Are CA Solar Installers Accurately Representing Solar Project Economics?

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Originally published on Energy Toolbase.
By Adam Gerza

California residential solar installers may be using a flawed approach to calculating and presenting the economics of solar projects and not even know it. Earlier this year the California Public Utilities Commission (CPUC) finalized and approved the biggest reforms to residential electric rates in a decade. These structural changes to rate design change the value proposition of a solar project, but are not likely being accounted for in the modeling.

Policy background:

Governor Jerry Brown signed Assembly Bill 327 into law in October of 2013, which directed the CPUC to reform residential electric rates to “allow for a more accurate allocation of costs that fairly reflect the cost of service.” In July of 2015, after a long and contentious proceeding the CPUC unanimously voted to approve a final rate reform package. The final Proposed Decision can be seen here. Some of the most significant changes mandated by the CPUC were: to transition from a four-tier structure down to a two-tier structure, reduce the pricing differentials between the tiers down to 25%, institute a minimum bill, and implement a super user charge. These changes will be phased-in gradually through 2020 when the “end-state” rate design is ultimately reached. CALSEIA (California Solar Energy Industries Association) prepared a summary of the changes and phase-in schedule which can be viewed here:


Implementation of this landmark rate reform in California has officially begun. On 9/1/15 PG&E and SDG&E implemented their first rate changes related to this proceeding, and SCE began a month later on 10/1/15.

Calculating solar project economics:

The standard method for calculating the economics of a project are to calculate the ‘annual dollar savings’ (aka avoided cost) for a specific customer. This calculation is generally run based on the current/effective utility rates in place at the time, which would be representative of the dollar savings at that point in time. That ‘annual dollar savings’ value is then escalated based on a utility escalation rate assumption, which is typically between 3 to 6% for residential projects in California. The ‘payback period’ and ‘rate of return’ are then determined by adding up all the project costs, subtracting out any incentives, and then escalating the avoided cost over the life of the project. This method has worked well for the solar industry because it’s simple, transparent and easily understood by the customer.

But it’s easy to see that this method is inadequate when structural rate reform changes are scheduled to be phased-in, like the current situation in California. Basing 25 or 30 years of dollar savings entirely on current rates, when those rates are fundamentally changing doesn’t provide an accurate representation of economics over the projects’ lifetime. Using a simple escalation rate does not capture the impending rate reform changes ahead. The methodology works for rate changes, but it does not work well for rate reform.

What then is the best way to calculate project economics in light of impending rate reform changes?

Calculating the ‘annual dollar savings’ separately for each year based on the phase-in schedule would be a more technically accurate way of modeling. But this sacrifices simplicity. It would difficult to convey this methodology to a customer, which could make the value proposition too confusing. Alternatively it would be simple to calculate the ‘annual dollar savings’ using the ‘end-state’ rates. At the very least it would be worthwhile to know how the annual avoided cost compares when using the ‘end state’ rates versus the current/effective rates. (Quick plug: our platform Energy Toolbase has the proposed ‘end-state’ rates for all three IOU’s, both with and without the assumed 3% escalator loaded into our database, making it quick and easy to determine what that difference would be for a specific homeowner).

This blog is meant to be informative rather than alarmist. Many California residential solar salespeople may not be fully aware of these dynamics. At the very least solar installers should be educated on this, and be prepared to talk on this issue if a potential customer asks. From a consumer protection perspective, homeowners considering going solar today have a right to know.

Adam Gerza is VP of Business Development for Energy Toolbase.

Reprinted with permission.

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