I think that Arizona's decision not to go on DST is a great one. Being outside in the summer sunshine in Phoenix can be miserable, but the desert cools very quickly once the sun goes down. The earlier the sun goes down in the summer, the better as far as I am concerned. Within an hour or two after sunset, it is pleasant to sit and eat and play outside.
A new study seems to show that DST increases electricity use, rather than reducing it. DST was, if my memory serves, a WWII innovation to save electricity. It does so quite well if electricity demand is driven mainly by lighting. It lets one read and function by sunlight in the evening hours. However, as air conditioning has become a larger element of electricity demand, that equation is changing. DST can lead to higher air conditioning loads in the evenings.
Our main finding is that"”contrary to the policy's intent"”DST increases
residential electricity demand. Estimates of the overall increase range
from 1 to 4 percent, but we find that the effect is not constant
throughout the DST period. There is some evidence of electricity
savings during the spring, but the effect lessens, changes sign, and
appears to cause the greatest increase in consumption near the end of
the DST period in the fall. These findings are consistent with
simulation results that point to a tradeoff between reducing demand for
lighting and increasing demand for heating and cooling. Based on the
dates of DST practice before the 2007 extensions, we estimate a cost of
increased electricity bills to Indiana households of $8.6 million per
year. We also estimate social costs of increased pollution emissions
that range from $1.6 to $5.3 million per year.