PV for ZNE, rah rah rah!

Our new house in Pacifica is intended to be “zero-net-energy”, ZNE for short. While the phase has slightly varied meanings, the basic message is that the house will produce as much energy as it uses.

Why would you want this, when PG&E offers relatively low-cost electric and gas services? There are a couple of reasons. The primary one is that our society needs to move in the direction of sustainability, for the sake of our planet, our health, and future generations. PG&E provides natural gas, a fossil fuel, and electricity, most of which is still produced by burning fossil fuels (though we are making considerable gains producing power from wind and solar sources). Fossil fuels, even with all the new production enabled by fracking, will eventually run out, and if we continue to burn them our civilization will fry while drowning in melted glacial ice (yikes!). Sustainably means reducing our energy use, and then getting what we need from the most sustainable source around: the sun. Furthermore, local production of power is generally more efficient than centralized power, as the line losses are minimal. Local production can also be more resilient than the power grid – ask any resident of Puerto Rico who doesn’t have solar panels on their roof and a back-up battery.

Another reason is that ZNE is going to be the law: in 2020 California’s building regulations will require that all new homes be zero net energy.  The state’s definition of ZNE has unfortunately been watered down recently to mean that the electric energy used must be ZNE (ignoring that natural gas provides almost half of the energy needs of California’s houses).

How does a house provide as much energy as it uses? Sustainably and healthily? What about a running stream with a hydroelectric plant in the basement? While we do have a creek at our rear property line, it doesn’t run year-round (though there are some interesting possibilities for low flow hydro energy, from local Bay Area companies like Natel.

What about a wind turbine? We thought seriously about having a wind generator mounted to the house, but even in moderately windy Pacifica there aren’t the kind of strong sustained winds that make a wind generator practical. Plus, wind generators tend to be noisy and vibrate structures.  In most areas to be effective they need to be mounted dozens of feet in the air, even hundreds of feet.  They just weren’t practical for producing the amount of power we would need.  I still wanted a small unit as a design feature, but I was persuaded not to by our colleague and future neighbor, Ann Edminster, who noted that advertising a non-effective technology would be doing a disservice to the community.

The option we were left with was photovoltaics, PV for short, the cost of which has plummeted in the recent years. We were early adopters of Solar City’s PV leasing option ten years ago and have been entirely happy with the 2.7 kW system on the roof of our current home. It provides about 65% of our electrical needs and has saved us money every month since installation.

Photovoltaic panels turn sunlight directly into electricity. Because they create direct current (DC) power, an inverter is also necessary to convert the DC into alternating current (AC), which is what our houses and the utility grid conventionally run on.  Why be connected into the grid? Photovoltaics obviously don’t produce power at night, and battery technology, while becoming more common, is still at a youthful stage of development, and is expensive. We’re told it’s best to wait a couple of years for batteries. The grid provides stability as an ‘energy reservoir’ we can dip into when our own production is minimal and can dump into when the sun is shining. With time of use monitoring and  (at least currently) fair payment for electrical production, it’s effective to be grid tied.

Our new house, unlike our existing one, was planned to be all-electric (no fossil fuel burning), so our electric needs would be greater. And unlike our current system, all of our power needs would be met by our PV system. We furthermore decided that we’d like to power an electric car with our PV system, so that an even greater share of our lifestyle would be powered by the sun.

That’s a lot of power. I ran some calculations using our family’s historic yearly electric usage as a starting point, then adding the projected usage of the appliances (clothes dryer, cooktop, water heater and space heater) that are currently gas but will be electric. Then added the energy needed to run a Tesla (dream on!) driving for 15,000 miles.

Final Load Calculation

All of this totaled about 12,000 kW-hours: enough energy to light a conventional 60 Watt incandescent light bulb continuously for twenty three years. To generate this much power, we would need a system with a peak capacity of about 8 kW: 8000 Watts.   With the increasingly efficient panels on the market today, we can provide this much power with twenty-two 360 Watt panels.  Each panel is about 40” x 66”, so our whole house plus a car can be powered using just 400 square feet of panels, about the same area as a two-car garage. Not bad!

We got quotes from three different vendors for our system, Occidental Power, Northern Pacific Power, and Golden Gate Power.  All three of them gave us good service and competitive quotes, with slightly different equipment specifications. While Sun Power has the most efficient panels, we have plenty of roof area, so individual panel efficiency was not as critical to our decision as panel price. After some back and forth, changing some oranges to apples so we could get a good comparison, their quotes were very similar. It was very hard to choose. We finally picked Occidental Power based on their superior experience (oldest PV vendor in San Francisco), their friendly manner and craftsman-like approach to the work, and their partnership with an energy efficiency lender, Salal, currently offering loans at 2.99%.

The cost of this system today – parts and installation — is about $34,000 minus about $10,000 in Federal tax credits. Ten years ago the cost would have triple this amount. This sounds like a lot of money but amortized over a thirty-year loan it is far less than the utility costs would be. Leasing and other creative financial options are also available.  For homeowners with low property taxes, a PACE finance program that funds your investment through your property taxes would make sense. For us building a new house, we will reach the new $%@#$ Republican Tax Limits of $10,000 before solar.

Imagine all of your personal power needs, plus local transportation, cleanly powered by the sun for less cost than burning fossil fuels.  Solar power is for real, this is where we need to go, all thanks to our beau soleil! Sis Boom Bah!

(If you’d like more information of Zero Net Energy homes, we highly recommend our colleague Ann Edminster’s book, Energy Free Homes for a Small Planet.)

Contract Pages from Occidental Power showing generation and cost savings over time.

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