Solar Power for Charging The Electric Car

Many people forget that most electric cars are recharged by plugging into an electric grid which is customarily fueled by coal, nukes or other unsavory power sources. Consequently, most “electric cars” are merely automobiles fueled by sources that continue to be costly to consumers while producing negative environmental impacts.  In most cases, this is probably better than burning gasoline - but try explaining all that to your yoga class...

Many federal and local governments offer rebates and tax incentives for purchasing electric cars, recharging equipment, and solar power systems. In addition, an increasing number of financial institutions offer low interest loan programs for purchasing electric cars and solar power systems, so the conversion to a solar powered life has become surprisingly inexpensive and practical. 

How big of a PV system would you need to power your electric car?

There are really two ways to power an electric car with photons:

1. Charge a battery bank, then use the stored energy to charge the car battery. This is a way to be completely off-grid, but relatively inefficient as the power is pushed through various conversion devices - up to 30%, depending on the car charger and battery.
2. Size the grid-tied PV system to produce enough energy to offset all the energy a car would use during a charge. Ideally, the car would then be plugged in at night and would charge with lower cost, off-peak power.

When buying a PV system there are a number of things to consider. In order to adequately size a system we have to approximately calculate the following:

1. Average electrical usage in the home taking into consideration potential DC to AC conversion inconsistencies (many experts believe up to 15-30% of energy is lost during the DC to AC conversion phase due to inadequate or substandard inverters)
2. Average electric vehicle power usage and manufacturer recharging guidelines.
3. Determine what size and type of PV system would enable you to receive the maximum possible rebates, tax incentives, loan programs, and extended warranty benefits available. 

An average 2,000 to 3,000 square foot home using energy efficient appliances would need an estimated 4-kilowatt PV system to supply all energy needs. 

Considering various manufacturer guidelines, charging an electrical vehicle from a full day’s solar production in an un-shaded area will require a PV system ranging from 2kw to 14kw. (Supplying power for a home up to 3,000 square feet and an electrical car may require a PV system of at least 6kw to 18kw)

Specific estimated guidelines as per manufacturer information are:

• Chevy Volt – the Volt is a plug-in hybrid vehicle (PHEV) that is designed to go the first 40 miles solely on electric power. Thereafter, a gasoline engine provides an additional electric charge that recharges the battery, while also propelling the car. The Volt has a 14kWh battery pack. Fully charging your Volt from a full day's solar production, may require a PV system of 3kw or larger. 

• Toyota Prius – the Prius is a PHEV with a 4kWh to 10kWh battery pack depending on model year and specs. The Prius has an all-electric range of 14 miles and then works in hybrid gasoline-electric mode thereafter. To fully charge your Prius, you may require a 4kw PV system.

• Tesla Roadster – the Roadster is a battery electric vehicle (BEV) has a 53kWh battery pack that provides up to 236 miles on a charge. Charging your Roadster from a day's solar production may require at least a 14kw PV system.

• Nissan Leaf - the Leaf is a BEV that has a 24kWh battery pack providing up to 100 miles on a single charge. In order to fully charge your Leaf from a day's solar production, your PV system should be 4kW or larger.

• Fisker Karma - The Fisker Karma is a PHEV with a 22.6kWh battery pack and a range of 300 miles on a single charge. Fully charging your Fisker Karma may require a PV system of at least 4.5kw or larger.