ᐅ Heating System Quote Comparison – Request for Your Experiences

Hello everyone. We have received three quotes for an air-source heat pump, underfloor heating, photovoltaic system, and decentralized ventilation with heat recovery. As expected, all offers differ from each other.

Regarding the proposed heat pumps:

Brötje BWL Split 8 C with electric heating element €9207.95
Elco Aerotop Split €10,222.50
Viessmann Vitocal 200-S €8829.31

The prices include accessories. From my research, I am most inclined towards the Elco. It seems to have the best specifications on paper. Overall, the offer for this heat pump is also the most affordable. Unfortunately, I found little information about the Brötje system.

Now my questions:
- What do you think about these systems? Do you have any experience? How would you assess the prices?
- What size should the hot water tank be? Considering an air-to-water heat pump combined with photovoltaics? The Brötje system includes a 150-liter (40 gallons) tank plus a 100-liter (26 gallons) buffer tank. The Elco option has a 180-liter (47 gallons) tank.
- What else should be taken into account?
- Are these systems appropriately sized? The building’s energy demand is 21.1 kWh.

Tx-25 schrieb:

- Are the systems properly sized? Building energy demand: 21.1 kWh

Per day? Per year? For the entire building? Or is it per square meter—then the area is missing...

Yes, for the entire building. That should be the annual requirement. The usable area is listed as 164.1 square meters (1766 square feet). The living area is 146 square meters (1571 square feet). The primary energy demand is 37.9 kWh. It is a new build.

Tx-25 schrieb:

What else should be considered?

I am currently planning a new build myself and have to say that air source heat pumps really put me off. You should definitely listen to them outside during the heating season (frost) before making a decision. You wouldn’t want to impose that on any neighbor, nor really on yourself. Ideally, you get a demonstration and see if they can be load-controlled indoors.

Apart from the fact that the unit on the house is not exactly attractive, you also need to have the necessary space available (ideally not in front of windows). Consider where you would place it, how it would look, and which neighbors would be exposed to the noise.

In severe frost conditions, you are effectively heating about half with electricity. Heat pumps generally do not pay off, despite a lot of optimistic claims. The price difference between gas (5 cents/kWh) and electricity (28 cents/kWh), so a factor of 5.6, is higher than the realistic annual performance factor (3.5 – 4.5) of heat pumps—so there is no real gain. Total acquisition costs including all works, materials, and possibly a base platform are consistently higher with air source heat pumps than with very good, properly sized gas condensing boilers.

All my calculations based on actual quotes showed that heat pumps end up more expensive for the builder than gas condensing boilers. Many lean towards them just to meet the requirements of funding programs like KfW. However, that should not be the main reason for making a purchase decision.

Tx-25 schrieb:

What about an air-to-water heat pump combined with photovoltaics?

Photovoltaics provide lower generation costs for electricity, which makes the heat pump more cost-effective. However, keep in mind that during the coldest frost period, solar yield is low and in the sunniest periods, the heat pump consumes the least energy. Unfortunately, a lot of overly optimistic claims are made here as well.

The generation costs of photovoltaic electricity (yield divided by investment, maintenance, and repair costs) are around 11–13 cents/kWh—significantly cheaper than grid electricity but by no means free.

Costs for electricity storage add another 12–15 cents/kWh depending on the model and purchase price. The total generation cost of photovoltaics plus storage is therefore not noticeably cheaper than supplied electricity. Battery storage is still mostly a gimmick and money pit. However, falling battery costs could improve this in the future.

One should not forget that most builders are rather cash-strapped during the construction phase and unnecessary investments can be painful, potentially resulting in interest on higher loan amounts. Additional technology can break down and inevitably leads to maintenance costs.

Photovoltaics are generally quite attractive, though. This strongly depends on purchase prices—the offers vary considerably depending on the provider and region.

Tx-25 schrieb:

Yes, for the entire building. That should be the annual requirement.

So, 21.1 kWh energy demand per year. That would also be covered by running the toaster for 10 minutes a day. Better to research that again.

Detlev69 schrieb:

I’m currently planning a new build and have to say that air-source heat pumps really put me off. You definitely should listen to one outside during the heating season (frost) before making a decision. You wouldn’t want to subject any neighbor to that noise, nor yourself, really. Ideally, you see a demonstration and check if it can be switched to load control indoors.

Aside from the fact that the unit on the house isn’t exactly attractive and you first need to have the right space (no windows there), think carefully about where you would install it, how it would look, and which neighbors would be exposed to the sound.

During severe frost, you’re essentially heating half the time with electricity. Heat pumps generally don’t pay off; there’s a lot of sugarcoating. The price difference between gas (5 cents/kWh) and electricity (28 cents/kWh), that is a factor of 5.6, is higher than the realistic seasonal performance factor (3.5–4.5) of heat pumps — so you won’t gain anything there. The total investment costs, including all labor, materials, and possibly a base, are consistently higher for air-source heat pumps than for very good, properly sized gas boilers.

All my calculations with actual offers showed that heat pumps cost a builder more than gas condensing boilers. Many only lean towards them because they can meet KfW requirements. That shouldn’t be a decisive reason for a purchase decision.

Here’s someone ranting again without the slightest clue...

- A proper air-to-water heat pump isn’t heard even at -10°C (14°F); any controlled ventilation system is louder.
- Whether a unit is considered attractive is subjective; there are many options for installation locations.
- If your air-to-water heat pump only achieves a coefficient of performance (COP) of 2 in winter as you claim, it’s probably broken.
- In many places, gas costs 7 cents and electricity 25 cents, and with a heat pump tariff even only 18 cents — so your calculation is invalid, not to mention the costs for chimney sweeping, gas connections, etc.
- A gas heating system often costs more than an air-to-water heat pump, due to chimney installation, gas connection, solar thermal integration, and more.
- Yes, your calculations are simply wrong. Both options can be worthwhile depending on the case; sometimes one is more expensive, sometimes the other.