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Inventor Karl Kemnitzer Sheds Light on his Solar Electric Cargo Bike

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Karl riding his second bike up Mt.Washington
Photo credit: Mt Washington Auto Road

Source: Jenevra Wetmore, EAN/Middlebury College Internship Program

In 2010, Karl Kemnitzer decided that he was going to use his gas-powered car less, in keeping with his off-grid lifestyle.  Unlike the rest of us, who might look into an electric vehicle or carpooling, Karl decided to design his first solar electric bike. Why a solar electric bike, instead of a regular, human-powered bike? Karl lives on a hilly dirt road in Hartland, that requires a lot of physical exertion to bike regularly, especially with a load of groceries.

He now uses his electric bike year-round, even in winter, and regularly travels distances of 45-50 miles without breaking a sweat.  Read on to learn how he does it, why he does it, and his plans for the future of solar bikes!

A Knack for Building

Karl has worked in garages as a mechanic, but does not attribute this work to his machine-oriented, inventive mind.  Rather, he credits his childhood.  Karl grew up on an apple orchard surrounded by farm equipment.  Karl says, “when you’re in a rural setting, that’s what you play with. I’ve been building stuff since elementary school.” In fact, he began experimenting with motorized bikes when he was just 9 years old– he attached a lawnmower engine to his sister’s bike.


After speaking with Karl, one is left with the impression that he will never be completely satisfied with his bikes. He is always striving for a lighter, more efficient bike.  He finished building his first solar bike in 2012 and it cost him $1,200, all out of his own pocket. Karl recycles parts of old bikes to build his electric bikes, but still has to purchase the solar battery and motor. Those cost him $900 on that first bike.  The solar component of this first bike weighed 22 pounds and had a 60-watt solar rating.

His latest bike– the bike he rides more frequently– cost $1,500, and was finished in 2014. He got flexible solar panels for this bike, which are much lighter. The solar component for this bike weighs 7 pounds, and has a 100-watt solar rating.  It’s 15 pounds lighter and has a solar rating 40 watts higher than his first bike– that’s a big improvement.

How Do They Work?

Karl has lived off the grid for roughly 30 years and powers his home with solar panels. Now those same solar panels also charge his bike. It takes about a half hour of charging off solar for every 10 miles traveled. The panels attached to the bike are used to top off the electricity while riding. The solar electricity then charges a lithium battery, which powers a direct drive hub motor that is part of the bike’s wheel hub. To make the bike’s motor kick in, Karl presses down on a lever on the handlebar. Otherwise he can move forward by pedaling, the old-fashioned way.

When he rides, Karl typically pedals lightly to moderately and lets the motor do the rest of the work. On a screen between the handlebars he can see how many amp hours he has used, with the knowledge that there are 20 amp hours on his battery. He typically rides at 16 to 18 miles per hour, but strong pedaling combined with the motor can get the bike to 25 or even 30 miles per hour. Karl has calculated that his bike gets the equivalent of 3,200-3,600 miles per gallon. (He uses the EPA’s estimate that 1 gallon of gas equals 33 kilowatt hours, and the knowledge that his bikes usually get 10-13 watt hours per mile.)


In rural Vermont, it can be difficult to find sustainable methods of transportation that don’t involve cars. Since he lives off the grid and heats with wood, Karl focused in on changing his method of transportation because, as he said, “I’m not going to walk and I’m not going to take the bus. That left biking.” Karl’s main agenda is getting more cars off the road, especially fuel-burning cars, but he’s also interested in energy efficiency and environmental problems on a larger scale. He’s the Upper Valley Group Representative for the Sierra Club of Vermont and serves on the town of Hartland’s Energy Committee. He tries to loan his bikes out to people as much as possible, and loves going to events to get the word out about solar bikes. Sue Minter even rode one of Karl’s Bikes at the Vermont State House when she was Secretary of Transportation.

Plans for the Future

Karl is currently building his third solar electric bike. He plans for this bike to have a motor with multiple speeds, unlike the previous two bikes, which are single speed and therefore not as efficient when he’s going slowly. The new bike might even have eight speeds! “I’ve got a really good testing lab where I live,” Karl says, because of the hilly terrain, and he’s ready to experiment.

When Karl started his electric bike project, he didn’t even know whether he could get to the Upper Valley Food Coop and back, a distance of roughly 16 miles from Hartland. Since then he and his bike have climbed Mount Washington, which runs 7.8 miles up from 1565’ elevation to 6200’ at the parking lot. He estimates he could travel 190 miles on a sunny day, with light to medium pedaling.

Looking to buy one of Karl’s bikes? Unfortunately, you’ll have to wait. Karl is still experimenting, and isn’t ready to sell them or warranty them. Don’t lose hope though– in the future years, he said he could see starting a business in solar electric bikes.

For more information visit Karl’s blog: