By John Mott-Smith

Cross Posted from the Davis Enterprise From page A10 | July 06, 2016

Each year I try to assemble data from each of the cities, and Yolo County, on the number of solar photovoltaic systems installed on homes and businesses. The quality of record-keeping varies but each jurisdiction has a pretty good handle on the numbers for their community, with those that have an adopted Climate Action Plan generally providing the best data.

The numbers for systems installed in 2015 indicate that rooftop solar is really taking off in Yolo. Much of this activity can be ascribed to the federal 30-percent tax credit, which was recently extended for five years.

But it also seems that something else is going on: The Paris Climate Talks shined a light on what appears to be a global paradigm shift with virtually every nation moving away, at varying speeds, from fossil fuels and to renewable sources of energy. It is, at times, not easy to see the big picture and we in Yolo County certainly exist within a small bubble of progressive policy, but it looks like the planet is, in fact, in the process of a transformation.

That’s a pretty big statement to make, and requires substantiation to separate it from a hope or opinion and I will do that in a future column, but this one is about solar in Yolo, in particular, solar PV.

So, starting with Davis. Back in 2010 the city adopted a Climate Action Plan that included a goal of about 1,750 rooftop solar PV systems by 2015. City staff recently reported to the City Council that, according to data from PG&E, not only did the city meet this goal, it surpassed it, with a total of 2,360 rooftop systems, of which 2,229 were on single-family residential buildings, with an installed capacity of a tad more than 10 megawatts of electricity.

Systems installed on non-residential (commercial, municipal, schools, etc.) properties added another 19 megawatts. Together, these systems are producing about 20 percent of the ”total annual community electricity demand.” Not too shabby.

Rather than rest on our laurels, staff recommended, and the council approved, setting new goals for the year 2020. First, double the number of single-family residential rooftop systems to a total of 4,500. This would mean that approximately 50 percent of owner-occupied single-family homes in Davis would have solar panels on their roofs.

A “business as usual” approach that relies mostly on private efforts to identify new customers might get us there. The average number of new systems installed has been just under 350 per year over the past five years, but if the 2015 number (440) is matched or exceeded, the city will reach its goal.

But, staff is not noted for sitting on its hands when facing a challenge, and noted that adoption of the new goals by the City Council dovetails with the launching of a Cool Davis community outreach campaign (“Double Up On Solar”) to accelerate the pace of new PV installations.

At any rate, PV on 4,500 owner-occupied single-family homes may be approaching the maximum penetration rate for the city, given that a large percentage of homes have shading, orientation or other reasons making solar infeasible.

Fortunately, there is a pathway even for these homes. The city, in conjunction with the county, recently voted to form a Community Choice Energy program that permits the city/county to decide the source of electricity consumed by residents and businesses. Assuming an initial mix of about 50 percent from renewables, every ratepayer — whether an owner or renter, whether we have solar on our roofs or not — can claim participation in the challenge of reducing greenhouse-gas emissions.

The city of Woodland’s Climate Action Plan set a goal for 2020 of 5,000 residential rooftop systems producing 13 megawatts of electricity, based on an assumption of an average system size of 2.7 kW. Data on actual installations thus far, however, indicates an average of 4.07 kW per installation. So generating capacity for 5,000 rooftop systems actually would produce just over 20 megawatts.

Woodland has good data back to 2005. Adding in data from PG&E back to 2000 results in 1,590 residential rooftop systems in Woodland producing about 6.5 megawatts. Add in the commercial sector (3.0 MW), schools (an estimated 2 MW) and municipal installations (2.4 MW) and the city has nearly 14 MW on its way to its goal of 40 MW from renewable sources.

Woodland didn’t have as many early adopters as Davis but the number of systems installed has been doubling over the past few years, culminating in 651 residential systems installed in 2015 and nearly 150 in just the first three months of 2016.

For its part, West Sacramento indicates 416 PV systems installed in 2015. It doesn’t track the generating capacity of installed systems, but using an average of 4.5 kW results in nearly 2 megawatts in 2015 alone.

The city of Winters had 90 systems installed in 2015, pretty darn good for such a small town.

Unfortunately, Yolo County’s tracking system broke down so there is not a number for the unincorporated areas of the county for 2015.

— John Mott-Smith is a resident of Davis; his Enterprise column is published on the first and third Wednesdays of each month. Send comments to