This is the question procurement should ask before price, and it is the one most often absent from a quotation.
Start From the Static Rate
Static evaporation rate, also called normal evaporation rate, is given as litres per day or a percentage of capacity per day, measured closed and undisturbed. Multiply by seven for a floor figure. It is the single honest comparator between two vessels, because it is measured the same way for both.
Then Add for the Fact That You Open It
Every lid lift admits warm room air, every retrieval carries heat in, and every warm object introduced has to be cooled at the expense of the liquid. None of that appears in a closed measurement, so real consumption in a working IVF store commonly runs at several multiples of the static rate. That is normal rather than a fault.
Replace the Estimate With Your Own Figure
Log every fill with date, vessel and litres, alongside a daily dipped level taken with a 100 cm dipstick, which needs no power. Within two months you have a litres per week baseline for your own room and workload, and from then on the trend matters more than the number.
