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Monday, October 24, 2011

PV Solar Array Installation - Preliminary Information

We are about to install a 23,760 watt photovoltaic array.  It will consist of 3 strings of 33 panels having peak production of 240 watts each. Each of the 3 strings will feed a 7KW inverter.  A combiner will join the inverters to feed through a production meter with a system disconnect handle -- a safety device that allows the power company to safely work on transformers and other devices without risk of shock from PV producing households.  The system engineer was here today and said most of the PV systems produce only up to 85% of rated values.  So 23,760 watts x .85 is 20,196 watts.

Sadly the performance data for existing solar panel systems in Glendale and Phoenix is lacking when I use internet search engines.  I intend to blog my system production numbers routinely throughout the next 12 to 24 months and provide a benchmark reference for those who may be considering a residential solar PV array for grid-tied co-generation.  During that time I am changing this blog to publish only the solar articles and photos.  I'll return to the occasional hobby postings later.

Earlier today APS (electric company) called to discuss rate plans.  They allow PV producers to change rate plans only one time in any 12-month period.  Also, they do not allow credits for excess production to carry over into a new rate plan.  Credits are settled only at year-end.  Also, at year-end they will ask for a meter reading of the production meter, for their own and for federal government mandated reporting requirements.

Since my PV system is sized to slightly exceed my peak summer usage, I expect to carry credits forward throughout the entire year. I have heard that credits cannot exceed 125% of usage.  If that's the case then I will need to find some way to turn extra electricity into cash.  Maybe there's someone with ideas on that?

Also, another rumor that I have not confirmed, is that the distribution and meter reading and billing services charges will continue each month... billed to me even if I produced excess power.  So I expect I may be paying a token bill... or not.  I looked at a recent bill and the non-generation charges are about 50%.  The only way that can be reduced by co-generation is if the other charges are calculated as a percentage of billable power usage.  Here's the charges, taken directly from last month's bill:


Charges for electricity services
Cost of electricity you used
Basic service charge $6.90
Delivery service charge $73.67
Environmental benefits surcharge $11.20
Federal environmental improvement surcharge $0.42
System benefits charge $5.53
Power supply adjustment* -$14.89
Metering* $5.39
Meter reading* $1.80
Billing* $2.03
Generation of electricity on-peak* $92.65
Generation of electricity off-peak* $56.80
Federal transmission and ancillary services* $13.68
Federal transmission cost adjustment* $11.08
Cost of electricity you used $266.26
Taxes and fees
Regulatory assessment $0.63
State sales tax $17.97
County sales tax $1.91
City sales tax $5.99
Franchise fee $5.34
Cost of electricity with taxes and fees $298.10
Total charges for electricity services $298.10


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