Teaching the duck to face west: California's new solar incentive | SEPA Skip to content

Teaching the duck to face west: California’s new solar incentive

The California Energy Commission recently took a small, but significant step toward creating solar incentives that balance the interests of solar owners, utilities and the grid itself.

Issuing the latest update of guidelines for its solar rebate program for new homes, the CEC announced it was adding a new incentive for the installation of west-facing solar panels. On top of the per-watt rebates developers or homeowners already get for installing solar on new homes — now ranging between $1.50 and 75 cents per watt — west-facing panels will earn an additional 15 percent of the total rebate amount, up to a maximum of $500.

Like California’s better-known and highly successful rebate program for homeowners installing solar on existing houses — the New Solar Homes Partnership is set up to provide a descending scale of per-watt rebates, based on the amount of solar installed on new homes across the state. The more solar installed, the lower the rebates will go.

So why west, when conventional wisdom has long held that south-facing panels provide optimum energy output from a roof top array? Simply put, a west-facing orientation can extend production into the late afternoon hours, when energy demand starts rising.

Using the bump in the incentive amount to promote that shift could help solve one of the critical challenges California and other states now confront as they integrate increasing amounts of solar onto the grid.

Yes, I am talking about that much overused trope and bane of water fowl everywhere — the solar duck chart. However overused, the chart aptly shows the disconnect between rooftop solar’s midday peak in power output and the late afternoon and early evening hours when demand for power from the grid is at its highest. The steep ramp of the duck’s “neck” corresponds to the rapid rise in demand that occurs 4-9 p.m. as panels stop producing and people come home, turning on lights, appliances and other electronics.

Duck Chart _CAISO-1
Solar duck chart courtesy of the California Independent System Operator, The chart is based on the net load for March 31, 2012.

Without new strategies, the curve will likely grow steeper as more solar is connected to the grid. To fill the gap, utilities turn to more expensive power produced by natural gas “peaker” plants that can fire up or shut down quickly — something baseload nuclear and fossil-fuel power plants can’t do.

West-facing panels, with their slightly later production profile, can lessen or at least delay the need to pull electricity off the grid and fire up peakers.

Providing incentives for west-facing panels is one of the options often mentioned in reports exploring possibilities for replacing net metering, the primary solar incentive now in use in many states, with a smarter, more sustainable mix of incentives and rates.


In his  much-discussed paper, “Teaching the ‘Duck’ to Fly,” Jim Lazar suggests that solar owners with west-facing panels might also receive rates or incentives recognizing the greater value of electricity they generate at times of high demand.

In general, most net metering schemes reward the amount of power produced — which is optimized with south-facing panels. Time-variable rates and incentives that reward west-facing panels could more closely align solar output with power demand, helping to smooth out the duck curve and improve grid reliability, Lazar said.

They would also ensure that solar owners would be fairly compensated for any loss in power production from their rooftop panels earlier in the day.

In the often heated debates over net metering reform, proposals for incentivizing west-facing panels could be a possible focus for agreement and collaboration among utilities, their customers and the solar industry.

And focusing on issues on which all stakeholders can work together may help them overcome the divisions that still remain.