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Lots of good discussions about water heating in this thread. But it's such a tricky topic. Tankless water heaters are pretty efficient, but when you need hot w
by elric 5y ago
Lots of good discussions about water heating in this thread. But it's such a tricky topic.
Tankless water heaters are pretty efficient, but when you need hot water, you briefly use huge amounts of energy. It's for this reason that they almost always use natural gas. Electric tankless heaters are a great way to cause brownouts. They're roughly the size of a microwave oven, so they can fit in pretty much any kind of dwelling.
Water heaters with tanks, on the other hand, take up huge amounts of space and require frequent (but lower) energy input. This can use heat from a variety of sources, including low quality/unrealiable heat sources like solar heat pipes.
Then there's space heating. Unless you live in a Passivhaus, keeping a comfortable indoor temperature is challenging. Central heating using hot water and radiators is the most common approach where I live. But this again relies on burning hydrocarbons. Or, increasingly, on heat pumps, which require a lot of space, are noisy, and drop in efficiency as the temperature drops.
As far as I can tell, there are no silver bullets in either space heating or water heating. If you have a really big house, a big tank is probably a good solution for hot water. But living in a really big house is horribly inefficient in its own way. So I'm guessing that's not the greener approach. Living in a smaller dwelling is more efficient. But it seems there are basically zero good ways to heat small living spaces and hot water for a family of 1-2 living in small houses.
- devwastaken 5y agoTankless are also useless if you don't have perfect water, and even if you do you have to descale them every year. The calcium, iron, and others in your water builds up in the small copper pipes, and an acidic cleaner is required to remove it. If youve ever used a Keurig it's similar. Propane water tanks are pretty bulletproof. Even with bad water they just truck, and require no electricity to operate, unlike some other gas appliances.
- dvdkhlng 5y agoWhere I live, tankless heaters are pretty wide-spread. They connect to 3-phase power supply, heating at a variable power level up to 24 kW [1]. They need almost no maintenance, nobody I know has ever descaled one. I think the better units directly run the heating wires through the water, so they do not calcify due to small surface area (or maybe the huge temperature gradient when operated breaks the calcification layer). Usually you operate them until they break (maybe around 10 years), then get a replacement heater for like 400 €. [1] https://www.stiebel-eltron.co.uk/en/products-solutions/dhw/instantaneous_waterheater/convenience_instantaneouswaterheater/dhb-e_lcd/dhb-e_18_21_24_lcdset.html https://www.stiebel-eltron.co.uk/en/products-solutions/dhw/i...
- elric 5y agoHere in Belgium, electricity metering is switching from merely "kWh/year" to peak power draw (kW). Running a heater at 24kW will become very expensive.
- devwastaken 5y agoIs that on well water or city water? In the country in the U.S. every body has individual wells, which comes with a lot of iron and calcium.
- thehappypm 5y agoHeat pumps are not noisy, though. Mine are completely silent.