The plate figure is a laboratory number
Ratings are taken at stated air and water temperatures, and those are usually a good deal kinder than a working kitchen. The defaults here take a 500 lb machine rated at 70 °F air and 50 °F water and put it at 90 °F air and 70 °F water: 20 degrees over on both. At 45 lb per 10 °F of air and 20 lb per 10 °F of water that is 90 plus 40, so 130 lb gone and 370 lb a day left — 74 percent of the plate.
None of those slopes come from this page. They come from two rows of the capacity table in your own manual, subtracted and divided by the step between them, which takes about a minute with the book open.
Air is usually the bigger half
On most air cooled machines the air slope is roughly double the water slope, which is why where the machine sits matters more than what feeds it. On the defaults, one degree of air temperature is 4.5 lb a day. Ducting condenser air out of a hot corner, or simply moving the machine away from the cook line, is often worth more than anything done to the plumbing.
Water cooled machines shift that balance and bring a large water bill with them, which is what the water per 100 lb field is for.
The bin is the thing that saves you
Production is a daily average and demand is not. What gets you through a busy Saturday is the bin filling overnight while nothing is being drawn. On the defaults, 370 lb a day is 15.4 lb an hour, so ten quiet hours makes 154 lb — the 350 lb bin does not refill from empty overnight, and a 450 lb peak day pulls 80 lb out of whatever was banked.
That is the calculation worth doing before buying: not whether production covers the average, which it usually does, but whether production plus the bank covers two heavy days in a row.
Where this stops
The slopes are straight lines through a curve, and the curve steepens as the room gets hotter, so take the two table rows either side of your actual conditions rather than the ends of the table. Energy per 100 lb also degrades with air temperature and the page holds it fixed, so the running cost is the optimistic end in a hot room. And nothing here is a sanitation, water treatment or food safety figure — those come from the manufacturer instructions and your health department.
Questions people ask
Why does my ice machine make less than the rating?
Because the rating was taken at stated air and water temperatures and your kitchen is warmer on both. On the defaults, a 500 lb machine rated at 70 °F air and 50 °F water, running at 90 °F and 70 °F, makes 370 lb a day. The two slopes that produce that come off the capacity table in your own manual.
How do I get the derate slopes for my machine?
Open the capacity table in the manual, take two rows a known number of degrees apart, subtract the production figures and divide by the step. Do it once down the air temperature column and once down the water column. That is all this page needs, and it is why the page carries no capacity data of its own.
Does air temperature or water temperature matter more?
Usually air, by roughly two to one on an air cooled machine. On the defaults each degree of air costs 4.5 lb a day against 2 lb for water. Moving the machine out of a hot corner or ducting the condenser air is normally the cheaper lever.
How long does an ice bin take to fill?
Production divided into bin capacity. At 370 lb a day the machine makes 15.4 lb an hour, so a 350 lb bin takes 22 hours and 42 minutes from empty. That is longer than most overnight windows, which is exactly why running the bin down on a busy day matters.
How much does ice cost to make?
On the defaults, 20 gal of water at 12 dollars per 1,000 gal is 24 cents per 100 lb, and 6 kWh at 15 cents is 90 cents, so 1.14 dollars per 100 lb. At 300 lb a day that is 3.42 dollars a day. Energy per 100 lb gets worse in a hot room and this page holds it at the figure you entered, so treat that as the low end.