Outlier

The Triumph of Gmail? How Yahoo users are spending $110 more per year on electricity.

In this inaugural post of the Outlier, we delve into our storehouse of household energy data (covering 40 million US homes) to examine how people’s energy usage is correlated with their email address.

We looked at the correlation between email address and electricity usage across 2.8 million American households.  Of those, we focused on Yahoo Mail and Gmail because they were the most popular domains in our dataset. The email addresses correspond to the member of the household who manages the electricity bill.

We realize that Yahoo has had a rough stretch lately:

Barbados

Now we have more bad news for Yahoo…

We found that the average Yahoo Mail household uses 11% more electricity per year than a Gmail household.  It’s a sizeable, statistically significant difference (see Methodology).

Consider this: the aggregate difference in annual electricity use between 1 million Yahoo households and 1 million Gmail households is…equal to the entire annual electricity consumption of Barbados, a reasonably well-off country of 287,000 people.

Let’s dig into the numbers and find out what’s going on here…

The average Yahoo Mail household spends $110 more per year on electricity than a Gmail household.

The usage difference — 939 kilowatt-hours per year — is stark: Yahoo households consume almost a whole extra month of electricity relative to Gmail households. At an average going-rate of 11.8 cents/kWh, that’s a difference of $110 per year.

Yahoo subscribers consume 11% more electricity than Gmail users

It’s as if, relative to the average Yahoo household, the average Gmailer is strictly hang-drying their laundry, forgoing high-definition TV, and hand-washing their dishes with cold water for a year.

939 kWh is equivalent to...

We can establish off the bat that the “email-domain versus usage” relationship is one of correlation, not causation. So then, what underlying differences exist between Gmail and Yahoo users that can help explain their dramatic disparity in electricity usage?

Exploring reasons for the disparity between Gmailers’ and Yahoo users’ electricity consumption

There are some key demographic and lifestyle differences between Gmailers and Yahoo users that are likely to affect their household electricity usage.

We’re not the first researchers to think that Yahoo and Gmail users are different:

  • Last year, Hunch.com discovered, among other things, that Yahoo users tend to lounge around in pajamas at home and enjoy sweet snacks; Gmail folks, on the other hand, are more likely to lounge in jeans and prefer salty snacks.
  • The personal finance company Credit Karma has found that Yahoo users have noticeably lower credit scores (652) than Gmail users (682).
  • Last week, the online-dating site Circl.es determined that Gmail users tend to have a higher “desirability quotient” than Yahoo users

But let’s explore some of the differences between Yahoo users and Gmailers that are likely at play in driving the disparity in their electricity consumption.

Do Yahoo users and Gmailers live in fundamentally different climates or use different fuels to heat their home?

No.  It’s true that climate and heating fuel vary significantly by region, and can have a large effect on energy consumption. For example, of the 1.8 million Michigan homes in our database, nearly 60% of them get through frigid winters by heating their homes with natural gas.  In contrast, the majority of the 780,000 North Carolinian homes in our database use electric heating systems (and they also face a milder climate).

But neither climate nor heating fuel should be expected to correlate meaningfully with email address domain here.

The reason is that the 1.15 million Gmail and Yahoo users in our dataset are spread out across 23 states and several distinct climate zones. There is no clear pattern that emerges wherein Gmail or Yahoo Mail is more popular in one particular state or climate zone than another.  This geographic spread of Gmail and YahooMail makes sense: anyone is free to sign up for either domain.

Do Yahoo users consume more electricity simply because they live in larger homes?

Yes and No. Yahoo users do appear to live in larger residences, which increases their total energy needs. But they also consume more electricity per square foot than Gmail users.

How do we know that Yahoo users tend to live in larger homes? Our friends at Experian and Hunch.com have found that Yahoo users tend to live in suburbs and rural areas, while Gmailers live in cities.  Data sourced from the 2009 US American Housing Survey suggest that suburban-rural residences (i.e. where the Yahoo Mailers live) are on average 7-13% larger than in cities (where Gmailers live), and also have more occupants (i.e. extra electricity-using human beings in Yahoo homes).

Our own household characteristics data similarly suggest that Yahoo users reside in larger residences: Yahoo households are approximately 10% more likely than Gmail households to live in single-family residences (as opposed to apartments and condos).

But, even controlling for home size, we found that Yahoo households are still more energy-intensive than Gmail households. Based on square footage data that we have for single-family residences, we found that the typical YahooMail household uses 12% more electricity per square foot of living space (6.84 kWh/sqft) than the typical Gmail household (6.09 kWh/sqft).

Yahoo subscribers consume 12% more electricity per square foot

Do Gmailers and Yahoo users have different lifestyles?

Yes. Hunch.com and Experian have found that Gmailers are more likely to be younger, single people.  Credit Karma found the average Gmailer’s age to be 34, while the average Yahoo user clocked in at age 38.  Being young and single means going out more; less time at home – and fewer occupants – means less electricity usage.

By contrast, Yahoo users are more likely to be in relationships and have children. Additionally, Hunch found that Gmail users are more likely to be active travelers (having journeyed to 5 or more countries), and so might be away from home more often.

Our own data also suggest that Gmail users may have a greater interest in energy-efficiency. Among the approximately 10 million US households that have access to utility web-based energy-efficiency advice tools that Opower manages, Gmail users are 30% more likely than Yahoo users to sign up for an in-depth analysis of how they can reduce their energy usage.

Gmail users are 30% more likely to sign up for an online energy analysis

It’s not definitive, but it appears that several lifestyle choices correlated with Gmail use are also correlated with lower home energy use.

What are Yahoo Mail users to do?

If Yahoo households want to slash their energy consumption to Gmail levels, it’s probably going to involve more than just switching to a Gmail account (nice try!). For the benefit of Yahoo users and Gmailers alike, we’ll aspire to sprinkle in energy-efficiency advice in future posts that will help all folks reduce their energy bills.

Update: Some commenters were curious about AOL and Hotmail. That got us curious too. Check out those results here.

Special thanks to my data-crunching partner Jillian Cairns and our all-star designer Efrat Levush. They are proud Gmail users.
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Methodology: Annual electricity usage of households is based on 2011 data. Of the 2.8 million household electricity customers with email addresses in Opower’s dataset, 1.15 million were Gmail or Yahoo users.  The usage difference between Yahoo users and Gmail users is statistically significant at the 99% confidence level based on a t-distribution.

Barbados’ electricity consumption in 2008 was 945 million kWh. Dryer usage based on 1.89 kWh/cycle, derived from LBNL paper. TV usage based on 40″ Digital HD model from US DOE. Dishwasher usage based on 1 kWh/cycle (Energy Star) from NRDC.

Data Privacy: All data analyzed here are anonymous and treated in strict adherence to Opower’s Data Principles.

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