To compare an ice machine with purchased ice, define the usable quantity and service over the same period. Base each cost item on an invoice, meter record or written quote.
Calculate the full cost of purchased ice
Add delivery invoices, transport or minimum-order charges and storage costs. If you can weigh ice left unused, record it separately; do not assume a melt quantity without observation. Check dispatch records for delivery times and stockout days.
For a machine, calculate installation and financing along with electricity and water from meter readings or manufacturer data, and service from quotes. Check whether capacity covers demand using shift and peak-day records; rated output does not mean the same amount of ice under all conditions.
Divide by an equal quantity and period
Choose a period in which both methods provide the same usable ice quantity. Divide total operating cost by that quantity and calculate peak and quiet periods separately. Confirm ice type, water quality and food-use suitability against manufacturer instructions and the operating process. Recalculate when tariffs or supplier terms change.