Electrical concept for outdoor facilities

The cistern was intended for the garden from the beginning and since we have to build a retention cistern anyway according to the development plan, the only question left is how much usable volume I want in the cistern. Automatic irrigation is not planned for now.

I wouldn’t start with 5x1.5 at all. That is, for example, definitely too little for the sauna. And also for the possible wall box(es). So at least 5x2.5 because it also looks like at every extraction point at least one major consumer is planned.

I would use 5x1.5 at most for the garden lighting.

What are the advantages and disadvantages? And how complicated is it with an intermediate distribution board and branch? I am a software person and this is clearly a hardware problem

The effort stays about the same. But with the approach of three separate cables you have to plan for more space in the house distribution board and consider the lengths more critically. Also, you may need an additional installation conduit in the floor slab/basement wall. But you can then switch everything off from the inside if you want.

With a sub-distribution in the garden house or something like that you need the distribution board itself and other small things. Additionally, the supply line definitely no longer has to be done with 5x2.5 but with 5x4 because from here the three cables to the consumers branch off.

In the end, it will most likely be about the same price-wise.

Take the cistern as large as possible and try to drain everything that can go in there. Saves fees for rainwater and gives you more water available. Also helps if you ever want to water automatically.

House, garage, carport all have to be connected to the cistern anyway. Originally, about 5-6 cbm was planned, which should be plenty for the garden. The problem is that I now have to bury 3.5 cbm of air, which is well over half of the originally planned cistern. A classic case of good intentions and modest implementation. The consideration now is a cistern with a total volume of 7-8 cbm. And looking at the drawings, the retention of rainwater on the property can certainly be "optimized" with simple means ;)

With 3.5 m2 you won't get far if you want it to be "green." For example, lawn requires 15 liters per m2 per week when it's warm. If it doesn't rain for two weeks.... Install a [Retensionszisterne] which can be "optimized" later ;) If possible, I would also connect the terrace, yard ...