Most "is mining profitable" articles skip the only number that matters: what MLRT price would cover your electricity bill. This procedure walks through the calculation in five steps, using numbers you can measure today.
Step 1: Measure your power draw at the wall
Plug your mining PC into an inline power meter. Run the miner under normal conditions for at least an hour. Record the steady-state watts. Spec-sheet TDP numbers are not a substitute; real draw is often different.
Step 2: Convert watts to daily kWh
Multiply your watts by 24 and divide by 1000. A 300W system uses 7.2 kWh per day. Write this in your spreadsheet.
Step 3: Multiply by your real electricity rate
Use the rate on your actual bill, including taxes and delivery charges, not the headline number on a comparison site. A 7.2 kWh/day setup at $0.15/kWh costs $1.08/day to run.
Step 4: Find out how much MLRT you actually earn per day
Run your miner for 24 hours at normal settings, against current network conditions. Record the MLRT credited to your wallet or pool account. Do not use a marketing-page estimate; use what your hardware actually produced.
Step 5: Divide
Divide your daily power cost by your daily MLRT yield. The result is the MLRT price at which mining exactly covers its own electricity. If today's MLRT price is above that number, you are net-positive on electricity. If it is below, you are subsidising the network from your wallet, which is fine if you are doing it on purpose.
What this number is not
This is not a profit number. It does not include hardware depreciation, cooling costs in summer, or your time. It is a clean floor: at this MLRT price, the lights stay on. Anything above that is the actual margin you have to play with.