Instantaneous HWS in a new house - gas or electrical?

Do people have experience with insta electrical HWS? Thinking to ditch gas completely in the new house, since we prefer electrical cooking appliances and are planning on solar with battery in the future. Don't want to have a water tank either on the roof with solar, or next to the house. So considering insta electrical system, but don't seem to find many choices.

Is it something anyone can comment on, whether they are powerful enough and what's the electricity consumption/cost like? Any products to consider?

They use a lot of power. You also use most of your hot water when the sun isn't up so unless you have a battery, solar isn't much help for instantaneous.
Is there nowhere you can put a tank? If you can, get yourself a Sanden heat pump hot water unit. Extremely efficient and can be set to heat during times of sufficient solar output. The tank can also be installed separate to the heat pump if necessary i.e. in a garage or cupboard.

It's a small lot and we're building the house to the minimum allowed setbacks so would rather not have anything that takes more space. The set backs on the sides/back vary between 1.3m and 1.8m.

I'm not a fan of having HWS with tanks, would rather go insta gas if insta electricity turns out to be too expensive. Also reading up on various sites it seems that insta electric HWS ends up being cheaper than tank ones on a normal tariff. Wondering if that's true, or just marketing.

We are considering batteries, but probably not straight away.

I had insta gas at an old rental. That wasn't exactly cheap to run either.
I guess it's one of those things where you'll need to compromise somewhere.
Heat pump: extremely efficient but takes up space.
Instantaneous gas or electric element: takes up much less space but costs much more to run.

I suppose it depends on the perception of what's 'cheap'. Currently, our gas bill for insta HWS comes between 200 and 250 per quarter. Out of which 108 is the supply charge, which we can't do anything about while we continue using gas. So if we continue to pay the same for electric insta, at the very least this would remove the fixed component of our bill that we can't do anything about no matter how much we try and reduce our consumption.

You can only use gas (instantaneous or storage) or Solar on a new house unless it is a 1 bedroom house (apartments are in the same boat as a 1 bedroom house) then you can use an electric storage system. There maybe a state exemption but you would have to suss it out, you can download the national plumbing and building code from the abcb (Australian Building Code Board) and that will have what you can and can't use for water heating.

Similar with us, but we're building and not having gas at all. Our options were heatpump or instant electric. Our builder preferrs the instant electric. It seems it may cost more in terms of electricity usage, but it seems like the longevity and reliability of heat pump hot water is questionable.
Installed costs $4000 vs $1500, with life expecancy of 5-10 year for heatpump, and 10+ with instant. Not sure if there'd be much different over the lifetime of either.
We're in Canberra, so the efficiency of heatpumps seems pretty poor with our cold winters. But Im still not 100% convineced and comfortable with the desision.

We're building a new house too. Which brand/model did you go with? Also where are you installing it? I was thinking to put it internally, on the wall above the toilet so it's out of sight and close to the taps, but yet to talk to builder.

Thanks for raising this point. Is that phase out still a thing? I can't find any recent information on it, and it seems that a lot has changed since 2010. Also most info I've found was talking about electric storage tank type, not the insta.

If you have space under your basin/sink then May be you can have a look into these - https://www.bunnings.com.au/brands/s/stiebel-eltron

Yep, that's the brand I currently have in mind, but a different model:

https://www.appliancesonline.com.au/pro ... -del27plus

I was thinking of having one of them in each bathroom above the toilet, so each powers a bathroom and either kitchen or laundry.

How are you going to install it ? On the wall ? I think this would require the plumbing connections and if its already built house then you may need to find the connections. I would be keen to understand the install as I may also look into something similar down the track.

Keep in mind that's a 40A 3 phase unit.
Very convenient but will suck a lot of power.

yeah on the wall. this isn't a replacement for existing gas system. we are building new house to fix all the things we don't like in the current one, so it would be all done during construction.

Attached is a snippet of our draft floor plan with the areas that will need hot water. So the units will be on the toilet back wall.

Do you really want it on display in the house? You could mount it in the garage or within one of the linen cupboards in the house.

That's one of the things i'm trying to figure out. I would expect the electricity consumption to be a product of temperature delta between temperature of cold water and 50 degrees (or whatever we set the unit to), and the flow rate at any given moment. So 40A would be the maximum when we have all the hot water taps running open. But if someone just opens one tap to brush teeth - that should consume way less power. The single phase unit would consume the same amount of power to heat the same water to the same temperature, wouldn't it? Or is my understanding incorrect?

Yes that's correct single phase and 3 phase will still consume the same if they have the same rated output. I only mentioned it as it's the one you linked.
Unfortunately with a heating element attempting to instantly heat water to a certain setpoint, there's no way around the power consumption. It's definitely not a deal breaker just something to consider.

the only time i will be looking at it is when standing in front of the loo
i'd rather not use up storage space for these.

also one of the current problems we have is that we got a large two story house and you have to run water for a good minute or two in winter before it gets warm. hence wanting to mount these as close to the point of consumption as possible.

Fair enough. If you still have a few areas in need of hot water that's are spaced further apart take a look at a hot water recirculation system.

It’s a shame you can’t do electric storage to use excess solar when you get it. This is my production and usage for last week with 250L tank from 1995 with a 9kw system. Element is 2.4kW on timer. I have installed a steibel eltron, found it very good, need 3 phase and issues running tap slow so hot water can cut in and out. Sometimes you need to open the hot water tap more to cool it down, paradoxically. I prefer storage types.