Four years with solar power


Electricity generated from solar power offset yearly usage by 104%.  We used 5,119 kWH / year (averaged over nine years).  Our 4.3 kW system generated 5,338 kWH / year (averaged over four years).

I still clearly remember when the solar carport was built as if it were yesterday, yet it’s been four years.  As a new year dawns, I wanted to plot our average electricity generated and benchmark relative to the original PVWatts estimate made (and posted below) before the panels were installed.

I am now even more in awe of PVWatts.  As you can see from the graph, the yellow curve is the estimated generation, based on our location, solar array size and panel angle relative to the sun.  The green curve is four years of actual data, and it it overlays almost perfectly.  As I’ve noted below, now with emphasis, PVWatts really and truly is a solar seer.

Solar Seer

A seer is someone who can predict the future.  In this case, the Solar Seer is PVWatts (, a program that calculates how much power a photovoltaic energy system will generate.  When I crunched the numbers back when our solar carport was commissioned, PVWatts predicted our system would generate slightly more power than we typically use in a year (106% more to be precise, see post below).

With 2013 over, I looked over the numbers.

Our solar carport generated 5,306 kWh (5.3 megawatt hr) in 2013.

This is 105% more power than we used in 2013 (we used 5,045 kWh).  PVWatts was thus dead on when it came to predicting power production.

So there are two take home messages:  1) By going solar, we’ve now eliminated our electricity footprint on this earth (at least with respect to our home electricity usage).  2) PVWatts is amazing.  Believe what it tells you.