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Kilowatt vs Kilowatt hours?? Help please !

In a casebook question, revenue per kilowatt hour is $0.1, and they gave monthly usage a 1000kW per month. So to find revenues across 22 months, they just took 22*10, but how does this make sense though?

We are only given that they use 1000kW in TOTAL for a month, how did the conversion to hours work here? Am I misunderstanding something? 

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Top answer
Thabang
Coach
edited on Mar 18, 2025
Ex-McKinsey Consultant | McKinsey Top Coach & Interviewer | Special Offer: Buy 1 Session Get 1 Free (Limited time!)

Hey there, 

From my experience, I've seen many casebooks use kW and kWh interchangeably, which is technically not correct

In this example you're giving, that conversion didn't happen correctly too. Most probably they meant to say 1000 kWh (and not 1000 kW)

Most cases will not have this issue, but that's also why it's important to verbalise your approach and clarify assumptions and conversions in the interviewer. 

All the best

on Mar 19, 2025
Ex-BCG Principal & Senior Recruiter in Germany | 300+ real recruiting interviews at BCG | Free 15min intro call

You are correct. Mistake on their side. Supposed to be kWh

You probably meant 22 x 100 and not 22 x 10 though, right? 

Best, 
Sebastian

David
Coach
on Mar 18, 2025
xBCG Dubai Partner | 300+ Interviews incl. Final Round | Booth MBA | 15 years Consulting Exp.| Free 15 min Intro Call

Kilowatt (kW) measures power (rate of energy use), while kilowatt-hour (kWh) measures energy (power × time).

Your case states “1000 kW per month,” which is ambiguous. If it meant 1000 kW continuously, then: 1000 kW × 720 hours (30 days) = 720,000 kWh/month, which doesn’t match the given calculation.

Instead, they likely meant 1000 kWh per month, making revenue: 1000 kWh × $0.1/kWh = $100/month, then 22 × $100 = $2200 total revenue. (I assume you meant either 22*100 or 100kW per month right?)

The issue is just poor wording—they should have written 1000 kWh per month instead of 1000 kW per month. Your logic was correct.

Pedro
Coach
on Mar 18, 2025
Bain | EY-Parthenon | Former Principal | 1.5h session | 30% discount 1st session

They forgot an "h". They should have written 1000 kWh per month.

Alessa
Coach
on Mar 25, 2025
xMcKinsey & Company | xBCG | +200 individual & group coachings | feel free to schedule a 15 min intro call for free

Hey there 😊,

This is a super common confusion—kW vs. kWh trips up a lot of people! Here's a quick and simple breakdown to clear it up:

⚡ kW vs. kWh — What's the Difference?

  • kW (kilowatt) = a rate of power (how much energy is being used at a moment in time)
  • kWh (kilowatt-hour) = a unit of energy used over time (what you pay for)

So 1 kW used continuously for 1 hour = 1 kWh.

💡 Your Case:

They say “1000 kW per month” → this likely means the company uses 1000 kWh per month, i.e., energy consumed over time.
The revenue is based on $0.1 per kWh, so:

Monthly revenue = 1000 kWh * $0.1 = $100
Then over 22 months → $100 * 22 = $2,200

So yes, it works because they’re assuming kW = kWh/month, which is common shorthand in cases.

Let me know if you want help with more case math tricks—I’d be happy to support! 😊

Best,
Alessa 😇

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