Home energy report programmes are being increasingly adopted in the energy industry, with their potential for energy saving. However, there is surprisingly little clarity about what is driving such savings, or on other issues such as what types of households tend to be “high savers” or what behaviours they are adopting.
In order to address this, the US State and Local Energy Efficiency Action Network (SEE Action) has investigated Pacific Gas & Electric’s (PG&E) Wave One home energy report programme. Smart meter data associated with the program was analyzed, in order to unpack the hour-by-hour savings into savings related to air conditioner use.
The pilot programme, whose rollout began in February 2012, includes 500,000 households in the top three quartiles of energy use, drawn from most geographic regions in PG&E’s service territories. The data used in the analysis covered the three months, August-October 2012. This period includes six of the ten highest hourly consumption levels in 2012.
An earlier study on the data found that a significant amount of savings of the Wave One programme was happening during peak times. [Engerati-Peak-Hour Energy Savings – Smart Meter-Based Behaviour Programmes Show Potential]
For the present study, the air conditioner households were identified through a model that uses monthly billing data in addition to other easily accessible public data sources to estimate the likelihood of owning and using air conditioning.
Air conditioner use enhances savings
The analysis provided two key results, firstly that households with air conditioning drive much of the energy saving. While both households with and without air conditioning achieved savings during almost every hour, those households with air conditioning saved more than twice as much as non-air conditioner households. Further the air conditioner households saved more, almost three times as much, during the peak hours.
Put in numbers the air conditioner households represent 60% of the population and used 67% of overall energy and 68% of peak-hour energy, but provided 78% of the overall savings and 81% of peak-hour savings.
The second key result is that air conditioner households saved more on hot days and peak hours. On cold days the savings for air conditioner and non-air conditioner households was similar, and the non-air conditioner households showed similar savings during hot and cold days.
Based on these findings, implications are:
- Behaviours associated with air conditioning may drive much of the savings achieved by this home energy report programme. With the “best guess” that people are changing their thermostat settings to save energy, at least some of the savings is likely to be driven by one-time or habitual savings behaviours, rather than equipment purchases
- Targeting households estimated to use air conditioning may lead to higher overall and peak savings per household
- Targeting households estimated to use air conditioning may lead to higher savings during peak hours on the hottest days.
The researchers note there are many issues that the study does not address. For example, while part of the savings may be driven by actions related to air conditioning, the results clearly show there are statistically significant savings for non-air conditioner households, savings during cold days, and savings during off-peak hours. This suggests that other behaviours are contributing to these savings, but it is not known what these are.
In addition, the findings do not help understand measure life and persistence issues. If thermostat settings are driving the savings, it is unclear whether this is a behaviour that will last (and, if so, for how long), or if it will degrade over time.
Finally, it is noted the results may be specific to this particular programmes in this specific situation, and they should not be generalized to other home energy report programmes.