TRON Energy calculator

100 USDT TRC-20 transfers a month need 8,480,000 Energy. Burning TRX for that costs 883 TRX; renting the same Energy costs 356.16 TRX — a saving of 526.84 TRX a month.
A transfer to an address that already holds USDT needs 65,000 Energy; one to a new address or an exchange deposit address needs 131,000. The amount of USDT you send makes no difference.
Result

Your monthly cost, both ways

Burning TRX883 TRX≈ $247 per month · 10,596 TRX a year
Renting Energy356.16 TRX≈ $100 per month · 4,273.92 TRX a year
You save526.84 TRX≈ $148 per month · 6,322.08 TRX (≈ $1,770) a year
TransfersEnergy eachEnergy totalRentedBurned
70 to active addresses65,0004,550,000191.1 TRX479.5 TRX
30 to new addresses or exchanges131,0003,930,000165.06 TRX403.5 TRX
See full pricing
Figures use a one-hour rental at 42 sun per Energy against the network burn price of 100 sun. Bandwidth and one-off address activation are not included — pricing lists both.