This article explores the efforts of an indigenous non-governmental organisation (NGO) to solve two related problems in San Miguel Totonicapán: the lack of clean drinking water and deforestation. Drawing on participant observation conducted during field stays over 10 years and survey data collected over 18 months, the article examines the affordability of bio-sand drinking water filters and high-efficiency wood cooking stoves. It considers whether savings over typical current practices for the procurement of drinking water and cooking fuel off set the purchase price of new sustainable technologies. The article also outlines data-driven recommendations offered to the NGO. While there are significant obstacles to market distribution, the acquisition of a bio-sand water filter or an improved wood stove makes good economic sense for households that presently purchase drinking water or firewood.