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These numbers vary by 9.4%, more than x4.5 the energy numbers, due to the LADWPs crazy pricing games and ever changing prices.  I follow this closely since I am interested in whether our array will ever pencil out.  The grand total savings so far is $1.302M on a purchase price of $3.423M so a simple minded analysis would suggest the array will pay for itself in 13.1 years.  With a warrantied life of 25 years it is looking good.  However getting money is not free.  I assume we borrowed it from our endowment and are slowing returning it.  All of the cleaning, weeding and inverter repairs are not free.  Energy prices are increasing at about 5% per year.  Throwing all of that into the mix I predict our array will pay for itself (surpass earnings we would have gotten if we had left the money in the endowment) in 17.4 years.

 

Finally here’s a disturbing trend and a challenge for you, the Occidental community.

 

 

The horizontal axis is Year and the vertical axis is Energy per Year (calendar) in GWh.  The solid orange line shows the total energy billed to the college over the past 15 years.  You can see a big break in 2013 when the solar array was installed.  If I add the solar energy produced to what we are billed for I get the total, college, energy usage.  This is the solid line until 2013 and the dashed line thereafter and fit with the thin black line.  The college’s overall usage is going up at a rate of about 2 GWh every 15 years.  Thus by the time the array pays for itself the environmental benefit of it will have been wiped out by increased usage! I challenge you to not let that happen.  Saving energy is often much more cost effective than producing energy.  The LED lights going in around campus are a great example of that.  If you have a good idea, and can put in some time, I urge you to consider writing a proposal to the Occidental Sustainable Investment Fund (OSIF).  The OSIF is a $3.5M green revolving fund to encourage sustainable and fiscally sound improvements to facilities at the college.  I am happy to share what data and help I can.