The question to be asked now is the following:
What technology solution are the most suitable for these 12 sites to meet the technical specifications at the least cost?
We will first size and cost the solutions to help make these choices.
Electrical energy from the grid
It would be out of the question to supply these very low monitoring points from a medium voltage EDF grid by connecting from a line at the edge of the road: a special transformer would be needed, with independent metering as for an individual dwelling, without counting the cost of the trench necessary to reach the location of the flowmeter.
On the other hand, if a 230 V AC feed was available near at hand, it would be possible to install a buried cable. The economics of this solution depend on the distance involved. If the terrain is relatively easy, the cost of such connection is estimated at €50/m of trench. The maximum power consumed is 300 mA x 12 V = 3.6 W. A small 5 W transformer 230 V AC/12 V DC would be necessary, but its cost is low (€10-€20). The investment would therefore be €2500 for 50 m and €5000 for 100 m (depending on the distance between the monitoring point and the 230 V mains supply).