Madelyn, a Santa Fe, New Mexico homeowner and single mother upgraded her 3200- square foot home with solar power. Her building was less than 10 years old, and the building insulation, all equipment and appliances were energy-efficient and well-maintained.
She decided to opt out of a formal energy audit and felt it was unnecessary to do further energy-efficient upgrades. After the completion of the $44,000 solar upgrade, she realized potential savings of over $200-$250 a month.
- The home is heated in winter by a natural gas radiant heat system built into the concrete slab flooring.
- The home is a typical southwestern style, stucco walls, flat roof.
- The home is not conventional in that it was custom built by the original owner; it is a split-level with a sectioned roof of several different dimensions. The split-sectioned roof proved a challenge in configuring the PV system as the panels had to be divided among the roof sections instead of continuous arrays.
- The PV system was specified to be 24 220w panels manufactured by Schott, a subsidiary of the Carl-Zeiss Stiftung non-profit foundation, with a manufacturing plant in Albuquerque, NM.
- These panels were chosen mainly because they are high-quality and manufactured locally.
- Total output of the panels is 5,280 watts.
- The PV system was grid-tied with a Sunny Boy SB6000 grid-tie inverter.
Now the Utility Company Pays the Homeowner
The installation was completed in January, 2011. As part of the grid-tied system, a contract was performed with the local power company, PNM, which offers a program for independent power generation with the goal of meeting New Mexico state mandates for renewable energy quotas. The net result was that the homeowner was paid a KwH fee for all power generated by her system in addition to reducing her grid net energy usage to near zero.
The solar PV system generates between 25KwH to 35 KwH per day, depending on weather conditions and season. Santa Fe has over 300 days of sunshine a year, an ideal candidate for tapping into solar energy. The report on the following page illustrates all economic data on project.
NOTE: In this case study the building owner chose to pay cash for her system. Not everyone has extra capital, and most people will need to finance their improvements. If at all possible, it‘s always best to lend the money to yourself, and to balance the interest paid with interest earned.
Energy Efficiency Case Study Data
| PROPERTY CITY, STATE | Santa Fe, NM | |||
| SQUARE FOOTAGE | 3200 | |||
| NEW/EXISTING | Existing | |||
| COST OF CONSTRUCTION | $ 0 | |||
| COST OF LAND | N/A | |||
| EXISTING PROPERTY VALUE | $ 500,000 | |||
| COST OF RENEWABLES | $ 45,000 | 5.28 kW System | ||
| TAX CREDITS, REBATES | $ 13,500 | |||
| Utility (Elec) kWh rate | $ 0.09 | PG&E Utility | ||
| Monthly electricity savings | $ 170 | |||
| Yearly electricity savings | $ 2,040 | |||
| Monthly energy production | $ 52 | |||
| Yearly energy production | $ 377 | |||
| Yearly utility savings | $ 2,417 | |||
| 2011 | Usage (kWh) | Generation (kWh) | Net (kWh) | Net Energy Payment |
| April | 64 | 878 | 814 | $ 106 |
| May | 14 | 879 | 865 | $ 101 |
| June | 45 | 1015 | 970 | $ 117 |
| July | 311 | 766 | 455 | $ 58 |
| August | 391 | 757 | 391 | $ 91 |
| September | 287 | 790 | 503 | $ 95 |
| October | 515 | 729 | 214 | $ 59 |
| November | 941 | 621 | -320 | -$ 29 |
| December | 1563 | 187 | -1376 | -$ 124 |
| January | 1376 | 469 | -907 | -$ 132 |
| February | 770 | 606 | -164 | -$ 15 |
| March | 465 | 872 | 407 | $ 49 |
| TOTAL | $ 377 | |||
| Formula 1, PV | $ 30,115 | |||
| Formula 2, SQ Ft * $20 | $ 48,330 | |||
| INCREMENTAL PROP VALUE | $ 39,222 | |||
| Total Upgrade Investment | $ 31,500 | Cost of renewables less tax credits | ||
| NEW PROPERTY VALUE | $ 539,222 | $ 500,000 (existing property value) + $ 39,222 (IPV) | ||
| Traditional Payback | $ 49,893 | $ 31,500 (loan) + $ 18,393 (interest paid 20.0 years) | ||
| **GEM Payback Method | $ 40,382 | $ 31,500 (loan) + $ 8,882 (interest paid 10.4 years) | ||
| FUTURE VALUE (FV) | $ 79,904 | @ 5%, 20 years | ||
| Could include future electric vehicle power generation instead of net energy pmt from utility | ||||
| **GEM Payback Method includes extra energy savings pmt + Bi-Weekly payment | ||||
| Utility prices expected increases of 30% in next 5 years not used in calculation | ||||