Comparing PVWatts Estimates to Actual Solar Production

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PVWatts is a website run by the National Renewable Energy Lab (NREL) which can be used to estimate how much energy a given solar array might produce, based on historical mesurements of insolation.  If you ever have a site analysis done, the installer will probably use it to estimate your potential for annual production, and you might wonder how close the the mark it’ll be.  Now that I’ve had solar PV for almost 2 years, it’s interesting to look at how close the estimates were for my situation. Continue reading

Hanlon’s Razor and Online Comments

Never attribute to malice that which is adequately explained by stupidity. – Hanlon’s Razor

 

Boy, but sometimes it is hard.  There was a recent article in the local paper about a solar manufacturing plant going up on Minnesota’s Iron range.  And you can bet that any article about alternative energy will bring out the interesting comments in droves.  (Maybe this is true about any article about anything?)  Warning: If you don’t want a boring rehash of anti-solar comments and my attempts to bring a few factual nuggets to the conversation, you should stop reading this post now.  You have been warned… Continue reading

3MWh and counting …

We hit 3MWh (that’s megawatt-hours) of solar PV production yesterday, a few weeks ahead of the 1-year anniversary of the install.  In that time, we:

  • Generated 3000 kWh
  • Pushed 1877 kWh onto the grid
  • Pulled 3278 kWh off the grid

So, that means we used (3000 – 1877 + 3278) = 4401 kWh in that time (for about 360kWh/month average), and we generated 3000 / 4401 = 68% of the electricity we used in our home.  A bit shy of the 75% I’d hoped for but not too bad!

The monetary value of those 3000MWh is about $300 here in MN, at about $0.10/kWh (my baseline for comparison is the cost for electricity with Windsource, since we have subscribed to that program for many years now.  It’s only slightly higher in cost, about $0.009/kWh, since the fuel charge gets removed for Windsource customers).