title: Data Visualization: How to represent kWh usage by year against average temperature
body: <p>Just for fun, I want to chart my monthly household power consumption year-over-year.  However, I wish to include some reference to monthly temperature so I can determine if my home or behavior is improving, worsening, or holding steady in regards to kWh usage.</p>
  
  <p>The data I am working with:
  <code>
  +----------+--------+-----------+----------------+----------+-----------+------------+
  |  Month   | # Days | kWh Usage | Daily kWh Avg. | Avg. Low | Avg. High | Avg. Temp. |
  +----------+--------+-----------+----------------+----------+-----------+------------+
  | Mar 2015 |     32 |      1048 |             33 |       40 |        60 |         50 |
  | Feb 2015 |     29 |      1156 |             40 |       32 |        54 |         43 |
  | Jan 2015 |     33 |      1143 |             35 |       38 |        57 |         47 |
  | Dec 2014 |     30 |       887 |             30 |       39 |        61 |         50 |
  | Nov 2014 |     29 |       645 |             22 |       45 |        67 |         56 |
  | Oct 2014 |     29 |       598 |             21 |       60 |        78 |         69 |
  | Sep 2014 |     32 |       893 |             28 |       70 |        85 |         77 |
  | Aug 2014 |     30 |       965 |             32 |       72 |        87 |         79 |
  | Jul 2014 |     29 |       784 |             27 |       72 |        87 |         79 |
  | Jun 2014 |     32 |      1018 |             32 |       69 |        87 |         78 |
  | May 2014 |     30 |       702 |             23 |       63 |        82 |         72 |
  | Apr 2014 |     33 |       722 |             22 |       50 |        71 |         60 |
  | Mar 2014 |     29 |       830 |             29 |       41 |        62 |         52 |
  | Feb 2014 |     28 |      1197 |             43 |       32 |        52 |         42 |
  | Jan 2014 |     33 |      1100 |             33 |       38 |        59 |         49 |
  | Dec 2013 |     30 |       856 |             29 |       40 |        63 |         51 |
  | Nov 2013 |     33 |       686 |             21 |       48 |        70 |         59 |
  | Oct 2013 |     30 |       527 |             18 |       61 |        77 |         69 |
  | Sep 2013 |     30 |       817 |             27 |       69 |        86 |         77 |
  | Aug 2013 |     28 |       991 |             35 |       72 |        86 |         79 |
  | Jul 2013 |     31 |       993 |             32 |       73 |        86 |         79 |
  | Jun 2013 |     30 |       847 |             28 |       66 |        83 |         74 |
  | May 2013 |     29 |       605 |             21 |       59 |        76 |         67 |
  | Apr 2013 |     34 |       791 |             23 |       47 |        66 |         57 |
  +----------+--------+-----------+----------------+----------+-----------+------------+
  </code></p>
  
  <p>I started with a column chart easily comparing month-to-month values:</p>
  
  <p><img src="https://i.stack.imgur.com/m9awd.png" alt="Month-to-Month Usage Column Chart"></p>
  
  <p>I envisioned a nice background area or line graph mapped to a secondary (right) vertical axis showing the high/low ranges but realized that would be problematic with the multi-year groupings.</p>
  
  <p>It would be easy with one single year:</p>
  
  <p><img src="https://i.stack.imgur.com/r1yF6.png" alt="2014 kWh Usage with Temperatures"></p>
  
  <p><strong>I am curious to know if anyone can recommend a way of combining all the yearly data into a single chart with temperature comparisons?</strong></p>
  
  <p>Is there some ratio I could use that could effectively relate the kWh usage to average temperature... or some other display technique I am overlooking... or am I stuck with one chart per year?</p>