Life cycle costs (LCC) calculated using standard databases and first-stage cost estimation methods were used to compare selected tertiary treatment processes used to treat secondary treated municipal wastewater (MWW) for reuse in thermoelectric power plant cooling systems. Use of MWW increases challenges such as scaling, bio-fouling and corrosion. Tertiary treatment coupled with chemical inhibitors can enable use of MWW in cooling systems. To determine LCC for different treatment options, a life cycle conceptual costing (LC3) tool was developed to estimate costs within conceptual accuracy range (15–40%), defined by the International Association for the Advancement of Cost Engineering. LCC estimation showed that treatment alternatives with higher chemical consumption were most expensive. Operational phase of tertiary treatment and use of chemical conditioning agents dominates annual costs. Of various tertiary treatment alternatives evaluated, range of total costs to treat 7.75 million gallon/day (1 gallon = 3.79 L) – amount of water required by a 550 MW thermoelectric power plant recirculating cooling system – was estimated to be $0.91–1.32/kgal (2009 USD) excluding taxes and overhead costs. This range was found to lie between rate charged for river water withdrawal with filtration and chemical conditioning, i.e. an average of $0.74/kgal (2009 USD) for some areas of the USA, and the national average rate for potable city water, i.e. $2.95/kgal (2009 USD).