It's been seven years since the five star energy system was introduced in Victoria, now it's being taken one step further.
"What'll happen for most houses now there has to be either a choice between a solar hot water system, or a water tank connected to laundry/toilet on the side of the house," Doug Bell, from WaterStore Poly Tanks, said.
"Most systems have a tank to toilet system, whereby your rainwater goes and fills the water tank, that then goes and flushes your toilets. So rather than seeing water go down the toilet literally, it's actually free from the sky," Mr Bell said.
A range of measures will also make homes more energy efficient.
"Often you'll have double glazed windows, you'll have larger size water tanks, you'll have increased electrical capacity off the roof. It's a complete range of aspects that makes it much more efficient," Mr Bell said.
In most cases, homes extended by more than 50% must be updated in line with the new ratings.
"You can come home of a night time and you're freezing cold, but you walk inside and there's still warmth in there, even though the heater ain't going," Mr Threlfall said.
Mr Threlfall has been in his home only three weeks, but says he isn't worried about his next energy bills.
"Our others were getting up around the $400 to $500, and they tell me around the $250 to $300. So let's see how close they are."