Boulder - GoElectric: Fossil Fuel Free
Owner: Dave Penzkover
Mechanical: MidWest HVAC
Plumbing: Gould Plumbing
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SUMMARY
Built: 1996, retrofits: 2018-present
Size: 3,250-SF
Budget: Not disclosed (100% performance premiums)
Type: Retrofit
Performance: All-Electric, Net Zero
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NARRATIVE
This South Boulder home, remodeled in 2006, became the Penzkover family's in 2018. Dave Penzkover, Boulder chapter leader for Go Electric Colorado, has a background in architectural design, sustainable development, and energy efficiency. After nearly a decade of incremental steps, he's been freed from fossil fuels entirely, ceremoniously removing the gas line just recently.
The house came with a 7.2 kW solar array from 2009. The first move was the thermal envelope: air sealing, attic insulation to R-60, crawlspace and rim joist work, and a vapor barrier that also serves as radon mitigation. Appliances followed as they wore out: an induction cooktop and the family's first EV in 2019–2020, then in 2022–2023 a 4-ton cold-climate Mitsubishi heat pump system replacing two aging furnaces. It has held through -20°F with no backup heat. A heat pump water heater replaced two 19-year-old gas units in December 2025; rebates kept it inexpensive. In January 2026, Xcel Energy disconnected the gas service (after asking three times if he was sure).
The lesson: electrification doesn't have to happen all at once. Improve the envelope first, then replace equipment as it fails. The result is a quieter, more comfortable house, largely powered by its own roof, with annual bills no higher than on cheap gas.
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SPECIFICATIONS
WINDOWS
Spec: Uf: 0.3
ENVELOPE + INSULATION
Airtightness: 3.0 ACH50
MECHANICAL
Heat Pump: (2) Mitsubishi 4ton, MXZ-SM48NAMHZ
Heat Pump Water Heater: GE GeoSpring 50 Gallon 240v
ON-SITE RENEWABLES
PV: 7.2kW, SMA Inverter
OTHER GREEN FEATURES
Induction Cooktop
EV Charging (2)
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