Does variation in household vulnerability influence the effects of switching to new energy-efficient electrical appliances in the home? Using the Australian Capital Territory (ACT) Energy Efficiency Improvement Scheme (EEIS) as a case study, this paper examines impacts on energy consumption and greenhouse gas emissions from replacing natural gas heaters and hot water systems with more energy-efficient electric alternatives. To do so we use quarterly billing data over 2015–2020 for a sample of residential customers of the ACT’s largest energy retailer, ActewAGL. Based on fixed effects panel regressions, we find that the electric replacements led to large decreases in residential natural gas consumption and smaller increases in consumption of electricity from the grid in energy content terms. Reductions in natural gas use from switching to electric hot water heaters were particularly large for the more vulnerable households in the scheme. The emissions effects depend on the emissions factor applied for grid electricity and underline the key role that residential electrification can play in decarbonization efforts if electricity is from low-emission sources.