What makes a good home energy display?

Exploring consumer preferences for energy display designs

Project duration: March 2009 to September 2009

'In-home energy displays’ are increasingly popular gadgets that show you how much electricity your home is using. But what sort of display is preferred by householders? The Energy Saving Trust engaged CSE to find out.

Most home energy displays will tell you your current electricity consumption as well as historic information: how much you used last week etc. They can show this in terms of power (in watts), spend (in pounds) or resulting CO2 emissions (tonnes), and do so in a number of different ways: in text, numerically, graphically, through movement or change in colour.

Households that start using these gadgets are reckoned to become more energy aware and, as a consequence, their electricity usage declines – by 5-15% according to some estimates.

This is why recent amendments to the Carbon Emissions Reduction Target (CERT) allow energy suppliers to meet a portion of their carbon saving targets through distribution of clip-on electricity displays to households, and also why the Government wishes to see smart meters in every home by 2020.

Appealing to consumers

But what makes a good energy display? It’s an important question, because while good displays have the potential to engage consumers and influence their behaviour, poorly designed ones are likely to confuse, mislead or bore them. What little research exists in this area was undertaken by energy suppliers and remains under wraps for reasons of commercial sensitivity.

CSE’s research involved three techniques. Firstly, two expert literature reviews were undertaken. One focussing on the existing literature on displays, the other assessing the psychology of human interaction with displays.

Secondly, we conducted interviews with individuals from companies selling displays.

And thirdly we undertook focus group work - the core part of the study. Five focus groups were recruited, each containing seven or eight people.

Each group met twice. At the first meeting the groups collectively designed a real-time energy feedback display. After the meeting each member of the group was given a real one to take home and use.

At the second meeting, eight days later, participants described their experiences of using their display and, in the light of this, reviewed their initial designs and prepared new ones [see photos].

Although participants were generally able to use the displays they were given, and many changed their behaviour as a result (although measuring this was not part of the research being undertaken), their experiences were mixed. In some cases the display was considered unreliable, difficult to read or difficult to understand, or provided either too much information or not enough.

Along with the focus group process, this practical experience of using displays teased out differences between what people initially thought they would like on a display and what they actually ended up wanting. The experience therefore helped to clarify what was genuinely informative and useful and what was superfluous.

What we found

Below is the briefest of headline findings from the focus group.

1) All the groups eventually opted for a ‘speedometer’ design to show how ‘fast’ electricity was being used at that particular moment.

2) By and large, all groups ultimately opted for describing the rate of consumption in pounds per day. Watts were very poorly understood by most participants and not a driver for reduced consumption.

3) Without exception all five groups decided they wanted cumulative daily spend presented.

4) All final designs included the ability (not necessarily on the main default screen) to access historical data on spend and to compare it to current levels.

5) There was a strong desire to keep the display screen simple.

Of the 15 energy displays on the market at the time, only one met the preferences expressed by the focus groups.

Based on the literature reviews, interviews and focus group work, the report’s authors, Will Anderson and Vicki White, concluded that a 'minimum specification' is required to ensure they display in the way that consumers want and expect them to – which isn’t the case for most of the displays currently on the market.

1) The default display should include: a clear analogue indicator of current rate of consumption, the current rate of consumption as a rate of spend in pounds per day (numeric) and the cumulative daily spend in pounds (numeric)

2) The display should show, through interaction (by pressing a single button), the spend in the last seven days, day by day and the spend in the last complete week, month and quarter. The historic periods should match the utility’s billing periods in order that the display is consistent with household bills.

3) The display should offer the option (by pressing a single button) of switching units from money to power, i.e. from pounds per day to kilowatts and kilowatt-hours.

4) The display should be mains-powered but have an internal battery to enable mobility in the home.

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