Use the result as a scenario, not a black box
This tool models the electrical energy consumed by the lights themselves. It does not hide ventilation, HVAC, pumps or dehumidification inside the number, which makes it useful for comparing fixtures apples-to-apples. The heat-load estimate converts the electrical watts into BTU per hour so you can see why lighting choice affects cooling requirements as well as the power bill.
How the math works
Connected watts = fixture watts × fixture count. kWh/day = connected watts ÷ 1,000 × hours/day. Billing-period cost = kWh/day × billing days × utility rate. Approximate heat load = connected watts × 3.412 BTU/h per watt.
Eight 650 W fixtures draw 5,200 W when on. At 12 hours per day they use 62.4 kWh per day. At $0.16/kWh, the lights alone cost about $299 over a 30-day billing period.