Are Solar Cell Systems Practical?

First, I'd like to say that I think solar cells are the coolest thing ever.  Think about it, sunlight directly converted to energy!

But...........

In 1975 solar cells were mostly not mentioned in discussions concerning alternative energy.  The reason: COST.

Here is a Solarex Unipanel solar cell ad showing a 12 volt 0.08 amp capacity panel for $75.00.

That is ONE WATT for $75.00 in 1975!

Adjusted for inflation to 2009 cost gives us $299.00 per watt.

Here is a different company selling a 12 volt 0.3 amp 3.9 watt solar panel for $319.00.

That is $81.79 per watt in 1975.

Adjusted for inflation to 2009 values equals $1,272.00 per panel which works out to $326.00 per watt.

Notice the panel size of 19 3/8" by 16".  This equals 80 square inches required per watt of output.

In 2010 there are many different brands and configurations of panels available.

Here is a 2010 Kyocera panel at  $345.00.  It's nominal voltage is 12 volts 3.75 amps and 65 watts.

That is $5.31 per watt!

The size of this panel is approximately 30" x 26" or 780 square inches. Divide that by the 65 watts produced shows that only 12 square inches are required to produce one watt of electric.

So, solar cells are dramatically less expensive and much less area is required to produce the electricity!  Sounds great doesn't it?

Well, step back, it is still very expensive and the payback time is very long.  Let's look at an example of a potential solar installation.

We will use a 2,400 sq ft home located in the Southeastern United States for the calculations.  Average monthly electric bill is $150.00 which at 0.11 cents per kilowatt hour works out to 1,364 kWh per month.

A grid-tie system (no batteries, all power generated is used immediately or fed back to the utility) designed to generate 50% of the electricity used would cost approximately $56,520.00 (this could vary +/- 10% depending on installation variations).  Federal and State tax credits could, depending on your tax situation, bring this down to $27,695.00. 

Theoretically this system could increase the value of your home $18,000.00.  Of course, it would also affect, possibly negatively, the salability of your home as well.  Not everybody is comfortable with alternative energy.

Also, keep in mind that a grid-tie system is NOT a backup power system, if the electric supplied by your utility is interrupted, you still lose all power.

Now to the cost effectiveness of this investment.

Using yearly utility savings (50% of total electric used) which is  adjusted for annual kWh cost increases (at 3.78%) and the replacement of the inverter at the 15 year point, the break even point is in 17 years.  At the end of the 25 year useful life of the system you would be $24,754.00 ahead of the game.  But wait, that 25 thousand is in dollars adjusted for inflation to 2035 values.  To give us perspective in 2010 we would have to reverse the inflation.  That would bring if down to about $12,000.00. 

And....

Solar cells lose their efficiency over time so..... it is time to replace the entire system because it has reached the end of its service life. 

To me, it doesn't seem worth while at this time.  Look at the dramatic changes the last 35 years have brought to the solar cell industry.  At this time 60% of the cost of this system is the solar panels, surely that will change soon.

If you wanted to supply ALL of your power needs with a grid-tie system, it would cost roughly twice as much.  $113,000.00.

To supply all your needs AND have power available when the utility power grid was inoperable, you need batteries sufficient to carry the load, with an inverter and charging system to control it.  With the cost of the batteries, environmentally controlled storage area, inverter, charge controller, house wiring transfer gear and additional labor you could easily spend another $30,000.00 on top of the double amount mentioned above. We're up to $143,000.00.  AND the batteries only have a usable life of 7 to 15 years depending on the batteries you buy. (the long life ones are 3 times more expensive)  You get the idea.  I don't believe there would ever be a breakeven or payback time for a completely independent system able to supply a modern (all the luxuries) home.

So, unless utility costs skyrocket (which it appears there is a very excellent chance of happening) it just isn't financially practical yet for most people.

However, after saying all that:

The home used in the example above through electricity generation causes the release of 27,372 pounds per year of carbon dioxide.

Yuk!

That is equivalent to driving 30,332 miles in an average car.

So, let's keep the pressure on for technology improvements!

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clyder@practicalgreensystems.com

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