Saturday, December 7, 2013


Electric Cars and Solar Power

We have a lot of customers that are looking to install solar on their homes and are also considering an electric car. We call this our Electric Car Option. Although we can’t help you get your new Tesla any faster due to the long lead times, we can help you generate the power so you won’t ever have to go to a gas station again.

Here’s how it works. From Wikipedia, I pulled the following information.

The Roadster is the first production automobile to use lithium-ion battery cells and the first production EV to travel more than 200 miles (320 km) per charge.

The world distance record of 501 km (311 mi) for a production electric car on a single charge was set by a Roadster on October 27th, 2009 during the Global Green Challenge in outback Australia.
According to an independent analysis from the U.S. EPA, the Roadster can travel 244 miles (393 km) on a single charge of its lithium-ion battery pack, and can accelerate from 0–60 mph (0–97 km/h) in 3.7 seconds. The Roadster’s efficiency, as of September 2008, was reported as 120 mpgge (2.0 L/100 km). It uses 135 W·h/km (21.7 kW·h/100mi or 490 kJ/km) battery-to-wheel, and has an efficiency of 92% on average.

So, let’s believe the EPA for a moment and assume that the Tesla can indeed go 244 miles on a single charge. How much electricity does a single charge require? Well, we go back to Wikipedia for an answer.

A full recharge of the battery system requires 3½ hours using the High Power Connector which supplies 70 amp, 240 volt electricity; in practice, recharge cycles usually start from a partially charged state and require less time. A fully charged ESS stores approximately 53 kWh of electrical energy at a nominal 375 volts and weighs 992 lb (450 kg).

A little math shows that 70 Amps x 240 Volts = 16,800 Watts or 16.8 kWatts. If we charge the car for a full 3 1/2 hours, we get 16.8 kWatts x 3.5 hours = 58.80 kWatthours.

Thus and Therefore, if we charge the car with 58.80 kWhs and we can go 244 miles then we get the result that the car requires 0.24 kWhs per mile.If you drive 30 miles per day, we can then assume that 30 miles/day x 0.24 kWhs/mile = 7.23 kWhs/day to run your car.

Well, how many solar panels are required to generate 7.23 kWhs/day. In general, a good rule of thumb is that one module will generate 1 kWh per day, on average, over the course of a year.
Approximately 8 solar modules will power your car 30 miles per day!!!

All this math adds up to one thing. It is and will become incredibly cost effective to power your car with solar panels. Right now, with State and Federal rebates cutting the cost of solar by about 40%, it is similar to having the government pay for half of your gas bill.
When thinking about putting solar on your home, consider the electric car option.