Storage water heater vs instant

I'm confused . storage water heater or instant is better. Thanks.

If you are rarely going to use hot water, then instant is the better option IMO.

If you have a reasonable sized family, then storage would be better.

You then get in to the gas versus electric, and then the heat pump versus the two different types of solar heating, and then what do you boost with.

For me at my place, solar using Evacuated Tubes with electric boosting is the way to go, as gas boosting would become expensive as have LPG cylinders as our gas supply here.

Thanks mate

Why is it better ? particulary when not enough information has been provided by the original poster.

Could ask you the same question, re statement below.



Why do you think storage is better for families? Personally I've had instantaneous since 2000, including with a family and have never had an issue what so ever. There is hot water when we want it, every time and never been unhappy about the cost.

Must admit the only issue is when one of the kids stays in the shower too long. But simple fix is to turn the controller off, they get the hint. Speaking of controller another plus for instant. Set the temp to what I want when having a shower, no mixing in cold.

Okay, since you asked.

Costs of instantaneous can add up fairly quickly, be that gas or electric. as both will continue to rise. Families can show total disregard to the one who pays the bills, and just kick your bills right up.

Obviously in your situation instant works very very well for you.

I was making a comment based upon my own and friends experience with hot water systems, plus what I've heard and read in other forums.

Instant hot water is particulary great in situations such as holiday homes, where there's no need to keep the hot water there all the time.

Must admit first time I've heard of instantaneous running costs being higher.

Look at the attachment in the link that shows consumption of various hot water heaters and lets choose a system for a medium sized family.

Instantaneous (any of the name brands), delivering ~26l per minute uses ~200mj/h only whilst running.

Storage system tank around 300l uses 30mj/h 24 hours a day, so 720mj a day.

So for instantaneous to use 720MJ you would need to run it for 3.6 hours a day. Thats a lot of run time.

http://www.reece.com.au/new/pdf/product ... -guide.pdf

In our previous place we had a gas storage unit (natural gas). We changed it to a new Bosch instantaneous gas unit and our gas bill halved (our hot water was the only gas appliance we had). However, that is for a young professional couple with no kids etc - the dynamic will change depending on use and diversity. Also, our storage unit was getting on to 20 years old. New storage units have much better insulation, therefore less heat loss, therefore less energy use.

Electric instantaneous units are quite efficient, but they draw a very large amount of power for a short amount of time. This often means you may need 2 or 3 phase power to your home, unless you go for small single phase units near each of your bathrooms, kitchen and laundry. This is actually not such a bad idea if you can afford it, because it means you only need to wait a couple of second for hot water as the water doesn't go cold sitting in the pipe (referred to as a "dead leg". Although it would be more expensive to buy several small instant hot water units, some of this cost would be offset because the plumber only needs to run cold water lines through your house, then it's just a short run of hot water line from the hot water unit to the hot tap/fixture. The units themselves are so small they can fit under your vanity and kitchen bench.

The most energy efficienct way to heat water is obviously to use the sun. That is why I have a solar hot water unit now. A solar hot water system will cost you more but the extra cost will eventually turn into savings in energy bills over the life of the system.

I guess that's where part of my storage system 'bias' comes in.

Mine is a Evacuated Tube systems with a 315l storage tank, and so far we have never boosted it, in fact the sun heated it up from the get go, so it has so far cost us zero in electricity to boost it since the start of the year.

We were going to go for gas boosted, but realised in the end that gas boosting would cost us a lot more, as with solar PV boosting it would would cost nothing.

Whilst obviously solar uses a tank and is stoage, if your talking storage vs instantaneous solar is not what comes to mind.

Of course even with solar you still could have the debate of tank only or tank plus instant bost.

Instant water heater is the better option if you are rarely going to use hot water otherwise, Storage water heater is better.

I wonder whether I could revive this thread, given various technologies may have advanced in four years, and costs may have changed.

We're building to the SW of Sydney. A big single-storey house, so will need at least two HWS, just to reduce wait times. I'm really hoping to avoid connecting natural gas to the house at all. Kitchen is to be electric (induction cooktop, electric oven etc). Two fireplaces I'm hoping will be electric since they're mainly for looks (still looking into that). That leaves hot water as the remaining reason for a gas line. Keeping in mind we plan to add a decent (12kW+) solar PV system, ideally with battery (eventually, if not right away), so the price of electricity hopefully won't be a major concern.

Given all that, it seems as though the options are solar with/without tank, or electric with storage, or electric instantaneous, or possibly heat pump. I'm leaning toward either solar with electricity boost (from PV/battery), or electric instantaneous, but what are the considerations? From the earlier discussion here I gather we can go with a couple of larger units requiring 3-phase power, or smaller single-phase units near each area of usage.

Anyway, we've just started to explore the options and would appreciate any input.

P.S. If anyone saw my thread about the fireplaces, yes, I'd completely forgotten about the HWS when I posted. Too many things to think about all at once lol.

P.P.S. Given the lack of response, perhaps I should have started a new thread - not really familiar with how the forum works.

The idea with solar PV panels these days is self-consumption. You get paid very little FIT to export power to the grid, while still being charged a lot to import power. So it's best to use your own solar generated power, instead of exporting it & importing power at another time.

One of the largest power users in a home..... hot water.

So you want to be using your solar generated power to heat your water.

You can't do that with gas, whether gas instantaneous, or gas storage. You can't really do that with electric instantaneous, it draws very high amounts of power, usually when the sun isn't shining.

You can do it with electric storage hot water. This of the storage tank as a thermal battery. A battery that stores your solar generated power, & does it much, much cheaper than a Tesla Powerwall home battery.

The choice for electric storage hot water. Electric resistive, cheap, but energy hungry. Or a heat pump, extremely efficient, using only a quarter the power of the electric resistive heater.

The choice for me would be a heat pump, & a decent quality one. In QLD, solar thermal hot water is also a good option. But in VIC they need to much winter boosting. In Sydney, probably the heat pump is best.

Same goes with space heating. Your electric heaters will be resistive heaters, expensive to run. A reverse cycle AC (a form of heat pump) is far, far more energy efficient, using about a quarter the power.

Very informative post ddarroch.

Stewie

Thanks for the response. I haven't been on for quite a while, but believe it or not the house hasn't even got past Council yet. Lots of delays.

We're going with electric-boosted solar HWS (x2), and a PV power system - 20kW, I think. As you say, the idea is to power the place with as little reliance on the grid as we can manage. In that regard, we'll be looking at electricity storage of some sort - presumably a battery of some stripe. I hear good things about BYD?

We expect to eventually be charging at least one electric vehicle, maybe two. We're putting in three-phase for a fast charger (and the AC). We've been told that if we want to run two fast chargers, it'll cost about $20,000 to upgrade things to take the load. I doubt it would be worth it, but does anyone have an opinion?

Both heating and cooling will be by reverse cycle AC - that was always a given. The fireplaces are just for ambience.

The AC will definitely be there. But we've also been thinking about far-infrared heating panels. I gather they're more energy-efficient (and just plain effective) than your old-style red-glowing radiators, and the "sun on your face" aspect sounds inviting (see also the fireplace thread). But the cheap one I bought from... um, Amazon or Kogan I think, was pretty disappointing. It does warm a bedroom fairly well. But as far as I can tell, just by letting warm air rise up out of it. You can only feel the warmth radiating from it if you're within about 2m. That's probably for a new thread though. (Actually, wouldn't be surprised if I already started it months ago).

Re 2 fast chargers - how often will you be in the position that you have 2 vehicles that both need to be charged in the next hour, as opposed to overnight (or in 2 hours if you do the cars back-to-back)? Most EV users don't require a fast charger at home at all, let alone 2. I wouldn't spend $20k on that - who knows what the technology will look like by the time you're in the situation where you think you'll need it.

That's actually kind of the point. This isn't about what we're likely to be doing anytime soon, but about the future.

One of the main areas of battery research these days is improving charging times. People are talking about batteries that can charge in a few seconds (not anything that's likely to be practical anytime soon, but gives an indication of where we might be heading).

But...

Think about it. Let's say you've got a car that stores a similar amount to current EVs, or more. It can charge in a minute or two. That energy has to come from somewhere, at a huge rate.

I'm not saying I'm going to run out and spend $20k on the possibility now, but it is another thing to consider.

In more general terms, do you think we're likely to be using less electricity in future, or more? My guess is more, possibly in ways we haven't even thought of yet. I'd like to be ready, if I can manage it.

I need to do some more research, of course. For instance if would cost a similar amount to upgrade things later, then I'd be insane to even consider it now. But what if, like a lot of changes to a house, it costs three times as much once everything's installed? That might change the equation.

it's not something that makes financial sense to future proof, unless it will be impossible to run new circuits in your garage for whatever reason. it will probably be cheaper to add the fast chargers when you actually need them, provided you've got the 3 phase connection done now, and it's sufficient to handle reasonable future loads.

tbh i doubt that we'll see residential fast chargers that can charge a car in a matter of seconds and require insane amount of energy. precisely for that reason you mentioned, very few households will have the wiring to support it. also it flies in a face of maximising solar energy benefits. it's more likely that we will have chargers matched to the solar systems so the car doubles as a home battery.

I think the fast chargers that can charge a car in seconds (or even minutes) will be destined for the electrical equivalent of petrol stations. after all, if you can drive up to a charging station and spend exactly the same time there you would currently spend at petrol station, why would you spend lots of money trying to install the same infrastructure in your own house? you'd have something that utilises the 'free' electricity from your solar instead.