Power Saving on a Hot-water system.

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Originally Posted by 81stubee

From a sparky point of view.

The Off Peak Hot Water is designed to take advantage of the power generated during off-peak peiods. The only spots its really used now are in areas without gas, and even then some of the new rinnai/bosch instantaneous heaters are efficient enough to run off bottles. 125L is really too small to take advantage of off peak. The common way is to have about a 300L Storage tank with off-peak element in the bottom and a booster in the top. During OP times the bottom element heats the water, as the water heats it rises to the top, thus giving a full tank of HW heated at a cheap rate. If you use all that water, the top element kicks in and only heats the top section.

The old style meters used to use a time clock to control when the OP was active, problem with this was that after a blackout, the SEC had to go around and reset all the time clocks. With a modern meter they just send a pulse down the line at anytime whenever there is a power surplus and this activates all the Off Peak equipment.

Seeing as you already have off Peak and No gas, I would get a 300L electric system with boost, or maybe a solar with booster.

My two cents

Stu

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Thanks for advice stu , I think I'm leaning more towards a larger HW system of say 300L with a bottom element and top booster, that way we have hot showers in the morning and will not be needing hot water for rest of day other that for cooking , the washing machine already has a heating element which we don't really use. Solar looks to be much more expensive even with a Governement rebate where as electric heating is a direct replacement of the existing hotwater system but perhaps not the most efficient way of hot water systems...

Five years ago when we had our new house built we had to install a heat-pump style water heater. This uses a reverse refrigerant system, pulling heat out of the air and sending it into the water. This system is cheap to run as it only uses a 1/4 h.p. motor to turn the fan and compressor. Better still it is manufactured in Newcastle. This system will even work in the snowfields as even though the air is cold it is far hotter than compresses refrigerant.

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Originally Posted by Slunnie

That is stunning! I'd love to know more about that one!


Also, have you looked into the use of electric instant hot water? These units cost about the same as an instant gas hot water unit

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I am pretty sure they are by far the most expensive to run.

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Originally Posted by vnx205

I am pretty sure they are by far the most expensive to run.

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I'm not sure, everything I have heard has suggested the opposite. Apparently when the electric instant hot water are operating they pull some good power, but I was under the impression that overall they use about 30% less power that a regular HWS. I also thought they scored better than the regular HWS on the Basix.

These things are hard to find info on.

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Originally Posted by Slunnie

I'm not sure, everything I have heard has suggested the opposite. Apparently when the electric instant hot water are operating they pull some good power, but I was under the impression that overall they use about 30% less power that a regular HWS. I also thought they scored better than the regular HWS on the Basix.

These things are hard to find info on.

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There are a lot of variables. Depends if your storage electic system is inside or outside, how well insulated your pipes are, etc. As far as I remember, you get the biggest rebate switching from one of these systems to solar - so it has obviously been assessed as being pretty bad.

I am surprised someone said gas systems are more $$$. We pay about $200pa for gas - 2ppl. That includes Hot Water, gas oven and cooktop (both of which get a lot of use), and gas heating (rarely used).

How many KWh are people using for an electric system in a 2 person household?

Basix here
BASIX - Building Sustainability Index

Some details about HWS from Basix help here-
http://www.basix.nsw.gov.au/help_det...elp_single.htm
Under Energy section down LHS of the page.

Simon

I used to work in the domestic gas industry. The following comment refers to reticulated gas not bottled, with which I have had little to do other than in camping gear. Do not get an instantaneous gas or electric heater, or a gas fire (room or space heater). These appliances are an introduction to bankruptcy. Use a gas stove but be very careful in the purchase of other gas appliances. My experience has been that the cheapest HWS to run is an electric off-peak. As a matter of interest to Aulro users from elsewhere, any electric HWS in Brisbane must be off-peak if you want the preferential hot water rate, otherwise they are charged at full rate. You MUST have ventilation or a flued system if you use a gas room heater. Gas storage HWS are bloody expensive also. The cheapest domestic sytem to have, and which forgoes the convenience of reticulated hot water, is the old gas geyser in the bathroom, and a sink heater in the kitchen. If you live in cold climates and need room heating, then get a woodburner. We live in Brisbane near the bay and river and don't own or need a room heater of any description.

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Originally Posted by vnx205

If you have a solar system with an electric boost (as I did in Yass), my experience was that the best time for showers and big loads of washing was in the morning.
If you drain your hot water in the evening, the electric booster heats the water over night. Then when the sun comes up next morning, the water is already hot.

On the other hand if you don't use a lot of hot water at night, the booster doesn't do much overnight because the water is still pretty hot. When you drain off hot water in the morning, solar energy is available to heat the water, so you don't use the booster as much.

I suppose there is some combination of automatic and manual overide on the booster that could make a different regime better, but with the Solarhart setup I had, that worked best for me (or at least it did when I could convince SWMBO to operate that way).

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Yes,we actually had a switch for the booster in the hall cupboard so we could control when it was used. Except for middle of winter, we could get enough hot water to have showers and do washing without needing to turn on the boost at all . ( only two people in the house though ). However, a household with teenagers would be harder to manage.

Some friends of ours have both solar panels and a wetback on their Coonara stove, and NEVER need to turn boost on.

If I lived in the more tropical climes of our great country, I'd seriously consider the need to shower with hot water anyway ( In some Asian countries I've had a struggle to get HW turned on in some hotels - it's only used by the "Westerners" )

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Originally Posted by waynep

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Some friends of ours have both solar panels and a wetback on their Coonara stove, and NEVER need to turn boost on..........

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My kitchen stove boosts the hot water in cold weather as well as heating the whole house - and I don't have a booster (or mains power).

The actual costs of hot water methods will vary widely according to local charges (and charge structures) for electricity and gas, but a reasonable assumption is that all energy costs are set to rise, the only question being which one will do it most rapidly. With that in mind, the ideal one is probably a solar system with heat pump boost, but the initial cost has to be considered as well, as does the expected life of the system (which is very dependent on the water quality, regardless of type of system, and varies according to area). The advantage of an instantaneous system, whether gas or electric, is that they do not lose heat from stored water (plus the further advantage that there is unlimited hot water). Whether this translates into monetary savings will depend on cost, cost of installation, and the relative cost of the energy for instantaneous heating and base load heating (which, of course, can be changed by the supplier at the stroke of a pen).

John

A few years ago I did some apartments in Brighton, where they installed electric instantaneous hot water. These were 2 bedroom townhouses. To cope with the supply demands of the HWS's each unit had 3 phase 16mm (3 X 80A) supplies with 3 phase 10mm (3 X 60A) just for the hot water :eek: Your average 3 bedroom suburban house has a 1 phase 16mm (80A) Supply.

I think they would of been expensive to run.

Stu