My AC unit used to pump its condenser water right into my laundry sink. All I needed to do to access this water was to put the end of the tube into a jug. Any overflow would just go down the drain.
However, we ended up moving our HVAC equipment into the attic. Now the condenser water is piped into the house drain. This means that I will need to purchase distilled water on an ongoing basis. On a hot day the plants go through almost a gallon of water, which starts to add up at over $1 per gallon.
One of my local markets has a reverse-osmosis water vending machine, so I will probably start using that in September and October (our hottest months here in the SF Bay Area).