Cooling Cost Analysis
PTAC Usage Timeline (Dome 15, Summer 2014)
The resident used AC on only 23 of 122 summer days. Usage stopped after July 9 — likely moved out after Spring graduation or Summer Session I.
Indoor Temperature Model
Without AC: Indoor = 0.555 × Outdoor + 40.9°F
(R² = 0.68, 4-dome aggregate, PTAC days excluded)
| Outdoor | Indoor (no AC) | AC Needed? |
|---|
| 70°F | 80°F | No |
| 80°F | 85°F | Threshold |
| 90°F | 91°F | Yes |
| 100°F | 96°F | Critical |
| 110°F | 102°F | Dangerous |
Indoor exceeds 85°F when outdoor exceeds 79°F — this happens 104–132 days per year in Davis.
Estimated Occupancy Over Time
Weather Context (CIMIS Station 6, Davis)
Annual Comparison
| Year |
Total kWh |
Total CCF |
Avg Occupancy |
kWh / Resident |
Per-Resident Usage (Normalized for Occupancy)
Per-Capita Electricity (kWh/person)
Per-Capita Water (CCF/person)
Electricity vs Temperature
Weather data: CIMIS Station 6, Davis
Historical Baseline (2014-2015 SWARM Data)
Source: HOBO U30 data loggers deployed as part of the SWARM IoT sensor network.
11 months of continuous monitoring across multiple domes.
Indoor vs Outdoor Temperature (2014-2015)
Residents activated space heaters when outdoor temp dropped below 57°F. Indoor temps reached
90°F in summer with no AC — SolMod mini-split would address this.
Ground Source Heat Pump (Dome 13 — Experimental)
Winter Performance
67°F indoor
Outdoor avg: 49°F — +17°F gain
Moderate heating benefit from ground loop
Summer Performance
78°F indoor
Outdoor avg: 67°F — +11°F gain (worse than passive!)
Indoor was WARMER than outside in summer
The ground loop experiment was the worst thermal performance on campus. Indoor temperatures
were higher than outdoor in summer — the system added heat rather than removing it.
Dome 6 Daily Circuit Usage (2014-2015)
This is the level of circuit visibility SolMod’s SPAN panel would restore.
What SolMod Monitoring Would Show
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Real-time circuit-level power (kW) per dome — not just community total
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Indoor temperature alerts — flag when any dome exceeds 85°F
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Appliance detection — identify space heaters, forgotten devices
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Solar production + battery status — track net export per dome
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Cost per dome per day — not just monthly community total
The SWARM loggers provided this visibility from 2014-2015. They have been offline for 11 years.
SolMod makes it permanent.