[jabl]

> And even with perfect insulation, you will loose approximately 30 to 40% of heat in your piping.

At least here in Finland the norm is losses in the range of 5-20%, with the upper end of the scale for smaller scale networks with smaller diameter piping and low flow rate. In the larger cities losses are closer to the low end of that scale.

In the summer when the consumption is very low (essentially only hot tap water production) losses can rise up to 50%.