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Potential Energy - Hydropower

Elevation and potential energy in hydropower.

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When a body of mass is elevated against the gravitational force - the increase in it's potential energy can be calculated as

Ep = Fg Δh

    =  m ag Δh                                (1)


Fg = gravitational force (weight) acting on the body (N, lbf)

Ep = potential energy (J, ft lb)

m = mass of body (kg, slugs)

ag = acceleration of gravity on earth (9.81 m/s2, 32.17405 ft/s2)

Δh = change in elevation (m, ft)

Example - Potential Energy of Elevated Body - in SI units

Potential elevation energy

A body of 1000 kg is elevated 10 m. The change in potential energy can be calculated as

 Ep = (1000 kg) (9.81 m/s2) (10 m)

    = 98100 J

    = 98 kJ

    = 0.027 kWh

Elevation and potential energy

Example - Potential Energy of Elevated Body - in Imperial units

A body with weight (force) 500 lbf is elevated 30 ft. The change in potential energy can be calculated as

 Ep = (500 lbf) (30 m)

    = 15000 ft lb 

A body with mass 15 slugs is elevated 30 ft. The change in potential energy can be calculated as

 Ep = (15 slugs) (32.17405 ft/s2) (30 m)

    = 14478 ft lb

Potential Energy in a Tank or a Reservoir - Spreadsheet Calculator

Hydropower - energy accumulated in water reservoir

You can estimate potential elevation energy (hydropower) in a tank or a reservoir by dividing the volume in horizontal slices and calculate the elevation energy for each slice - as it is done in the spreadsheet calculator below:

Potential energy accumulated in a water reservoir - hydro power

You can copy the spreadsheet to your Google Drive or to your local drive if you want to use it as a template for your own calculations.

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  • Engineering ToolBox, (2008). Potential Energy - Hydropower. [online] Available at: [Accessed Day Mo. Year].

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