Just some info for anyone thinking about getting a dehumidifier for the shed or anyone who hasnt thought about it.
Humidity around 60% or more will promote rust so if you've got expensive toys in your shed its something to be aware of.

Adelaide this time of year (winter) the outside humidity is in the 90% range all night every night.
My shed used to be about 80% with condensation driping from the roof insulation every morning and a dark grey concrete floor as though it held a few hundred litres in it.

I noticed the bed on my lathe started to get surface rust and the drill press.
So whats it doing to my cars and bikes and tools? Cant be good.

Step #1 seal the shed make it air tight if you can.
Step #2 seal or paint the floor.

So I bought a dehumidifier a couple of years ago and the humidity in my shed hasnt gone above 50% since that day.
Its adjustable so I could set it anywhere from 35% and up but that'll chew more power for little gain.
Switches on and off automatically and mine runs about 3 hours a day in winter.
It pulls several litres of water out of the air every day and pumps it outside.

I got the 'AlorAir Sentinel HDi90' for $2,400
Wasnt cheap but I'd highly recommend it if you're looking for a quality dehumidifier.

Wayne