Choosing and Using Carbon Calculators the Right Way

Dozens of governments, nonprofits, and companies have introduced carbon calculator websites and apps that promise to help each of us understand our carbon footprint. But it is still early days for these tools, and many questions need to be answered. Are they useful? Do they provide accurate information? How can we choose the right calculator?

Choosing a carbon calculator should be pretty straightforward. However, different calculators return different estimates when the same or very similar information is entered. So, which one is right? Earth911 will look at this and other issues and provide guidance about how to find and use information about your energy consumption, purchases, and more to get the most accurate carbon footprint estimate. We’ll also help you understand how to act on that information to reduce your environmental impact.

Getting Past Big Oil’s Carbon Footprint Spin

Although the concept of a carbon footprint was originally described as part of an “ecological footprint” by two academics at the University of British Columbia — William Rees, a Canadian ecologist, and Mathis Wackernagel, a regional planner — it was British Petroleum, now known as BP, that popularized the idea shortly after the turn of the century. In 2004, the company introduced the first carbon footprint calculator, which was widely criticized for pushing responsibility for emissions onto consumers.

Despite the oil industry’s blame-deflecting spin, counting our individual contributions to climate change can be a constructive way to understand what changes we can make to reduce the emissions associated with our diet, transportation habits, home heating, and other aspects of daily life. Fossil fuel companies do extract and sell emissions-intensive oil, plastic, fertilizers, and chemicals, but people and organizations keep buying.

The climate problem is everyone’s to solve, primarily by reducing our reliance on oil, which is responsible for the vast majority of human-made carbon dioxide in the atmosphere. Without tools to track our impact, it’s difficult to make changes or hold companies accountable for their contribution to the problem. Counting also helps you understand how changing certain habits will reduce your environmental impact the most.

Today, dozens of carbon calculators vie to be used and useful. But, too often, they don’t explain how they work or provide clear instructions about how to enter data.

Same Data, Different Footprints

We selected representative carbon calculators from the more than 30 carbon tracking options Earth911 has identified and entered similar information into each for two scenarios, a three-person gas-heated home and a single person living in an electrically heated apartment. The results were wildly inconsistent, both in terms of the estimated impact across the different carbon calculators and between the results for the large and small homes.

These differing results illustrate the immaturity of carbon counting standards and lack of standardized approaches to gathering and tracking the impact of different activities, such as the availability of renewable energy, travel habits, or the way each of us shops.

Calculators are also created for different purposes — some to help people understand their impact while others are designed to sell carbon offsets. We recommend choosing a calculator based on its accuracy, not the ability to purchase offsets, which can be purchased from a variety of reputable organizations.

Transparency, Comparability, and Accountability

Science relies on validated, reproducible results that allow anyone to examine the data and methodology used to calculate the results. Climate leaders have endorsed science-based targets that can be measured and compared easily, but most climate footprint sites and apps do not provide any insight into their calculations. This makes comparing one calculator’s results to another’s estimated footprint impossible for consumers.

For example, The Nature Conservancy carbon footprint calculator is powered by another site, CoolClimate.org, which offers a link to “documentation” that consists of a 2013 research paper funded by the American Chemical Society, which is funded by the oil and plastic industry. The research paper does not offer any information about how CoolClimate calculates its carbon footprint results, so consumers must take the information on faith. This reflects the immaturity of carbon accounting and doesn’t necessarily mean there is something nefarious going on.

Making matters worse, the results from different carbon calculators cannot be compared reliably because they often use different units of measurement (Imperial or metric weights, among others) and vague descriptions of shopping or travel habits the user is supposed to choose from. One calculator’s “average shopper” may be another’s “heavy shopper.” The result from every carbon calculator we have tried using similar data — adjusted for the way the calculator asks for information — produced very different results.

Vague Questions, Inaccurate Estimates

Energy consumption questions in the calculators also vary.  Some ask for energy consumption in kilowatt hours per month while others ask for your yearly or monthly energy cost. In our initial testing of six calculators, one reported that a single-person household spending $60 a month on electricity produced 3,058 pounds of CO2 annually. Yet, another calculator using the same data reported an impact of 4,526 pounds of CO2, a 48% difference.

And tracking travel impacts is wildly inconsistent. Some calculators ask for the miles flown and which cabin you sat in, which does influence your footprint. But others asked only how many trips were taken or, in a few cases, how much you spent on travel with no reference to specific distances. Since air travel is one of the most influential factors on one’s total footprint, these diverging approaches can result in startlingly different footprints.

Local factors, such as the percentage of renewable energy that a utility in a specific region generates, are also used inconsistently across different calculators. For instance, entering a ZIP code is often the first step to measuring your footprint. There may be multiple utilities serving the area but we did not find calculators that let you select a specific utility, which may have a different renewable energy mix than others in your area. More advanced calculators ask for a percentage of electricity generated from renewable sources, something most people don’t know how to find.

We’ll show you how to collect the information you need to estimate your carbon footprint in the next article in this series.