Air heat pump or use gas and solar?

[QUOTEYou can relatively quickly part with an uneconomical car, but it is much more difficult with a building][/QUOTE]

That’s true!

A well-known heating and sanitary friend said to me: I would choose a gas heating system. If it fails in winter, there is quick help. With an air heat pump, there could certainly be more difficulties.

Nevertheless, the air heat pump still doesn’t let me go.

Maybe I should first get a gas heating system and after 10-15 years buy a well-developed air heat pump and couple it with the gas heating system at low temperatures. Is that even possible?

What also interests me:
Can the heating element in an air heat pump be completely turned off, or are there problems with the Vaillant at such cold temperatures? I don’t know Vaillant at all. What are the experience reports?

Background:
My relative has a ground source heat pump (deep drilling) and has turned off the heating element for 3 years in winter. Last winter we had -20°C and the one before -18°C and it worked for him.
His average heat consumption (water/heating) is €1000/year for a 160 sqm KfW70 house (14 cents/kWh tariff and a three-person household).

...A well-known heating and sanitary friend told me: I would choose a gas heating system. If it fails in winter, there is quick help. With an air heat pump there could definitely be more difficulties.

Not known to me, even with an air heat pump there is quick help. Besides, how often does a precisely planned heating system fail?

...Maybe I should first take a gas heating system and after 10-15 years buy a well-developed air heat pump and couple it with the gas heating at low temperatures.

Well-developed air heat pumps already exist today. Unfortunately, you won’t find these in general contractor projects, because almost every piece of junk is pushed on the clueless builder there.

...Is that even possible?

In principle yes, but whether it makes sense is worth questioning. At least heating surfaces and pipe hydraulics must be "heat pump suitable."

...Can the heating element be completely switched off in an air heat pump, or is there a problem with that at Vaillant at such cold temperatures?

The fear of the "evil" heating element leads to some curious missteps that usually only fill the pockets of the installer and result in a low annual performance factor for the operator. A typical example is the on/off "sewing machines" of general contractor projects. In well-planned systems, the pure heating element proportion amounts to just 0.2 to at worst 2 % of the annual heating workload. So no reason to faint

...My relative has a ground heat pump (deep drilling) and has had the heating element switched off in winter for 3 years. Last winter we had -20°C and the one before -18°C and it worked for him.

Ground source heat pumps fundamentally do not need a heating element, at best in the heating up phase to protect the source. Good system installers lend these for the mentioned purpose, bad ones sell them without any need for use.

...His average heat consumption (water/heating) 1000€/year for a 160sqm KfW70 house (14 cents/kWh tariff and three-person household).

Jesus help, I would make the cause strongly participate in this failure here. At best, about one third should be accounted for, provided the building is not located on the Zugspitze, room temperatures of 30°C are not demanded, windows are not open in winter, and there are no exorbitant bathing orgies.
How can he still sleep calmly? Probably saved a few euros on exact system planning, then one should grant him this school money

v.g.

Hello Euro

How else can an economic system be found, to evaluate an investment?
I would rather prefer the option with 50 Euro Also, you don’t have to live later with some undefined consumption, but can influence it yourself during the planning phase.

That’s why I wrote that I assume a best possible planning. But even after the best planning, you still have heating costs to pay – no matter how high or low they are. I had also written that a heat pump requires more precise planning than gas.

Higher demand always leads to higher consumption. 25°C room temperature requires more energy than 20°C room temperature. It is not for nothing, for example, that the desired room temperatures are agreed upon for calculating the heating load.

Which brings us back to my objection – I can’t even estimate my demand today, because there are many parameters that will be new to me (wood stove, bathing habits, controlled residential ventilation).

But you can answer them beforehand, by defining a general feel-good scenario for yourself.

I don’t yet know how many baths per week I will feel comfortable with or how much wood I will chop for the wood stove (If I have to chop more wood, I sweat more – so I have to bathe more ).

Anything that later deviates from this means a change in consumption.

That is exactly what I mean.
Since I have no experience with many parameters, I can only guess – and may be completely wrong – and thus the demand planning is totally useless.

Who buys a car without knowing the consumption data beforehand? Those who drive little may be able to settle for a cheap gas guzzler; those who have to drive a lot will pay attention (have to) to low consumption values and therefore prefer the somewhat more expensive vehicle.

Maybe I know the consumption of the car – but only to a limited extent, because consumption also depends on my individual driving behavior! Even if you and I had the same car – your driving style is certainly different from mine – we would definitely have different consumption with the same car!

But even if I know the exact consumption – if I have no idea how much I will drive, I can only guess the consumption costs at best – but not estimate or even calculate them reliably.
For a calculation, I would need to know how many kilometers I drive per month and how many of those are in the city and how many on the highway (which highway? I will have a different consumption on the A40 again than on highways where I don’t stand in traffic jams so much :rolleyes

Regards
Micha

The energy prices of all energy sources will rise sharply. One can get rid of an uneconomical car relatively quickly; with a building, that is already significantly more difficult [/QUOTE]

Hello Gigi,

before you start looking for a construction company and let them give you a complete offer for the house including the heating and possibly also let the construction company choose which heating system you want, you should try once again to involve an HVAC planner, because only through this will you get what you really want.

Often enough, one reads in other forums from home builders who have not been very happy with such general contractor companies (GU = general contractor and means that you only have one contact person who works directly for you), because the consultation, especially in the area of building services engineering, was not as agreed at the beginning. Unfortunately, these GU companies often have only salespeople who unfortunately do not understand more about the technology than you do.
That is why building services engineering is often excluded from such GU contracts and is managed separately by a specialist planner.
In the course of an energy calculation, this planner can determine the essential design details for the system before continuing with further planning. In addition, they can also create a cost forecast for various options, both for the investment and the running costs. What you can also consider for the cost comparison is the observation period: the lifespan of heating systems is about 25 years, which could be the observation period. But the question arises of how long you want to use the house, since other observation periods can result from this. Also, the question of whether you want underfloor heating or radiators installed affects the selection of the heating system. Especially with heat pumps, a surface heating system should be planned, because only then can an optimal efficiency be achieved. This can also be an essential detail when it comes to adapting the heating system optimally to the building.

And also with possible subsidies, a specialist planner can be helpful, because often only small details are required to qualify for a subsidy, but just as quickly the subsidy cannot be obtained. What has already been mentioned is that when using a gas heating system, the requirements of the energy saving ordinance must be further undercut in order for you to receive the subsidy without a solar thermal system. Also for this planning, you should get help from a specialist planner to ensure everything really works out.

Best regards

....I don’t know yet ....

When I read all this, it seems that complete ignorance is present here. But even then, one can help with usual average values. The worst-case scenario is also, as already mentioned, doable. That would at least quantify a range from-to. However, those who want to be surprised out of sheer ignorance are allowed to do so. However, these "surprises" are usually of a negative nature. I also deal a lot with botched practical installations; frustration, annoyance, and disappointment are the order of the day. A main issue: excessive consumption costs despite the partly considerable investments. Completely different from what was originally suggested. If it gets too much for you, you can chop more wood. The stupid thing here is that the utilization rate, not to be confused with the combustion efficiency, is perhaps around 50%. Based on experience, after the initial enthusiasm has settled, chopping wood decreases after 2..3 years.

@€uro There are so many variables here. How close do your calculations really come to the actual consumption? Have you ever calculated a system in advance and recalculated it after a few years to see if it was actually the right decision? With the "botched practical systems" you are always wiser than the planner because you know the actual figures. Do you see what information the client gave the planner back then and which price increases were taken into account? How close are the different systems really to each other? Could it be that one system is attractive for my predictions? Considering a worst-case scenario, another system is sensible. Based on actual usage behavior, it is a third system? Could it even be that in the beginning one system is sensible, but if a child is planned or unplanned later, another becomes attractive? Or I become more heat-loving in old age and the average temperature is then a few degrees warmer than originally planned. How do you want to factor that in? We currently live in an uninsulated natural stone house in a river valley. Unless the heating runs through extreme cold nights, after turning off the heating around 9:00 pm, the temperature drops so quickly that I have to heat higher beforehand than I would actually need. I don't want the bedroom to be freezing. So in the evening I have to preheat to over 20° so that the temperature is not far below 10° in the morning. I can't say what average temperature I have now. I don't have a bathtub at the moment either. No child yet. And you want to know now how it will look later with insulated house, child, underfloor heating, fireplace, and bathtub?