Capital One Data Scientist Interview Experience — The Energy One Mini Case and a Same-Day Power Day Callback

Mini case, midday on 3/18/2025. The question was one someone had already shared here before — the Energy One case.

The interviewer gave a short self-introduction, then asked about my background — worth remembering to prep for that too, I was so focused on the mini case that I answered it pretty roughly.

Then we got into the actual case. There's an energy company called Energy One that wants to transition from fossil fuels to renewable power.

Q1: What factors do you consider for this transition?
Standard-formula answer: 1. Market trend 2. Financial feasibility 3. Competitors 4. Brand awareness — then I added my own details on top of that.

Q2 (a calculation): Power plant capacity is 8.8m MW/H a year, lease cost is $5m/month, fixed cost is $25m/year, variable cost is $20 per MW/H, sales price is $40 per MW/H, initial investment is $400m. How many MW/H of production generates a return covering 10% of the initial investment?

Let X be the MW/H of production needed to cover 10% back.
Revenue − lease cost − FC − VC = 40m
40X − (5*12) − 25m − 20X = 40m
X = 6.25m

Q2 follow-up: The interviewer then asked whether 6.25m made sense. I didn't get what he meant at first — turns out he meant relative to the maximum capacity of 8.8m MW/H, so 6.25m does make sense.

Q3 (continuing from above): If the government now limits a company to producing only 5m capacity from fossil fuels, what other sources can we tap into? — I'd already practiced this one so I answered pretty easily, but if it were the first time hearing it I probably wouldn't have been able to answer.
My answer: anything that can keep profitability stable, like solar, wind, and hydro — then I briefly went over the pros and cons of each.

Q3 follow-up (I think the interviewer added this one himself, I hadn't seen it in practice): If the company decides not to tap into new power sources, what else could it do to keep profitability up?
Answer: I answered this through revenue/cost and supply/demand — 1. set a higher price 2. lower costs — then briefly mentioned what levers could move.

Q4 (continuing from Q3): The company decides to build two mini test plants, one solar and one ethanol, to produce additional power.

Solar: initial investment $12.5m. Over a year, 75% of the time is sunny days producing 150k MW/H, 25% of the time is cloudy days producing 50k MW/H, VC = 0, still sells at $40 per MW/H. How many years to cover the initial investment?

Let X be the number of years needed.
(150k75% + 50k25%)40X = 12.5m
X = 2.5

Ethanol: initial investment $2.5m. Produces 100k MW/H a year, VC = $30 per MW/H, sells at $40 per MW/H. How many years to cover the initial investment?

Let y be the number of years needed.
100k*(40−30)*y = 2.5m
y = 2.5

Q5 (continuing from above): Which test plant would you recommend?
Answer: I asked if there was any budget limit — the interviewer said no — so I said solar, because its VC is 0, though the 75%/25% sunny/cloudy split could be unstable; ethanol's VC isn't fixed and a lot of its raw material is imported from abroad, so its future profit is hard to call. Long-term, it has to be solar.

After that it was some small talk, and then I asked the interviewer a few questions.

I'd actually already practiced this exact case beforehand and even had a few notes written out next to me, and then it really did come up. Honestly I already had the answers the whole time, but I still had to act it out a little and ask some clarifying questions along the way, ha. One thing to watch for on this one — the numbers are all pretty big, and having millions and thousands mixed together makes it easy to get nervous and miscalculate, so be careful.

About an hour later HR called to say I'd passed and that they'd schedule Power Day for late March or early April.

Thanks everyone, hope your interviews go well — and wish me luck for Power Day too!