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Why don’t they put solar panels on EVs?

At JuicePoint, we are not just into in EVs, but the wider Smart Grid and energy use. For instance our JuiceBox chargers can be interfaced to charge off excess solar. 

A question we often get asked is “why don’t they put solar panels on EVs?”

Using our solar design software, we zoomed in on Tesla’s old yard in Great North Road, Auckland, and stuck two 300W solar panels on a Model X. These panels retail for around $300 each. Putting aesthetics aside, one panel fits flat across the bonnet and one flat on the roof as the panels are 990mm x 1650mm. 

 

Lets assume the EV gets no shade all day and some losses from power conversion. The simulated solar output table for the two panels in Auckland, New Zealand is:

Month Output (kWh)
January 94.6
February 76.3
March 69.4
April 51
May 36.1
June 28.2
July 34.9
August 44.5
September 57
October 75.5
November 85.2
December 96.6
Total  749.3

How far can you go on 749kWh? It depends on the EV, most are around 15kW/100km. However Teslas are around 20kW/100km due to running a computer for the Autopilot & sensors and the heavier weight of the larger batteries found on Teslas. Note we have also added around 40kg of extra mass from the two panels and extra electronics to charge the battery, and we probably haven’t done the aerodynamics any favors either. Smaller, more efficient EVs tend to have smaller bonnets and roofs, which would limit the amount of solar that could be generated. So you could probably get 300W of solar on a Nissan LEAF, and half the power and range. So, using efficiency of 20kW/100km we get:

Month Output (kWh)

Distance in km
(at 20kW/100km)

January 94.6 473
February 76.3 381
March 69.4 347
April 51 255
May 36.1 180
June 28.2 141
July 34.9 174
August 44.5 222
September 57 285
October 75.5 377
November 85.2 426
December 96.6 483
Total  749.3 3746

So 600W of solar in Auckland will get your EV approximately 3746km in total for the year. But note for the entire month of June you would only get 140km distance from the solar panels in full sun. 

The average car does approximately 14,000km/year in New Zealand, so the solar would provide 26% of the energy usage for the EV. For comparison, according to Rightcar website,

The on-road fuel cost of this vehicle is estimated at $440 / year based on driving 14,000 km per year (20.8 kWh/100km).
Cost assumes electricity price of $0.15 per kWh. 

At 15c/kWh for power the solar saves $112 per year, considering the panels, plus mounting and inverter costs the payback would take approximately 8 years.

There is lots of research going on in the solar panel space, with lighter and flexible panels being developed with greater efficiency. But we really would need some major breakthroughs in solar technology to make solar panels worthwhile on EVs.

Also note this is best case as it this assumes the EV is parked in full sun for the entire day, every day. Shade from buildings, trees and light posts will dramatically reduce the amount of power and hence range.

If you really want a solar powered car – put the panels on the roof of your house. JuicePoint’s JuiceBoxes can be used to run off excess solar PV. If your EV is not at home during the day, with our partners Paladin, you can use solar energy to heat your hot water during the day and then use night rate power to charge your EV instead of heating your hot water – effectively turning your hot water cylinder into a battery.  

 

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