> The major energy cost for clothes washing is heating the water. A rooftop solar water heater dramatically reduces energy use, often more than one would get from using the same space to install solar panels.
Most modern washing machine are cold-water only, washing machines with a hot water inlet tend to be prosumer. Same with dishwashers.
OK, that's very interesting. It's not true in the US, never seen a cold only machine.
Wait, are you talking about the machines that have an electric heating element inside the washer? And you can still wash warm and hot cycle, but they don't require a connection to the hot water heater? Or are you talking about machines (which I've never seen but am willing to accept exist in other countries) that actually only offer cold cycle as a washing option?
If we're talking about ones with an internal heating element, those generally use about twice as much energy to operate than ones that rely on a hot water intake. But with the two input machines one has to figure out the energy to heat the water as a separate cost, which is what I was mentioning. Gas heated hot water heater will be more efficient than electric heated, and solar heated will be most efficient of all.
> Wait, are you talking about the machines that have an electric heating element inside the washer? And you can still wash warm and hot cycle, but they don't require a connection to the hot water heater? Or are you talking about machines (which I've never seen but am willing to accept exist in other countries) that actually only offer cold cycle as a washing option?
The former. I don't think I've seen a consumer-grade dual-intake washing machine in 10+ years.
OTOH Japan might actually have the second, I dimly recall my sister mentioning something along those lines.
Most modern washing machine are cold-water only, washing machines with a hot water inlet tend to be prosumer. Same with dishwashers.