You might have an window air conditioner or dehumidifier. Both result in the condensation of moisture from the environment into water that is collected. That water can be seen leaking down the side of buildings under these units.
Might as well make use of this natural resource. Have the excess run off go into a planter. This creates an automatic plant watering system. Easy to setup, no water lines need to be run to your plant, hang the planter below and near the unit and redirect the water to the plant.
The extra heat generated by the exhaust and reflective heat from the unit might help some plants, tomatoes for example, grow even better.
