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The City of Portland, Oregon

Portland Water Bureau

From forest to faucet, we deliver the best drinking water in the world.

Customer Service: 503-823-7770


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Solar on the Slough

Energy Generation

Q: When did the array begin generating electricity?
A: 12/21/2009

Q: How many kWh will the panels generate? What is that equivalent to?
A: The panels will generate 300,000 kWh of electricity each year, equivalent to the energy consumed by about 50 homes. Check real time energy info!

Q: Can the panel generate energy even when it is cloudy?
A: Yes, on the winter solstice (the shortest day of the year) the panels were generating 9,000 watts. That’s enough to power 2-3 homes.

Q: What is the peak amount of electricity the panels can generate?
A: 267,000 watts

Q: How much of the total bureau electricity use will these panels offset?
A: The panels will produce about 1.5% of total bureau electricity used.

Q: What happens to the electricity that is generated?
A: Solar panels absorb the sun’s light. The light (photons) is absorbed by semiconductors in the panels and converted to electrical energy (electrons). That process generates DC (direct current) electricity. The DC electricity is routed to the inverter. The inverter converts the DC electricity to AC (alternating current) electricity. AC electricity is the kind used in (home) consumer appliances.

From there, the energy runs through the meter. The meter carefully measures the amount of electricity generated by the array. The electricity is then sent to the pump station where it is used to keep the facility up and running. When electricity is generated that is not used by the pump station the energy is sent to the PGE utility grid where it is used by PGE customers. If we use more electricity then we generate we pay our normal rates to PGE for difference of power used vs. generated.

Q: If the array generates more power than is used by the Water Bureau does PGE pay the bureau for the electricity sent to the grid?
A: No, our meter acts like a bank account, debiting and crediting solar generation and electricity consumption for a year. In one year if we generate more than we use, then the excess electricity is donated to PGE low-income customers.

Q: How many panels are there?
A: There are 1274 total panels. Each panel is rated at 210 watts.