System Overview
This residential installation is located in central Phoenix on an asphalt shingle roof with an azimuth of 178° (almost true south) and an 18° tilt. Under Arizona Public Service (APS) territory, solar customers operate under net billing rather than traditional 1:1 net metering.
Under the APS Resource Comparison Proxy (RCP) rider, electricity sent back to the grid is credited at a fixed rate established at the time of interconnection, rather than the higher retail tier. For this system, self-consumption is the primary driver of monthly bill savings.
Year-1 Production & Economics
- Total Year-1 Production: 8,840 kWh (measured via Enphase Enlighten monitoring).
- Self-Consumption Ratio: Approximately 58% (elevated during peak summer air-conditioning season from May through September).
- Exported Energy: 3,712 kWh credited at the APS tranche rate ($0.0761/kWh).
- Avoided Retail Cost: 5,128 kWh offset at average retail cost (~$0.148/kWh).
- First-Year Utility Bill Reduction: $1,045 net savings.
Key Learnings
- Self-Consumption Timing Matters: In Arizona's net billing environment, running pool pumps, dishwashers, and precooling the home during peak sun hours (10:00 AM to 3:00 PM) yielded substantially higher savings than exporting excess noon power to the grid.
- Summer Heat Degradation Coefficient: Phoenix summer ambient temperatures frequently exceed 110°F, pushing roof surface temperatures above 150°F. Selecting panels with a low temperature coefficient (-0.26%/°C) prevented severe mid-day clipping.
- No Battery Required for Day-One Payback: While a battery provides backup resilience during grid outages, the system achieved a healthy payback period without the added $10,000+ capital cost of chemical storage.