UNSW research pinpoints residential energy guzzlers

Energy guzzling appliances, oversized houses and poor thermal performance mean some households are paying up to $12,000 a year in power bills, new research into residential energy use has found.

The research, undertaken by the UNSW School of Photovoltaic and Renewable Energy Engineering and funded by the CRC for Low Carbon Living, analysed more than 1.9 million electricity use records gathered from more than 9000 households over the course of a year across Greater Sydney, the Hunter and Newcastle.

The two biggest culprits for high residential energy use were pool pumps and ducted airconditioning systems. The findings also highlighted the extent to which poor building design and standards are contributing to the carbon footprint of the residential sector, according to co-author Dr Alistair Sproul.

The data included both energy use figures, and also surveyed households on factors including household demographics, dwelling type, utilities, white goods, weather, behaviours and whether they had undertaken any kind of energy efficiency activity or saw efficiency as important.

The modelling showed households with ducted airconditioning used on average 79 per cent more electricity than those with none, while those with a split airconditioning system consumed 34 per cent more. The 23 per cent of households that had a pool had average daily electricity demand 93 per cent higher than those without one.

“A key reason for the study was that in the residential sector, which represents around 30 per cent of global electricity consumption, the underlying composition and drivers of energy use have until now been poorly understood,” Dr Sproul, who is associate professor at the UNSW School of PV & RE Engineering, said.

Pool pumps were known to be big energy users, he said. That the data showed such a strong correlation between owning a pool and high household energy use made them really “stand out”.

Because it is known that household income is also a driver in electricity usage, the team looked for a correlation between the household income brackets and the pool pump findings. Dr Sproul said the data showed even in low income households, those with a pool had high energy bills.

The conclusion, he said, was that choosing to have a pool had an impact on electricity use regardless of income.

Heating causes high energy use

When the data was examined to see what influence different climate zones had on energy use in the greater Sydney region, another interesting finding emerged that heating more than cooling contributed to high use.

Dr Sproul said this reflected the poor performance of many dwellings.

The message that needed to be heard, he said, was that basic measures like good use of thermal mass, insulation, passive solar orientation, double-glazing, sealing buildings well and preventing “leaky” housing needed to be the norm.

“We need to be building better thermally efficient homes,” Dr Sproul said.

“It is obvious [these] buildings are not responding well to extreme weather events and have poor energy performance in winter. The thermal envelope performance is poor.”

McMansions a recipe for disaster

Other implications of the study’s findings for the residential sector are that the fashion for large “McMansion” style homes, with multiple fridges and inefficient appliances, pools and ducted airconditioning systems, is a recipe for bill disaster.

“All our studies are aimed at saying, ‘What are the drivers of energy use?’” Dr Sproul said.

The energy-intensive home trend, he said, arose back when energy was cheap. Now prices have gone up his researchers have come across homes that are paying power bills of around $12,000 a year.

“We need to ask now if these are sensible pathways,” Dr Sproul said.

“Energy costs have risen and we also have this problem of climate change.”

Behaviour change needed

One home a researcher visited had all of the big energy-ticket features, and also household members that made the HVAC work harder by not shutting doors. Dr Sproul said the researcher suggested to the home owners they could reduce bills simply by encouraging everyone to shut doors, but the homeowners rejected the suggestion.

This, he said, showed clearly how occupant behaviour also influences energy outcomes.

Given the difficulty most households would face in trying to substantially rectify a poorly performing home, Dr Sproul said the data showed there were some simpler fixes.

As pool pumps are such a high energy user, switching to a 7, 8 or 9 Energy Star rated pump would pay for itself quickly, with up to $800 a year in savings on power bills compared with a standard inefficient pool pump.

He suggested this would be a smart move for anyone “unless your hobby is paying more money to the utility company”.

Ducted airconditioning, another of the items that correlated to high energy bills, was difficult to retrofit to zone off rooms, he said.

What can be done is check the thermostat is not set too high in winter, and too low in summer.

Let’s raise the standards

Dr Sproul said there also needed to be standards for energy efficiency for heating and cooling equipment put in place. And home owners need to be choosing the most energy-efficient appliances possible.

“The current coefficient for performance under the Australian Standard is one unit of electricity equals 3.1 units of heating or cooling. The most efficient equipment available has a coefficient of six – that is almost double the energy efficiency of the Australian Standard,” Dr Sproul said.

“The question is, shouldn’t we be raising the energy efficiency of Australian heating and cooling equipment?”

One of the real issues here, he said, was the “mentality of the past”. The big McMansions built with no insulation, no shading for summer heat, ducted air conditioning and a pool were using double or triple the energy of average household.

“They are the ones paying thousands of dollars in energy bills, and they are the ones driving peak demand,” Dr Sproul said.

At the core of the energy use picture are Australian lifestyles based on “badly built homes and inefficient appliances”.

“That lifestyle is built around big homes that use lots of energy,” he said.

“I would say we need more efficient homes, more efficient appliances, and less heating and cooling.

“The next trick is how can we can help change these energy-guzzling houses and people into more efficient users.”

UNSW PhD student and lead author Hua Fan said the model investigated the consumption of both individual households and communities.

“There are limits to what can be achieved modelling single households given the myriad factors that go towards overall consumption including, importantly, the behaviour of the people living there. However, the model tested extremely well for forecasting the overall electricity consumption of communities,” Mr Fan said.

“We concluded that models like this are useful to a range of stakeholders, including individual households striving to understand the implications of different choices they might face such as whether to put a pool in, utilities looking to better forecast the impact of different residential trends as they plan their networks, as well as policy makers seeking to improve energy efficiency.”

Associate professor Iain MacGill, electrical engineering, UNSW, and another co-author, said the study was undertaken in the context of a largely unexpected fall in Australian residential electricity consumption over the past decade.

“Studies such as this can also make a useful contribution towards assessing recent efforts by some of the network businesses, under pressure from falling revenue due to lower sales, to change their tariff arrangements,” he said.

“In particular, how can we ensure that households undertaking energy efficiency activities or putting on solar home systems are not penalised for doing the right thing in saving both money and the environment, while still ensuring we all fairly contribute towards reliable and secure supply.”

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