Net Zero Home: Lessons and Regrets After Two Years Off-Grid

Practical lessons from two years of living in a purpose-built net-zero home with 20kW solar, geothermal heating/cooling, and battery storage. ## Lesson 1: Run Conduit Everywhere The single most important construction decision: install empty conduit to every room and exterior wall during framing, at a cost of $1,500-3,000. Technology evolves — EV charging, battery storage, additional solar, new smart home standards — but retrofitting wiring through finished walls costs 2-3x more than the original installation. Future-proofing isn't about picking the right technology; it's about creating pathways for technology that doesn't exist yet. ## Regret: Hot Water Storage **Installed:** Geothermal desuperheater feeding a Rheem heat pump water heater. Works but cannot time-shift hot water production to peak solar hours. **Wished for:** SunAmp Thermino heat battery using phase-change materials (salt compounds) that store 4x more thermal energy than water in the same volume. Charges during peak solar production, provides hot water on demand. Studies show 36% of hot water can be heated entirely by stored solar. Uses one-third the floor space of a conventional tank. Was not available in the US market at the time of construction. ## Regret: EV Charging Capacity Installed one Level 2 (240V) charger. With two EVs now in the household, the second charges on a standard 120V outlet overnight — functional but slow. Should have run 240V circuits to multiple garage locations during construction (see Lesson 1: conduit). ## Regret: Battery Backup Scope Has battery storage for essential loads but not whole-home backup. During grid outages, the geothermal system (a major load) cannot run on battery. A whole-home battery system like Tesla Powerwall or Enphase IQ would allow the house to island completely from the grid during outages while still running HVAC. ## What Worked Well The 20kW solar array consistently produces more electricity than the household consumes annually — true net-zero on a yearly basis. Geothermal provides highly efficient heating and cooling with no outdoor compressor noise. The combination eliminates gas service entirely (no gas bill, no gas infrastructure).