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How to calculate an electric motor's operating cost

When deciding on an electric motor supplier, it’s easy to focus on the purchase price. However, the up-front payment is a drop in the ocean compared to the motor’s electricity demand over its 10-15 years’ service.

So how do you go about calculating a motor’s operating cost? We’ve put together a straightforward guide to help, using as an example a 37 kW IE1 motor with 90% efficiency that runs on average eight hours per day, five days per week.

1. Take the power of your motor and divide it by its efficiency for the input required:

37 kW / 90% = 41 kW

2. Calculate how many hours your motor runs for per year:

8 hours per day x 5 days per week x 52 weeks = 2,080 hours per year

3. Work out the annual energy usage by multiplying the input power by annual running time:

41 x 2,080 = 85,280 kWh hours per year

4. Finally, multiply the annual energy usage by the rate of electricity (currently around 10 pence per kWh for businesses):

85,280 kWh x 10p = £8,528 annual cost

Assuming your electric motor has a service life of 15 years, this works out at a total operating cost of £127,920 for a machine that cost around £1,000 to buy - meaning you’re spending around 100 times the purchase price on energy. That’s before you even consider the cost of downtime and maintenance.

There’s a lot to consider, so if you’d like to get an idea of the best-value electric motor for your application in the long term, call Sales Manager Paul Scott on 01621 868138 or email

Electric Motors


  • Date: 31 October 2016 km hasibullah
    thank u for advising to calculate electric motors. we can easily calculate..
  • Date: 2 June 2018 Kumar
    I want to know what will be the Per ton power consumption For
    having 7 motors of 50 HP,
    All run together and producing 10 ton per day.
    electricity cost is Rupees 7/unit.

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