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HVAC Cost Estimator.
HVAC Cost Estimator
Indoor cultivation HVAC math: lighting heat + transpiration latent load → cooling tonnage → kWh → monthly cost.
How this works
Indoor cultivation HVAC sizing comes from three loads:
- Lighting heat: nearly all electrical energy into a fixture becomes heat (small percentage becomes photons absorbed by plants — the rest dissipates as heat). Conversion: 1 watt = 3.412 BTU/h. A 3,000W lighting load produces ~10,236 BTU/h that must be removed by HVAC.
- Plant transpiration (latent load): as plants transpire, the water vapor must be removed by dehumidification or condensed by AC coils — both consume energy. Latent load typically scales with active leaf area and DLI; rough estimate is 15-40% of lighting BTU.
- Other equipment heat: fans, pumps, controllers, dehumidifiers all add small amounts. Sum the watts and convert.
Total BTU/h ÷ 12,000 = tons of cooling required. EER (Energy Efficiency Ratio) is BTU per watt of HVAC electrical input; higher EER means lower cost. Modern mini-splits run EER 12-18; older central AC 8-10.
cooling_kW = total_BTU_per_hour / (EER × 1000) daily_HVAC_kWh = cooling_kW × photoperiod_hours monthly_cost = daily_kWh × 30 × $/kWh
HVAC runs primarily during photoperiod (when lights produce heat); light load drops in dark period. The estimator here approximates HVAC running for the photoperiod hours; in practice, residual heat keeps HVAC running 1-2 hours into dark.
Reducing cost
| Strategy | Effect |
|---|---|
| Higher-PPE lighting | Same DLI, less wattage, less heat. PPE 2.7+ vs 2.4 = 12% less heat. |
| Higher-EER HVAC | Mini-split EER 16 vs central AC EER 10 = 60% lower cooling cost. |
| TOU rate optimization | Shift photoperiod to off-peak hours; can save 30%+ in TOU markets. |
| Heat recovery | Route warm exhaust from flower rooms to mother / dry rooms; reduces heating elsewhere. |
| Solar PV during photoperiod | Daytime solar offsets HVAC; battery storage shifts to night. |
| Sealed CO₂-enriched rooms | Lower air exchange = less HVAC reheat; CO₂ unlocks more growth per photon. |
| DLC-listed fixtures + utility rebate | Initial cost subsidized; encourages high-PPE adoption. |
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