title: T-SQL select sum of each year, and forecast next year
body: <p>I've got a pretty simple table with:</p>
  
  <pre><code>Date, kWh
  </code></pre>
  
  <p>It's got about 4 years of data.</p>
  
  <p>How can I produce a result set like:</p>
  
  <pre><code>Year, Result
  2010, 123211
  2011, 123213
  2012, 123211
  2013, xxxxxx
  </code></pre>
  
  <p>Where xxxx is a forecast for the year.  </p>
  
  <p>The forecast would combine the sum of the dates in 2013 so far, added to an average kWh multiplied by the days remaining in 2013.</p>