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723 Spring Street – Solar System Case Study

723 Spring Street – Solar System Case Study. Scott Phillips October 8, 1012. Summary. The SunPower 8.64 kW system generated 10,429 kWhs and provided 55% of the of the annual energy usage

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723 Spring Street – Solar System Case Study

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  1. 723 Spring Street – Solar System Case Study Scott Phillips October 8, 1012 723SpringStreet.com

  2. Summary • The SunPower 8.64 kW system generated 10,429 kWhsand provided 55% of the of the annual energy usage • Based on BTU’s per square foot, 723 Spring Street uses 50% of similarly sized homes. • The net cost of the system after utility rebate & federal tax credit was $29,276 or $3.39/watt. • Year 1 Savings were $2,367 including an 11 cent/kwh renewable energy credit, first year total utility cost was $0, the simple payback was 12.5 years and the annual ROI equals 8%. 723SpringStreet.com

  3. Home Construction & Design • 723 Spring Street was Ann Arbor’s first LEED Platinum house, constructed in 2007 by Meadowlark Builders. • The envelope of the home consists of ICF walls, SIP panel roofs and the home has geothermal heating & cooling. • Other efficiency factors include an energy recovery ventilator, recirculating hot water system, low flow water fixtures and solar powered window blinds. • 723 Spring Street scored a HERS Rating of 40, using approximately 60% less energy than a Code built home 723SpringStreet.com

  4. SOLAR SYSTEM DETAILS • 8.64 kW system comprised of 36 SunPower E19/240 solar panels at 240 watts and 19.3% efficiency - Enphase Energy Micro-inverters. • The panels were mounted with UNIRAC SolarMount rail systems. RoofGrip Easy Feet mounts attach the rail system to the SIP roof. • The system also includes an Envoy Communications Gateway and web-based Enlighten monitoring website. • The system was installed in August of 2011 by Mechanical Energy Systems 723SpringStreet.com

  5. SOLAR SYSTEM PERFORMANCE • Based on system design, the projected KWh production for was 10,301. • The actual production was 12,380 kWh or 120% of projection. • Peak daily generation was 53.7 kWh. • This chart displays monthly kWh actual production Vs. estimated. 723SpringStreet.com

  6. ENERGY USAGE • Total energy usage for this twelve month period was 23,319 kWh. • The PV system provided 55% of annual electrical energy usage and 41% of total energy usage. • At 105M British Thermal Units (Btus) of annual energy usage, 723 Spring uses 65% of the energy of similar sq. ft. homes. 723SpringStreet.com

  7. COSTS, REBATES & CREDITS • The gross invoice cost of the systems was $57,375 or $6.64/watt. • The DTE Solar Currents Program provided an up-front rebate of 2.40 per DC watt which totaled $15,552 and an on-going production incentive 0.11 per kWh. • Less the federal tax credit of $12,547 ($41,823 X 30%), the net cost was $57,375 – 15,552 - $12,547 = $29,276 or $3.39/watt. • This charts compares 723 Spring Street’s utility cost per sq. ft. for new construction, single family homes & similarly sized homes. 723SpringStreet.com

  8. PAYBACK / ROI / REAL ESTATE VALUATION • Based on net cost of $29,276, generation of 10,761 kWh and savings of $2,367, the payback is 11.3 years &ROI is approximately 9%. • The annual savings of $2,582 is comprised of $1,398 in energy purchase reductions & $1,184 in renewable energy credits. • Based on research from Clean Power Research, this ROI & payback is slightly better than the U.S. annual average of similar homes. 723SpringStreet.com

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