Room nights are not guest nights
An occupied room night means one room occupied for one night. Two guests sharing a room create one room night but two guest nights. For apartments, define whether you count the whole unit or individual bedrooms. Keep the definition consistent. Do not automatically include cancelled bookings or nights that were never actually occupied.
Energy per occupied room night = energy consumption in kWh ÷ occupied room nights. Water per guest night = water in m³ × 1,000 ÷ guest nights. Do not interchange occupied and available nights. Occupancy is occupied room nights divided by available room nights, multiplied by 100. Record how out-of-service rooms and closed days are handled.
Worked example: lower consumption, higher occupancy
Fictional learning example, not customer data: Period A uses 12,000 kWh across 600 occupied room nights, or 20 kWh per room night. Period B uses 10,800 kWh across 720 room nights, or 15 kWh per room night. Total consumption falls by 10%, intensity by 25%, while occupied room nights increase by 20%.
Relative change is (new value ÷ old value − 1) × 100. A negative result means a decrease. Percentage change is undefined when the starting value is zero. Intensity cannot be calculated with zero occupied nights either. These cases should be shown as not calculable, rather than as an apparent one-hundred-percent saving.
At the original intensity, 720 × 20 would equal 14,400 kWh. Compared with the actual 10,800 kWh, the arithmetic difference is 3,600 kWh. This is a comparison scenario, not a measured or causally demonstrated saving. Weather, base load, opening hours and other changes may explain the difference.
Comparability: five questions before judging a result
First, do meters and occupancy data cover the same buildings? Second, are periods equally long and seasonally comparable? Third, were a restaurant, spa, apartments or charging points added? Fourth, are bills based on readings or estimates? Fifth, did the weather change substantially? Record the answers with the analysis so that someone else can understand the comparison.
A hotel consumes energy while empty, for basic operations and necessary building functions. Higher occupancy spreads this base load across more room nights. Intensity can therefore fall without any technical improvement. Conversely, closure can reduce total consumption while increasing consumption per occupied night. More detailed analysis can use suitable weather data and justified adjustment methods. The simple calculator deliberately does not adjust for weather.
A manageable set of E, S and G indicators
For Environment, useful measures include total kWh and kWh per occupied room night, litres of water per guest night, laundry weight per stay and waste weight by stream. For Social, consider training hours per employee, reported workload problems and response times for individual guest needs. Governance measures can include reviewed user accounts, reconciled cash closes and documented actions with named owners. These management suggestions are not a complete reporting standard.
Begin with three to five indicators that genuinely influence a decision. Each needs a definition, unit, source, collection frequency, owner and target. Mark missing values clearly and keep estimates identifiable. A temperature-setting change without meter data is an implemented action, not yet a demonstrated consumption result. Similarly, a faster process is not automatically a better working condition.
Keep consumption, costs and emissions separate
A lower energy bill may result from a cheaper tariff. Less electricity use can coincide with higher costs. Use kWh for technical comparisons and show cost separately. Emissions calculations require suitable factors for the relevant time and location, plus a documented inventory boundary. Applying one generic factor to every energy source can mislead.
Consumption multiplied by an emissions factor is meaningful only with explained units and assumptions. Separate electricity, gas and district heating, and record the source of each factor. This calculator does not produce a carbon footprint or calculate offsets. Formal reporting or public climate claims require an appropriate methodology and further review.