Operating Economics
Average daily cost: $4.28. The greenhouse runs on rooftop solar, Tesla Powerwalls, and natural gas — at 4,979 feet where solar irradiance peaks at 1,028 W/m².
Solar + Storage
The greenhouse electrical panel connects to a Tesla Powerwall + rooftop solar system. The $0.111/kWh rate is the City of Longmont’s residential self-generation solar rate.
62.6% of all greenhouse electrical consumption occurs during peak solar production hours (8AM–5PM). The heaviest loads — fog machine (1,644W), grow lights (1,446W), fans (104W) — run when the sun is strongest. Overnight, one Powerwall (13.5 kWh) covers the full greenhouse load with headroom.
Power vs Solar
Green = greenhouse power draw. Yellow = solar irradiance. When the yellow band is up, the greenhouse runs on sun. The smooth 30-minute averaging eliminates the spiky noise from equipment cycling.
By Circuit & By Cost
Left: power by circuit — red heating, green fans, blue fog/lights. Stacked to show total load composition. Right: daily cost split — yellow electric (solar-offset), red gas (not offset), blue water.
Cost Breakdown
The Gas Problem
Solar covers electric. Powerwalls cover the night. But the Lennox 75,000 BTU gas furnace — the single largest winter cost — runs on natural gas that solar can’t offset.
| Month | Electric (solar-offset) | Gas (not offset) | Water | Total |
|---|---|---|---|---|
| August | $7 | $2 | $11 | $20 |
| January | $90 | $176 | $4 | $270 |
| March | $51 | $62 | $9 | $122 |
January’s $176 gas bill is 65% of total operating cost.
Heating Economics
Gas is 3.9× more cost-effective per BTU — but electric is solar-offset:
| Heater | $/hour | BTU/hr | Solar offset? |
|---|---|---|---|
| Electric (Heat1) | $0.167 | 5,120 | Yes — daytime free, overnight Powerwall |
| Gas (Heat2, Lennox) | $0.623 | 75,000 | No — natural gas |
Electric-first staging makes sense when solar covers the cost, even though gas is cheaper per BTU at face value.
Efficiency
Monthly
The High-Altitude Solar Advantage
Longmont at 4,979 feet receives ~15% more direct solar radiation than sea-level locations at the same latitude. Peak irradiance hits 1,028 W/m² — near theoretical maximum. Colorado averages 300 sunny days per year. The greenhouse’s solar offset performs better than most locations on Earth.