Pellet heating + solar: Is the offer good?

....The energy consultant does not care at all which manufacturer or heating technology is used. At first we favored the brine heat pump but unfortunately the offers were not so good.

Good is relative if you consider exclusively only the initial investment. In addition, for example, cost-effective trench or surface collectors are possible with the brine heat pump, provided that you can or want to contribute your own work. This partly significantly relativizes the cost expenditure for source development. Heat pumps generally "live" particularly well from low temperature differences between source and sink. This means on the sink side usually large heating surfaces like floor heating or WH are possible. Conventional heat generators (gas condensing, pellets, wood, oil) can achieve system effort numbers only more or less clearly, depending on dimensioning > 1. With heat pumps, on the other hand, 70 ...80% free environmental energy can be used, depending on type and dimensioning. Whether one should simply unchecked give away such potentials, I would not assume at first ;-) Superficiality has rarely led to the ultimate optimum!

Best regards

Was a heating load calculation ever done to verify if these 30 kW actually apply? Just because the old heating system had 30 kW doesn't mean it fits. We had a heating engineer here who wanted to sell us a 25 kW boiler for 180 m2 – his statement: 1 kW per 10 m2 living space always fits – plus hot water. Our heating load, however, is 6 kW and not 18 kW. That would have been a nice flop. Hot water is also not done via the boiler, but via a domestic hot water heat pump. Solar on the roof is not worthwhile – and the roof is already fully equipped with photovoltaics. Now we have a "suitable" pellet boiler that modulates from 3 to 15 kW – smaller was not available – for 3600 euros. Already a slight difference in price. It is also subsidized by [BAFA], so that will be deducted. Installation 1000 euros, since it is a boiler that can be connected like a stove. Plus 800 for a 500 L buffer tank. For the transitional period, heating is done with a climate split unit that can cool in summer, heat in spring and autumn, with heat pump technology and even [kfw]-subsidized – 3.5 kW for 600 euros. The domestic hot water heat pump also costs about the same – 700 euros. Installation each extra, I don’t do that myself, it’s too tricky for me. But it doesn’t cost an arm and a leg and you have the security that a professional did it. Minus 2900 for the [Bafa] subsidy, the entire heating and hot water stuff including cooling for our house costs about 4500 euros including installation (excluding small parts, such as stove pipe).

Was a heating load calculation ever done to see if this 30 kW is even correct? Just because the old heating system had 30 kW doesn't mean that fits...

Correct!

....- and the roof is already fully covered with photovoltaics.

A heat pump would have been predestined as the primary heat generator. High own consumption share, you should have calculated that beforehand. I have planned heat pump systems in combination with photovoltaics where heating, cooling, and hot water were possible at net zero cost over the year!

Best regards

We had it calculated. But it was no use. The photovoltaic system produces the least exactly where the heat demand is highest. In December and January, it only generates 1-6 kWh per day.
That means operating a heat pump with photovoltaics in winter would not have been possible. The expensive household electricity, which is not getting any cheaper, would have driven the costs even higher. The heat pump tariff here is only slightly lower, but an additional meter would have been required. In the end, simply too expensive.
The heat pump subsidy from Bafa is a joke compared to the pellet subsidy (twice as high as the heat pump subsidy), but the costs including installation for the heat pump are much higher. Heat pump offers started at 10k. Pellet offers were not even half of that.
The climate split unit then runs purely on photovoltaic surplus during the transitional period, as there is still enough yield. And when it gets really cold, the boiler comes into play, which then also has a reasonable load.

Heat pumps at zero cost via photovoltaics only work with large systems; ours has only 7 kWp. And with a daily yield of 4 kWh in January, which is not even always reached – there were plenty of days with 2 kWh or less – I honestly don’t believe a heat pump can keep the house warm without drawing additional electricity. If you have 20 kWp or more, it might look different.