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List your machines, type your rate and see how many kWh and how much money each one uses per month, which weigh most on the bill and how much you can save.
Pre-sizing and estimating tool: results do not replace design, calculations or reports signed by a licensed professional, nor verification against the applicable codes and standards.
Monthly energy cost of each machine, from highest to lowest, with its share of the bill and the cumulative percentage.
How to read: each bar is one machine (or group); its length is the monthly cost. The label shows the amount, the share of the bill and, on wide screens, in brackets, the running total up to that bar (also in the table below). The top bars are the priorities: once the running total passes 80%, the rest of the list matters little.
Monthly cost of the chosen machine today, with fewer hours on, with a higher-efficiency motor, and with both measures.
How to read: the first bar is today’s cost; the others show the cost after each measure. The gap between the first and last bars is the total monthly saving. If the motor bar barely moves, a motor swap alone yields little: compare it with the new motor’s price before deciding.
Key: avg kW = electrical power of one unit (nameplate ÷ efficiency, or V × I × PF) × quantity × load factor; kWh/month = avg kW × hours/day × days/month; cum. % = running total of the shares. The full table is in the .xlsx button at the end of the page.
Take this page’s results to another calculator with the fields already filled in.
The calculation report gathers this page's inputs, results, equations, assumptions and references, with fields for project, engineer and revision. The full report also includes the charts and interpretations, in color. In the print dialog, choose Save as PDF.
Multiply electrical power (kW) by the load factor and the hours it runs: kWh = kW × load × hours. For a motor, electrical power is the nameplate rating divided by efficiency. In the example, the 50 hp compressor draws 41.0 kW (50 × 0.7457 ÷ 0.91); at 75% load, 16 h a day and 22 days it uses 10,817 kWh per month, $1,190 at $0.11/kWh.
It is how much of the nameplate power the machine uses, on average, while it is on. Motors seldom run full: machine tools sit at 30% to 50%, compressors at 60% to 80%, thermostat-controlled ovens at 50% to 80%. The safest way is to measure current with a clamp meter in normal operation and divide by nameplate current.
Usually those combining high power and long hours: furnaces and ovens, air compressors, large pump and fan motors, and refrigeration. In the example, the hardening furnace ($2,677/month) and the compressor ($1,190/month) make up 66% of the $5,849 bill. The ranking shows where to act first.
Under time-of-use pricing, energy used during the utility’s on-peak window on weekdays costs more. Choose “On-peak and off-peak”, type both prices and mark which machines run in that window. The page shows how much of the bill comes from on-peak use and how much you save by moving load out of it.
Choose the unit “A 3-ph” or “A 1-ph” and type the measured or nameplate current. The page works out kW = √3 × V × I × PF ÷ 1000 for three-phase (or V × I × PF ÷ 1000 for single-phase), with the voltage and power factor from the fields just below the list. If current was measured in normal operation, use a 100% load factor.
New energy is current energy × current efficiency ÷ new efficiency. Going from 91% to 94.5%, the saving is 1 − 91/94.5 = 3.7% of the motor’s energy. In the example, that is $44 per month on the compressor. Together with switching off 2 h a day, the saving reaches $187 per month. For payback, use the motor and VFD replacement calculator.
It is an estimate from nameplate and usage data. It excludes demand charges ($/kW) and power factor penalties. Motor efficiency is an average value. For investment decisions, confirm the consumption of the largest machines with metering.
Important notice: Indus Metrics tools produce estimates and pre-sizing results from the data you enter and from published engineering methods. They do not replace design, calculations or reports signed by a licensed professional engineer (PE), nor verification against the applicable codes, standards and regulations, such as OSHA rules and the ASME codes. Material and fuel properties vary: check manufacturer data or your own process analyses before deciding. By using this site you agree to the Terms of Use.
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