This seems to be a big question on peoples minds: How much does it cost to make ice in your freezer for a Homemade Air Conditioner versus using a store-bought A/C?
A straightforward calculation will answer this:
Consider a small air conditioner rated at 600 Watts running for, say, 5 hours (tops) on a hot day. At 15 cents/kWh this amounts to a cost of 45 cents for 5 hours of use (0.6 kW x 5 hours x 15 cents/kWh = 45 cents).
Now, how much ice can you make in your freezer using 45 cents worth of electricity? And how long will that amount of ice last you if you are using a homemade A/C?
From before, 45 cents of electricity is equivalent to 0.6 kW x 5 hours = 3 kWh.
Now, large energy efficient ice makers (used in restaurants, hospitals, hotels, stores, etc) use 4.7 – 5.8 kWh to make 100 pounds of ice. Let’s round this up to 6 kWh/100 lb of ice (ref: http://www.mge.com/business/saving/madison/PA_31.html).
Modern energy efficient freezers used in the home would usually be smaller and less efficient, requiring maybe 16 kWh/100 lb of ice. They are much less efficient than ice-makers because (by design) they are not capable of making nearly as much ice at one time. If you want to make ice efficiently, make a lot of it using an ice-maker. An ice-maker can typically make hundreds of pounds of ice within a 24 hour period.
It follows that the same energy required to power a 600 W store-bought A/C for 5 hours (3 kWh) would produce 50 pounds of ice using a large scale ice-maker (costing 45 cents of electricity). Now, a smaller freezer in the home might make 3/16 x 100 = 19 pounds of ice with the same 3 kWh (45 cents of electricity). But in both cases this is enough ice to last for at least a few days. You just fill up your (homemade A/C) container with ice, add cold tap water and you’re good for a few hours. You won’t even have to add ice on a regular basis if you fill up the container enough at the onset.
Furthermore, you can make ice at night time, when electrical demand is lowest. This helps reduce power consumption during the day, since you don’t have to run an air conditioner. If enough people do this it will significantly cut peak energy use during the summer months, helping to reduce grid capacity requirements. And if you’re using a smart meter, you can significantly reduce electricity cost as well, given that electricity use is less expensive at night time than during the day, due to lower demand.
Alternatively you can:
• Use cold tap water (12-15 degrees Celsius works fine).
• Make a bunch of ice outdoors in the winter (I made around 80 lb) and store it in the freezer for use in the summer. Just make sure it’s -18 degrees Celsius, or colder, outside, which is freezer temperature. It’s actually good to have a freezer full of ice anyway. It runs more efficiently because it uses less energy to maintain internal temperature when you open and close it.