Conservation, Economics,
and Array Performance


The entire pie represents the average energy consumed during the two previous
January billing cycles. That average was 749 kWh. This year (2004) we "only"
consumed 646 kWh. This is reflected in the chart above as 103 kWh or 14%
conserved. I largely attribute this to the replacement of nearly 30 lights in my home
with compact fluorescent (CF) bulbs. I also have to mention that everyone in our family
is doing their best to turn off lights, televisions, etc., when they're not in use.
Of the 646 kWh that were consumed 270 were generated by the solar array,
and 376 kWh came from the electric company, leaving me with an energy
charge for the month of $44.00. Last year's energy charge was $119.06.
Note: The solar array installation was completed part way through the January
billing cycle and was not online for several days



The solar array was in full swing in February and provided more that 2/3 of the
energy we consumed for the month. We also saw a 22% reduction in our consumption
compared to the last two years. Last year's energy charge was $93.06.



March shows our days are getting longer. The solar array generated over 75%
of the energy we consumed. Last year's energy charge was $90.04.



April looks really amazing to me, with the solar array generating nearly 95%
of the energy we consumed. Last year's energy charge was $99.40




In May the solar array generated over 95% of the energy we consumed. In fact
if it hadn't been for some unseasonably hot weather at the end of April which
forced us to use a our air conditioner for a few days, we should have
finished the month with a credit. Last year's energy charge was $92.41
I also suspect that our conservation number has been going down because the
longer days mean we're using our lights less, so the CF bulbs are making
less of a difference.




June is the first month that the solar array produced more than we consumed.
Although our meter read 56 kWh lower at the end of the June billing period
than the beginning of the period, SCE reports the ending number on our bill
as being the same as the beginning number so they don't have to deal with
negative amounts and credits. My actual bill for the month was $1.32
based on some minimum charge they have.

The chart above shows that of the 438.2 kWh that we consumed,
100% of that was generated by the solar array. In addition to that it
generated a surplus of 56 kWh. The "Conserved" amount is somewhat
meaningless because although we used 270 kWh less than the average
of the last two years it's mostly, although not entirely, due to a late
start in the air conditioning season.

In June we also experienced our highest single day energy
output from our solar array:  18.9kWh.




Because of our energy surplus from June we started July with a 56 kWh, or $7.06,
credit. Our energy charge for July was less than $9.00 even though we actually
consumed about $16.00 more energy than we generated. In fact, we were 25 days
into the billing cycle before we were in positive territory. A few days of
air conditioning made certain of that.

One interesting observation was that the meter reading on July 10th was
the same as the meter reading on March 8th. So basically, during this period
of give and take between positive and negative days, the net result was
that for 4 months we were a "zero energy" home.




This was our highest electricity bill since January, but not bad considering
our energy charge for August last year was $227.44! This summer's weather
has been mild thank goodness. Last year because of the tiered rates
SCE uses we paid $.15 to $.26/kWh for the electricity we used over our
baseline allowance. If we had our solar array last summer and generated
the same 470 kWh, it would have saved us over $119.00.