Measuring Head

You will need to measure the vertical drop in feet or meters (referred to as head or fall). 

Altimeter - obtain an altimeter accurate to 10 feet (3m), this is good for measuring falls greater that 70 feet (20m). Take the average of several readings.

Builder’s optical level - measure the fall of the river as you progress along its length. This is good for lower falls and it is very accurate.

Low cost laser level - at dusk or in low light conditions project a horizontal beam and using a long staff measure the vertical drop, as you progress down the stream. You may have to repeat this at a few locations.

Pipe - lay a length of 3/4 inch (20mm) plastic pipe or hose in the riverbed, fix a pressure gauge to the end and measure the pressure of the water with the pipe full, 14.5 psi is 33 feet of fall (100 KPa is 10m of fall). Make sure you clear the line of all air first. This is a very accurate method and easy to do.

Measuring Flow

IMPORTANT: "Gallons," "gals," and "gpm" refer to the US Imperial Gallon , as opposed to the UK Imperial Gallon.

Try and find a place in the stream where it drops quickly over a rock, place your bucket below and measure the time to fill it.

At lower flow rates, less than 150 gpm (10 l/s) you need to be accurate in measuring the flow. If you have a 2 gallon paint pail and the river can fill it in 2 seconds you have 1 gps = 60 gpm, this equates to 227 l/min, 3.79 l/s.

Use the largest possible bucket you can find as the longer it takes to fill the more accurate your reading will be.

For flows greater than 150gpm try to estimate your flow using a larger bucket in the river and measure at various places across the river. It will not be as accurate but at higher flows it is not that critical.

Pipe Length

You are trying to identify a section of your river/stream that falls quickly over the shortest possible distance. There may be several places that are suitable on your river. You also want the turbine to be as near to your house as possible to save on cabling costs.

Measure the pipe length using a long tape or wheel, be accurate, as this information will be required to buy the pipe and it’s important to get it right. Our web power estimator will advise the pipe size required, normally 2 inch (50mm) or larger.

Cable Distance

Measure the cable distance accurately with a tape measure.

The shorter you can keep the cable distance the better, distances of up to 1600ft (500m) are OK but beyond this it is better to use our ME or GE PowerSpout to save on cabling costs.  Distances can then be up to 10,000ft (3000m) when using the ME or GE models. Long run cable costs can kill the economics of micro hydro unless you have a very good site and an economic need, for example displacing high cost fuel generation.

Preferred Voltage

New clients should use 48-volt systems. This ensures cable/regulator and inverter costs are lower and that the systems efficiency is higher. For smaller systems, 24 or even 12 volt might be appropriate.