Unfortunately, most of the cost of water desalination is capital cost. You simply can't afford to build a desal plant and run it only 25% of the time.
Take the Carlsbad plant in San Diego. It cost $1 billion to build, and it produces about 200k tons of fresh water per day. Let's say you build a similar plant and to finance the build you use municipal bonds that have a yield of 3.6% (the current level for 30 year muni bonds). That's 0.30% per month, or 0.01% per day. So only the interest on these bonds is $100k per day, which is 50 cents per ton of fresh water. According to wikipedia, it takes about 0.3 kWh to desalinate 1 ton of water [2]. In my state (NY) the average cost of electricity for industry consumers was about 7 cents for 2023 [3], so that would mean 21 cents per ton of water. If that cost goes to zero, you save 21 cents for each ton of water. But if you reduce the plant utilization from 100% to 25%, you increase the interest cost by 150 cents.
In order for desalination to be a useful target for peak electricity consumption, we need to find ways to massively reduce the capital cost of building desal plants. By "massively", I mean a factor of 10 or more. Is it possible? Yes. Is it guaranteed? No.
Take the Carlsbad plant in San Diego. It cost $1 billion to build, and it produces about 200k tons of fresh water per day. Let's say you build a similar plant and to finance the build you use municipal bonds that have a yield of 3.6% (the current level for 30 year muni bonds). That's 0.30% per month, or 0.01% per day. So only the interest on these bonds is $100k per day, which is 50 cents per ton of fresh water. According to wikipedia, it takes about 0.3 kWh to desalinate 1 ton of water [2]. In my state (NY) the average cost of electricity for industry consumers was about 7 cents for 2023 [3], so that would mean 21 cents per ton of water. If that cost goes to zero, you save 21 cents for each ton of water. But if you reduce the plant utilization from 100% to 25%, you increase the interest cost by 150 cents.
In order for desalination to be a useful target for peak electricity consumption, we need to find ways to massively reduce the capital cost of building desal plants. By "massively", I mean a factor of 10 or more. Is it possible? Yes. Is it guaranteed? No.
[1] https://en.wikipedia.org/wiki/Claude_%22Bud%22_Lewis_Carlsba...
[2] https://en.wikipedia.org/wiki/Desalination
[3] https://www.nyserda.ny.gov/Energy-Prices/Electricity/Monthly...