Instantaneous Water Heaters

12kW changes the game if you want to run off solar imho, rather stick with 3kW R4.5k 150l geyser.
 
I don’t know hey, at the cost of those you could install two regular geysers (which I suspect there is already at least one of) for half the money with timers etc.

The odds of breaking even on these would only make sense if you plan to live there forever, but they also don’t really last and will need replacement or maintenance.

Not to mention if there is load shedding you are now sitting with cold water everywhere.
 
SauRoNZA said:
I don’t know hey, at the cost of those you could install two regular geysers (which I suspect there is already at least one of) for half the money with timers etc.

The odds of breaking even on these would only make sense if you plan to live there forever, but they also don’t really last and will need replacement or maintenance.

Not to mention if there is load shedding you are now sitting with cold water everywhere.
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Don't even need timers. Timers actually make them less efficient. As you're now preventing it from warming up when it needs to and actually making it use more power when it turns on.
 
Lupus said:
Don't even need timers. Timers actually make them less efficient. As you're now preventing it from warming up when it needs to and actually making it use more power when it turns on.
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He means when you have 2 geysers.
 
wingnut771 said:
What sucked about it? Was it electric?
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It was an instant hot water strapped to the wall. Also had one in reading and it was even worse would turn off after 2 minutes.
 
Lupus said:
Don't even need timers. Timers actually make them less efficient. As you're now preventing it from warming up when it needs to and actually making it use more power when it turns on.
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Timers just allow them to run only when necessary.

No point having geysers on at night for instance.

Over a month of pointless night time water heating it makes a difference.

And if you run a fancier setup can also just have them turn off when not at home.

It’s just about removing pointless heating times. And if you run solar to make the most use of it.
 
Grant said:
4 of these perhaps: (house has 3phase power)
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FOUR 18 kW heaters? And you are happy to trip power any time say, two hot taps are opened simultaneously?

Maybe your own electrical installation is up to it... then I would be worried about your municipal feed!

These things demonstrate a fun fact about water: it's got a very high heat capacity. It takes a lot of energy to raise its temperature. And to raise it quickly, you need insane power.

Let's say you shower at 10 L/minute. That's about 170 mL/second.
Let's say your water comes in at 15 °C and you want it at 40 °C.
You need 18 kJ/sec to heat that water at that flow rate.
And that is... 18 000 W.

So the full 18 kW just about manages one shower, assuming your inlet temperature is not too bad and you're happy with that flow rate.

If your water comes in any colder though your options are a colder shower, or a slower one.

I think these can make sense in a boost configuration, where there's already a solar heated tank at say 20-30 °C. It's more economical to heat the rest of the way on demand, and it's definitely more convenient than waiting an hour or so for a normal ac element to do the job.
 
Do not listen to misinformation spreaders like Lupus. Gas is much cheaper for certain things like cooking. Gas is terrible as a room heater. But gas is cheaper than electricity for water heating, since it heats on demand. There is also the option of mini-geysers. But the best option besides a massive solar system, is to get a Geyserwise pv panel solar geyser.
 
SauRoNZA said:
Timers just allow them to run only when necessary.

No point having geysers on at night for instance.

Over a month of pointless night time water heating it makes a difference.

And if you run a fancier setup can also just have them turn off when not at home.

It’s just about removing pointless heating times. And if you run solar to make the most use of it.
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Freaking odd thing is my messages are being changed. I didn't type that
 
SauRoNZA said:
Timers just allow them to run only when necessary.

No point having geysers on at night for instance.

Over a month of pointless night time water heating it makes a difference.

And if you run a fancier setup can also just have them turn off when not at home.

It’s just about removing pointless heating times. And if you run solar to make the most use of it.
Click to expand...
We tested the geysers this month on solar. We have three geysers but used two to test, one in the roof and one mounted outside.

The numbers fluctuate a lot due to usage patterns but with the inside geyser running on timers where it is on for 4 hours a day we used on average 13kWH. Keeping it on used an average of 11 kWH. Roughly the same numbers on the outside geyser although it was marginally higher.
 
Crowley said:
We tested the geysers this month on solar. We have three geysers but used two to test, one in the roof and one mounted outside.

The numbers fluctuate a lot due to usage patterns but with the inside geyser running on timers where it is on for 4 hours a day we used on average 13kWH. Keeping it on used an average of 11 kWH. Roughly the same numbers on the outside geyser although it was marginally higher.
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Repeat test with using no hotwater. Yes, you'll have to not shower for 2 days. :p

IMHO, timers are to either manage the load or to save ones batteries overnight. That is all.

The geyser in the cottage uses about 5kWh per day with no hotwater being used.
 
Crowley said:
We tested the geysers this month on solar. We have three geysers but used two to test, one in the roof and one mounted outside.

The numbers fluctuate a lot due to usage patterns but with the inside geyser running on timers where it is on for 4 hours a day we used on average 13kWH. Keeping it on used an average of 11 kWH. Roughly the same numbers on the outside geyser although it was marginally higher.
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I only switch the geyser on once per day for 30 mins. If I keep it on, especially in winter, it will be on a lot more than that. I think it will be on 3 to 4 times more if always on during winter.
 
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