Solar Power is Contagious, Study Finds

A new study “Peer Effects in the Diffusion of Solar Photovoltaic Panels” looks at how solar power spreads like a “contagion.”  Here’s an analysis of an early draft.

by John Farrell

The study notes that for every 1 percent increase in the number of installations in a single ZIP code, there’s a commensurate 1 percent decrease in the amount of time until the next solar installation.  As [Adam Browning] writes, “solar is contagious!”

I’m a data lover, so I thought it would be interesting to see what this looks like over time.  If you start with a neighborhood with 25 solar installations, where it was 100 days between the 24th and 25th installation, this peer pressure effect will reduce the time between installations to just 10 days by the 250th PV project. (see chart)

Of course, this process takes a while to unfold.  In fact, if solar PV was being installed only once every 100 days at the outset, the peer pressure effect will take over 15 years to reduce the time between neighborhood installs to 10 days.

The second line on the chart (red) looks at the change if you start with 25 solar installations but with a time between installs of just 30 days.  By the 250th PV project, the time between installs has dropped to 3 days.  And because the lag time between installations started so much lower, the 10-fold drop in lag time takes less than 5 years.

The basic formula – written another way – seems to be that a 10-fold increase in local solar installations will result in a 10-fold drop in the time between installations. This will hold true through the second iteration, as well.  In the neighborhood with an initial 100-day lag between installations, it will take another 15 years for the lag to drop to 1 day from 10 days, reaching this level when there are 2,500 local PV projects installed.

Perhaps I can amend Adam’s statement: solar is contagious, but it’s not yet very virulent.

(Adam’s reply): I would note that the current strain  (solar expensivus) is not a virulent as future strain (solar cheapus).  Minnesotans are expected to have low resistance — we are talking major epidemic levels of contagion.

Note: If only the experience cost curve for solar PV worked at the neighborhood level, since it typically shows a halving of installed cost for every 10-fold increase in total installed solar capacity (worldwide)!

John Farrell, in a repost from Energy Self-Reliant States

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7 Responses to Solar Power is Contagious, Study Finds

  1. My own anecdotal tale proves this to be correct. After we installed our own solar array we got tons of calls from neighbors asking how we liked it and who we used. Two of our neighbors have already installed their own PV systems as a result.

    Now we drive an electric car and our same neighbors are inquiring about THAT. Marketers have long known the power of early adopters to influence friends and neighbors, but I really think people are interested and craving energy efficiency and green technology in their daily lives. No one wants to throw their money away on high utility bills.

  2. Dr.A.Jagadeesh says:

    Excellent post on Growth of Solar.

    Dr.A.Jagadeesh Nellore(AP),India

  3. This is a specific example of what in the economics literature is called “increasing returns to scale”. There are many different forms of this effect, including economies of scale, network externalities, learning by doing, and zero marginal costs for reproducing information (by using information technology). Virtually all economic models ignore it, but it is pervasive, and it will make reducing greenhouse gas emissions cheaper and easier than the models predict.

  4. Leif says:

    Exactly Jonathan. Add to that the ever increasing cost, both direct and indirect, of the ecocidal fossil industry and it is clear to see the winning strategy. The big mystery is whether society/humanity responds fast enough to make a difference in the otherwise ultimate doomsville outcome. I know which side I am rooting for…

  5. John Batteen says:

    I’m a Minnesotan, and I’m certainly not offended, but I just don’t get it. It’s not exactly a hotbed of solar development up here. We do love our winters though.

  6. Kelvin says:

    This is an interesting report on Solar Energy. It’s really good to know that how fast solar energy is catching up across the globe. Recently came across a article which stated that India is planning to build 48 solar cities. Hope this too becomes contagious…And when there is so much scope for solar energy international brands like Siemens which has such innovative technologies for harnessing solar energy are surely to open new avenues for solar energy usage…(blog[dot]siemens[dot]co[dot]in)

  7. Leif says:

    Wind is solar and perhaps a better fit for Minnesota. Efficiency is the most cost effective to implement and pays the fastest return to the consumer, you. The least expensive watt is the watt you do not use. All else will follow. Do nothing, nothing gets done.