Free tool
Energy cost calculator
Work out what a machine or a line costs in electricity a year, how much of it goes on running without producing, and what that means per unit. Enter the rated power, the load and the hours; change the price and see the result at once.
Cost = rated power × load × hours × days × price per kWh
The formula
How a machine’s energy cost is calculated
A machine rarely draws its full rated power. What it uses is its rated power times the share it actually draws, times the hours it runs. Count the hours it produces and the hours it runs without producing separately: the second group is where the easiest savings usually are.
- Production energy
- Rated power × average load × production hours per day × days per year
- Idle energy
- Rated power × idle load × idle hours per day × days per year
- Cost
- Total energy × price per kWh
- Per unit
- Total energy ÷ units produced in the year
- CO₂
- Total energy (MWh) × grid emission factor (t CO₂ per MWh)
Use the price per kWh you actually pay, with taxes and network charges, not the energy component alone. A nameplate tells you the maximum; a meter on the machine tells you what it really draws, hour by hour.
Worked example
A compressor, step by step
A 75 kW compressor running 16 hours a day at 80% load and 8 hours a night unloaded at 25%, 300 days a year, at an example price of €0.15 per kWh and 1,200 units an hour. The calculator opens with these values; replace them with your own.
- Production energy 75 kW × 80% = 60 kW × 16 h × 300 = 288,000 kWh
- Idle energy 75 kW × 25% = 18.75 kW × 8 h × 300 = 45,000 kWh
- Cost 333,000 kWh × €0.15 = €49,950 a year
- Per unit 333,000 kWh ÷ 5,760,000 units = 0.058 kWh, €0.009
Where the easy saving is
In this example the hours without production use 45,000 kWh, 13.5% of the total, and cost €6,750 a year for nothing produced. Switching the compressor off at night, or fixing the leaks that keep it loading, is usually cheaper than any new equipment.
Beyond the estimate
Measured kWh instead of nameplate estimates
This calculator works from nameplate values and your estimates. Proxus reads the energy meters a plant already has together with its production counters, and shows each machine’s real consumption, energy per unit and the hours it runs without producing, live.
- Consumption by meter, line and plant, hour by hour.
- Energy per unit produced, from meters and PLC counters together.
- Night and weekend consumption that shows a machine left running.
Before you ask
Questions about a machine’s energy cost.
- How do I find a machine’s power consumption?
- The nameplate or datasheet gives the rated power, the most it is designed to draw. What it really draws depends on the load and changes through the day; an energy meter or analyzer on its supply gives the actual figure.
- What load factor should I enter?
- The share of rated power the machine draws on average while producing. If you have a meter, divide the measured kWh by the rated power times the hours. Without one, use your best estimate and treat the result as a range.
- Which electricity price should I use?
- The all-in price per kWh from your bill, with taxes and network charges included. If your tariff has time-of-use periods, use the average for the hours the machine runs.
- How is the CO₂ calculated?
- Energy in MWh times the grid emission factor in t CO₂ per MWh. For Türkiye, the Ministry of Energy and Natural Resources gives 0.474 for a site connected to the distribution grid and 0.442 for one connected to the transmission grid (2022). Elsewhere, use your supplier’s or your national authority’s factor.
- How accurate is the result?
- As accurate as the inputs. Nameplate power and an estimated load can be off by a wide margin; a few weeks of metered data give the real consumption and show when the machine runs without producing.