Power consumption varies considerably between device types. The most energy-intensive device (Primus) consumed 134% more than the least energy-intensive device (Care Station 750) during operation. A common feature of all devices is the high power consumption during standby, 88–93% of the power needed during operation. This high percentage reveals potential to save electricity, GHG emissions and cost by switching devices off instead of leaving them on standby wherever feasible. In our hospital, between 8.5 and 19.8 tons of CO2-equivalent and between 4974 € and 11,606 € could be saved annually by avoiding standby during off hours in 80% of the anesthesia workstations. Electricity costs for the operation of one anesthesia workstation amount to 118 € to 273 € per year. The CO2-equivalent emitted per year ranges from 201 kg to 466 kg per device.
Our study confirmed previous analyzes demonstrating that scope 2 emissions from electricity consumption of medical devices represent only a small part of the total GHG emissions generated by anesthesia and surgery [
3,
4,
20]. Especially with desflurane, scope 1 emissions from volatile anesthetics or nitrous oxide constitute the main share of GHG emissions from anesthesia [
4,
7]. Scope 2 emissions in anesthesia and surgery are much more heterogeneous than scope 1 emissions. A considerable percentage of scope 2 emissions originate from infrastructural characteristics of operating theaters (e.g., heating, ventilation, lighting) and are used for anesthesia and surgery, whereas scope 1 emissions apply to anesthesia alone. In this analysis, we chose to investigate an item of scope 2 emissions that can be controlled by anesthesiologists themselves without external influences. As described above, the absolute electricity consumption of anesthesia workstations is modest compared with other sources of scope 2 emissions [
3,
20]; however, it is noteworthy that the power consumption in standby mode is approximately 90% of that during an operation. As it appears to be common practice in many hospitals to leave machines on standby during prolonged times, if not constantly, this gives a leverage point to reduce electricity consumption and thereby to reduce GHG emissions and cost by simple behavioral changes. If approximately 80% (76/96) of the machines in our hospital were switched off instead of being left on standby during off hours, between 8.4 and 19.5 tons CO
2-equivalent could be saved annually at the current emission factor. The carbon footprint of this intervention largely depends on the emission factor of the respective hospital. The emission factor largely depends on the sources of energy used for the generation of electricity. With the average emission factor in Sweden, the lowest in the European Union due to a high share of renewables and nuclear energy, the same power saving would result in a reduction of emissions of 0.14 to 0.32 tons, whereas with the average emission factor in Poland, the highest in the European Union due to a high percentage of coal combustion to generate electricity, it would imply a reduction of 13.2 tons to 30.9 tons. At the average emission factor in Germany, emissions could be reduced by 7.3 tons to 17.0 tons. Considering that the annual CO
2-emissions per capita are 8.1 tons in Germany [
21], the potential savings by avoiding standby in our hospital equals the emissions of one or two citizens in Germany. Compared with the impact of volatile anesthetics, which can create more than 1000 tons CO
2-equivalent per year in a large hospital [
3], this is a small potential for CO
2 reductions. Interventions targeting at reducing the consumption of volatile anesthetics carry a much higher potential for reduction of GHG emissions: A recent study calculated a potential of a reduction of 1.8 kg CO
2-equivalent (global warming potential 20 years, GWP
20) due to saving of sevoflurane during a 45min case if modern anesthesia workstations were used most efficiently [
9]. A clinical decision support tool aiding anesthesiologists to use volatile anesthetics more efficiently led to a saving of 4.1 ml desflurane or 3.8 ml per MAC‑h sevoflurane [
22]. Depending on the estimation of the relative GWP of volatile anesthetics, this amounts to a reduction in CO
2-equivalent (GWP
20) of 22 kg to 41 kg for desflurane and 2.0 kg to 4.6 kg for sevoflurane [
23‐
26]. Avoiding standby and switching the device off instead only leads to a reduction of emissions of less than 0.1 kg CO
2-equivalent for one anesthesia workstation per hour even at a high emission factor. Hence, the impact of saving electricity by switching off medical devices is smaller than the impact of reducing the consumption of volatile anesthetics. Also compared with other electricity consumers in the operating room, such as forced air warming blanket devices or anesthetic gas scavenging systems [
27], the saving potential appears modest; however, this easily feasible measure to reduce emissions should not be left unused.
The electricity costs of anesthesia workstations are between 118 € and 273 € per device per year for 2527 h of operation and standby mode during the remaining 6233 h. For the 96 devices in our department, this amounts to 11,296–26,199 € per year, provided that the relatively low price for commercial consumers remains. By avoiding standby in 80% of all devices during off hours, approximately 40–45%, or 5000–11,000€ of electricity costs could be saved annually. In the light of the total budget of a large clinical department, the financial savings that could be reached by this intervention are humble but easily achievable. From a merely economical perspective, different electricity consumption does not seem to play a major role in considerations of different types of anesthesia workstations.