Frequently Answered Questions

I’ve been asking questions about solar bikes since 2006 when I first got it into my head that I wanted to build one for myself. I’ve been answering questions about solar bikes since 2007 when I started riding around Oakland, California on my first solar ebike prototype. It’s mostly the same 10 questions over and over. Basically, my life is like the movie Groundhog Day.

An early version of this FAQ is still online. Most of it still applies today with the notable exception of my take on regenerative braking. In 2007, I wrote “regenerative braking would only add 2-3% to the battery’s range.” This was based on my reading of a white paper which in turn was based on outdated assumptions. I now have an ebike with regenerative braking and it extends my range by 10% on flat roads and 20% or more in hilly terrain. I love being wrong about stuff like that. Regenerative braking is awesome.

The following is a sampler platter of the kinds of questions I’m asked while test riding my rig around Berkeley and Oakland. Looking back over my choices, I seem to have selected questions based more on how much I’ve had to think about the answer than on frequency of the question. It’s a challenge to craft one-size-fits-all answers when the person asking the questions might be a conspiracy theorist or a Nobel Laureate. We have more than our share of both types around here.

Did you, like, make that?

Yes. My earliest builds had a very home-made look to them. As my fabrication skills improved, this question gradually evolved from “Did you make that?” to “Did you make that?” to “Where did you buy that?” I’m choosing to interpret that pattern as a compliment.

What about wind?

Sometimes, this question is phrased along the lines of “Were you dropped on your head as a baby?! I live in X and the winds here are so epic that you would immediately be blown under the wheels of the first passing lorry. I’ve spent a few seconds looking at images of your bike and I can tell that you clearly have no idea what you are doing.”

Dear internet stranger, thank you for your concern.

Short answer: wind is not a problem.

I’ve spent many years and many thousands of miles designing, building and testing this bike and trailer. My local rides include a bridge over San Francisco Bay and stretches of bike trails adjacent to open water where it’s never not windy. The most extreme 80° left/right tilt is only useful at sunrise and sunset when the sun is directly to my left/right. I tend to show this trailer position on camera because it looks dramatic and shows off the tilt range. The full tilt is most useful when I have to squeeze the bike through a tight spot or when charging while parked at sunrise or sunset but is rarely needed while riding.

Most of my riding happens when the sun is at higher elevations and the optimal trailer tilt angle is closer to horizontal. Light breezes are not a problem under these conditions. When wind speeds increase, I use a handlebar-mounted control to limit the maximum tilt angle until the effect is minimized. In strong winds, I simply stop the panel in a horizontal position and keep riding without problems.

On a recent 1300 mile trip along the California coast, I ran into crosswinds which made riding very difficult for about 2 miles while crossing Salinas Valley next to a berm which funneled the wind across the road in a dangerous way. Admittedly, it wasn’t safe or fun. I slowed down and got through it. The remaining 99.8% of the time, wind was a non-issue.

It’s electric… so you don’t have to pedal?

I get this one all the time so you might think that I’ve gotten good at answering it but nothing could be further from the truth. I find it’s an ongoing source of frustration. When linguists discuss the theoretical challenges of communicating with extraterrestrials, they point out that the basis of communication is a shared frame of reference. I believe this is my problem: the person asking lives in a completely different reality from my own. They’re an alien.

My sense is that these aliens haven’t been on a bike since they first got their driver’s license and would only consider riding a bike if their car broke down and both Über and Lyft had banned them for life. Perhaps they view bicycles as toys for children and hipsters? They hear electric bike and think “Finally! A bicycle without all that bothersome pedaling!”

But I like pedaling! I didn’t get an ebike because I lost my driver’s license to a DUI or because I have a physical limitation that prevents me from operating a traditional bicycle. I got an ebike because I wanted to build a solar powered long distance touring machine that would extend the daily range of a loaded touring bicycle on a trip around the world. It’s a hybrid. The electric motor and pedal power are not mutually exclusive. They go great together. Think chocolate and peanut butter, not chocolate or peanut butter.

This question is typically asked with a tentatively hopeful expression so I suspect the alien my new friend is not looking for a lecture on semiotics. I think the answer they’re looking for goes like this:

Yes. The motor is powerful enough to make the bike go without any pedaling whatsoever. You could just use the pedals as foot pegs if you really wanted to.

Next time, I’ll just lead with that.

How much solar power are you getting?

Short answer: about 100 miles (160km) per day.

For each hour of full sun, I get enough energy to travel 15-20 miles. If I’m moving, that energy is immediately converted to mechanical energy. If I’m stopped, it’s stored in the battery for later.

Most people asking this question really want to know “Are you getting a useful amount of solar energy?” and “What can you do with it?” The answers are “yes” and “go farther and faster than a touring bicycle without a motor and solar panels.”

Sure, I could give you numbers measured in watts or amps or hours to charge the battery from empty to full. Unless you’re comparing the performance to another electric vehicle in the same weight class, battery size and voltage, those numbers are easily misinterpreted.

The total solar energy production per day varies significantly based on location and time of year, not to mention daily variations due to weather and shading along the route. Overall, my setup gives me a range of 50 to 200 miles (80 to 320 km). The low end is a rainy day with mostly pedal power. The high end is an ideal day with an early start, short breaks, cloudless skies, minimal headwinds and few hills on good roads. Your mileage may vary.

How much did it cost?

I could build a solar ebike for less than $40. I would buy a new solar charge controller on eBay and source the rest through scrap finds and donations and craigslist free listings.

If you already own an ebike and a bike trailer, the cost to add 170 watt SunPower panel and a charge controller is less than the cost of a second battery.

I spent around $15,000 on parts and materials to build my bike because I wanted the ultimate touring machine.

Why didn’t you try X?

Short answer: I almost certainly researched and tested X and X didn’t work.

Second-guessing other people’s design decisions from the comfort of your arm chair is fun, isn’t it? I get this one all the time. Usually, it’s intended as a helpful suggestion from a well-meaning individual who is blurting out the first thing that pops into their head upon seeing a solar bike for the first time. Mostly, these suggestions are impractical or unfeasible because they either fail to consider the design goals of the vehicle I’ve built or they violate the laws of thermodynamics. L

I’m sympathetic to people who don’t get it because they’ve never done any bike touring and try to imagine impractical use cases formed by their own experiences. I’m less sympathetic to the conspiracy theorists who feel compelled to educate me about the shadowy cabal of lizard people with a hidden agenda for keeping Nicola Tesla’s secret free energy discovery off the market. I suppose I’m kind of asking for it by riding around on a perpetual motion machine.