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Energy Calculator

With any renewable energy system, performance should be understood before investing and installing a device. A properly sized SunHopper-D™ system with adequate sunlight will reduce energy consumption up to 75% and can support off-grid installations. Our Energy Calculator estimates the system performance, and energy savings per year to help size the system and set realistic expectations.

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Backup Power Source
Heater Power (kW)
Please Select Backup Energy
Water Usage profile
Array Size (Wp)

DISCLAIMER: This calculator uses PVWatts V8 from NREL for expected solar output energy along with calculations from GreenPWR to calculate hot water energy demand and supplied energy. These figures assume no shading during the day, a flat plate installation set at optimal tilt, and azimuth of 180°. This data is meant to show long-term averages of the expected system performance. Variations will occur in real installations due to several factors including but not limited to PV panel variation, any shading conditions, weather conditions, and water temperature variation. This calculator shows estimated performance and is not guaranteed.

Model assumptions: electric immersion storage water heater UEF: 0.92. Natural gas storage water heater UEF: 0.60. Propane storage water heater UEF: 0.61. Fossil backup using tankless will yield lower energy cost than calculated.




System Diagram

Estimated Performance

Press 'Submit" to calculate results.

Estimate Water Usage

Hot Water Tap

Estimate hot water use from the following:

  1. The average shower consumes 20 gallons of hot water, though this can vary wildly.
  2. Sink usage for food preparation or hand dishwashing consumes 3 gallons of hot water.
  3. Automatic dishwashers on average consume 7 gallons per use.
  4. Clothes washing consumes 15-25 gallons of hot water per use.

The average US household consumes 64 gallons of hot water per day. Reference figures are taken from's article "Sizing a New Water Heater".