Objectives: A fifth of UK households live in fuel poverty, with significant health risks. Recent government strategy integrates public health with local government. This study examined barriers to switching energy tariffs and the impact of an energy tariff switching `intervention' on vulnerable peoples' likelihood to, success in, switching tariffs. Study design: Participatory Action Research (PAR), conducted in West London. Methods: Community researchers from three voluntary/community organisations (VCOs) collaborated in recruitment, study design, data collection and analysis. VCOs recruited 151 participants from existing service users in three groups: Black and Minority Ethnic (BME) communities, older people (> 75 yrs) and families with young children. Researchers conducted two semi-structured interviews with each participant, a week apart. The first interview asked about demographics, current energy supplier, financial situation, previous experience of tariff-switching and barriers to switching. Researchers then provided the `intervention' e advice on tariff-switching, printed materials, access to websites. The second interview explored usefulness of the `intervention', other information used, remaining barriers and information needs. Researchers kept case notes and a reflective log. Data was analysed thematically and collaboratively between the research coordinator and researchers. Quantitative data was analysed using SPSS, with descriptive statistics and Chi-squared tests. A total of 151 people were interviewed: 47 older people over 75 years, 51 families with young children, 51 BME (two were missing demographics). Results: The majority were not White British or UK-born. Average household weekly income was 230 pound. Around half described `difficult' financial situations, 94% were receiving state benefits and 62% were in debt. Less than a third had tried to find a better energy deal; knowledge was the main barrier. After the intervention 19 people tried to switch, 13 did. Young families were most likely to switch, older people least. The main reasons for notswitching were apathy (`can't be bothered'), lack of time, fear or scepticism and loyalty. Older people were particularly affected by apathy and scepticism. The personalized advice and help with websites was especially valued. Conclusions: Low-income consumers appear to have considerable apathy to switching energy tariffs, despite potential savings and health benefits, in part due to their complex lives in which switching is not a priority. An independent, one-on-one, personalized `intervention' encouraged switching, particularly for young families. However, older people still experience significant barriers to switching with specific interventions needed, which take account of their status quo bias, energy use habits and scepticism. The recent integration of public health and local government in the UK may provide the ideal environment for providing similar services which are desperately needed to reduce fuel poverty in these groups in line with the new Public Health Strategy. (C) 2013 The Royal Society for Public Health. Published by Elsevier Ltd. All rights reserved.