Let's compare ROI if electricity is of minimal concern, as it would be with a paid off solar power plant.
We can go into ROI's starting from scratch of a new buildout later.
I think the maths are good
You need to compare Antminer S19j+ with other modern ASICs. Antminer S21 is already outdated. But if you have a choice of only 2 ASICs, then in your case Antminer S19j+ is more profitable, but the bad thing is that you can mine only one third of the day.We can go into ROI's starting from scratch of a new buildout later.
I think the maths are good
Comparing ROI of Older vs. Newer Equipment
Equipment Specifications
Antminer S19j+
Hash Rate: 95 TH/s
Power Consumption: 3,250 W
Price per Miner: $300
Antminer S21
Hash Rate: 200 TH/s
Power Consumption: 3,500 W
Price per Miner: $4,000
Proportion of Network Hash Rate
S19j+ Proportion:
Proportion = (95 × 10¹² H/s) ÷ (663 × 10¹⁸ H/s) ≈ 1.432 × 10⁻⁷
S21 Proportion:
Proportion = (200 × 10¹² H/s) ÷ (663 × 10¹⁸ H/s) ≈ 3.016 × 10⁻⁷
Expected BTC per Miner per Day For 24-Hour Operation:
S19j+:
Expected BTC/day = 450.72 BTC × 1.432 × 10⁻⁷ ≈ 0.0000646 BTC/day
S21:
Expected BTC/day = 450.72 BTC × 3.016 × 10⁻⁷ ≈ 0.000136 BTC/day
Adjusted for 8-Hour Operation:
S19j+:
Adjusted BTC/day = 0.0000646 BTC/day × (8 ÷ 24) ≈ 0.0000215 BTC/day
S21:
Adjusted BTC/day = 0.000136 BTC/day × (8 ÷ 24) ≈ 0.0000453 BTC/day
Daily Revenue per Miner
S19j+ Revenue:
0.0000215 BTC/day × $62,125.31 = $1.34 per day
S21 Revenue:
0.0000453 BTC/day × $62,125.31 = $2.82 per day
Payback Period
S19j+:
Payback Period = $300 ÷ $1.34 ≈ 224 days
S21:
Payback Period = $4,000 ÷ $2.82 ≈ 1,418 days
Annual Revenue and ROI
S19j+ Annual Revenue:
$1.34/day × 365 days = $489 per year
Annual ROI:
ROI = (($489 - $300) ÷ $300) × 100% ≈ 63%
S21 Annual Revenue:
$2.82/day × 365 days = $1,029 per year
Annual ROI: Negative until after the payback period (~3.89 years)
Investment Comparison
Investing $4,000:
Option 1: 1 S21 Miner
Total Hash Rate: 200 TH/s
Daily Revenue: $2.82
Payback Period = $4,000 ÷ $2.82 ≈ 1,418 days
Option 2: 13 S19j+ Miners ($300 each)
Total Hash Rate: 13 × 95 TH/s = 1,235 TH/s
Proportion = (1,235 × 10¹² H/s) ÷ (663 × 10¹⁸ H/s) ≈ 1.862 × 10⁻⁶
Expected BTC/day = 450.72 BTC × 1.862 × 10⁻⁶ ≈ 0.000840 BTC/day
Adjusted BTC/day = 0.000840 BTC/day × (8 ÷ 24) ≈ 0.000280 BTC/day
Daily Revenue = 0.000280 BTC/day × $62,125.31 = $17.39 per day
Payback Period = $4,000 ÷ $17.39 ≈ 230 days
Conclusion: Investing in multiple S19j+ miners yields higher hash rate and faster ROI compared to a single S21 miner.