Measuring Our Family’s Carbon Footprint

My 2020 New Year’s resolution is to learn as much as I can about the climate crisis, to help my family get to a net-zero carbon footprint, and to share my journey with friends.

This is the first of many posts about my family’s journey to carbon net-zero and is about what I learned measuring our carbon footprint.

I am far from an expert on climate change and certainly my intent is not to make anyone feel guilty about their own consumption or to make personal comparisons. I hope these blog posts can be a helpful source of info and I welcome your thoughts or suggestions in the comments.

I calculated our family’s carbon footprint using several different carbon footprint calculators and I learned a ton. Here are a few takeaways:

  • A carbon footprint is made up of four primary sources: the energy to power, heat & cool your home, your travel (car, air, public transit, etc), the food you eat, and goods/services you purchase. Lots more detail to come on this…
  • The food we eat and the goods & services we purchase are the biggest source of carbon. This probably should be obvious, but I expected that our cars, electricity & natural gas would be the biggest source–turns out this was a small portion relative to food, goods & services. The food we consumed was 1/3 of our carbon footprint according to one calculator. Another calculator had the goods & services we purchased at 50% of our footprint.
  • Flying is the second largest source of our family’s carbon footprint. Last year was a big year for us as we took a family trip to Europe, so this doesn’t represent an average year, but regardless, one of the calculators shows air travel as 60% of our total! In a regular year flying would still be like 30%. This is good and bad news… This is theoretically simple to reduce–just stop flying. But eliminating flying is challenging with Eleanor going off to college next year in New York, and family in California and Minnesota. We are going to try to reduce our flying miles, but we can’t stop altogether. To get to carbon net-zero, we’ll have to buy carbon offsets to cover flights.
  • How your electricity is generated has a big impact. We are lucky in Seattle that Seattle City & Light obtains 90% of it’s electricity from hydro-power, which is a renewable source. In fact, Seattle City & Light has been carbon neutral since 2005, as they purchase carbon offsets for the small percent of power they generate from non-renewable sources (and to offset other portions of their carbon footprint such as their vehicles, employee travel, etc). So our electricity bills did not impact our footprint at all.
  • Measuring our carbon footprint was a challenge. There are many different calculators online and gathering the data was time consuming. However, my goal is to use these calculators to help me understand where to focus our efforts, not to get a precise measurement.
  • Getting to carbon net-zero won’t be simple, but with time I think we can get there. Having calculated our carbon footprint in several different ways, the path to get to net zero is now pretty clear. It is not going to be easy and will take months, but at least we know what to do. This is going to have to be a team effort and I’m sure there are some tough conversations ahead. Getting there will take a lot more thinking and research. How much air travel can we limit ourselves to? How can we best change what we eat and buy? I’d love to shut off our natural gas–how do we wean ourselves off of forced air heating and our gas grill? Can we replace our gas cars with electric without a driveway/garage and a reliable access to an outlet? These are the biggest questions we’ll be exploring….

I went through 4 different carbon footprint calculators:

I didn’t spend too much time selecting these… they were the first few that came up on a google search. I dismissed a few calculators that looked dated or too commercial. If you think there is a better one out there please post in the comments below.

I completed each of these for my whole family so they reflect the carbon emissions for 4 of us:

  • UN carbon offset: 79 tons of CO2/year
  • EPA calculator: 32,615 lbs of CO2/year (16.3 tons)
  • Nature Conservancy: 107 tons of CO2/year
  • Terrapass: 77,963 lbs of CO2/year (38.9 tons)

Widely varying results! 16 tons to 107 tons is nearly a 7x spread. What happened?

The differences are almost totally accounted for by what is included in the calculator, not by how similar impacts are calculated. The EPA calculator only looks at home energy use and emissions from your cars. The Nature Conservancy adds in water use, other travel including airline miles, type and amount of food you consume and goods & services you purchase. These latter categories get pretty hard to calculate but seem right to include.

Most stats globally look at this data per person not per household, so to understand our carbon footprint per person we need to divide by 4 (we’ll leave our dog Kuma out of this for the moment…) Using the highest number of 107 tons (Nature Conservancy), we get to 27 tons of CO2 per person/year emitted by my family. To give that number some context on how that compares to people in the US and other countries I dug up the chart below.

Worldwide CO2 emissions 2016


The US average is 16 tons of CO2 per year per person. The world average is 4 while India is less than 1. So as of today’s date, January 12th, twelve days into the year, I have emitted about as much carbon as the average person in India will for the entire year. We have some work to do!

Calculating our carbon footprint took 2-3 hours as I had to gather data about our historical electric & natural gas bills, air travel, miles driven in our cars, etc. Here are the primary inputs into the calculators for us:

  • Electricity usage: our average over the last 2 years has been about 750 kWh per month or 9000 kWh per year
  • Natural gas usage: average use over the last year is 73 Therms per month or 880 Therms per year. This one is highly seasonal. We have a gas furnace and use 10x the natural gas in February that we do in August.
  • Miles driven in our cars: We have 2 cars and 3 drivers (soon to be 4 drivers). Our 2010 Honda Pilot is our primary family car and is what we drive on our long family vacations. We have a 2014 VW Jetta that Eleanor mostly uses to dart around the city. We travel about 10,000 miles a year in the Pilot and 5,000 miles in the Jetta
  • Airline miles flown: 2019 was a huge year for us as we did a family trip to Europe. We flew roughly 135,000 miles. In 2018, we traveled ~50,000 miles and it probably more representative of an average year. This is the miles flown for our whole family and is both miles flown for work reasons & personal, but fortunately neither Laura nor I travel for work. One thing that is time consuming to calculate is the actual air miles flown for non-direct flights. I did not take the time to go back and figure out exactly the miles for each segment. Rather, I just rounded up by about 20%, which I’m not sure is accurate. The goal isn’t to be precise with this however, but just to understand the rough order of magnitude, so I’m ok with a guesstimate.
  • Food consumed is a pretty blunt calculation, with most calculators just asking about how much meat & dairy you eat, and how local your food sources are. These were rough guesses.
  • Goods & services purchased was the most squishy exercise within this whole experience. I think this is perhaps where we can have a big impact and there will be a lot more I’ll share later on this.

Full results below…

Nature Conservancy:

Nature Conservancy calculator

The United Nations carbon offset platform

The EPA calculator:

EPA calculator


Terrapass calculator

Post #2 – The next post will be about why I’m doing this.


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