Faucet without mixer? Only hot/cold?

Hi,
That is precisely the advantage of the fully electronic [DE], they can regulate their power almost continuously, while the hydraulic ones can only turn the 3 heating cartridges on or off.
Kermit

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I once looked up an expensive hot water heat pump from Stiebel Eltron for calculation purposes. I found the technical data for the cheapest heat pump (unfortunately also with significantly the worst performance factors; there are certainly better providers; but it’s better to calculate conservatively): 200l hot water storage tank, performance factor about 3.5, cost 2000€, if you don’t heat the hot water to maximum about 1kWh heat amount (! not to be confused with electricity amount) per day distribution loss. (If you can heat with photovoltaics, obviously less relevant). This results in X € electricity costs and an annual hot water energy demand of Y costs of: X*((Y+365)/3.5) In contrast, the instantaneous water heater simply tries to produce costs of: X*Y The difference between the two costs thus shows how much cheaper/more expensive the heat pump is compared to the instantaneous heater: X*Y - X*((Y+365)/3.5) If the value is positive, heating with the heat pump is cheaper (and the number is the amount per year). Special features such as pipes/other losses/efficiency of the instantaneous water heater (less than 1 for short durations), which may possibly balance out in certain cases, are not taken into account. Example: X = 0.2 (20C electricity costs), Y = 600 (kWh hot water demand) 0.2*600 - 0.2*((600+365)/3.5) = 120 - 55.14 = 65€. So you save 65€ per year, but have to invest 2000 euros. In this example, it would not be worthwhile. However, if you find a cheaper heat pump, or have more demand, it can look completely different. Incidentally, you can also perform the same calculation here with a gas boiler, since the ratio of costs per kWh is comparable to that of a heat pump.

If you don’t turn the tap fully on (hot), no hot water comes out at all because the instantaneous water heater doesn’t even start. It is an electronic one, not a hydraulic one, but it still requires a minimum flow rate for the thing to turn on.

Then you could just as well use a cold water tap.

My tap is no-name; I don’t know if the principle exists with brand-name taps as well. I think it’s great because you always first automatically turn on the cold water, and only when you really turn it all the way does hot water come out. With taps that have the lever, for example, on top, you always turn it to a middle position. This usually results in lukewarm water, even though you usually don’t need it.

I think it really strongly depends on how much water the storage tank holds and how much hot water is used daily. You certainly can’t just say 20 days across the board. It’s quite logical that an instantaneous water heater is more worthwhile the less hot water is needed. For us, with 2 people and only showering and 33 cubic meters of water consumption (hot and cold) per year, it definitely makes sense with the instantaneous water heater. Calculated down, we use 90 liters of water per day with 2 people, including cold water. Compared to the rental apartment, it probably comes out the same, although there we still paid for the neighbors’ hot water. So the operating costs are similar, it’s just a question of whether a new installation is worth it. The hot water heat pump would cost about 700 euros, which you can hardly make back. The only advantage would be that it could charge during the day via photovoltaics and the kWh would thus cost only about 10 cents. Here, showers are mostly taken at night and noon, spaced far apart, so I don’t expect any problems with storage capacity. Basically, we also thought we would definitely need the heat pump for the kfw 100 certification instead of the instantaneous water heater, but that wasn’t the case because the share of renewable energy was easily exceeded by the pellet boiler alone.

How can one get by with 45L per day per person including everything???
Just when Madam showers, 150L rushes through here (which admittedly is due to the Raindance and very leisurely showering).
Still, even if everyone flushes the toilet 5 times a day, that’s probably 30-40 liters even with a water-saving flush button.
Plus washing machine, dishwasher, cooking, etc...
Sure, if the meter only shows 33m³ that might add up, but I wonder how...

Besides, I don’t always shower at the same temperature and it’s much easier to turn the dial in the shower than to go into the shower thinking, oh no, I want it a bit cooler today, hmm no, that’s too cool.
So I think that’s more of a gimmick and you probably can’t really speak of a saving effect...

Hi,

Just when Madama showers, 150L run through here (which admittedly is due to the Raindance and very comfortable showering.

That’s not showering, that’s dissolving ... For showering, you roughly calculate 40 liters.

Kermit

Told you, this is partly due to the Raindance, which allows 18L/min and, of course, very extensive showering. But even with 2 x 40L there are still 10L left for cooking, dishwashing, laundry, and flushing the toilet, for both!!!