Tracking your carbon footprint isn’t the easiest thing to do. There are several online calculators, but a footprint is a moving target, changing with each meal, each type of mile driven and each time we turn up the heat or air conditioning.

In this post, I’ll review some of the biggest or best online carbon footprint calculators I could find. This will be eye-opening for me personally, but I hope it will help you determine which calculator might best serve your needs.

Let me start with some specifics about myself, even though they weren’t all asked for in each calculator. I live in a multi-unit apartment building, in a one-bedroom apartment. I drive about 6,300 miles per year and haven’t flown in the past 12 months.

I eat meat, but not with every meal. I have electric heat, but purchase 100% green energy – it’s more like a carbon trade – through Green Mountain Power. I’m pretty economical and environmental when it comes to my footprint, but I was surprised at my impact in some areas.

So, let’s get started.

The Nature Conservancy

http://www.nature.org/greenliving/carboncalculator/index.htm

The Nature Conservancy breaks out questions into four categories: Home Energy, Flying & Driving, Food & Diet, Recycling & Waste.

For each question, you can hover over an “i” for more information and specific examples. However, the Home Energy section is a little vague. For example, asking me, generically, if I’m efficient doesn’t provide any true data. My “efficient” may be different than your “efficient,” so how does this question help The Nature Conservancy assess each of us?

And while the calculator asks for the state of residency, which might help them calculate some specific averages, humans vary, so they should have asked me to whip out my last electric bill to get more specific.

These were my emissions in each area:

• Home Energy: 2.4 tons of CO2
• Flying & Driving : 3.8
• Food & Diet: 2.8
• Recycling & Waste: 0.9
• Total: 10 tons

• US Avg (for 1 person): 27
• World Avg (for 1 person): 5.5
• To offset: $136.50

EPA Household Carbon Footprint Calculator

http://www.epa.gov/climatechange/ghgemissions/ind-calculator.html

This calculator divided the questions into The Basics (where you live, number of people in the household, etc.), Household Vehicles, Home Energy and Waste.

The EPA calculator was definitely the most specific of the calculators I tested. They ask you to reference your energy bill, ask about specific categories of recyclables (plastics vs glass vs paper), and generally take each question to the next level in terms of details.

With this calculator, I was told I emit 4,501 lbs CO2 per year, which is about 2.251 short tons per year. You can see that this is very different from the 10 tons The Nature Conservancy estimated for me. Also, the US average, for this calculator, is 20,750 lbs or 10.375 tons. Compare that to The Nature Conservancy’s US average of 27 tons.

This calculator offers the next step: reduction suggestions. Here, again, they’re very specific. For example, one of the suggestions is to wash your clothes in cold water and they even ask how many loads per week you wash. Automatically, if you agree to this, it calculates how much this effort will cost, how much it will save, how many pounds of CO2 it will conserve and what percentage of your emissions it will reduce.

Conservation International

http://www.conservation.org/act/get_involved/carbon_calculator/Pages/default.aspx

This calculator was very similar to The Nature Conservancy’s and told me I emit 8.5 tons of CO2 per year and could offset it for $101.

Native Energy

http://www.nativeenergy.com/household-carbon-calculator.html

Several years ago, I offset my vehicle’s carbon emissions with Native Energy. I even received a bumper sticker from them that said “This car is on a low-carbon diet.” In revisiting the calculator, I found it way too blunt, basically asking for the number of homes and the number of cars for which I was calculating. They told me I emitted 16 tons of CO2 – the worst rating yet – for which I could pay $224 to offset the crude calculation.

However, Native Energy has two very nice functions, one of which might bring me back.

They have a travel carbon calculator, so you can offset specific trips (either driving, flying, via rail or bus). This could be handy for future travels, although they are definitely the priciest calculator out there, so I don’t know if I can trust their numbers.

Then, when calculating your household carbon emissions, it’s pretty cool to be given several specific projects that your carbon offset will fund.

I tried a few other calculators through a Google search, but the one at Terrapass gave my computer the blue screen of death and shut my laptop down twice. Earthday.org directed me to a sitemap, so I’m assuming their calculator is no longer functional or available.

Comparing the Data

My carbon footprint

• The Nature Conservancy: 10 tons
• EPA: 2.251 tons
• Conservation International: 8.5 tons
• Native Energy: 16 tons

Average US footprint

• The Nature Conservancy: 27 tons
• EPA: 10.375 tons
• Conservation International: N/A
• Native Energy: N/A

My carbon offset costs

• The Nature Conservancy: $136.50
• EPA: N/A
• Conservation International: $101.00
• Native Energy: $224

At this point in the searching and testing, I was feeling more and more comfortable with the EPA calculator. There may be a motivational bias in action here, though, since that calculator also told me I had the lowest emissions of all four systems. But it was the most specific and made me feel like my current attempts at reducing my carbon footprint were taken into consideration. Also, the EPA has the least motivation to trump up my emissions, since they weren’t asking for a donation to fund carbon offset projects.

Hard Data

There are two areas of my life in which I have hard data: my electric bill and the number of miles I put on my car in a year.

My current apartment is a kWh hog; it’s the least efficient place I’ve lived yet, plus it heats with electricity. I’ve never figured out why the electric baseboards were installed under the windows – it seems like I rarely feel the heat before it goes out the window.

However, earlier this winter, my landlord installed frames with plastic stretched across them over the windows. This makes the plastic reusable, versus the usual method of taping the plastic over the windows and just tearing it all down in the spring. We’ll see if this makes a difference.

I also used to put more miles on my car, when I worked farther from home. These days, I’ve got a whopping 3 mile commute, which I walk in warmer weather. So I’m doing about 6,300 miles per year.

Still, I sometimes drive for joy or make multiple trips when I haven’t planned out my day better.

Each of these two data points are ripe for improvements.

Carbon Footprint Calculation Wishlist

I’d like to see a carbon calculator for food and drinks. Some of the above-mentioned calculators ask very vague questions about organic diets or meat-based meals, but I’d love to have an app into which I could put each meal and drink and get a carbon footprint or even a water footprint.

I’m hearing, for example, that almond milk has a high water footprint, but I find it to be healthier than regular milk. So how do I compare their footprints?

In the same way that companies can get very specific energy audits, it’d be nice if those services were affordably available to individual consumers.

Have you heard of anything like this?

Have you used any other carbon footprint calculators? What do you think?