The total weight of the cannabis, from the eight plants, was 7661 grams, estimated to be worth about $10,500.
Police also discovered that the power meter at Ferguson's home had been tampered with and re-wired to allow the electricity used in the grow room to bypass the meter.
An electrical inspector determined Ferguson had been bypassing the power for at least seven weeks and said about $816 worth of power had been used, unmetered.
Ferguson said he had been growing the cannabis for his use, for pain relief.
Defence lawyer Ian Hard said Ferguson had several ongoing medical conditions.
"This was out of desperation and the need to self-medicate.
"He was on 90 grams of morphine daily and that wasn't doing it for him, he has intense back and neck pain ... he didn't want to be loaded up with a large amount of morphine."
Judge Chris Tuohy said Ferguson's claim he was growing the cannabis for pain relief was supported by a letter from his doctor.
"That letter indicates that you have an extensive list of medical problems ... in particular you have chronic pain relating to your lower back, you also have a head injury which has an ongoing impact on your thinking process."
Judge Tuohy said he accepted Ferguson was growing the cannabis for his own pain relief.
He convicted Ferguson, fined him $1500, and ordered him to pay $816 in reparations to the electricity company.