How to calculate electric motor 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 0.55 kW motor with 70% 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:

0.55 kW / 70% = 0.79 kW (79 W)

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:

0.79 x 2,080 = 1,643 kWh hours per year

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

1,643 kWh x 10p = £164.30 annual cost

Assuming your electric motor has a service life of 15 years, this works out at a total operating cost of £2,464.50 for a machine that cost around £50-100 to buy - meaning you’re spending up to 50 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 paul.scott@gibbonsgroup.co.uk.