Objective: The aim of the present study was to quantify hospital steam steriliser resource consumption to provide baseline environmental data and identify possible efficiency gains. We sought to find the amount of steriliser electricity and water used for active cycles and for idling (standby), and the relationship between the electricity and water consumption and the mass and type of items sterilised. Methods: We logged a hospital steam steriliser’s electricity and water meters every 5 min for up to 1 year. We obtained details of all active cycles (standard 134°C and accessory or ‘test’ cycles), recording item masses and types. Relationships were investigated for both the weight and type of items sterilised with electricity and water consumption. Results: Over 304 days there were 2173 active cycles, including 1343 standard 134°C cycles that had an average load mass of 21.2 kg, with 32% of cycles <15 kg. Electricity used for active cycles was 32 652 kWh (60% of total), whereas the water used was 1 243 495 L (79%). Standby used 21 457 kWh (40%) electricity and 329 200 L (21%) water. Total electricity and water consumption per mass sterilised was 1.9 kWh kg–1 and 58 L kg–1, respectively. The linear regression model predicting electricity use was: kWh = 15.7+ 0.14 × mass (in kg; R2 = 0.58, P < 0.01). Models for water and item type were poor. Electricity and water use fell from 3 kWh kg–1 and 200 L kg–1, respectively, for 5-kg loads to 0.5 kWh kg–1 and 20 L kg–1, respectively, for 40-kg loads. Conclusions: Considerable electricity and water use occurred during standby, load mass was only moderately predictive of electricity consumption and light loads were common yet inefficient. The findings of the present study are a baseline for steam sterilisation’s environmental footprint and identify areas to improve efficiencies. What is known about the topic?: There is increasing interest in the environmental effects of healthcare. Life cycle assessment (‘cradle to grave’) provides a scientific method of analysing environmental effects. Although data of the effects of steam sterilisation are integral to the life cycles of reusable items and procedures using such items, there are few data available. Further, there is scant information regarding the efficiency of the long-term in-hospital use of sterilisers. What does this paper add?: We quantified, for the first time, long-term electricity and water use of a hospital steam steriliser. We provide useful input data for future life cycle assessments of all reusable, steam-sterilised equipment. Further, we identified opportunities for improved steriliser efficiencies, including rotating off idle sterilisers and reducing the number of light steriliser loads. Finally, others could use our methods to examine steam sterilisers and many other energy-intensive items of hospital equipment. What are the implications for practitioners?: We provide useful input data for all researchers examining the environmental footprint of reusable hospital equipment and procedures using such equipment. As a result of the present study, staff in the hospital sterile supply department have reduced steam steriliser electricity and water use considerably without impeding sterilisation throughput (and reduced time inefficiencies). Many other hospitals could benefit from similar methods to improve steam steriliser and other hospital equipment efficiencies.