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Marketing Solar, Part Two

Several weeks ago I blogged about a solar quote my family received. The quote suggested that we could spend $12,400 to save $39,500 on our future electricity bills. My post raised two issues about the quote, including that the savings summed over the next twenty-five years were not discounted and that the company was projecting that our electricity payments without solar would rise at over 5% a year.

marketing solar image

In this post, I provide some promised extensions, and address several issues and suggestions that were raised in the (generous and voluminous!) comments.

Recall that the company is trying to forecast what my family’s savings will be in the future if we spend $12,400 for their panels. Forecasting is a tricky business, but we do it when we make many investments, whether it’s buying stock in the hopes of reaping future dividends and capital gains or buying a house in the hopes of avoiding rent and possibly realizing capital gains when we move out. In the case of solar panels, the expected future returns are lower electricity bills. Calculating those returns requires forecasting what you would have paid for electricity had you not installed solar panels.

Electricity bills reflect the price we are charged for power multiplied by the amount of power we consume. In California, and many other states, the price we are charged varies as a function of how much power we consume. For instance, my family pays PG&E 13 cents per kilowatt-hour (kWh) for about the first third of our power, 15 cents for the next third and, in most months, 30 cents for the last couple kWh of electricity. People who consume more than us in Berkeley can pay as much as 34 cents per kWh. (The kWh thresholds, where the rates change, vary as a function of climate zones – they’re higher inland. They also differ between summer and winter.)

PG&E is using what are called “increasing block rates”: the price per kWh is increasing in the number of kWh we buy – the opposite of a volume discount. Here’s the thing: California regulators are currently considering flattening the increasing block rate structure. This could have a large impact on the savings from solar panels.

Keep in mind that the solar panels proposed for our family would not offset all of our power consumption. We’d still be buying about a third of our electricity from PG&E.  It would offset the most expensive 30 cent power, and leave us paying 13 cents for most of the remainder. But, if regulators flatten the rate structure, the savings from offsetting the high cost power will be lower, and our remaining charges will be higher.

One suggestion on my last post was to be more concrete: how much lower would the savings be if we discounted them, for instance? To get some sense for specifics and to devise some rough estimates of the impact of bill restructuring, I have devised a very crude spreadsheet.

To calculate discounted savings, I have to take a stand on the appropriate discount rate. One way to think about this is to compare the returns my family would earn if instead of buying the solar panels we made another investment, such as in the stock market. Historical stock returns, say over the past twenty-five years, have been around 10 percent, and given that we are making an estimate over the next 25 years, that’s probably a reasonable prediction. But, to allow for the fact that solar panels are probably less risky than an investment in the stock market, and returns from solar are most likely uncorrelated with the stock market (low beta), I used a 5 percent discount rate. If your alternative investment is something like a Treasury Bill, you might want to use a lower rate. At 5 percent, discounted cumulative savings, net of the panel costs, are negative through the first 12 years and only $13,500 cumulatively, compared to the $39,500 we were quoted.

Rate restructuring could have a big impact as well. I am not aware of specific proposals, so I considered a couple different options. If instead of 13 cents, 15 cents, 30 cents, the rates were changed to 15 cents, 16 cents and 24 cents, our discounted cumulative savings would be over 20 percent lower:  $10,500 instead of $13,500. To me, this seems like a big impact from a relatively small adjustment to rates.

If the restructuring is more dramatic, say a flat rate at 16 cents, the savings are reduced by more than half: less than $5,200 instead of $13,500. Note that I am assuming the rate restructuring is effective the first year we own the panels and then kept at the same relative levels into the future, but still escalating at over 5 percent a year. If these new rates only go up at 2.5 percent a year, our solar panels would never pay off.

It’s important to note that I am making pure guesses about rate restructuring. Regulators will have to consider many factors, such as whether the new rates provide PG&E the correct revenue. For most utilities, but not PG&E, households pay a fixed charge no matter how much power they consume. If this is on the table for PG&E in the future, the savings would be lower still.

A team of researchers at Lawrence Berkeley National Labs have put together a comprehensive analysis of the impact of different rate restructuring scenarios on bill savings for solar customers. They conclude that future regulations place substantial uncertainty on future bills, so that, “simple assumptions that project a flat or increasing value of bill savings over time (in real terms) may not be accurate.”

My own hope is that regulators will address this issue and, for instance, devise a more sophisticated version of my spreadsheet, both for potential consumers to use and to constrain how solar marketers display information.

One of my colleagues took pity on the solicitor noting, “Wow, did that company ever knock on the wrong door!” It could be, but everyone will eventually benefit if consumers are making well-informed choices.



Catherine Wolfram View All

Catherine Wolfram is the Cora Jane Flood Professor of Business Administration at the Haas School of Business, Co-Director of the Energy Institute at Haas, and a Faculty Director of The E2e Project. Her research analyzes the impact of environmental regulation on energy markets and the effects of electricity industry privatization and restructuring around the world. She is currently implementing several randomized control trials to evaluate energy efficiency programs.

11 thoughts on “Marketing Solar, Part Two Leave a comment

  1. From all of the comments it must be clear that the economics of solar depend entirely on the government regulator — who can change the outcome on a dime by changing rate design(unlike the “investor”). If you trust the government to be right now and to be consistent for the next 25 years, invest away.

    • True.

      I’ll add another wrinkle to the retail solar investor’s analysis: the government, if/when it decides to adopt a socially cost-effective rate design, could decide not to have it apply to existing installations. In fact, to me that seems likely as I have an idea what the uproar from existing customers would sound like. I don’t think there’s a scenario where they’d really stiff existing rooftop PV investors.

      • Yes, true. Just to be clear, if existing solar customers are grandfathered and kept on their existing rates, this would keep the rate they pay with solar on the first tier or tiers low, but it would not change the calculus on their avoided costs for higher tier consumption if they hadn’t gone solar.

  2. These issues will not be resolved in any satisfactory way until the technology advances and the cost of solar generation come down–or the cost of energy from the utility rises appreciably. Today the cost is great and by the time a solar installation pays for itself, the equipment will have worn out and require replacement. Installing solar today should be motivated by an interest in protecting the environment but not in saving money.

  3. It is very hard to figure out what the California PUC is likely to do, in part because they’re hemmed in by a large number of constraints. Anything they do to flatten rates will likely not sit well with the Governor, who has committed the state to 12,000 MW of distributed PV, but if the rates aren’t fixed, SCE and PG&E could find themselves losing their most profitable sales. There’s cost pressure from both the renewable portfolio standard that won’t be known until it starts to hit customer bills, smart meters that are unlikely to live up to their potential, and a push by the IOUs to start replacing poles and wires.

    If money was no object and I didn’t have to cut down some trees, I think I’d put up PV to end the uncertainty

  4. As an engineer I cringe when I read-hear people buying ‘power’ > power ” .. is the RATE at which electric energy is transferred by an electric circuit. The SI unit of power is the watt, one joule per second… ” We pay for the ENERGY consumed, though we may pay something in the form of a fixed charge for assurance of the power that we may need. Semantics is important in this case. Power is expressed in WATTS (or kilo or mega); energy is kWh or MWh.

    As the author already points out, all analysis for forecasting are based on assumptions, and SIMPLE assumptions just wont do. Complex assumptions will not be easy for the consumers to understand.

    I have come to the conclusion that PV does not make sense as an investment; I have already tried it, and the investment did not pay off, ie the system failed (not worth repairing) before the actual savings ‘paid’ for the installation, even with the tax rebates. Only when the TOTAL cost of fossil energy is reflected in the price that we pay (to PG&E for example) may PV and renewables start making sense.

  5. Thank you very much by the very interesting post. I have been troubled by the 4-5% rate increase forecasts. Usually they are made by looking at data from about 2000-2010, which includes extraordinary increases in 2001 due to the energy crisis. Long term residential rates have increased more like 2% in California. Though this increase is forecast to be higher in the near term due to a) large utility capital expenditures to replace distribution systems, and b) some higher priced renewable contracts coming on line.

    Another issue – have you analyzed the finances of leases and pre-paid leases, which might show the different discount rates applicable to the consumer versus the solar installer? I have seen very low quotes for a pre-paid 10 and 20-year lease.

  6. Catherine, you might try using the NREL Systems Advisor Model (SAM) to do this analysis. It’s at I too did my own spreadsheet for my Berkeley PV system, but got bogged down in the various time and quantity bins, monthly charges, etc.

  7. …thank you for the information. In your quest for determining a true “value” of investment, you provided some of the more “linear” or “hard” values that come into play. While the detail is interesting to review I am left wondering how to value such things as the offset in carbon being dumped into our atmosphere. The added costs related to ground water pollution associated with “hydro-fracking” or even the cost of maintenance associated with solar panels that cause a gradual degradation of service over the lifetime of the panel(s).

    …predicting anything these days can be tricky but I would suggest that neither you nor the solar marketer provide consumers with sufficient information. As I see it, investing in a solar system has the pure economic benefit you described but also a benefit to society in general which may or may not be greater in the long-term but it is also with considering..

  8. I am really pleased that the author considered regulatory uncertainty in this post. Given the sorry future prospects for reliable power generation in California, it is highly likely that the top tier rate, in the future, will still be higher, even if they flatten the tiers.

    I read this yesterday. The author borrowed against his own funds to finance his solar installation. It illustrates that there is more than one way to skin a cat:

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