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Comment by londons_explore | Hacker News Reader

Dishwashers aren't very solar-friendly if you don't have net-metering.

They typically have a very powerful 2.5 kilowatt heater they run in bursts - for like 5 mins when prewashing, for like 10 mins when starting the main wash, and like 10 mins again when drying.

In between those times, the machine uses only ~60 watts for pumps.

I have often pondered what a world of machines designed to meet solar output looked like - and for a dishwasher it would involve the heater being modulated to match the solar output (and knowing that sometimes the wash cycle would take longer if a cloud was overhead so heating was delayed by a half hour).

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Just have more dishwashers, and use them as storage cabinets: pick from a clean cabinet if you need tableware, deposit in a dirty cabinet when you are done and if you have at least three of them the transition is free to take a lot of time.

That sort of thing seems solvable with batteries used as a a capacitor, rather than trying to reprogram the dishwasher logic

I guess you could also use a small battery to help smooth things out.

The money efficiency isn't great - if you had control of the design of the dishwasher, simply having a hot block of concrete inside that you heated when there was spare energy would work out far cheaper.

Concrete costs far fewer $$$'s than batteries do, per kwh of heat stored, it also doesn't require inverters, balancing or safety systems, ad lasts millions of cycles rather than thousands.

How expensive would it be, transportation included, compared to an insulated water container of comparable heat capacity?

Or maybe store hot water and heat it up at the best time...?

The water is too hot to store safely.

You can still slowly heat it up to 70 or 80°C and just add some extra heat on use, but that will still leave a lot of immediate power to deal with.

I can't imagine a scenario where you've got a large enough solar system that you'd want to be running a dishwasher off it, and you don't already have some battery storage elsewhere in that system.

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However, since my array is currently 4.4kw at 3 in the afternoon, a 2.5kw burst isn't a problem.

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