Pellet-solar combination - Issue in summer?

What is this actually about? Renovation, refurbishment, or new construction? I can't quite understand the focus on the pellet heating system in new construction.

It's a new construction. I find it an efficient way to heat - independent of outside temperatures. And ecological as well. Basement and space are available.

”Harvesting and burning forest biomass moves carbon out of forests and into the atmosphere right at the time when it is most important to reduce emissions.”

Forests bind CO2. CO2 remains bound in wood houses or furniture for at least a long time. When burned, a 100-year-old tree is used up within a single heating season. Additionally, the logistics of pellets are often questionable.

Personally, I do not agree with the statement that a pellet heating system is ecological, to quote Kachelmann. However, I have already caused a stir with this opinion in this forum.

So here is a thought-provoking idea for alternatives. Correctly designed and adjusted (!) a heat pump in new buildings combined with photovoltaics should be much more sustainable without fine dust pollution for the neighborhood and subsidy hassles. What is NAT for you when outside temperatures are a factor?

Basement and space are available.

Nope - you have to build the space first. You could save it (and save money) if you heat ecologically with a heat pump (using green electricity). And whether burning wood is ecological, I'll leave open... (fine dust, CO2). I prefer to let the trees stay in the forest and enjoy them. But as often, it’s a matter of belief.

independent of the outside temperatures.

And that is exactly what is inefficient. A heat pump adapts much better to the outside temperatures (modulating).

Well, I buy the pellets from the neighboring town. They are freshly pressed there, and the wood mostly comes from trees that would have been cut down anyway. Especially with the issue of beetle-infested wood, which we will probably have to deal with for the next few decades with the current tree species and forest structures, my view is that only wood that has already been felled is being destroyed here. This is also the reason why some people (at least those with space) in my area are building new houses with pellet or wood chip heating.
On the topic of fine dust, I agree with you – that can probably never be completely avoided with combustion processes. But with the current technology from the leading manufacturers, the fine dust emissions are reportedly many times lower than with pure wood heating systems.
But clearly -> It’s a matter of philosophy. Everyone sees it differently.

And regarding the matter of space: Sure, the 9m2 room for the pellets could be used differently, but that one room doesn’t bother me.

For pellets/wood chips/firewood, a decent balance can be achieved through the forestry industry – after all, the resources are allowed to regrow. Through purchasing, you can directly control how climate-friendly your bought product is. With fossil energy, nothing regrows – it is simply taken from long-term storage and not compensated. With electric energy, you can buy "green" and give your money to a green producer, but you still get the energy from the dirty plant next door (e.g., coal in the western Rhineland). There is no other way than to regulate this through balancing groups. During the heating season, using sustainable self-generated energy is still quite expensive – who actually has a wind turbine or an electrolyzer with an H2 storage... There are many ways that go in the right direction; you don’t have to pit them against each other. Pellets are just as much a part of it as heat pumps.

Some view the topic of self-consumption purely from the perspective of profitability. Others see additional aspects such as autonomy and climate contribution, perhaps they also enjoy tinkering with the technology. There are many good reasons not to choose the most economical solution. At least I have never placed consistent profitability at the forefront when making important decisions in life and have done quite well with it. By the way, this also applies to less important decisions.

For a pellet heating system, the HB should preferably live in the neighboring town. I have gained a few years of professional experience with it; these things are still quite prone to malfunctions, and replacement parts are really expensive. If at all, then definitely get a full service contract (but it usually doesn't come cheap).