The speed at which many energy efficient technologies have been adopted has been very slow and the reasons why this is the case are often not well understood. An important area for New Zealand is domestic hot water which typically accounts for one-third of a household's electricity usage. We use in-depth interviews to examine the decision processes of six householders who were replacing existing hot water systems or building new homes. We also interviewed different trades people and professionals advising those households. Seven themes emerge from the interviews which demonstrate huge inertia to change. Using methods from decision sciences we also construct an information processing model describing the possible steps in the adoption decision. This model emphasises the complexity and difficulty a householder currently faces if they wish to pursue an alternative system for heating hot water. (C) 2012 Elsevier Ltd. All rights reserved.