The physics: every watt becomes heat
A computer does no mechanical work: it does not lift loads or turn wheels. Almost all the electricity it draws from the wall ends up as heat — that is the law of conservation of energy. A tiny share goes into screen light and sound, but that too eventually becomes heat in your room.
So a 250 W graphics card heats a room exactly like an oil-filled heater running at 250 W. The only difference is that the heater just heats, while the graphics card mines at the same time.
The key idea: if you heat the room with electricity anyway, every kilowatt-hour the computer uses is a kilowatt-hour the heater does not. In that case the electricity spent on mining is not an extra cost — it is the same heating.
How much heat a GPU gives off
A graphics card’s heat output equals its power draw. Here is how much heat popular models put out and what they earn (income at the rate of October 25, 2026):
| GPU | Heat output | Heat per night (8 h) | Income / mo |
|---|---|---|---|
| RTX 3060 12 GB | 170 W | 1.4 kWh | $42.19 |
| RTX 4060 | 115 W | 0.9 kWh | $52.31 |
| RTX 4070 | 163 W | 1.3 kWh | $101.25 |
| RTX 4070 SUPER | 200 W | 1.6 kWh | $118.12 |
| RTX 3080 10 GB | 304 W | 2.4 kWh | $90.28 |
| RTX 3090 | 350 W | 2.8 kWh | $99.56 |
| RTX 4080 | 255 W | 2 kWh | $185.62 |
| RTX 4090 | 441 W | 3.5 kWh | $266.62 |
For comparison, a household oil-filled radiator or fan heater usually runs at 1–2 kW. A PC with an RTX 4090 (441 W from the card alone) is a noticeable heater for a small room, while one with an RTX 4060 is more of a gentle warmer that keeps the room from cooling down overnight. Add the CPU and the rest of the system on top of the table — another 50–150 W of heat.
When winter mining is almost free
Homes with electric heating
The best case is when you heat with electric heaters, convectors or an electric boiler. The computer simply takes over part of the heating: a thermostat-controlled heater switches off more often, and your total electricity use barely changes. Mining income then becomes almost pure profit — whatever the card earns, you keep.
A room that needs extra heat
A corner room, a cold bedroom, a home office in a cabin or garage — if there is a heater running there anyway, leave a mining PC on overnight instead. Same heat, but with a paycheck.
When this trick does not work
- Central heating. If you pay a fixed amount for heating, the computer’s heat saves you nothing — the electricity for mining stays a regular cost. Mining can still pay; just count profit after electricity in the calculator.
- Gas heating. Heat from gas is usually cheaper than heat from electricity, so replacing it with a computer does not pay.
- Heat pumps or air conditioners in heating mode. They deliver 2.5–4 times more heat than the electricity they use — more efficient than any heater or computer.
- Summer. In summer extra heat just gets in the way, and if the air conditioning is on, it has to pump out the computer’s heat as well.
How to turn your PC into a “smart heater”
- Put the computer in the room you want to heat, not in a cold hallway or storeroom. The heat should stay where it is needed.
- Mine at night and while you are out so the room is warm when you get back. In FlowHash, just press “Start” before bed.
- Close the door so the heat does not escape to the rest of the home.
- Turn on the CPU too: it adds both heat and income in Monero.
- Keep the heater’s thermostat. Let the computer provide base heat and the heater kick in only when it gets colder than your set temperature.
Safety
- Never cover the computer or place it right against curtains, furniture or a radiator — the case needs free airflow.
- Do not shut the PC in a closed cabinet: the heat should go into the room, not build up around the graphics card.
- Keep the computer free of dust — in winter it runs longer than usual.
- Do not plug a powerful PC and a heater into the same extension cord.
FlowHash pauses mining if the graphics card overheats. Which temperatures are safe and how to extend a card’s life during long sessions is covered in “Does mining damage your GPU?”.
An example
Say a heater runs in your bedroom for 8 hours every winter night. Instead, you leave a PC with an RTX 4070 mining: the card alone gives off about 163 W of heat and earns about $101.25 per month running around the clock — mining only at night brings in roughly a third of that. If the thermostat-controlled heater now switches on less often, the difference on your electricity bill is small, and the earnings stay with you.
The mining calculator gives exact figures for your hardware and rate, and “From mining to Steam” has ideas for spending what you earn.
Bottom line
A computer turns all the electricity it uses into heat. If you heat your home with electricity, winter mining costs you practically nothing extra: you would pay for that heat anyway, and the card’s income is a bonus. With central heating, gas or a heat pump, count mining as usual — after electricity costs.
How much will your PC earn?
Pick your GPU and CPU in the calculator — it estimates income and profit at your electricity rate.