(1,000/Watts/Meter2), however, the temperature was
increased to 90°F and a wind of one meter per second was
used for cooling. This rating results in about a 20%
decrease in panel performance.
Check the panel’s PTC rating at www.consumerenergy
center.org/cgi-bin/eligible_pvmodules.cgi. Some retailers
will include both the STC and PTC ratings.
Check the inverter’s CEC rating at www.consumerenergy
center.org/cgi-bin/eligible_inverters.cgi. If the retailer
includes a CEC rating, this is the PTC rating derated by the
Wiring efficiency will vary with the size of the wire
and the length of the wire runs. Unless you calculate and
specify the wire yourself, figure 97% efficiency.
In my case, the 187 watt panels were rated at 167 and
the inverter was rated at 94%, so I calculated my wiring at
98% efficient. To size my system for 100% utilization, I
needed a system rated for
<Daily Consumption (k WH)> / <Hours of full sun> /
<inverter efficiency> / <Wiring efficiency> = <system size
in k W>
20 / 5. 8 / . 94 / . 97 = 3.782 k W CEC.
The selected system should be this size or larger.
Financials of a Solar System
htm, the Sunwize 5 kW system has a PTC rating of 4.717
kW. The Fronius IG 5100 inverter has an efficiency of
94.5%. This would give a CEC rating of 4.457 kW and a
price tag of $35,400 ($7.94/watt) — no small sum.
In addition to financing, there are generally a number
of federal, state, and utility rebates that are available —
easily totalling many thousands of dollars. Most large solar
installation companies will give you the information you
need to apply for the rebates and tax credits.
In addition, many companies now offer package deals
that will even include assortments of compact fluorescent
light bulbs to help you minimize consumption of your
freshly converted sunlight!
If you have the itch to “go solar” on your house, now
is a great time to take the plunge. Panel efficiencies are
higher than ever and the technology/dollar ratio is certainly
moving in your favor. With energy prices guaranteed to
always steadily increase, this is one capital upgrade to your
house that not only adds resale value, but might even earn
you a check from the utility company instead of a bill! NV