Theme 2: Using multiple cues to infer consumption

Theme 3.3.2 lists the different cues that participants used when making judge-ments about the energy consumption of appliances (see Table 3.5). Theme 2 explores how participants used more than one cue when inferring the energy consumption of appliances and how they resolved contradictory inferences from multiple cues.

Participants often perceived more than one cue to be relevant when inferring the energy consumption of appliances. In some cases inferences made from mul-tiple cues corresponded with each other to provide stronger evidence for a judge-ment about an appliance’s energy consumption (e.g. both cues led to an inference of high energy consumption). In other cases, inferences made from the cues tradicted each other (e.g. one cue would lead to an inference of high energy con-sumption and one would lead to an inference of low energy concon-sumption) so the participant had to decide which cue was a better indicator of energy consump-tion for that appliance. This could be especially complicated if two cues led to opposing contradictory inferences about two appliances.

3.3.3.1 Combining corresponding cues to infer energy consumption

When multiple cues led to the same inference about energy consumption, partici-pants did not need to make further considerations and could be confident in their judgements.

large size + heating up = high energy consumption Large appliances and ap-pliances that heat up air or water were both perceived to consume high amounts of energy. Larger appliances can hold more water, food, or air which would take more energy to heat up than the smaller amounts of water, food, or air that can be contained in smaller appliances: “if they’re bigger, there’s more of a space to fill, whether it be either heating it with the oven or the dishwasher. . . It’s all got to be heated hasn’t it?” (PC07). Appliances that can hold a lot of water need to consume a lot of energy to heat up that water: “I think the dishwasher’s. . . I think it’s about 60 litres isn’t it or something? The water it takes, and it’s got to heat that water up” (PC08).

large size + long duration of use = high energy consumption The duration of time that the appliance was switched on or in use was also perceived to influence the amount of energy consumed in conjunction with other cues. Large appliances used for longer periods of time were perceived to consume more energy than smaller appliances used for shorter periods of time:

I think there is an element of sizes and the length of time that you use them for. So, you know, the tumble dryer may be on for 45 minutes,

whereas a kettle will only be minutes. . . So size of the appliance but also the usage period as well would sway me as to what uses more than others (PC05).

heating up + long duration of use = high energy consumption Heating thing up was perceived to indicate greater energy consumption but heating some-thing up for a longer duration of time was perceived to indicate, perhaps, even more:

I’ve got this thing in my head about if it has to heat things for a long period of time, like tumble dryers, electric ovens, washing machines, has to heat the water, anything that has to heat something, I dunno almost says to me that it’s going to use more energy (PC05).

low frequency of use + short duration of use = low energy consumption Ap-pliances that are used infrequently and apAp-pliances that are used for only short periods of time were both perceived to consume smaller amounts of energy. Ap-pliances that are used both less often and for less long were perceived to consume very little energy: “My camera is maybe charged once a week for a few hours so very tiny amounts.” (PC04).

3.3.3.2 Resolving contradictory cues to infer energy consumption

In some cases, when using more than one cue to infer energy consumption, par-ticipants found that their inference from one cue contradicted their inference from another cue for the same appliance. Participants had to decide which of the cues is more indicative of the appliance’s energy consumption. In the following illus-trative quotations, where the most indicative cue is not mentioned, it is deduced based on the participant’s ranking of the appliances’ energy consumption during the card sort tasks (see Table 3.3).

higher frequency of use > lower energy intensity Some participants mentioned situations in which the frequency of use of the appliance was important but also noted that the perceived energy intensity that the device needs to operate is also relevant: “electrical appliances like tablets and things, there just kind-of like, you know, high frequency but low [energy] usage” (PC01).

high usage > lower intensity PC04 perceived her household’s computers to be quite efficient (which she put down to them being both small and fan-less) and so requiring lower energy intensity. She did, however, also feel that they used the computers a lot, especially as her husband used his for work as well as leisure.

While she still ranked the computers relatively low in terms of energy consump-tion, she clearly felt that they would be much lower if they were not used as much: “We have good computers which consume low amount of electricity so I think that’s quite low, but it’s used a lot, so in-between.” (PC04)

short duration > higher intensity PC10 judged the kettle to consume a moder-ate amount of energy because she had observed (by taking readings from the elec-tricity meter) that it required a high energy intensity but for a very short amount of time: “the kettle does use short bursts of electric” (PC10).

short duration of use > high frequency of use Most of the participants men-tioned, explicitly or implicitly, that the frequency of use usually has to be bal-anced against the duration of use (and maybe other dimensions too). Appliances used frequently were seen as consuming less energy than they might otherwise have done if they were only used for short periods of time: “hoovering, once every other day, but it’s not on for very long.” (PC10).

3.3.3.3 Comparing appliances using contradictory inferences

Making inferences about energy consumption, and resolving contradictory cues, was often for more than one appliance at once. Even if the participant was not explicitly comparing one appliance with another, they were usually making an implicit comparison, as can be seen from the use of terms like “a lot of energy”,

“large”, and “used frequently”. See Table 3.3 for participants’ rankings of the appliances’ energy consumption.

(higher usage + lower intensity) > (lower usage + higher intensity) PC07 con-sidered the fridge freezer to consume more energy than the tumble dryer, because the fridge freezer is on all the time, even though she perceived the tumble dryer to require higher intensity of energy than the fridge-freezer: “I’ve only put the fridge freezer here because it’s on all the time. The tumble dryer when it’s oper-ational is using more than the fridge freezer when it’s operoper-ational” (PC07). She

judged the greater usage of one appliance to be more indicative of higher en-ergy consumption than the higher enen-ergy intensity required to operate the other appliance.

(longer duration + lower intensity) > (higher intensity + shorter duration) Sim-ilarly, PC04 considered the longer duration of use to indicate higher energy con-sumption in the fridge-freezer, radiators, and boiler than the higher energy inten-sity or high activity for a shorter duration in appliances such as the dishwasher, fan, and washing machine:

there are a few factors. One is whether they are on all the time, or whether they are just used occasionally. So fridge-freezer uses a lot because it’s connected all the time, whereas these [dishwasher, fan, and washing machine] uses a lot when they are in use but they are fine when they’re on standby. . . And the boiler’s always on, so these one are high-consuming because they are always on. Whereas the other ones are intense but in short periods (PC04).

(shorter duration + higher intensity + higher activity) > (longer duration + lower intensity + lower activity) In contrast, when comparing the consump-tion of a car against a fridge-freezer, PC07 perceived the high energy intensity and high level of activity (presumably the amount of movement) of the car to be more indicative of energy consumption than the longer duration of use of the fridge-freezer:

the amount of energy that’s being used in the car and what it’s actu-ally doing is probably more than a fridge freezer to be fair isn’t it, it’s just hard to compare them. The fridge freezer is obviously on all the time and is always using power but the car, when it is being used, uses? I don’t know how many more, more, much more power, dunno probably five times more power when it’s being used (PC07).

It is not clear how PC07 perceived the car to require much greater energy intensity to operate than the fridge freezer. She might have been using other cues that were not apparent in what she said during the interview, perhaps associating high intensity with high activity.

(higher activity + shorter duration) > (less activity + longer duration) Appli-ances that were perceived to be highly active when switched on and appliAppli-ances that are switched on or used for a long time were both perceived to be high energy consumers. PC06 felt that the appliances that are “on pretty constantly” consume the most energy, mentioning the central heating and the washing machine, which were two of the top-three in her card sort ranking of appliances. When consider-ing the fridge-freezer, though: “the fridge and thconsider-ings like that are on all day. I’m guessing they’d be up there even though you don’t feel like you’re using energy when they’re on” (PC06). She ultimately ranked the fridge-freezer as consuming less energy than the central heating, which she said is on only during the winter, and the washing machine and other appliances that would be used often but not, as she described the fridge-freezer, “on all day”.

(cooling down + higher usage) > (heating up + lower usage) PC08 was the only participant who directly contrasted the activity of cooling something down with that of heating something up. He perceived the fridge to consume more energy than the cooker because the fridge is on more than the cooker but then added support to that judgement by using the additional cues of cooling and heating to cement the relative rankings: “the fridge is constantly on, whereas the cooker is intermittent. It’s more expensive and it takes more energy to make cold than it does to make hot” (PC08).

3.3.3.4 Difficulty in resolving contradictory cues

Some participants demonstrated experiencing difficulty in resolving contradic-tory cues to decide which of the cues was more indicative of higher energy con-sumption. See Table 3.3 for participants’ rank ordering of appliances by energy consumption.

(heating food + lower intensity + longer duration) > (heating food + higher in-tensity + shorter duration) A comment made by PC05 suggested that the pro-cess of weighing up the relevance of the cues made her doubt the efficacy of using duration of use as a cue. She was trying to understand the relative energy consumption of the microwave and the oven. Both appliances heat food, which would suggest consuming a lot of energy but the microwave does it in a shorter time, which would usually mean that it consumes less energy. She wondered,

however, whether her usual rule that longer duration of use means higher energy consumption was untrue in this context and that the microwave consumed even more energy than the oven in order to get to the same temperature in a shorter time. Although she guessed a rank order, she claimed to be able to unable to decide:

Microwaves tend to only be on for a shorter period of time but then I’m thinking: does it still consume more energy to be able to cook things in a shorter space of time? Actually, so I’m thinking: yes, it’s quicker to use that, which makes me think that the electric oven consumes more energy because it’s longer. But actually to cook food quicker, does it actually need more energy? (laughs) I don’t know the answer to that one! (PC05).

(heating water + lower frequency + larger size) > (heating water + higher fre-quency + smaller size) PC02 initially decided that the washing machine and kettle consume similar amounts of energy on the basis that they both heat up water. However, she then considered the additional cue of the relative sizes of the appliances. The washing machine is larger than the kettle so the washing machine must consume more energy because it has to heat up more water than the kettle. However, she then also considered the frequency of use of each appli-ance. She ultimately concluded that the larger size of the washing machine was balanced out by the higher frequency of use of the smaller kettle:

I think [the washing-machine and the kettle] could be similar because . . . it’s the same, they have to warm water, okay, to heat water. On the other hand, you have more water to heat . . . in the washing machine.

. . . In the kettle it’s smaller but you use more often (PC02).

Adding more cues with contradictory inferences made her judgement more com-plex and caused her less certainty.

(larger size + smaller number) = (smaller size + higher number) PC05 also spent some time considering whether the smaller but more numerous and fre-quently used mobile phones in her household consumed more or less energy than the larger, single, and less used tumble dryer:

I would think the larger appliances would be consuming far more en-ergy than the mobile phones that are charged daily but then if you’ve got four of them, being charged daily, then it may be that that is com-parable to using a tumble dryer daily as well? (PC05).

She ultimately concluded that the large kitchen appliances would consume more energy than the mobile phones but that lights would consume more than the appliances “because of the number of lights” (PC05). The cue of the number of instances was perceived to be both less and more indicative of high energy consumption depending on the comparison.

3.3.3.5 Ignoring relevant cues to simplify the judgement

The greater complexity and difficulty of judgements when considering additional cues in inferences of energy consumption suggests that householders who want to simplify their judgements should restrict the number of cues they consider.

There was some evidence that participants did ignore potentially relevant cues in some judgements to simplify them.

(high frequency + higher heat) > (high frequency + lower heat) PC03 judged the tumble dryer to consume more energy than the washing machine. She used both machines every day so she could not distinguish their energy consumption based on frequency of use. By considering the additional cue of how much heat each produced, she was able to differentiate them, as shown in Theme 1.2 when she said:

I use my tumble dryer pretty much every day and, although I use my washing machine every day, I don’t think it uses so much energy as that because I just think a tumble dryer, they’re quite renowned for being just energy eaters. A washing machine obviously you can put on a lower setting so you can have your cooler wash so you’re not using as much energy but with a tumble dryer you don’t really get a choice (PC03).

She did not appear to consider potentially relevant cues such as the duration of use, the size, and the amount of movement and noise produced by each appli-ance. It might be that each of these cues would have been no more useful than

the frequency of use cue but she did not mention them at all. This suggests that participants were not necessarily conducting an exhaustive mental inventory of all the possible dimensions that they could use as heuristics in their judgements.

They were retrieving information about the appliances on the basis of one or two cues and ignoring any others.

(heating water + larger size) > (heating water + smaller size) When PC08 was comparing the hot water boiler and the kettle, which both heated water, he differ-entiated based on the relative sizes of the appliances and the amount of water that has to be heated: “the fridge and the hot water . . . what you want is to heat and cool, okay? You are doing the same with the kettle as well but on a much smaller scale” (PC08). He did not seem to consider the difference in temperatures being raised by the two appliances (typically 60+°C²for the hot water boiler but 100°C for the kettle), and did not mention how much each was used (neither frequency or duration). Again, he seemed to keep the judgement as simple as possible and just considered cues that would help him infer the energy consumption of each appliance enough to be able to make a judgement about which consumes more.

(smaller size + higher frequency) > (larger size + lower frequency) PC05 made a similar comparison between the hair dryer which is small but used frequently and the washing machine which is large but used less frequently:

hair dryer is used not just daily but, with two teenagers, it’s used sev-eral times a day. But for some reason I’ve associated that with not as much usage [consumption] as some of the big appliances, because it’s smaller? That’s probably completely wrong but, because it’s smaller, but then the usage on that is much higher (you know, my daughter dries her hair most days, I do). . . So it may be that actually even though it’s a smaller appliance, the usage means that actually it’s costing me probably maybe more than the washing machine (PC05).

Again, other dimensions (e.g. the amount of heat produced by the washing ma-chine versus the hair dryer; the duration of use of each appliance) were ignored.

Even the small number of dimensions that she did consider made the judgement complicated enough that she was uncertain about her answer.

2http://www.hse.gov.uk/legionnaires/things-to-consider.htm

3.3.3.6 Summary and implications of Theme 2

Participants inferred the energy consumption of appliances using the cues iden-tified in Theme 1 (see Table 3.5) but often made inferences based on more than one cue at once. When the inference of each cue was the same, judgements were straightforward. However, when inferences from each cue were contradictory, participants had to resolve the contradictions by deciding which cue was a better indicator of energy consumption and a more appropriate basis for the judgement.

The judgements discussed suggest that participants tended to judge the amount the appliance is used (or switched on) as being more indicative of the energy con-sumption of the appliance than the intensity of energy required by the appliance to operate. This might well be the case but would need to be tested more sys-tematically to conclude whether participants’ choices between conflicting cues are predictable. This increased complexity when considering multiple cues in a judgement corresponds with the “less-is-more” effect proposed by Gigerenzer and Goldstein (1999) and discussed more recently by (Gigerenzer & Gaissmaier, 2011). According to the less-is-more effect, people make judgements using as lit-tle information as they can and, contrary to more “rational” models of making

The judgements discussed suggest that participants tended to judge the amount the appliance is used (or switched on) as being more indicative of the energy con-sumption of the appliance than the intensity of energy required by the appliance to operate. This might well be the case but would need to be tested more sys-tematically to conclude whether participants’ choices between conflicting cues are predictable. This increased complexity when considering multiple cues in a judgement corresponds with the “less-is-more” effect proposed by Gigerenzer and Goldstein (1999) and discussed more recently by (Gigerenzer & Gaissmaier, 2011). According to the less-is-more effect, people make judgements using as lit-tle information as they can and, contrary to more “rational” models of making