Which Emits Less CO2 Per Mile: The 2016 Chevy Volt or the 2016 Toyota Prius

The next generation hybrid Toyota Prius and the plug-in hybrid Chevy Volt 2016 models are here.  They're both significantly better in efficiency, look, and drivability.  I happen to be on the market for a new car, and I'm strongly considering one of these options.

Neither option is perfect.  I'd really like a pure plug-in electric car but, except for the Tesla, the range is too small to be used as my primary vehicle. The new Nissan Leaf has a 107 mile range, but I'd really like it to be over 150 miles so that I can easily make round trips around the LA basin without worrying.

So, I'd like to know which of these cars will emit less CO2 given my family's typical driving habits.  It's not obvious.  The Prius gets significantly better fuel economy (~56 mpg vs. 42 mpg), but the Volt will emit about half the CO2 as the Prius when running on electric energy (especially where I live, where the electricity is fairly green).  So let's do some calculations. There is actually an "eco" version of the Prius, reported to get 56 mpg (combined) vs. 52 mpg (combined) for the other models. I'll do calculations for both.

Chevy Volt: 43/42 mpg (city/highway), 53 mile electric range

Toyota Prius (2 Eco): 58/53/56 mpg (city/highway/combined), 0 mile electric range. 

Toyota Prius (3):         54/50/52 mpg (city/highway/combined).

Assumptions: My wife commutes 23 miles round trip every weekday, so that can easily be done on electric.  We also drive another 60 miles per week on small scale trips (grocery store, visiting local family, etc.).  That gets us to about 9000 miles/year that could be driven on electric with the Volt, and maybe an additional 6000 miles/year that would be driven on gasoline (longer trips for vacations and visiting friends/airports on the west side of LA).  These numbers (60% of miles on electric) aren't too far off from what Chevy says will be the average for 2016 Volt owners given previous generation Volt driver habits.  In fact, they predict almost the exact same number, an average of 1000 miles between gas fill-ups and the car can go about 400 miles between fill-ups: so 60% of miles are on electric.  

So let's go with that.  

The nice thing about the hybrid electrics is that the city/highway fuel economy is very similar, so I don't need to fret too much about what fraction of my driving is city vs. highway. I'll just use the combined EPA fuel economies for each vehicle (42 mpg for the Volt, 56 mpg for the Prius 2 Eco), which should be accurate within a couple percent, regardless of city vs. highway.  

CO2 emitted per gallon of gasoline burned:  19.64 lbs (ref).  

CO2 emitted per kWh of electricity at my zip code: 0.650 lbs (ref). (btw, the national average is 1.14, or 75% more!)

One other piece of info needed, the Volt electric efficiency:  31 kWh/100 miles.  And another factor that is rarely mentioned, but is very important: when charging the battery, some of the energy coming out of the outlet is lost to heat energy.  Estimates range from 10-20% (or more if you're charging with high voltage).  Let's go with 15%.  So the actual electric efficiency when considering the total amount of energy used, is more like 36.7 kWh/100 miles. 

ok, now let's convert that to CO2 emitted per mile: 

Volt:  

CO2 emitted per gasoline mile:   0.468 lbs/mile

CO2 emitted per electric mile:    0.239 lbs/mile

Note, the Volt emits almost exactly half the CO2 emissions on electric as it does burning gas.  This number changes with location because the electric grid is cleaner or dirtier in other places.  But generally, this is a best case scenario because the CA grid is quite clean compared to much of the country (like the Midwest and South). 

Prius:

Eco:    CO2 emitted per gasoline mile: 0.351 lbs/mile
Other: CO2 emitted per gasoline mile: 0.378 lbs/mile

Total CO2 output per average mile: 

Volt (60% electric):     0.331 lbs of CO2/mile

Prius (Eco):                 0.351 lbs of CO2/mile

Prius (Other):              0.378 lbs of CO2/mile

Holy crap!  The Volt only emits ~6% less CO2. They're effectively the same given the considerable uncertainty in some of these assumptions!

This is very interesting.  Even in a pretty good scenario (for the Volt) of 60% electric and with a clean electric grid, the Chevy Volt is no better for the environment (at least in terms of CO2 emission), but the Volt is WAY more expensive.  The Prius is about $25k and the Volt is about $35k. Now, with federal, state and city incentives, it's only a few thousand more, but still!

So, really, the Volt is only better in terms of CO2 emissions if the vast majority of your miles are electric and you live in a region where the grid is fairly green (that is, the west coast). 

UCR: Sustainable or Unsustainable?

This will be the first in a what will probably be a long series of posts about UC Riverside and whether or not their practices/infrastructure/policies are sustainable.

UCR certainly puts a good face forward, advertising their recent efforts toward sustainability, which is great!  But I come across so many wasteful things on campus that it's hard to consider the university sustainable ... yet.  Literally, in every building I step into and in every way I interact with the campus, there is serious waste.  I guess it could just be a coincidence that only the buildings I walk into are wasteful, but obviously that's not the case.  I suspect it's systemic, and the faculty need to speak up to get things changed (and to secure funding to help that along).  We also need real metrics for improvement, and to be held accountable to those metrics.

But let me first start on a positive note.  As you know, California has been going through an epic drought the last four years, and everybody realized how bad it really was when we came out of the spring without much rain.  Well, over a year ago, I tried to find obvious locations on campus that waste a lot of water for turf grass that isn't used... and there's a LOT of it.  Well, the most egregious case, the most asinine example, was a very large plot of grass on the west edge of campus that was used by nobody and, in fact, nobody could even see it!

I estimated that this lawn has an area of about 60,000 sq. ft (about 1.4 acres), and uses about 3 million gallons of water per year, or about 0.4% of all of UCR's water use.  All one has to do is turn off a valve and you can instantly save the water use of about ~50 households, and with no harm to anybody.

Well, this morning I realized I needed to call out the university and make sure they do something about this.  I rode my bike to that side of campus to check it out and look what I saw!

Dead grass!  They killed it!  Well done UCR!  That's 3 million gallons of potable water saved every year.  Thanks!

Net Energy: 3 Year Update

I just finished my third year with solar panels on my roof. I'm happy to report that everything is great, I'm helping the environment and I don't have to do anything at all.  That's not entirely true, I wash the panels about three times/year but it takes less than 20 minutes each time (and less than 20 gallons of water).  So one hour of work per year to cancel out all of the CO2 emission from my house. That's pretty good.

So here's the tally of electrical energy produced compared to electrical energy consumed.

Year	Energy Produced (kWh)	Energy Consumed (kWh)
2012-2013	3915	3613
2013-2014	4027	3157
2014-2015	3937	3483

So, it looks like my average production is about 3960 kWh/year with only a few percent change per year (the first year would probably have been higher if not of a palm tree that was taken down) and my average consumption is 3418 kWh/year.  

I should say that my energy consumption this year was affected by one major event.  I could not use my (natural gas) heater during much of the winter because some skunks tore through the ducts under my house.  So I used an electric space heater during half of January and February. I think my electrical energy consumption was bumped up by about 200 kWh because of this. If we subtract the 200 kWh, the consumption is pretty close in line with the previous year, though not quite as low.  But that's ok.  A lot has happened this year.  We just had a baby, so for 8 of the last twelve months, somebody has been home all day every day, we've been lighting more rooms, running baby monitors, cooking/cleaning more, etc. And we've been running the A/C a bit more than normal.

And still, it looks like a typical year produces about 4.0 MWh and we will consume 3.3 MWh, leaving 0.7 MWh to spare.  That's enough energy to drive an electric car about 2000 miles each year on our excess (and we've already bagged ~5000 miles of excess energy in the bank).

4% of the home cost, 10% of the roof area.

There are no longer any hurdles preventing the wide adoption of solar power.  Why?  Because of these two facts.

1.  Cost:  The panels on my home are 4% of the value of the home.  4% and you never have to pay an electricity bill again.  It's a no-brainer.  It's especially a no-brainer to install solar when constructing the home, as it's even cheaper then.

2. Area:  The panels on my home cover about 10% of the area of the roof and they provide more than enough energy.  Even if your appliances aren't as efficient, or if you live in less sunny areas, you should still be able to power your home with panels covering only a fraction of your home.

So here's how to do it.

First:  Change your mindset/habits just a bit to significantly reduce your energy use.  Wear a sweater in the winter, and shorts in the summer.  This way, you don't have to heat your home quite as much in the winter or cool your home as much in the summer.  In moderate climates, this causes a dramatic decrease in energy use (most days you won't need to do either).  This costs zero dollars and zero time.

Second:  Make your home more efficient.  Identify the worst problems (single pane windows with aluminum frames, for example) and get them fixed.  Switch out your old lights for LEDs - they're very efficient and you'll never have to worry about a burned-out bulb again. Make sure attic insulation is sufficient and seal up any drafts in the home.  And any time you buy a new appliance (refrigerator, air conditioner, etc.) make sure it's very efficient.  It will pay off in the long run.  This costs a moderate amount of money.

Final Step:  If you've done the two steps above, you won't need as many solar panels, so that will save you a LOT of money.  Now go get panels.  Get estimates from several vendors, and consider both purchasing or leasing the system.  If you're leasing, this may not cost you any money at all.  So it's a pretty obvious thing to do.  

Now make some phone calls.

New Name, New Emphasis

Hi all.  I've decided to expand the scope of the blog. It used to be about making my home more sustainable, but now I'd like to include other topics of interest to me: broader sustainability issues, science (maybe even my science), and public policy.  

So I've also changed the name of the blog from Life Ecologized (since it's not just about home sustainability) to Tiny Blue Galaxies.  My research is primarily focused on very small galaxies in the distant universe, which often appear as tiny, faint and blue in visible images.  

So stay tuned, hopefully the post frequency will increase a lot.