Is this a good green idea?

I live about 6.5 miles from work. My car gets about 20 mpg city (and it’s city driving). So, I am considering biking to work and back a couple times a week when the weather is nice. This is Michigan, so I figure, y’know, about 6 times a year.

All jokes aside, I am presented with the following list of pros vs cons:

Use less gas
Get excercise
Must take a shower upon arriving at work.
Must take a shower upon arrival home (optional to the extent that I might not be doing anything else that night).

I guess I’m wondering if the greenness I gain by riding the bike (using less gas and oil) is offset by the additional water usage (and the energy necessary to heat it). Assume a 5 minute shower at 2.5GPM. At my house I have a gas water heater, about 60% efficient. I have no idea what they have at work, possibly a boiler or something.

The Water heater should require less energy and more importantly, produce less greenhouse gases than a car that gets 20 mph. However, I am incapable of calculating the numbers. I don’t have enough facts to work with.

What I do know, the exercise should out weigh any other concern. Go for it. It is better for you in the long run and almost definitely better for the environment unless your water heater is really inefficient or uses coal or something. :wink:


Hi CrazyJoe! I think that every little bit that you do will help the environment. I wouldn’t compare it to which action is the most green but more that if it makes you feel good about doing your part. I think you could combine the two… bike to work (also awesome excersice) and then take a cooler and very quick shower.

I also wanted to say hi to everyone! I’m new to the forum and wanted to give a quick intro. I live in the DC area and just started a new job in marketing/pr. I’m originally from PA and I’m a huge Penn State fan! I’m excited to get involved.

Are you showering at home before you leave for work and after you get to work or skipping your home shower and just showering at work?

Good point. I see no real reason to shower at home when I wake up and then require another shower upon arriving work. I would just go to work and shower. So it’s really just one extra shower per day, using whatever water heater they have at work. I have e-mailed our facilities administrator to see what type of water heater we use there.

Oh, and realistially, I will probably take a shower for more like 10 minutes.

The shower after work might be optional, too. I ride my bike everywhere, and 6.5 miles isn’t enough to work up much of a sweat, unless it’s really rugged terrain. Or unless it’s just really hot out, but in that case, you’d be sweating even without the biking.

OK, 2.5gpm for 5 minutes is 12.5 gallons of water, and let’s assume 60% of the water is heated from 50F to 130F, at 0.2 kilowatt-hours/gallon (these numbers come from here:, where they are calculating energy used during a shower. Just happened to be the first thing that popped up in Google).

So that’s 12.5gallons 0.60.2 = 1.5kilowatt-hours to heat your shower water. 1kwh is 3.6MJ so that’s 5.4MJ of energy.

Driving your car 13 miles at 20mpg uses 0.65 gallons, or about 2.5 liters. A liter of gasoline contains about 35MJ of energy ( so you burn about 87.5MJ to make the roundtrip to and from work.

5.4MJ<<87.5MJ. Put on your bike helmet and go for a ride!

Please note I am not claiming those figures are 100% perfect, this is 5 minutes work on Google to dig 'em up, but I think it’s in the right ballpark. Heating a few gallons of water to take a shower uses far less energy than driving your car to work.

No time to show my work, but I calculate that the shower, assuming it’s hot water mixed evenly with cold water, needs the energy equivalent of 0.08 gallons of gasoline, or about 1/8th of what’s needed for the round-trip drive.

If you shower in the morning before you ride your bike to work do you really think you would need to take a shower after such a relatively short ride? Even if it was hot out if you left right after the shower it would take a little while for the moisture to dry if you didn’t dry yourself.

Also, regardless of energy used, driving uses non-renewable energy sources*, and causes CO2-emissions - I hope those are not rivalled by your emissions riding the bike.

*Arguably, water use by showering might be worse for the environment, as the environment requires water but could not care less if we use up all existant fossil energy sources.

I ride to work (5 miles in Boston) and shower there. We have commercial hot water for the building, which I’m sure is more efficient then my home hot water heater, and I rarely take a shower upon arriving home unless I’m going out after.

It’s also faster, and I arrive at work invigorated and ready for work. Add the energy savings and it’s a win/win/win. :slight_smile:


  • Water is not used up however. The problems are more subtle. If your water supply is in an area where they are consume a limited fossil water supply (deep wells that don’t get replenished by rain). Then extra showers contribute to the local exhausting of a limited resource. In many areas, water is plentiful and continually renewed and the concerns are in the processing of the water for use and the disposal of the waste water. The variations in this are extreme.

All that said, the biking is green and healthy. Go for it.

Welcome TupeloHoney, you might want to start a thread in MPSIMS if you want to introduce yourself. Many have done so.


Thanks for the welcome Jim - I’ll definitely post in MPSIMS!

The water heater probably also uses non-renewable energy sources and causes CO[sub]2[/sub] emissions, but there are some mitigating factors. First, the water is probably heated by burning methane, which is cleaner than gasoline (in the sense of less CO[sub]2[/sub]. Second, it might be electric, which will be at least partly from hydroelectric or other non-polluting renewable sources. Third, even if it is natural gas or non-hydro electric (most of which is coal), natural gas and coal are both abundantly available in the US. This isn’t an environmental effect, but it means we have to import less fossil fuels from parts of the world we don’t get along well with.

Pedaling is greener. But mass transit may be greener yet.

I’m not sure why? But more importantly for me my bike commute is half the time versus taking the train, and I get 40 minutes of exercise each day. I have to shower in the morning regardless if I bike or take the T.

The train/bus/whatever goes whether you are on it or not. Thus, your presence doesn’t add significantly to pollutants.

For a couple of years, many years ago, I was biking almost exactly the OPs distance to work. The thing about such a short commute is that once you get halfway in shape, it can be done as a sprint, traffic permitting. 6 miles or so of hanging with 40 mph car traffic will definitely break a sweat.