The most remarkable thing about Michael Mobbs’ house is just how ordinary it is.
"I’ve had 20,000 people through on tours and the dominant comment that they all say is, ‘gee, it’s just like my place’," says Mobbs, who in 1993 decided to take his family home, a three-bedroom, nineteenth century terrace located in the inner Sydney suburb of Chippendale, off the grid.
While it seems like these days everyone is going off-grid, building a sustainable house was an unusual undertaking at the time. Finding the right information in a pre-internet era presented a unique challenge. "Google didn’t exist until ‘98, so I had a really difficult time researching," says Mobbs. "It took me three years of research to get the level of simplicity that’s here."
Mobbs installed a solar system and disconnected the house from sewerage and mains water. "All the waste water from the sink, the shower, the washing machine is recycled to flush the toilet and hose the garden, and then the surplus is discharged one metre down in the soil."
The terrace’s off-grid system has been designed to be low maintenance – "perfect for a lazy greenie"...
The switch to rainwater for all drinking-related functions came with a surprising amount of red tape. Rainwater at the Myrtle Street house was tested in partnership with NSW Health every two weeks for 18 months. "My water tested cleaner than mains water," he says.
The terrace’s off-grid system has been designed to be low maintenance – "perfect for a lazy greenie", says Mobbs. "It’s intended to be sold so that anybody could come here and use it and not know anything about the systems…You can come in and turn the lights on and not know about it, you can turn the tap on and not know it’s rainwater off the roof in the heart of the city."
The only update he has made since the initial renovations was in March 2015 to disconnect from mains power. "All of my electricity now is powered by the sun and by batteries. When I did it back then the solar system cost $26,000. The same size system today cost $3,000," he says.
The entire project, which cost $48,000 in 1996, would cost a lot less today. Mobbs, who runs a sustainability consultancy business, says he can now take a house off-grid for $20,000, delivering annual savings in water and energy bills of $2000 to $4000.
While off-grid houses like Mobbs’ Chippendale home are becoming more common, they still account for only one-to-two per cent of the Australian population, says Emily McMahon from Off-Grid Energy, an Australian company offering off-grid battery storage systems.
"They also say that they love owning their own electricity production, having energy independence and not being exposed to the sort of price shocks and reliability issues that you can’t control when you are connected to the grid."
McMahon explains the technical requirements needed to go off-grid. "An off-grid battery system contains a battery bank, solar panels, a solar inverter, a battery inverter/charger, a back-up generator (although some systems can go without), along with enabling equipment such as switchboards and fuses. In a few cases small-scale wind turbines or micro-hydro turbines are also suitable."
There are a number of factors to take into account when installing an off-grid system, including a home’s seasonal power and energy requirements, plus local weather conditions. "When you’re off-grid it’s especially important to have sufficient energy inputs and storage for the worst parts of winter – we usually allow three to four days’ worth of ‘autonomy’ (extra storage capacity), in addition to a backup generator," says McMahon.
The end of electricity bills is commonly cited by Off-Grid Energy customers as one of the best things about disconnecting from the grid. "They also say that they love owning their own electricity production, having energy independence and not being exposed to the sort of price shocks and reliability issues that you can’t control when you are connected to the grid," says McMahon. "The modern off-grid system is fairly maintenance free as well, but you must take responsibility for your power plant and ensure it achieves a nice long life."
The most obvious downside is the upfront cost of installing an off-grid system, making it unaffordable to the majority of people who otherwise have easy access to grid electricity, says McMahon, who puts the cost of going off-grid little higher than Mobbs’ estimate. "An average single-phase family home costs between $30,000 and $45,000 to go off-grid," she says.
By her calculations, an average-sized off-grid system would work out to be roughly 30 to 40 per cent more expensive than the equivalent grid electricity over the estimated life of the batteries. "This cost continues to fall at an ever-increasing rate, but it still remains the case that the vast majority of people that go off-grid are doing it because they were faced with an inhibitive cost to connect grid power to their property in the first instance."
Find out more about Michael Mobb's sustainable house.
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