Something else to consider is your start up price.. LEC/LEP take 4-6 units to get the same PAR read outs as a DIY Cob light. Also unless youre running DE HPS you dont have to worry about the ceiling height. The amount of lights depends on your budget. But If I had to throw a Light out without thinking I would go for something thats slightly more efficient than a DE HPS and then you can add more in as you go. Heres a start:
CXB3590CD36V3500K 10 COBS @1.75A ON 5.88 PROFILE HEATSINK
16 SQ.FT. CANOPY 92% EFFICIENT DRIVER @13 CENTS PER KWH
Total power watts at the wall: 675.0
Cobs power watts: 621
Total voltage forward: 355
Total lumens: 101596
Total PAR watts assuming 10% loss: 295
Total PPF: 1371.75
PPFD based on canopy area: 922.84
PAR watts per sq.ft.: 18.44
Cob efficiency: 52.87%
Power watts per sq.ft.: 38.81
Voltage forward per cob: 35.49
Lumens per watt: 163.6
Heatsink riser thickness / number of fins / fin's length: 0.27in/14/1.0in
Heatsink area per inch: 260.01 cm^2
Total heat watts: 293
umol/s/W / CRI: 4.65 / Estimated
Heatsink length passive cooling @120cm^2/heatwatt: 135 inches
Heatsink length active cooling @40cm^2/heatwatt: 45 inches
COB cost dollar per PAR watt: $1.61
Electric cost
@12/12 in 30 days: $32.09
Electric cost @18/6 in 30 days: $47.89
Cost per cob: $47.62
Heatsink cost per inch cut: $1.74
Total cobs cost: $476
Total heatsink passive cooling cost: $235
Total heatsink active cooling cost: $78
CXB3070BB3500K 10 COBS @1.75A ON 5.88 PROFILE HEATSINK
16 SQ.FT. CANOPY 92% EFFICIENT DRIVER @13 CENTS PER KWH
Total power watts at the wall: 692.39
Cobs power watts: 637
Total voltage forward: 364
Total lumens: 96060
Total PAR watts assuming 10% loss: 267
Total PPF: 1241.55
PPFD based on canopy area: 835.25
PAR watts per sq.ft.: 16.69
Cob efficiency: 46.53%
Power watts per sq.ft.: 39.81
Voltage forward per cob: 36.4
Lumens per watt: 150.8
Heatsink riser thickness / number of fins / fin's length: 0.27in/14/1.0in
Heatsink area per inch: 260.01 cm^2
Total heat watts: 341
umol/s/W / CRI: 4.65 / Estimated
Heatsink length passive cooling @120cm^2/heatwatt: 157 inches
Heatsink length active cooling @40cm^2/heatwatt: 52 inches
COB cost dollar per PAR watt: $1.21
Electric cost
@12/12 in 30 days: $32.9
Electric cost @18/6 in 30 days: $49.11
Cost per cob: $32.39
Heatsink cost per inch cut: $1.74
Total cobs cost: $324
Total heatsink passive cooling cost: $273
Total heatsink active cooling cost: $90
If you prefer more blue...
1212 4000K80Min 40 COBS
@350 mA ON 5.88 PROFILE HEATSINK
16 SQ.FT. CANOPY 92% EFFICIENT DRIVER @13 CENTS PER KWH
Total power watts at the wall: 518.04
Cobs power watts: 476.60
Total voltage forward: 1361.71
Total lumens: 90070.43
Total PAR watts assuming 10% loss: 239.83
Total PPF: 1265.78
PPFD based on canopy area: 851.55
PAR watts per sq.ft.: 14.99
Cob efficiency: 55.91%
Power watts per sq.ft.: 29.79
Voltage forward per cob: 34.04
Lumens per watt: 188.99
Heatsink riser thickness / number of fins / fin's length: 0.27in/14/1.0in
Heatsink area per inch: 260.01 cm^2
Total heat watts: 209.70
umol/s/W: 2.66 LER: 338.00 QER: 4.75
Heatsink length passive cooling @120cm^2/heatwatt: 97 inches
Heatsink length active cooling @40cm^2/heatwatt: 32 inches
COB cost dollar per PAR watt: $2.00
Electric cost
@12/12 in 30 days: $24.24
Electric cost @18/6 in 30 days: $36.37
Cost per cob: $12.0
Heatsink cost per inch cut: $1.74
Total cobs cost: $480.0
Total heatsink passive cooling cost: $168.78
Total heatsink active cooling cost: $55.68
What I wound consider even though its a bit more work to put together.
1212 3000K80Min 40 COBS
@350 mA ON 5.88 PROFILE HEATSINK
16 SQ.FT. CANOPY 92% EFFICIENT DRIVER @13 CENTS PER KWH
Total power watts at the wall: 518.04
Cobs power watts: 476.60
Total voltage forward: 1361.71
Total lumens: 87368.63
Total PAR watts assuming 10% loss: 239.73
Total PPF: 1294.55
PPFD based on canopy area: 870.90
PAR watts per sq.ft.: 14.98
Cob efficiency: 55.89%
Power watts per sq.ft.: 29.79
Voltage forward per cob: 34.04
Lumens per watt: 183.32
Heatsink riser thickness / number of fins / fin's length: 0.27in/14/1.0in
Heatsink area per inch: 260.01 cm^2
Total heat watts: 209.70
umol/s/W: 2.72 LER: 328.00 QER: 4.86
Heatsink length passive cooling @120cm^2/heatwatt: 97 inches
Heatsink length active cooling @40cm^2/heatwatt: 32 inches
COB cost dollar per PAR watt: $2.00
Electric cost
@12/12 in 30 days: $24.24
Electric cost @18/6 in 30 days: $36.37
Cost per cob: $12.0
Heatsink cost per inch cut: $1.74
Total cobs cost: $480.0
Total heatsink passive cooling cost: $168.78
Total heatsink active cooling cost: $55.68
