Voucher-based liquefied petroleum gas subsidies achieve nearly exclusive clean fuel use when affordable delivery is available

Introduction: Fuel subsidization can promote clean fuel adoption and reduce household air pollution. We investigated whether a voucher-based system could be as effective as a home-based fuel delivery program in achieving exclusive use of liquefied petroleum gas (LPG) within a randomized controlled trial in Puno, Peru. Methods: In the first year of the trial, we delivered unlimited LPG to intervention homes, while comparison group participants continued baseline cooking practices. In the second year, comparison group participants received vouchers covering the cost of two 10 kg LPG tanks per month but did not receive tank delivery. We assessed voucher use and compared LPG use between the voucher and home delivery schemes. We conducted qualitative interviews with 15 women to understand perceptions and use of the vouchers and LPG. Data were collected in 2020 but remain relevant given the unchanged LPG system in Peru. Results: Voucher use was high (97.6 % of vouchers were used). Participants receiving vouchers used LPG for 94.3 % of cooking minutes, which was only slightly lower than the percent of cooking done with LPG by participants who received free home delivery (98.2 %) (p < 0.001). Voucher participants cooked with biomass for 84.7 min per week, within the range estimated as acceptable for meeting the World Health Organization interim air quality targets (<1–3 h per week). Facilitators of voucher and LPG use included the ease and speed of cooking with gas, availability of LPG delivery in the region, access to several nearby LPG distributors, owning a second back-up LPG tank, and reinforcement of exclusive LPG use by study fieldworkers. Conclusion: A voucher-based system for providing subsidized LPG, paired with a reliable LPG infrastructure and behavioral motivation, effectively achieved near-exclusive clean fuel adoption. Findings can guide the design of LPG subsidization programs, which are increasingly important amid rising global LPG prices.