Half your home’s energy

We say that the thermostat controls about half your energy bills. This information comes from the US Department of Energy 2007 Buildings Energy Data Book, Table 4.2.1.

People don’t program their thermostats

A study by the Lawrence Berkeley National Lab about how people normally interact with their thermostats stated that 89% of Americans rarely or never program their thermostats to save energy.

Read the study

Programming saves

We say that a properly programmed thermostat can save you about 20% on your heating and cooling bills. Auto-Schedule remembers the temperatures you set and programs a personalized schedule for your home, so it allows homeowners to easily adopt a “properly programmed” schedule without programming it manually.

We reached this conclusion by studying data from our own tests. Here’s how it was done:

• We had reviewed data from two efficiency trial periods: one in the winter and one in the summer.
• Test participants across the country were asked to:
  • Use their thermostat manually, like they always had. They set temperatures to keep themselves comfortable, but didn’t program a schedule.
  • Let Nest learn their schedule with Auto-Schedule or program Nest manually.
• In winter, the average minimum temperature that people set was 61.6°F and the average maximum temp set was 69.5°F. We determined that a “good” schedule - one that saved homeowners energy - was one where the temperature went down 8°F for at least 4 hours during the day and/or night. In summer people change the temperature less, so to get a “good” schedule, testers only had to increase the temperature by 2.8°F.
• We normalized weather data and compared the numbers with and without a schedule.
• Results: in winter, testers with a good schedule saved an average of 19.6%. In summer, testers averaged a 20.1% reduction in AC usage.

More details about how these trials were run and what temperatures people set are available in our white paper​​.

99% of Nest have schedules

Of all the Nest thermostats connected to Wi-Fi in the winter of 2012, about 90% were using Auto-Schedule to create a schedule. 9% had turned Auto-Schedule off and were programming their schedules manually.

Nest Leaf

The Nest Leaf encourages people to choose more energy-efficient temperatures. When speaking about the Leaf, we sometimes state that changing the temperature one degree can cut your energy use up to 5%.

This data comes from our own tests and simulations:

• To determine winter savings numbers, we looked at two kinds of homes:
  • Type 1: These homes are usually occupied in the afternoon.
  • Type 2: There’s usually nobody home in the afternoon.
• To determine summer savings numbers, we observed the schedules from testers across the country who were asked not to have a schedule, then to use Nest’s Auto-Schedule or manually program their thermostat.
• Results: in our winter tests for two different kinds of homes, simulations showed that a 1°F change to temperatures throughout the day results in a 2-5% change in energy usage (heating runtime). In summer, we looked at tester’s schedules and inferred that changing the temperature 1° results in the the AC running an average of 8% less while cooling.

More details about how these trials were run and what temperatures people set are available in our white paper​​.

Auto-Away

Auto-Away is a Nest thermostat feature that automatically turns the Nest thermostat to an energy-efficient temperature when nobody is home. We say that Auto-Away works in 90% of homes, even when Nest is in a spot you don’t pass on your way out the door.

When Nest is first installed, it will take a few days to learn about its surroundings and figure out if it can sense enough activity to reasonably understand when people are home and when they’re not. When we looked at all Nests currently connected to Wi-Fi, 93% of them had high enough sensor confidence to activate Auto-Away. Only 7% of thermostats are in places that don’t get enough sensor activity, meaning they’re in a closet or unused room.

We mention this on the website because many people are concerned that Auto-Away won’t work in their home, simply because their thermostat isn’t in a great spot.

Airwave

Airwave is a Nest thermostat feature that turns the AC compressor off early but keeps blowing the fan until you reach your target temperature. We say Airwave cuts AC runtime up to 30%.

This is real data from our own tests:

• Airwave was released in April 2012.
• Data was compared from homes that ran AC frequently without Airwave in March against homes that used Airwave in April.
• The data shows that the compressor turns off up to 30% earlier when using Airwave.

More details about how these trials were run are available in our white paper​​.

Filter Change Reminder

We say that a clean filter for forced air systems can result in 5% savings. This information is from the Consumer Energy Center.

Seasonal Savings

We say that Seasonal Savings has helped Nest users save 5-10% on heating and cooling. This information is from our Seasonal Savings trial, outlined in the Seasonal Savings white paper.

Rush Hour Rewards

We tell you about how much we think you could earn from Rush Hour Rewards for each of our energy partners, for example “You could earn around $60 from SCE this summer.”

How much you get paid depends on your energy provider, the weather, the number of energy rush hours that summer, the size of your air conditioner, and the amount of electricity you save across your whole home during a rush hour compared to your normal electricity use on non-rush hour days. Our estimates can't account for all of these variables and even though we attempt to include relevant factors, a precise amount can't be guaranteed. Here are examples of how we calculated how much you could earn:

Saving energy example homes

On the Saving Energy page we created three simulated homes to show how different Nest features interact to save energy. We used real data to simulate three realistic scenarios:

• Johnny and Kate in Chicago, IL
• Angelina and Dillon in Seattle, WA
• Tina and Joe in Phoenix, AZ

Our basic premise was that these homes - with their different needs, locations and residents - can all save energy with Nest. Prior to having a Nest, we assumed that, like 89% of people, none of these families programmed their thermostats. Here’s a precise explanation of how we imagined their lives and the data we used to establish their schedules and savings numbers:

A. Johnny and Kate, Chicago, IL
Family with two kids. Kate stays home but is constantly on the go, dropping off/picking up kids, running errands, and going on an occasional outing with friends.

Lives in a 3,000 sq.ft. home. Forced air. Gas furnace. AC.

Before Nest: No schedule. Heated and cooled the house to 70F year-round.

Heating schedule: 7am 70F, 9pm 66F. Away temp 62F.

Cooling schedule: only turn on AC when needed. Away temp: 82F.

Kate wants to turn down temperature when she is away to keep her heating bills low, but her schedule isn’t predictable enough to do so during the day. However, they do turn down the temperature at night time by 4F, which Auto-Schedule remembers and results in 9% savings.

With their irregular schedule, Johnny and Kate take full advantage of Auto-Away. Auto-Away turns on three times a week for more than 4 hours at a time on average. Because Kate set their Away temperature to be 8F lower than her usual temperature during the day, she is saving 16% on days she goes to Auto Away. 16% for 3 days/week amounts to 7% savings every week. All together, winter savings from Nest total 15%.

During the summer, Kate and Johnny don’t use the AC too often. They turn it on during really hot afternoons, but they turn it off by early morning. AC typically runs fairly consistently during this time so Airwave doesn’t run too often. Total Airwave savings are 2%.

Because their heating use is 10 times higher than their cooling use, they are saving 14% overall from heating and cooling bills with Nest.

B. Angelina and Dillon, Seattle, WA
Newlyweds. Both work many hours. No kids. One dog.

Lives in a 1,500 sqft condo downtown. Heat pump with AUX. Forced Air. No AC.

Before Nest: No schedule. Heated their home to 70F in the winter. 

Heating schedule: 6am 71F, 8am 65F, 7pm 70F, 11pm 65F. Away temp: 65F.

Angelina and Dillon bought Nest because they heard it can reduce energy bills for heat pump with AUX, which are common in Seattle. Their Nest learned a schedule that reduces the temperature while nobody is home as well as when they’re asleep, but they have an older dog and want to make sure he’s comfortable. So they set both their afternoon temperature (while they’re at work) and Away temp to 65. Because their daytime temp and Away temp are the same, they don’t save much from Auto-Away. This schedule, however, is saving them 14%.

Nest activated Heat Pump Balance for the couple, and they set it to Max Savings. According to our savings simulations (based on the fact that auxiliary heat can be up to five times more expensive than regular heat and how Max Savings Heat Pump Balance setting automatically minimizes use of auxiliary heat) that saves them 9%. Finally, they pay attention to Nest’s Filter Reminder and change filter regularly, saving an additional 6%. Put it all together and their heating bills are 26% lower with Nest.

C. Tina and Joe, Phoenix AZ
Retired couple. Home a lot. Grandchildren stay at their house in the afternoon.

Live in a 2,000 sq.ft. home. Forced air. Electric heat. AC.

Before Nest: No schedule. Heated home to 72F in winter and cooled to 73F in summer. 

Heating schedule: 7am 72F, 9pm 68F. Away temp 62F.

Cooling schedule: 7am 74F, 9am 76F, 3pm 74F, 9pm 73F. Away temp 79F.

Phoenix summer is hot. While Tina and Joe’s schedule doesn’t have a large increase in temperature during the day, they made a conscious decision to increase the temp by 2F when the grandkids aren’t over. This schedule is saving them 10% from their cooling bills.

They like to go out to play golf about twice a week, so Auto-Away saves them 20% on those days. This is 6% savings total. Finally, Airwave is working quite well in their dry, hot home and they’re saving 9% with Airwave. In the summer, they are saving 23% with Nest.

The winter is mild so heating doesn’t turn on much during the day. However, it turns on a lot at night because it gets cold. They’ve turned down the night temperature, so they are saving 18% (mild weather places have larger percentage savings). Auto-Away in the winter is saving them additional 2%. In the winter, they are saving 20%.

With cooling usage being five times greater than heating usage, this family is saving a total of 22% on their heating and cooling cost with Nest.

There are two different ways that these savings number interact.

• First, it is good to understand how numbers “add” up. If Angelina and Dillon are saving 14% from Auto-Schedule and 9% from Heat Pump Balance, the savings aren’t exactly 14+9=23%. The savings are actually: 1 – (1-0.14)*(1-0.09) = 0.2174 (21.74%). So if the monthly bill without Nest was $100, with Nest it’s $78.26.
• It’s also good to explain how Auto-Away savings work. Kate set Away temperature to be 8F lower than her usual heating temperature. This choice is saving her 16% on days she goes to Auto-Away. She goes into Auto-Away on average three days a week, so to get the overall Auto-Away savings, this must be calculated into a seven day a week number. The calculation is: 16% x 3 days / 7 days = 6.86% savings overall from Auto-Away.
• Heating savings and cooling savings add up, but based on where a family lives and whether they have air-conditioner, these numbers add up differently. For example, assume that cooling bills savings are 20% and heating bills savings are 10%. If cooling bills are twice as expensive, then the overall savings are: (20%*2 + 10%*1)/(2+1) = 16.7%. So if the total cooling bill is $200 without Nest, it is $160 with Nest. If the total heating bill is $100 without Nest, then it’ll be $90 with Nest. So if this family used to pay $300, now they pay $250 with Nest.
• Finally, it’s good to understand that there are different kinds of interactions between these savings numbers. For example, savings from having an aggressive schedule doesn’t affect how much savings you’d get from Heat Pump Balance. And the amount of Auto-Away savings doesn’t affect Airwave savings. However, Auto-Schedule and Auto-Away savings both come from schedule changes, so you have a great energy-efficient schedule that’s set to save energy when you’re gone, Auto-Away savings won’t look large. And if you don’t get much savings from your temperature schedule because your real-life schedule is always changing, then Auto-Away could result in big savings.