ᐅ Air-to-Water Heat Pump: Current Consumption and Data

When I moved in December, I lowered the night setpoint slightly so the heat pump would mostly run during photovoltaic peak hours. From 5:00 AM onward, it goes back to the normal temperature to avoid cold feet in the morning. Out of sheer laziness, this has been my only "optimization" so far.

Since March, I have been over 90% self-sufficient. As of today in April, the total consumption was 283 kWh (heating, hot water, ventilation, household), with 15 kWh drawn from the grid and 750 kWh fed back in. The yearly total so far is 1,740 kWh consumption, 655 kWh grid feed-in (470 of which was in the difficult January), and 2,425 kWh supplied to the grid. I am more than satisfied 😀

All this is for 170 m² (1,830 sq ft) of living space in the permafrost region of the Hochsauerland area (we still have frost at night). I could probably optimize the heat pump consumption further... but considering these numbers, I somehow lack the motivation.

Hangman schrieb:

Since March, I have been over 90% self-sufficient. Today, the total consumption for April was 283 kWh (heating, hot water, ventilation, household), with 15 kWh drawn from the grid and 750 kWh fed back into it. The yearly total so far is 1,740 kWh consumption, 655 kWh grid usage (470 kWh of that in the frustrating January), and 2,425 kWh fed back. I am more than satisfied 😀

This is for a 170 sqm (1,830 sq ft) area located in the permafrost region of the Hochsauerland (we still get nightly frost). I could probably optimize the heat pump consumption further... but considering these numbers, I somehow lack the motivation.

How should this be interpreted? For April, that would mean a daily total consumption of 12 kWh. Normally, household electricity alone would exceed that amount.

That can’t be right, can it? And if it is, photovoltaics would be completely uneconomical with such low consumption. Please clarify.

Yes, you are right – photovoltaics is complete nonsense... I just consume too little 😉

guckuck2 schrieb:

What exactly is supposed to freeze, and what is the heating element supposed to do about it?
A theoretical fear of events that do not actually exist.

Of course, it also depends somewhat on the type of heat pump. We have a monoblock installed outdoors, where the supply and return pipes go directly to the heat pump, so the freezing of the pipes is a very real concern.

Bookstar schrieb:

That can’t be true, can it? And if it were, then photovoltaic systems would be completely uneconomical at such low consumption levels. Please clarify.

Photovoltaics pay for themselves by default; self-consumption is just the cherry on top.

halmi schrieb:

Of course, it also depends somewhat on the type of heat pump. We have a monoblock installed outside, so the supply and return lines go directly to the heat pump, and freezing of the pipes is a very realistic risk.

There is more than 150 liters (40 gallons) of tempered water inside, most of which absorbs heat from the ground and indoor air. So nothing freezes quickly. Maybe right at the appliance or near the building if circulation stops. An internal circulation pump would also prevent this, as would shut-off valves and a drain valve.

Apart from that, if freezing really were a risk, why is there no antifreeze in the system?

guckuck2 schrieb:

Photovoltaics pay for themselves, self-consumption is just the cherry on top.

A photovoltaic system doesn’t pay for itself even with self-consumption and feed-in under 12 years. How is it supposed to pay for itself at all without self-consumption? I’m curious about that!

I just did the calculations, the payback period is over 20 years. After that, the system is basically scrap. You can forget about it 🙂. And that doesn’t include insurance costs or the possibility that the inverter might fail during that time. In practice, you’re probably looking at 25 to 30 years.