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Comment by Gibbon1 | Hacker News Reader

This is one of the reasons I believe 'base load' demand is more fungible than people assume.

I think in California 6% of electricity demand is pumping water. I'm almost willing to go on record and say that's the California Aqueduct and the actual number is higher. Okay I'm going to look.

https://www.ppic.org/publication/water-and-energy-in-califor...

> The water system uses approximately 20% of the state’s electricity and 30% of its natural gas for business and home use, according to data from 2001—accounting for more than 5% of California’s greenhouse gas emissions.

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There's been other responses here pointing out that municipal water delivery pumping probably isn't a large electricity consumer, but it's also worth noting that even if it was you can't voluntarily shutdown water-delivery in large distribution systems - you have to maintain pressure and flow to prevent back contamination of the system from leaks. It's why you get boil-water advisories when there's a general outage - because dirt and bacteria can get back into the pipes and it takes time to be sure they've been flushed out of the system.

Did you miss the stat directly underneath that?

> Heating and other energy-intensive water uses in homes and businesses make up almost 90% of water-related energy use, while treatment, pumping, and conveyance of water and wastewater account for the rest.

That's 2% for everything which isn't heating water. Pumping is some smaller fraction of that.

you are right. The thing that is interesting is that pumping loads overall take a lot of the grid's energy, it's just that most pumps are refrigeration loads, not water transport.

Great thing about heating water, is that it stays hot after you’ve heated it.

Water heating is basically the poster child for “demand-response” technologies. You can easily heat your water a few hours earlier than normal with basically no consequences to the user. But you need to get reasonable smart about modelling people water usage, as people don’t tend forget or forgive a cold shower.

What about tankless water heaters? You can eliminate greenhouse gas emissions for heating and be more efficient with energy usage overall.

tankless heaters use slightly less energy, but they use it in a really annoying way. the optimal design for a heavily renewable grid is a heat pump water heater with a tank

The optimal design for a heavily renewable grid is solar water heating a tank in home whenever the sun shines, falling back on a heat pump water heater with a tank.

That's for maximizing energy efficiency. Tankless I think might be a tad bit more easier and cheaper to implement than this.

Regardless the point is eliminating the use of natural gas in heating water is itself a benefit.

That's only optimal if you know you'll need 100% of the heated water (or have a way to store it). While photovoltaics are going to be less efficient than direct water heating, you can direct the energy to other uses if you don't need more hot water.

Large tanks of water are about the cheapest way we know of to store energy. Batteries store more energy, but are extremely expensive.

Yes, but that only matters if we can easily consume that energy. If we need the hot water, then that's easy—no conversion loss. Otherwise, it gets trickier, especially in a small-scale setting like a home.

All homes use at least some hot water for showers. In many climates they can use a lot of energy for heating which means a very large tank could be useful in winter.

I read a study looking at the difference between tankless and tank water heaters.

Summary the more hot water you use the smaller the win is for tankless.

Other thing I've read and seems true is gas and heat pump water heaters cost about the same to run. I installed a heat pump unit five years ago. Works okay for two people. If you had three teenage girls and a wife that likes baths a tankless would be a better choice.

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