Y'all do things a little differently down under. Just FYI the breakers in the US are designed to trip if they are continuously at 80% of the rated amperage, they can handle the 100% just for an instant like compressor startup. We don't use any 16 gauge in the walls, #14 is the smallest we use and is suited to the 15 amp breaker. #12 is suited to our 20's. We never would put a 20 amp breaker on 14 awg.Mate im an electrician in Australia, so im pretty confident my input will be valid.
Are you an electrician? If not don't be an idiot and play with shit that can kill you. No matter how easy it might sound, no matter how easy it may in fact be it is just too easy to make a mistake and not only hurt your self but your loved ones who you will leave behind when you either A. Die or .B turn into a crippple. I seriously can't stress enough how stupid it is to play with the invisible dangers of electricity.
Assuming you take on this advise you won't be able to do anything anyhow. So to understand why you shouldn't just bump up the breaker size let's look at some theory first.
Current Carrying Capacity (C.C.C), The idea is that a cable size/guage has a maximum C.C.C (there are other derating factors but for this ill keep it simple.
Im my world when I wire a house i need to do the below formula (plus others) to figure out the most cost effective and safe cable sizes.
IB < IN < IZ
IB = maximum load
IN = Circuit breaker size (CB)
IZ = C.C.C of cable
So the load must be less than the CB size, and the CB size must be less than the C.C.C of the cable. We do this to protect the integrity of the cable. Its all about protection.
In australia we use (usually but not always), 2.5mm2 as the standard power point cables which is pretty close to your 14awg cable (2.59mm2 conversion) so if your cable is currently 14awg it could potentially be upgraded 20A CB but don't quote me on that,
You mentioned its only a 15a CB currently, I would be concerned because it could potentially be 16awg which would be equivalent to my 1.5mm2 and it only has a C.C.C of 18a. If this is the case and you do upgrade the cable, mate your not maybe going to cause a fire you will at some point. Insurance won't cover it.
I hope ive given you somthing to think about though, feel free to ask further questions. I would rather give information than have people misguided by un-informed or un educated people. Fyi in australia it is illigal for people to conduct electrical work without an electrical licence (4 year apprentiship). (Its also illigal to grow green in most states aswell haha)
Good luck happy growing