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Even In Seattle Solar Panels Easily Power 100% Of An EV’s Annual Miles

I’ve upgraded to an 8.5 kW solar panel array on my roof (from 4 kW on my old roof before I had to replace it). I’m pleased to say that, even in northerly Seattle, this is far more than I need to cover all the kWh my two electric vehicles need, so far.


The Seattle, Washington area is not known to be particularly sunny. But what people may not understand is that, during the warmer months, we have more hours of daylight than many southern US cities, and also far fewer rainy days than during our cooler months. So, at least in spring and summer (and early fall), this means the Seattle area is potentially making more solar energy than urban areas further south. Interestingly, in terms of total annual solar potential, Seattle isn’t too far behind Houston, Texas of all places (Houston tends to have more overcast summer days than Seattle does). 

The most electricity I made in a year with my 4 kW system was about 3,860 kWh, or roughly enough to drive my Tesla Model 3 EV 16,000 miles (more than I have driven it in any given year). I will note that I have two electric cars though, one of which is less efficient than the Model 3. After I removed my old panels, I also replaced my 2017 Chevy Volt with a 2022 Kia Sorento PHEV, which based on my driving and usage patterns consumes approximately 11 percent more electricity to drive the same distance as the Volt (I have a lifetime miles per kWh rating of 3.21 in my Sorento versus 3.6 for my Volt). Even so, I currently only use about what my 4 kW system produced driving both vehicles in a 12 month period. For example, in the last 12 months I used roughly 3,663 kWh to drive about 13,500 miles on electricity between my two plug-in vehicles, or roughly 3.7 kWh per mile, combined. 

Comparatively speaking, the most kWh I have ever used for driving in a 12 month period was in 2019 (5,156 kWh for a little over 20,000 miles of driving at 3.9 miles per kWh between my Model 3 and my Volt). This was just prior to the pandemic when my wife and I had to commute almost every day for work, compared to now where we commute for work far less (only about 20% of the time). 6 months into the ownership of my new 8.5 kW system, my panels have produced 6,280 kWh of electricity, which is about 600 kWh more than my entire house consumed in that period, including everything else that ran on electricity in my house besides my vehicles. This means I probably won’t make 100% of the power my household consumes (my original goal) because the next 6 months will be darker and my panels will produce only about ⅓ as much electricity as the first 6 months. I estimate that I will end up with a total of roughly 8,350 kWh produced for my first 12 months. Whether I make enough power to cover my entire household use also depends on how much I charge when I am away from home, which so far is about 25% of my total kWh consumed (between the two vehicles). I’ll check back in 6 months from now to see if 8.5 kW turns out to be close to the generating capacity we need to cover about 100% of our household use. Based on our use so far I expect it will be at least 20% shy of hitting the mark though.

One thing that surprises me a little is that my new panels, which are mostly installed in a west-southwest orientation, have produced as much power as they have. I have always understood that the optimal orientation for solar panels, for production purposes, tends to be south facing. My original 4 kW array was, more or less, oriented in that direction (they were actually southeast facing) and produced at most about 26 kWh in a day. My current 8.5 kW array made about 56 kWh on its best day in mid June this year, which suggests that my mostly west-southwest facing array is creating just as much electricity, per kW of installed potential, if not slightly more. I am inclined to think this is due either to more sunlight falling on the panels after midday in these sunnier months, and or due to slightly improved efficiency in my newer panels. If my 8.5 kW array comes up significantly short of my goal to produce about 100% of my power, I could install additional panels (there is still room for at least 8-10 more), but I doubt I would do this. Instead, I would look for ways I might reduce my consumption since there is a diminishing return after producing enough electricity to cover my primary draws (fuel for my cars, running all my major appliances, and running the HVAC). 

Ultimately, even in a northern US city that averages only around 164 sunny days per year, one can make enough electricity to drive 100% of one’s annual miles on electricity from solar panels on their roof, and then some. Even if you might be an edge case and drive far more than the high end of the average miles per year, given a more efficient EV and enough roof space for solar, one should be able to generate all the electricity needed for driving an EV.

Questions or comments? Please leave them below.

Images courtesy of Justin Hart.

Justin Hart has owned and driven electric vehicles for over 15 years, including a first generation Nissan LEAF, second generation Chevy Volt, Tesla Model 3, an electric bicycle and most recently a Kia Sorento PHEV. He is also an avid SUP rider, poet, photographer and wine lover. He enjoys taking long EV and PHEV road trips to beautiful and serene places with the people he loves. Follow Justin on Torque News Kia or X for regular electric and hybrid news coverage.