[stevehull]

Nibs - I applaud the use of 12 volt solar and batteries . . . . but.

The use of a 12 V water pump will be far more energy costly compared to an equal flow 120 V AC pump. Ohm's law dictates that as power = current squared times resistance (i**2 x R).

Compared to a 120 V circuit, a 12 V pump must use ten times the current to get the same power (P=Ei). Assume the winding resistance is about the same for both. It is the square of the current that kills the efficiency. That is why higher voltage water pumps are more efficient than lower voltage ones.

These hydronic pumps are going to be on a lot of time so even small (and the above is not small) decreases in efficiency will cost you a lot over even a few years - a huge amount over ten years. Do your homework carefully.

I am a BIG advocate of rational use of PV and stored power when applicable. If you were off grid, then I might (and this is a might) suggest a 12 V pump - but it is a very inefficient way to pump water. Most off gridders all have a 12 to 120 V AC inverter for appliances/applications that work best on 120 VAC.

I might suggest the use of the 120 V AC mains for this hydronic application and the use of a PV system and inverter (highly efficient) to create the 120 V power you need for this application.

As a PV advocate, I appreciate the used of stored power, but the 12 V pump inefficiency, the cost of the 12 V battery, its upkeep/replacement and the associated costs just make this a 120 V application.

Hope I am not disappointing . . . .


Steve