Good advice BC. My comment is a little off topic but related to mixers generally. I'm doing all I can to utilise sustainable options for a lot of things in my new house and was surprised to read on a govt power info page that mixer taps use more power than just about anything else! When I thought about it I realise I turn the taps on and take what I need, before it heats up if it's in that position, rather than ensure it's always on cold to start. The stop start of the HWS gets a workout here I know and I don't think we're the only household guilty of that. The website didn't recommend them. I've now changed my mind about a mixers for the new house and going back to hot and cold taps. Who knew :-0

We installed a Zip system during our kitchen renovation- the filtered boiling, chilled and soda. We LOVE it! Having the hot water at a moments notice is amazing. Not only do we find we're drinking more tea (great thing for health), but we use it to soak things, heat up cooking quicker, etc. I probably use it 10x a day! We start our day off with hot lemon water w/ apple cider vinegar- it's so nice to have it at our fingertips! I saw the comment about being too hot... the beauty is that you have the chilled water with the push of a button. So I know that I fill my Yeti just under 2/3 with the boiling water and then flip the function and top it off with chilled water. I can drink it instantly. The chilled filtered water is a bit noisy, but in a house with kids, dog, lots of activity... it doesn't bother us. I also saw the comment about filling Britas... with kids that play sports, filling up water bottles constantly is so much easier right from the tap. And they want cold water. They did need to reorganize the plans for the cabinet to make room for it under the sink, but it really wasn't a big deal. I also had to adjust the bubbles to get a higher volume b/c we like our soda water fizzy- it was not difficult. We were avid Soda Stream users... this is SO much easier. We used to plow through Co2 cartridges so fast with the Soda Stream. And then you have to send them back to recycle them. The tech for Zip said we'll probably have to change out the Co2 on this unit once a year. I would say that if you're going to use it- it's definitely worth the money, space and noise.

All comes down to how much you want to spend. All good to go the options as many others have suggested but this while being overwhelmingly a great sustainable option the costs are significant! Unaffordable for many when all they just want is cheap hot water. Gas Instantaneous is still a very cost effective option, easy to install, cheap to run ( at this stage anyway) but locate it as close as possible the preferred hot water tap. Heat Pump HWS are again very efficient but currently are still rather expensive. My electrician friend swears by his Heat Pump... The old school electric HWS is slowly being phased (no pun intended) out as they use a lot of electricity, etc. but many owners will just replace the old one with a new one. Sometimes its the cheapest option although not as sustainable nor as cheap to run. Your budget is the key (to everything) and is just as important as anything else. Get the best that you can afford thats within your budget!

watchedpoppy, here's something about heat pumps designed for cold temperatures. Note, these are reverse cycled air conditioners (air-to-air), not pool heat pumps (air-to-water). I don't know how heat pumps stack up. It's an American site, so FYI -13F equals -25C. http://www.mitsubishicomfort.com/benefits/hyper-heating On a side note, temperature is just the product of the motion of atoms & molecules (kinetic energy). These are in motion all the way down to zero Kelvin (-273C). So although it may feel cold outside, there's still energy available in the site, although heat pumps do become much less efficient when it's cold (the difference in input & output temperatures is important). One thing that has made heat pumps very inefficient in the past is that the condensing coil would ice up at around zero C. This would have to be thawed out with a plain old electric element (COP of 1). Greatly reducing the overall COP in temperatures around our below zero C. But the modern heat pumps, which use the CO2 compressors Luxury Home Heating has talked about don't have an electric element to thaw them out, greatly increasing their efficiency. As for the noise issues. Some modern heat pumps (but not all) are very quiet. So just pay close attention to the decibels they produce, listed on their spec sheets. FYI, here's a good read. Though it doesn't mention solar PV, which would be advantageous for a heat pump. https://www.pooledenergy.com/blog/choosing-a-pool-heater-what-are-the-relative-performances-of-solar-gas-electric-pool-heaters/