The inherent waste in household water heating (and, yes, the carbon footprint of flushing an upstairs toilet) are the kind of things that cause me grave concern on a daily basis. Going to the Building Energy conference in Boston helped. Kinda.
The hot water thing: We tend to heat a tank full of it, then spend more carbon-based energy keeping it hot even when nobody needs it. Each time we open a hot water faucet somewhere in the house, we draw that hot water from the tank and into cold pipes. Heat is lost. The farther the water travels through the pipes, the more heat it loses. And after you’ve received your hot water and you shut off the faucet, then all the hot water still in the pipeline slowly sheds its carbon-costly heat and returns to room temperature. *
(You rightly imagine that the hot water pipes in my basement are insulated with foam tubes. I got the tubes at Home Depot on clearance for 1 cent apiece, which spared me a ton of math on the financial arm of the equation.)
The old solution to this soul-killing waste was the “on demand water heater.” Fired by gas or electricity, it replaced the big tank in the basement, and heated water instantly** when you opened the faucet. But the heated water still had to navigate the same old heat-shedding pipes.
So at the trade show I was intrigued by a display of POUETs: Point Of Use Electric Tankless.
These are sized for each faucet, or “point of use.” There’s a tiny one for the powder room sink; a medium one for the kitchen; and a big one for the shower. The size is driven by physics–the faster you ask for water, the faster the element inside the box has to warm it.***
I love this, particularly for remodels or additions on a house. Yes, you’re using electricity to heat water, but you’re wasting approximately none of that energy. For a deeper analysis of the carbonaceous tangents, read this geek’s story of converting his household (and his grumpy family) to POUETs.
My quick recon finds no plug-in versions of POUETs, probably due to the meddling of “life and safety” regulators who will go to any lengths to prevent water and electricity from hanging out together.
Got any experience with these? Is my enthusiasm warranted? Can I stop worrying about this?
*If you recapture that heat to keep your house warm, good on you. But even in the winter, space-heating via pipes buried in walls and basements is a pretty weak method.
**”Instant” is a relative term, according to anyone who ever lived with an on-demand water heater. So is “on demand.”
***Yes, the carbon footprint of these many boxes of electric heating elements is starting to spread a little. It bothers me, too. I suspect “clustered plumbing” is the answer: designing homes where the bathroom backs up to the kitchen backs up to the laundry machine.