Christian charity Housing Justice Cymru found churches in the Caerphilly, Newport and Swansea areas served the destitute at 20 different centres across the period, amounting to that time.
Given that its figures do not include Cardiff where rough sleeping is highest, as well as other parts of Wales, the 18,000 hours is just a snapshot of what Welsh churches are doing for people who don't have anywhere to live.
The figures come ahead of a roadshow starting in Wrexham on April 27th which will help churches understand how they can help the homeless more.
Housing Justice Cymru has been working with the Church in Wales over the last three years to turn surplus land into affordable homes, with 30 being delivered so far. It has also helped train and set up support for 70 night shelters across England and Wales.
Bishop of St Asaph, Rt Rev Gregory Cameron, said: "Hospitality and hope are important parts of the Christian faith.
"Homelessness is not a problem that effects individuals, it effects communities and society more widely.
"It is something that can really only be addressed through all of the community acting together to tackle the causes of homelessness."
