying PG&E so much every month. As you may have noticed, PG&E raised residential electricity rates ~42% over the past three years, and there’s more to come …

2. Climate change: Everyone wants to do their part, and solar is a the most impactful measure a homeowner can employ to reduce their carbon footprint. Furthermore, our state is burning (no-duh) and homeowners acknowledge the latent liabilities PG&E is accruing for the Santa Rosa, Redding and other fires; there’s a general belief (we agree) that ratepayers will bear financial responsibility for PG&E’s liabilities. Hence, going solar insulates you from future rate increases.

3. Donald Tariff Trump: Regardless of your political stripes, nobody likes to pay more for something. President Trump’s first two tariffs were applied to washing machines and solar panels. (Washing machines?) Fortunately, the quantity of solar panels imported into the U.S. in the fourth quarter of 2017 increased 1900% (versus Q4-2016); the solar industry has been working through a surplus of stockpiled, pre-tariff solar panels. However, supply is dwindling — prices have most likely bottomed — and the solar industry foresees tariffs in the next few months.

4. Donald Tax Credit Trump: There’s much concern among homeowners that the POTUS will eliminate the 30% federal tax credit (for solar, wind and other forms of renewable energy). For now, the tax credit is galvanized into the tax code, at the full 30%, through the end of 2019. We believe it is unlikely Congress (and then Trump) will abort the credit; perhaps we’re being overly naive! The safe bet, of course, is to lock it in in 2018.

5. Investment accounts: This one’s common … if I’m making less than 1% in my checking/money market account and I’m nervous about the stock market and my 401K, solar is an investment vehicle where I can confidently generate 12%+ annual returns. We agree, and the math is quite simple. 

6. I need a new roof: We are currently helping six homeowners who are replacing their roof and, in concert, installing solar panels. The timing is perfect to maximize and optimize warranties from the roof material and solar panel manufacturers (minimum of 25 years) and the roof and solar installation contractors (25 years). Importantly, we orchestrate the process (roof + solar) on behalf of homeowners.

7. Electric vehicle: This one’s a no-brainer, particularly if you plan to own your home for at least five years. Leveraging PG&E’s electric vehicle rate schedule (EV-A), our typical eV + solar homeowner only needs their solar system to generate ~80% of the electricity they use to offset 100% of their electricity costs. (Simple math: Your amortized cost to generate solar electricity is in the 8 cents per kWh range, and you will garner ~4 miles of charger per kWh … so, your cost to drive is ~2 cents per mile.)

Are we missing any obvious motivations (to go solar)? If so, please advise, or feel free to contact us if you’d like to amplify any (or all) of the above.