Electricity cost calculator: Track consumption and costs
What does a machine cost per shift? What is the annual energy consumption of a lighting unit? With the electricity cost calculator, you combine average power consumption, operating hours, days of use, and the price per unit. The result shows the consumption-based costs for the entered period.
The calculator is suitable for equipment in businesses as well as a single appliance at home. It does not calculate a complete electricity bill: standing charges, demand charges and other fixed fees may also apply. You can use it to compare operating times or identify which device would benefit from more precise measurement.
The inputs: power, operating time and energy unit price
Enter the average power consumption in watts. One kilowatt equals 1,000 watts. The nameplate often specifies a rated or connected load; this is not necessarily the power consumed throughout the entire operating time. For varying loads, suitable measurements or documented manufacturer specifications are helpful.
Operating hours refer to a single day of operation. The number of operating days is the total number within the selected period, not necessarily the number of calendar days. Using 220 working days for a machine accounts for weekends and days of downtime.
Enter the energy unit price in cents per kilowatt-hour. Use the price from your contract and consistently use either net or gross values. With a time-variable tariff, a single price provides only a simplified estimate; an accurate calculation requires matching consumption and price for each interval.
Example: a machine in operation
An average power of 5,000 watts, eight hours per day and 220 operating days result in 8,800 kWh. At an assumed example price of 31 ct/kWh, consumption costs are €2,728. This is a calculation example, not a current electricity offer.
| Input | Example | Meaning |
|---|---|---|
| Power | 5,000 W = 5 kW | Average electrical input |
| Operation | 8 hours × 220 days | 1,760 operating hours |
| consumption | 5 kW × 1,760 h | 8,800 kWh |
| Price | 31 ct/kWh = 0.31 €/kWh | €2,728 during the period |
For refrigeration equipment or other devices that cycle on and off, do not simply multiply the maximum connected load by 24 hours. Measured energy quantities or average power draw over a representative period are more suitable.
Compare multiple devices or buildings
Calculate each device separately first, then add their energy quantities or consumption-related costs. This is helpful for pumps, lighting and office equipment, for example. Use the same periods and price basis when comparing them.
Across multiple buildings, clearly distinguish communal electricity, individual occupier units and technical systems. Without suitable metering, a bill for the whole property cannot be reliably allocated to individual devices. For guidance on procurement across multiple delivery points, see property and condominium management.
What determines the electricity price and the total bill
For an accurate cost calculation, use the energy price from your own contract. This price may include network charges, taxes, and other components in addition to the energy purchase price. The price list details which components are included. A published average household price usually doesn't reflect the specific terms of a commercial contract.
Your calculation is based on the specific consumption-based energy charge. Check your bill to see which components are already included to avoid double-counting. For business tariffs, the billed demand may also be relevant.
Switching providers can change contract terms, but savings can only be determined by comparing offers. Contract duration, start date, fixed prices, bonuses, and quantity requirements are all factors to consider. The Business Electricity Guide summarizes these points.
Calculate your own electricity costs: the complete formula
Consumption in kWh = Power in watts ÷ 1,000 × hours per day of operation × days of operation.
Cost in euros = consumption in kWh × energy unit price in ct/kWh ÷ 100.
The divisions are crucial: watts are converted to kilowatts and cents to euros. For this example, that's 5,000 ÷ 1,000 × 8 × 220 = 8,800 kWh. Then, 8,800 × 31 ÷ 100 = 2,728 euros.
Compare a changed operating time
If the operating time of the same example system is reduced by one hour on 220 days while its average power draw remains unchanged, the calculated difference is 1,100 kWh or €341 at the example price. Whether the shorter operating time is technically and organisationally feasible must be assessed at the site.
High power demand alone does not necessarily mean high annual consumption. A small appliance with very long operating times can consume more energy overall than a high-power device that is only switched on briefly. Therefore, power demand and operating time must always be considered together.
Frequently asked questions about the electricity cost calculator
How do I calculate my household's electricity consumption?
For each device, multiply its average power draw in kilowatts by its operating hours. Add the resulting kilowatt-hours. For total consumption, the difference between electricity meter readings over a clearly defined period is more reliable. For individual devices, therefore, calculate power multiplied by time. The difference between meter readings already records all the energy consumed.
What is the difference between kW and kWh?
Kilowatts describe power. Kilowatt-hours describe energy. A device that draws an average of two kilowatts for one hour uses two kilowatt-hours. A short-term peak value does not automatically reflect the consumption of an entire shift.
How do I measure instead of estimating?
For suitable plug-and-play devices, an approved energy meter can be helpful. Measurements on permanently connected systems and in electrical distribution panels should be carried out by qualified professionals. Existing meter or load profile data can be used as a supplement.
How important is lighting?
For a hall lit for long periods, consider the entire lighting group. Add their power draws and use their shared operating time. For example, twenty lights at 30 watts each have a total power draw of 600 watts; at 3,000 hours per year, that is 1,800 kWh. This lets you compare lighting with a machine on the same basis.
Can the calculator accurately reflect a dynamic tariff?
With a constant input price, only approximately. An accurate time-variable calculation requires the energy consumed and the applicable contractual price in each billing interval. The spot market chart explains market prices but contains no consumption data for your company.
From calculation result to energy discussion
First, save the calculation results and the assumptions used. If the operating time is only an estimate, a measurement is worthwhile; if the energy consumption is already accurate, the contractual price becomes the next point of reference. Your last bill, your contract, and any available measurement data will be helpful for a consultation with OPTUM. We will discuss with you which consumption and contract-related issues will determine the next comparison and what support you will need.
Prepare for a discussion about your company's energy needs →
