We recently gave our first Net Zero Energy talk to the Rotary Club of Menlo Park (thank you Maya Sewald of Ovation Homes Real Estate for the introduction). Besides putting together a nice slide show with photos explaining the energy efficient solutions we built into our new home, it was time to do the first analysis of the actual energy performance. This included both the output of the solar photovoltaic system over the course of a month in (foggy) Pacifica and the details of our electric use for a family of four, a busy home office, and a hybrid electric car (we currently own a Ford CMAX, a hybrid with an all electric capability of about 18 miles).
If you’re a regular reader of our blog, you might remember that we designed our new home to be Net Zero, meaning that over the course of a year, the solar system should be offsetting all the electrical demand. All the heating (air and water), cooling and appliances were selected to be electric as we did not want to bring a gas line to the house so as to avoid the installation cost, but most importantly, to avoid any use of fossil fuels in the operation.
So how are we doing? We turned the photovoltaic system on in late January and this graph shows our production to date. The production obviously goes up as the days get longer, June 21st being the longest day of the year. Months that have more rain or fog have less production. I love the Environmental Benefits number on the bottom – we have already saved almost 11,000 pounds of carbon dioxide, the equivalent of planting almost 275 trees!
And how do we do day to day with the coastal fog, you might ask?
This is our production during the “June Gloom” as we call it around here. Our lowest production was 19.3 kilowatts on June 15th, and our highest, on June 7th was 59.5kW. While the fog does decrease production, it obviously does not completely stop production. We were told by Solar City, who put a system on our previous home in San Francisco, that over the course of a year, the energy production of a system in a foggy neighborhood was only about 10% less than one in a sunny location.
And last but not least is the real test of our efficiency, our PG&E bill. This is from the same time period, the month of June, and as you can see, we have produced more than we used, resulting in a credit from PG&E of $48.35. That seems wonderful, but looking at the fine print, out PV generation for the month was almost 875 kWh and our usage only 547.5 kWh. PG&E does not pay very much for the surplus energy going back to the grid.
Hence it is time to get a new all electric car! We had been holding out for a smaller, more economical Tesla, but are a little unsure now of where the company is heading.
We’d love to hear your thoughts about your favorite electric cars! A huge bonus if the car is small, but still fits our son David, who is 19 years old and 6′-5″ tall!
And if you’re in the Bay Area and are looking for a solar PV vendor, please give Occidental Power a call. They have been in the business since 1989 and have excellent pricing and service. They also design and build their own aluminum racking. In our case this was a critical part of the design as the panels cantilever off the back edge of the house and also act as sun shades for the south facing windows.