How we calculate

Every number on this site comes from the formulas and sources below. If something looks wrong, tell us.

The formula

For each way you use the PC (gaming, other use, left on, sleep, off) we compute power at the wall:

Wall power = (graphics card + processor + rest of system) ÷ power supply efficiency + monitor

Energy per day is wall power × hours, summed over the states. Cost is energy × price per kWh. A month is 30.437 days.

Assumptions

• Rest of system (motherboard, memory, storage, fans): 40 W gaming, 30 W light use, 25 W idle. Sleep is 2 W and off is 0.5 W at the wall.
• Light use adds 15 W to idle component power for browsing, video and office work.
• Power supply efficiency is the typical figure for each rating at moderate load; at light load we subtract 7 percentage points, because power supplies are less efficient there.
• Range: the low and high results use light and heavy gaming loads, and ±15% on light-use and idle power.

Monitors

Component power figures

Graphics card board power is the maker’s rated total board power. Processor maximum power is the maker’s package power limit (PL2 for Intel, PPT for AMD).

Gaming draw is marked Measured when it comes from published measurements, which are linked on the part’s page. Otherwise it is marked Estimate:

• Graphics cards: 60%, 85% and 100% of board power for light, typical and heavy gaming. Cards often run close to their limit at high resolutions and lower at 1080p or with a frame cap.
• Processors: typical gaming package power estimated from published review ranges, with light and heavy cases at about 65% and 145% of that value. Games use far less than a processor’s maximum power.

We are replacing estimates with measured values as they are verified, including wall measurements from readers.

Electricity prices

• Europe: Eurostat, nrg_pc_204, Household consumers, 2,500–4,999 kWh/year, all taxes and levies included. Latest period: 2026-S1.
• United Kingdom: Ofgem energy price cap (GB average, direct debit). Unit rate only; the daily standing charge is not included.
• Switzerland: ElCom (Swiss Federal Electricity Commission), 2026 average tariff. Typical household, 4,500 kWh/year, national median tariff.
• United States: U.S. Energy Information Administration, Electric Power Monthly, Table 5.6.A. Average residential price, all charges divided by kWh sold. Recent months are preliminary. Latest month: August 2026.
• Currencies: European Central Bank euro reference rates, 2026-10-30. Currencies without an ECB rate are shown in euros.

Household prices are averages. Standing charges, tiers, time-of-use rates and your own contract can make your real price different; you can enter your own price in every calculator.

Live market prices

Live prices are day-ahead wholesale prices for each hour (quarter-hours averaged to hours), updated daily after the market publishes, for today and tomorrow. Countries with several bidding zones show the average of the zones we have; if only some zones are available, the page says which.

We only publish prices we are licensed to reuse: data from Bundesnetzagentur | SMARD.de under CC BY 4.0 (retrieved via the Energy-Charts API of Fraunhofer ISE), and ENTSO-E Transparency Platform data where configured. Zones currently covered: AT (SMARD via Energy-Charts), BE (SMARD via Energy-Charts), CH (SMARD via Energy-Charts), CZ (SMARD via Energy-Charts), DE-LU (SMARD via Energy-Charts), DK1 (SMARD via Energy-Charts), DK2 (SMARD via Energy-Charts), FR (SMARD via Energy-Charts), HU (SMARD via Energy-Charts), IT-North (SMARD via Energy-Charts), NL (SMARD via Energy-Charts), PL (SMARD via Energy-Charts), SE4 (SMARD via Energy-Charts), SI (SMARD via Energy-Charts).

Wholesale prices are not what you pay on a fixed tariff. They exclude network charges, taxes and supplier margins.

Other formulas

• Power supply size: (board power × power limit + processor maximum power + 75 W) × 1.2, rounded up to a common size.
• Undervolt performance: performance kept ≈ power limit^0.2. This curve is fitted to published power-limit tests, such as an RTX 5090 keeping about 95% of its performance at 450 W instead of 575 W. Real results vary.
• Everyday comparison: a typical fridge-freezer uses about 250 kWh a year.
• Heat: all wall power becomes heat in the room; heat pumps and air conditioners move 3 kWh of heat per kWh of electricity; gas boilers are 90% efficient.

Update schedule

Live prices and exchange rates update daily. Household prices are checked weekly and change when the sources publish new periods (Eurostat twice a year, EIA monthly, Ofgem quarterly, ElCom yearly).