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By SanDiegoDave100
October 18, 2006

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Subject: Solar Energy and the Tesla Motors Electric Car

Just thought you might want to see some numbers I ran on the case for solar energy and using such a system to provide electricity to an all-electric car.

My current home electrical usage is about 600 Kilo-watt-hours (Kwh) per month. This is pretty normal for a family of two in a single family house. San Diego Gas & Electricity (SDG&E) charge the following:
First 300 Kwh @ $.1238/Kwh = $37
Next 100 Kwh @ $.1440/Kwh = $14
Next 300 Kwh @ $.2518/Kwh = $50
Total = $101

Now, my fuel bill for the car is:
1500 miles/month / 25 mpg = 60 gallons/month (about a fill-up a week)
60 gallons/month * $3.00/gal = $180/month

Total energy bill = $101 + $180 = $280/month

Using conservative Tesla Motors numbers for power for their vehicle:
1500 miles/month @ .250 Kwh/mile = 375 Kwh

So, to power my household and provide power to recharge my electric vehicle, I need about 600 Kwh + 375 Kwh = 975 Kwh.

According to the "Clean Power Estimator" website:

An 8.0 KW system would provide an average of about 950 KWh over the course of a year. My zip code is 92024 (San Diego, CA) which is used to make the calculation.

At today's prices online at , I could purchase an 8.0 KW system for about $55,500 before rebates. This is before any tax breaks. California offers a $2.60/watt. This is described at the Cal Solar website: . If the system is "owner-installed" then a 15% discount on the rebate reduces it to $17,680. Thus, the system cost would be $37,820 after rebates.

A home equity loan of $37,800 at the current 6.5% rate would be only $239/month. Therefore, with rebates, such a solar system would actually save me $40/month in total fuel/energy costs. And I use NO OIL! I produce NO HYDROCARBON emissions.

When "NanoSolar" of Florida goes into production in 2007, I expect solar prices per watt to plummet by half.

Optimistically, I would hope that Tesla Motors could come out with a reasonable all-electric commuter vehicle within a couple of years.

Additionally, there are tax credit issues beyond the rebate. I admit I can't figure out the tax credits issue. It appears too complicated at this time for this simple analysis.

Finally, SDG&E tiered rates continue to increase beyond what I use or show above. The next 300 Kwh are at @ $.26/Kwh and the following 300 after that are at $.27/Kwh.

I did this analysis because my wife and I are planning on rebuilding our home in 2008 after our youngest daughter graduates from college. We will have grid-tie-in solar fully incorporated into the design.


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