My mistakes & corrections

No project runs error-free. This site lives on honesty — so here are the mistakes that taught me the most. Maybe they'll save you the same ones.

Mistake 1: comparing offers "by feel"

Early on I compared bottom lines without checking scope. That's almost always wrong: one offer looked cheaper — until I noticed backup and metal tiles were options not included at all (together ~€2,400). Correction: normalise every offer to identical scope first, then compare prices.

Mistake 2: underestimating the meter cabinet

I'd dismissed the meter cabinet as a minor detail. In fact it was one of the biggest differences between vendors (new cabinet vs mere modernisation, up to ~€4,000). Correction: make the cabinet scope an explicit comparison row and ask about it specifically.

Mistake 3: believing technical claims too quickly

At first I took manufacturer/salesperson statements at face value — e.g. about local controllability. Only reading the manuals revealed the fine, decisive details (such as certain inverters not allowing reading and writing at the same time). Correction: treat claims as hypotheses and check them against manuals/independent sources.

Mistake 4: nearly accepting an oversized heat pump

Early offers proposed markedly oversized heat pumps — sized on the old consumption, not the renovated state. Too big means short-cycling and worse efficiency. Correction: insist on a Heizlast that reflects the renovation.

Mistake 5: nearly giving up rights too early

I almost waived the cancellation right early to "order faster" — before a critical contract wording ("up to X kWp") was clarified. Correction: have scope- and price-critical points confirmed in writing before giving up protective rights.

The pattern behind the mistakes

Almost all the mistakes had the same root: trusting too early, checking too late. The correction was the same attitude every time — ask politely but persistently, everything in writing, everything checked against an independent source.

In short: the costliest mistakes were: scope not normalised, meter cabinet underestimated, claims believed unchecked, oversizing nearly accepted, protective rights nearly given up too early. The antidote: set priorities, equalise scope, everything in writing, verify claims.

That's the end of the learning path — and also its beginning: with this hindsight, back to the start, to the foundations, or straight to the topic that affects you most.