Watermelons are huge, cheap, and contain a lot of water. The edible part is about 92% water. I wanted to find out whether water from watermelons is cheaper than bottled water at the supermarket.
I compared prices with other beverages, each is the cheapest in its category. Because prices change all the time, these numbers should be taken with a grain of salt:
| Item | Price per litre (AUD) |
|---|---|
| Home Brand Cordial (diluted 1:4 with free water) | 0.23 |
| Water | 0.46 |
| Cheap soft drink | 0.63 |
| Milk | 0.89 |
| Watermelon Juice | 1.05 |
| Tropical Juice | 1.90 |
| Lipton Iced Tea | 2.57 |
So it’s settled. You wouldn’t save anything juicing watermelons unless you usually buy natural juice, which it turns out quite pricy!
This is how I got the price of a litre of watermelon water:
Water is 997.1kg/m3 (0.9971g/mL) at 25°C 1000mL * 0.9971g/mL = 997.1g water 997.1g / 91.45% = 1090g watermelon 1.090kg * 96c/kg = 1.05c/L for watermelon water.
This is not science: I ignored the watermelon rind, and the 6.2g / 100g of sugars which would be dissolved in the water. If anybody juices a watermelon in a lab then I will revise these numbers.