# How much energy does pumped storage waste?

Pumped storage wastes 25-30% of the energy it uses for pumping and regeneration. Putting this into perspective, the energy wasted at just the planned South Slope Pumped Storage plant will consume 13% of Colorado’s total wind energy output as waste each day, storing only 6 hours worth of electricity. Since our renewable output is fixed, the energy needed to make up for this will have to come from coal, gas or nuclear.

The calculations follow...

The plant's output power is 432MW. When fully utilized it will run 6 hours per day.

Colorado has 1,248MW of wind power capacity.

Using a typical capacity factor* of 0.30 for wind generators, and a pumped storage efficiency of 0.75 (75%), we can calculate the amount of energy lost during pumped storage:

** 1. Daily Output Energy of the Plant to Grid =** 2,593MWhrs (432MW **x** 6hours)

** 2. Daily Input Energy used by SPSS =** 3,457MWhrs (2,593MWhrs **/** 0.75)

** 3. Daily Input Energy Wasted** = 844MWhrs (3,457MWhrs - 2,593MWhrs )

** 4. Input Power Needed to Cover Waste **= 46.8MW (844MWhrs** /** (24hrs - 6hrs))

** 5. Required Wind Plant Power **= 156MW (46.8MW** /** 0.30)

** 6. Percentage of Colorado's Installed Wind Power wasted** = 12.5% ( (156MW**/**1248MW) x 100)

*Capacity factor specifies what percentage of the plant's maximum power can typically be produced in a given time period. For example: A 1000MW generating plant could in theory produce 24,000MWhrs of energy in a day (1000MW **x** 24hours). However, certain inherent characteristics might limit that generator to 60% of its full power over the day. Such a generator plant would have a capacity factor of 0.60, producing 14,400MWhrs of energy (24,000MWhrs **x** 0.60) in one day.