Author: rkelleyc

How to heat (and cool) your home: Choosing between Natural Gas and an Electric Heat Pump

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After 14 years, my HVAC bit the dust. In shopping for a replacement, I spent a lot of time considering this: Should I continue to heat my home with natural gas, or switch to an electric heat pump? Based on the lower operating costs, available rebates, and environmental factors, the heat pump was the clear winner. 

What is a BTU? 

Before diving into HVAC, let’s review one of the most important units in home heating and cooling: the BTU. BTU stands for British Thermal Unit, and it’s a way to measure energy — specifically, the amount of heat needed to raise the temperature of one pound of water by one degree Fahrenheit.

In HVAC terms, your system is sized based on how many BTUs per hour it can move. A typical home might need 20,000–60,000 BTU/hr depending on climate, size, and insulation. The higher the BTUs, the more heating or cooling power a system can deliver. An HVAC technician can do a load calculation to determine how many BTU’s per hour you need, or you can estimate it yourself using an online tool like this one. My own home, at 2,000 square feet in North Carolina, needs about 22,000–24,000 BTU’s per hour for heating and cooling each floor. 

At a glance, Natural Gas is a lot cheaper than Electricity per BTU

Natural Gas is sold in “Therms.” Each Therm is equal to 100,000 BTU’s, and Dominion Energy charges ~$1.29 per Therm.

Electricity is billed in Killowatt-Hours (KwH). Each KwH is equal to 3,412 BTU’s, and Duke Energy charges $0.1185 per KwH. 

So the cost of 100,000 BTU’s is $1.29 in Natural Gas or $3.47 in Electricity. Based on that, electricity is ~2.69x more expensive than Natural Gas per 100,000 BTU’s. 

However, Electric Heat Pumps can be much more efficient than Natural Gas Furnaces at bringing heat into the home 

Gas furnaces burn fuel to generate heat, and gas furnaces aren’t 100% efficient. If you input 1 Therm of Natural Gas (100,000 BTU’s) into a Gas Furnace, you’ll typically only receive an output of 80,000-96,000 BTU’s of usable heat that will be able to help warm your home. The rest of the energy is lost as exhaust. This efficiency is measured as the furnaces’s Annual Fuel Utilization Efficiency, or AFUE. A typical AFUE is 80-96%. For reference, my home’s gas appliance has an AFUE of 80%. 

Heat pumps are often more efficient than gas furnaces because they don’t generate heat — they move it. Instead of burning fuel, a heat pump extracts heat from the air outside (even when it’s cold) and transfers it into your home. This process uses far less energy than creating heat from scratch. For example, if it’s 47 degrees outside, my new LG Heat Pump can transfer 3.6 units of heat into the home for every unit of electricity it consumes. This ratio is called the Coefficient of Performance (COP), and it represents the ratio of heat output to electrical energy input. The tricky part is that the COP is a variable number that depends on the temperature outside. If it’s colder outside, the heat pump has to work harder to transfer heat into the home, which means it’ll have a lower COP at lower temperatures. 

If it’s really cold outside, some heat pumps can’t keep up and rely on a backup system known as electric resistance heat strips to provide additional heat. Heat strips are built into the air handler and generate heat in the same way a toaster does. They’re 100% efficient (meaning they have a COP of 1.0), however they’re far less efficient than the heat pump, which can carry a COP of 1.5-4 depending on the outdoor temperature. In my case, the analysis below ignores heat strip usage because I’m focusing on a cold-climate rated heat pump that can maintain full heating capacity down to 5°F. Given North Carolina’s relatively mild winters, I don’t expect to rely on the strips under normal conditions.

For example, if it’s 47 degrees outside, the heat pump costs ~40% less per hour to keep my home warm ($0.26/hr vs. $0.435/hr)

In this scenario, let’s assume I’d need ~27,000 BTU’s per hour to keep the inside of my home at 70 degrees. For simplicity, let’s ignore heat loss through the vents etc. 

  • With a Gas Furnace, since my existing gas appliance has an AFUE of 80%, I’d need 33,750 BTU’s of natural gas to produce 27,000 BTU’s of heat inside the home. That means I’d need 0.3375 Therms of Natural Gas, which at $1.29 per Therm, would cost me $0.435. So with a Gas Furnace, it’d cost $0.435 to heat my home for one hour.
  • With a Heat Pump, to provide the same 27,000 of BTU’s of heat into my home, I’d need to consume 2.2KwH of electricity (which corresponds to a COP of 3.6). At $0.1185 per KwH of electricity, it would only cost me $0.26 to heat my home for one hour. 

But as it gets colder, those savings drop. At 30 degrees, the Heat Pump is only 13% more efficient per hour ($0.378/hour vs. $0.435/hour).

Let’s pretend it’s 30 degrees outside now. The Natural Gas Furnace still requires the same amount of Natural Gas to produce 27,000 BTU’s. So the cost there is still $0.435/hour.

But the Heat Pump has to work harder to transfer heat now. To bring 27,000 BTU’s of heat into the home, it now needs 3.19kw of electricity per hour (which corresponds to a COP of 2.55). At $0.1185 per KwH, it would cost $0.378 to heat my home for one hour.  

When it’s really cold outside (~22 degrees F or lower), the Gas Furnace is more cost efficient per hour compared to the Heat Pump

The breakeven point is typically when the Heat Pump’s COP drops below ~2.5. Natural Gas is ~2.5x cheaper than electricity, so in order for the Heat Pump to be more cost efficient, it needs to be ~2.5x more efficient with its inputs.

With the Bosch heat pump below (which is very similar to my new unit), this breakeven point happened at 22 degrees F. If it’s warmer than 22 degrees outside, the Heat Pump is more cost effective. But if it’s less than 22 degrees F, the Gas Furnace is more cost effective. In North Carolina, the temperature doesn’t drop below 22 degrees very often, so the Heat Pump should be more efficient on an annual basis.

Overall, I expect this Heat Pump will save ~$336.74 per year in utility costs compared to my existing system

Cooling costs should be ~$182/year (35%) lower with the new system compared to my existing system

I estimate that I spent ~$525.79 on cooling my home last year (which is probably a low-end estimate). During the winter months of November-March (when the AC was off), my average electric bill was $83.68. During the warmer months of April-October (when the AC was on), my average electricity bill increased to $158.79/month. By subtracting those two numbers, I estimate that it cost ~$75.11 per month to cool my home , or ~$525.79 total for the seven months of April-October. 

The efficiency of Air Conditioners is measured by its SEER rating (Seasonal Energy Efficiency Ratio), which indicates the amount of cooling produced by a air conditioner for every unit of energy consumed. A higher SEER rating means the unit is more energy-efficient. My existing AC has a SEER 13, whereas the new Heat Pump has a SEER of 17.5. Therefore I estimate that the new system will be ~35% more efficient (17.5/13 -1) than my existing system, which will save ~$182 in annual cooling costs. 

Heating costs should be ~$232.95/year (28%) lower with the new system compared to my existing system 

Last year, I estimate that I spent ~$545.79 on heating my home (again this is probably a low-end estimate). My average natural gas bill during the summer months of April-October was $42.91, and the heat was off throughout this period. During the colder months of November-March, my average bill was $152.06, suggesting that having the heat on cost ~$109.15 per month on average ($152.06 – $42.91). Based on that, I estimate that the total cost for heating my home was $545.75 for the five month period of November-March ($109.15/month * 5 months).

It’s more difficult to estimate my projected heating costs for next year. I’ll estimate that a rough average temperature for the heating season (November-March) is ~47 degrees F. At that temperature, the new heat pump uses 2.2Kw per hour, and the system would run ~10 hours per day for this 150 day period. At $0.1185/hour, I project it will cost ~$391.05 to heat my home for the season, which is ~28% more efficient than my bill from last year. 

Heat Pumps are often more expensive upfront but I should make back the difference pretty quickly through: 

  • The government provides a $2,000 tax credit for upgrading to a high efficiency heat pump. 
  • Duke energy provides ~$825 in rebates for upgrading to a high efficiency heat pump. 
  • The monthly operating costs are expected to be $336.74 less per year compared to my existing system. 

Come back next year and I’ll update my analysis with the real-world results.

Blind Taste Test: Can You Tell The Difference Between Different Types of Apples?

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To help celebrate John’s birthday, Martha put together a blind taste test for seven different apples. Can most people tell the difference between different types of apples?

The answer was a clear “no.”

  • The math suggests we could have guessed the same amount of correct answers just by chance. For example, with each apple, you have a 1 in 9 chance of guessing the right variety since there were 9 options listed in the answer key. So across 7 apples, statistics suggest the average person would get ~0.778 picks correct (1/9 chance of a correct pick * 7 picks). As a whole, our group made 4 correct guesses across five contestants, meaning our group had 0.8 correct picks per person on average (4 correct picks / 5 people). This rate of 0.8 average correct guesses per person was almost exactly even with the blind guessing prediction of 0.778 correct picks per person.
  • That being said, if you have a favorite apple, you may be able to pick it out of a crowd. Kyla easily picked out her favorite (Cosmic Crisp), and I picked out my favorite (HoneyCrisp). In a way, this helps me justify paying the high price for Honeycrisp at $4.49/lb.
  • Snap Dragon, EverCrisp, Cosmic Crisp, SweeTango, and Honeycrisp were often confused for each other in the chart below, likely because they’re all similar in flavor and texture.
  • McIntosh stood out more clearly, maybe because of its distinct softness.

Want some bad apple recipes?

Or another blind taste test?

Getting to Know Bobby

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My core friend group is a tight circle that hasn’t changed in over 10 years… until recently. One of the core members got a new boyfriend (thanks online dating) and we’ve decided to fully welcome him into the group. The only problem is this new member hasn’t gotten to spend a lot of time with Bobby yet, who’s apparently too busy being a new parent to hang out with us every weekend now. Whatever. Bobby’s a simple enough guy that I can tell you everything you need to know about Bobby in just a few pictures.

1. Bobby is always hungry. His goal is to put 2,000 calories in every smoothie. And his idea of a side for a bagel is a croissant.

2. He never misses a good photobombing opportunity (especially when he’s in costume)

3. I’m pretty sure he could have been a model.

4. Although he’s also kind of weird.

5. And makes this one face he makes when he’s disappointed (although thankfully we don’t see this one very often).

6. But overall he’s a great friend and gives great hugs.

The Rising Cost of Groceries vs. Meal Delivery Kits: A Five-Year Comparison

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Almost five years ago today, I was on the fence if meal delivery boxes were worth the added cost. The COVID lockdowns had just gone into effect, and with all restaurants closed, I was looking for new foods and recipes. I also had plenty of time to run a cost-benefit analysis comparing the cost of the meal delivery box to buying the same ingredients at the grocery store.

Since 2020, the Consumer Price Index (an estimate for household inflation) has risen by 22.3% according to the U.S. Bureau of Statistics. So, how much does it cost to buy the same ingredients at the grocery store today vs. in March 2020? And has the value of meal delivery boxes changes? To find out, I’ve tracked, analyzed, eaten, and broken down the costs of four meals over time; Falafel Veggie Bowl, Loaded Black Bean Tacos, Chicken Caprese Sandwich, and Pizza Tortellini.

The cost of ordering these four meals from Dinnerly increased from $51.32 in 2020 to $67.91 in 2025, a 32.3% increase. This means that the cost of meal delivery boxes has risen significantly faster than inflation. And Dinnerly is actually one of the cheaper meal delivery options– a similar box from Hello Fresh would cost $92.73. The only way to argue that a meal delivery box would save money is by comparing it to the cost of eating out. For example, buying four #1 combos for two people at Chickfila would cost $74.05. Or even worse, using Uber Eats to deliver two Crunchwrap Supreme combos from Taco Bell four times would cost $135.

However, despite inflation, the cost of buying these ingredients at Harris Teeter actually went down over time, from $48.78 in 2020 to $47.06 in 2025. This fact doesn’t disprove inflation, rather I think it shows that I hit the sales right this year. The biggest savings came from a sale on taco seasoning ($1.99 down to $0.59), buns and tortellini (both down $1.01), and tortillas (down $0.99). Meanwhile, staples like cheese, chicken, and tomato sauce were all up (21%, 8%, and 79%, respectively).

In 2020, the added cost of ordering the meal delivery kit was only $2.52 per week, or around 5%, which I thought was worth. However, today that premium has increased to $20.85 per week, or 44%. Meal delivery boxes may still make sense for people who eat out for every meal or value convenience over cost. But for the rest of you, I’ll see you at Harris Teeter.

The Winners of the Losers

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The rules of our Fantasy Football Football league are pretty simple: if your team scores the least amount of points across the entire league for the week, you have to chug a Smirnoff Ice and send video proof to the group.

There are 10 teams in the league but only four of us have had the (dis)honor of being the biggest loser of the week. But of these losers, who’s the winner with the fastest chug?

Video replay confirms that yours truly is the undisputed winner of the losers, sweeping first, second, and third place. Props to Carter though for stepping up with a massive 24 oz. Smirnoff Ice—double the size of everyone else’s—and taking it down like a champ (featured in the top left and top middle-right squares of the video). Zach snagged 5th, 6th, and 7th place, earning a few brownie points for the unique backdrops in his videos. Will, in his rookie season, faced a tough initiation with subpar performances both on and off the field.

Welcome to the big leagues, where even the losers can be winners—if they can chug fast enough.

“I just need to run to Lowe’s real quick”

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My dad was a general contractor so I used to hear those words a lot growing up. Well, I’ve been hearing them (and saying them) a lot lately too…

Since Brittany and I bought our house in June 2022, we’ve been to Lowe’s 94 times over the course of about two and half years, or about once every 10 days. My personal record was five trips in one day when I was trying to figure out the right size pipe and fittings to install a new sink (fifth time was the charm).

Cost wise, we’ve spent $6,075.84 at Lowe’s since buying the house, according to our credit statements. That’s about $65 per trip, however that average was skewed by a few large purchases including a new oven (~$1200) and 15 gallons of paint to stain the fence (~$600). The median of $31 is probably a better representation of our standard trip to Lowe’s.

To be clear though, our house wasn’t in bad shape by any means when we bought it. However we’ve been trying to flex our DIY skills as we’ve learned how to do routine maintenance (like taking care of the lawn), basic repairs (like changing the garbage disposal), and also some tasteful upgrades (like updating the bathroom). Take a look at my last DIY blog to follow along with some of the projects we’ve tackled.

While spending $6,000 over 2.5 years sounds like a lot, homeguide.com estimates that home maintenance costs between 1-4% of a home’s value per year. We’ve certainly had to spend money at other places (i.e. 14 trips to Home Depot costing a total of $779.71), however we’re still probably on the lower end of that spectrum given that we’ve done a lot of the work ourselves. Rather than money, we’ve paid the price with our time… and trips to Lowe’s.

So next time you hear someone talking about the “joys of home ownership,” it really just means going to Lowe’s.

Can you guess where on the graph we bought the house?

Celebrating Two Years of Happiness

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A little over two years ago, our dear friend Terry was trying to figure out what to say at our wedding. It was her first time officiating a wedding and to put it simply, she wanted to know why I wanted to marry Brittany. Here’s how I responded on Thanksgiving Day 2022.

Hi Terry, Today especially, it makes sense to be thankful for Brittany on Thanksgiving. I know you’ve seen the photobooks of us smiling and posing for different occasions, but the best part of our relationship is really what happens in between those photos. Brittany is caring, sharp-witted, and full of love, which makes loving her so easy.

Brittany is caring

At times, I’d swear she was an angel. Earlier this year, I was sick for a full two weeks. Most people would have stayed away, or given up on me after a few days, but Brittany kept the tea kettle warm and would check on me in the middle of the night. I’ll never forget the compassion she showed as she poured warm water through my hair in the bathtub, bringing me back to life. This compassion extends to other people as well. A few years ago, we were driving through Chapel Hill and witnessed a terrible car crash, with one of the cars spinning twenty feet down a ravine and into a fence. Brittany instinctively pulled our car into a safe spot and ran down the slope to check on the driver. Another time, and very early in our relationship, Brittany got stuck taking care of both me and my dad at the same time after I’d just gotten my wisdom teeth taken out and my dad was recovering from a significant hip surgery. Brittany juggled both tasks with a smile… way above the call of duty for any caretaker, let alone a new girlfriend at the time. For my dad, an extra blanket in the middle of the night made a world of difference and cemented her status as an angel in the Kelley household. Her empathy and compassion seem to have no end, which makes her both a good medical provider and an easy choice for my lifetime partner.

Brittany is smart

And when she puts her mind to something, nothing can stop her. There was a brief period early in our relationship where Brittany and I were spending so much time together that her grades began to slightly slip. She was taking Calculus 2, an important prerequisite for pursuing a career in the medical field, and wasn’t happy with her first test grade. She looked me in the eyes and said, “I’m going to get an ‘A’ in this class.” Our dates quickly changed from ice cream and Old Chicago pizza to meeting up in Davis Library. But the results came quickly too; I don’t think she ever got anything less than ‘A’ throughout the rest of her time in school, including her master’s degree at ECU. Brittany’s not one to brag, but she scored in the top 1% of all PA school students on the final board exam. Plus, she’s not just school smart. She’s also good at answering my common questions like “what should we make for dinner?”, “what day was that event again?”, or “do you know where I left my shoes?”

Brittany has a kind and tender heart, and I’m so thankful she has chosen to share it with me

The sweetness and sincerity of her love is undeniable. If she has an early morning, she’ll leave a handwritten note on the counter to wish me a good day. When I get home in the afternoon, she’ll be waiting for me at the door with a warm embrace or a round of applause (silly but my favorite). Her favorite way to wake up in the morning is with a kiss on her forehead and a big smile on her face. I’m pretty sure she doesn’t know how to walk beside me without holding my hand. She’s the most thoughtful planner and gift-giver for birthdays and holidays. These may seem like little things, but they mean a lot and provide a snapshot of why I can’t wait to marry Brittany.

 This list could just have easily been a hundred pages long but Brittany’s compassion, intelligence, and kind heart are just three of the reasons why I love her. I can confidently look forward to our wedding without any nerves and a lifetime of happiness to follow. 

As we’re celebrating our two-year anniversary today, I’m happy to report back that things are better than ever. Just take a look at the cover photo here– we’re so in sync that we even got each other the same anniversary card.

Want more? Check out my recap from our first anniversary

Is Perkins $25 Grab Bag Worth the Cost?

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Our local produce stand has a deal where you can fill a bag with as much fruits and vegetables as you want, plus a free item of their pick, for a fixed cost of $25. As a numbers person, I wanted to know– is this a better deal than going to Harris Teeter?

This week, the answer was yes. I only spent $25 at Perkins whereas those same items at Harris Teeter would have cost $26.24, plus I felt good knowing the produce was fresh and locally sourced. If you only need a few things though, it probably makes sense to pay by the item.

Another pro of Perkins– they sell a lot of pumpkins! In typical fashion, they’ll sell you as many pumpkins as you can fit in a wagon, plus a bag of produce, for the reasonable cost of $100.

See you next time

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Logan didn’t like to talk about the “c” word, even though it loomed over him every day for six and a half years. It’s something that happened, but it’s not who he was. Logan was smart, funny, determined, and one of my very best friends, and that’s how I’ll always remember him.

I met Logan around 2014 when he joined KA at UNC. In the fraternity world, Logan was my “little brother’s little brother,” which meant that Bobby and I were both supposed to be mentors for him. But Logan was always determined to find his own path and ended up being more of a role model for both of us. Against all logic, he decided to pursue physics, probably the hardest major at UNC, driven by his innate desire to understand how things work, particularly everything related to space. This scientific mindset later led him to earn a master’s degree in analytics.

Logan was often quiet, but when he talked, people listened. Even though he could be serious a lot of the time, he was also funny in his own sarcastic but loving way. One time, I accidentally put milk in the pantry instead of the fridge. Logan was over at my house the next day and opened up the cupboard. He saw the milk and, with a sly smile, said, “Oh cool, you have your own milk shelf,” then closed the cabinet and went about whatever he was doing.

Logan’s passions were simple yet profound: he loved craft beer, Marvel movies, videogames, spending time with friends, and Tar Heel athletics. He proudly wore UNC’s colors through his master’s program at NC State and later through the halls of Duke Hospital. He always knew all the latest stats and transfer portal rumors. For ten years, Logan was my right-hand man at nearly every UNC home football game, the kind of fan who never left early to beat traffic. When he could no longer attend because of health reasons, he made sure the tickets found their way into a friend’s hands to carry on the tradition.

Logan was loved and supported by so many friends, family members, fraternity brothers, classmates, and colleagues. To illustrate what type of friend Logan was, I remember a story he told about going to the beach with his aunt and uncle on a hot day. They knew he loved craft beer but didn’t know much about it themselves, so they got him a six-pack of Duck Rabbit Milk Stout, which would be about as refreshing as a large glass of thick chocolate milk. Logan politely thanked them and pretended to enjoy one to avoid hurting their feelings. I think he told them later on, and they all laughed about it. Another time Logan had brought a first date to a football game, and in an unlucky turn of events, Bojangles sold me chicken tenders that were raw in the middle. I was either too shy or disgusted to do anything about it at the time but Logan and his date graciously offered to “handle it” for me. They returned the tenders to the store and warned everyone in line about what had happened. Bojangles felt so bad about it that they gave Logan and his date triple their money back in cash. They ended the day with a grateful crowd of people saved from food poisoning and a first-date story that left us all laughing.

We were playing on an adult kickball team around the time Logan was diagnosed with cancer. I remember taking him to one of his first doctor’s appointments because of what he thought was just back pain at the time. There were a lot of ups and downs over the next six and a half years, including a brief celebration in 2019 when the cancer went into remission. But no matter how hard things got, Logan’s personality always shined brighter than the pain he was going through. He was always there for us, and we were there for him when he needed us. Our close-knit group of friends visited him in every hospital room, offered rides, brought food, and even lodged a formal complaint when the handicap bathroom wasn’t actually handicap friendly. The most meaningful event was when Councill rented out a movie theater, and twenty of our friends came from near and far to join Logan in rewatching his favorite movie, “Interstellar,” on the big screen.

Logan was a great person and an amazing friend, and it hurts to think about how much I’ll miss his quick wit, late-night space talks, sports commentary, and everything in between. But I know he’d want us to hold onto the good memories until we meet again. To his friends and family, Logan didn’t say goodbye—he said, “I love you, and I’ll see you next time.”

Date Night Data: Analyzing Movie Trends and Stats

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Over the past year, Brittany and I have embarked on a cinematic journey, watching 46 movies in theaters over 365 days. From Halloween thrillers to box office flops, this has sparked our curiosity to learn more about the trends and insights into the movies we love. Join us as we dive into the data behind movie budgets, ratings, and profits, along with a brief refresher from your high school statistics class.

We prefer to go on Thursday’s when new movies are released. We saw 24 of 46 movies on opening weekend

Using the AMC A List (movie subscription pass), we paid ~$5.60 per ticket; 59% less than a standard ticket ($13.36) and 73% less than an Imax/Dolby ticket ($20.41)

Most of those movies we saw were dramas, action movies, or comedies (note some movies had more than one genre)

We saw six movies from both Paramount Pictures and Sony Pictures

Ready to dive deeper into the stats?

You could watch the shortest movie (Bottoms) 2.2x before the longest movie is over (Killers of the Flower Moon).

Of all the movies, these were the biggest financial hits (at least for opening weekend), generating more box office revenues during opening weekend (red) than the film’s budget (blue)

Generally, the production company gets to keep 50-60% of the box office revenues from opening weekend and the theater owner get to keep the remaining 40-50%. However, this split is contentious and often varies based on the strength of the film and the bargaining power of both the production company and the theater. After opening weekend, that split often shifts over subsequent weeks such that the production company’s cut decreases and the theater’s share increases.

There are plenty of exceptions but opening weekend box office revenue carries an outsized importance because it often sets the tone for the film’s entire theatrical run. By Sunday of opening weekend, studio executives can predict with great accuracy what a movie will earn by the time it leaves the cinema. Ticket sales are the largest driver of income for movies, although not necessarily the most profitable because of taxes and the cut owed to the theater. Other sources of revenue for the production company include DVD sales, on-demand rentals, licensing income from streaming services, and merchandising.

This reliance on opening weekend box office revenues is changing though. Film critic Bilge Ebiri explained, “Hollywood is in the midst of a transition… [they’re creating] Fewer gigantic productions that need massive opening weekends to justify their humongous costs; [and] more solid films that can turn a profit over a few weeks and months thanks to good word of mouth. The smash-and-grab opening-weekend strategy was never going to be sustainable, and the industry had become alarmingly reliant on an increasingly small handful of titles saving their bottom lines.”

This transition may include a larger reliance on sequels and related works. Of the five movies above, four aren’t entirely original stories. Barbie has the doll, Five Nights at Freddy’s is based on a video game, and Spider man and Maxxxine are both sequels. In total, 14 of the 46 movies we watched were direct sequels or part of a movie series, and several more were based on books or other works. TheFilmAutopsy explained sequels “just make more money,” and the limited data we collected tends to agree. On average, a sequel generated box office revenues equal to ~50% of its total budget during opening weekend, whereas novel movies only returned ~41%.

In general, longer movies had moderately better reviews (r=0.52, p=.002)

The correlation coefficient (aka “r” value) measures the strength and direction of the linear relationship between two variables. The value can range from -1 to 1. A value of 0 would indicate that two variables aren’t related at all (like your shoe size and reading ability), whereas a value of 1 indicates a perfect positive relationship between two variables (like degrees Fahrenheit and degrees Celsius). The r value of of 0.52 here indicates there’s a moderately positive relationship between a movie’s run time and it’d IMDb rating.

The p-value helps determine the significance of the results. In this scenario, the p-value is the probability of observing the results below if run time and IMDb rating were not correlated at all (meaning an r-value of 0). This dataset has a p-value of 0.0002 (0.02%), giving us confidence that these results are not random and that there is positive relationship between run time and IMDb rating. To be considered statistically significant, most fields look for a p-value of less than .05.

The line of best fit (aka regression line) shown in red is a straight line that best represents the data on the scatter plot below. The formula for the straight line can be line described by the formula y=mx+b, where y is the IMDb rating, m is the slope of the line, x is the movies run time, and b is a constant representing where the line crosses the y axis. Altogether, we can use this formula to estimate a movie’s IMDb rating as “IMDb Rating=0.016×Run Time+4.817.” The constant of 4.817 isn’t meaningful in itself, but suggest a movie with a run time of 0 minutes (a hypothetical scenario) would have an IMDb rating of 4.817. For every incremental minute, the slope of the line suggest that the IMDb rating would increase by 0.016 point.

This data makes intuitive sense given that longer movies have more time to develop characters and storylines, which could potentially lead to a better overall movie and higher ratings.

But strangely, getting better reviews doesn’t necessarily mean that more people are going to go see that particular movie on opening weekend (r=0.243, p=0.104)

The trend line in red does indicate a weak positive correlation between a movie’s IMDb rating and opening weekend box office revenue. However, the p value of 0.104 suggests that there’s a 10.4% of obtaining this result (or something even more extreme) even if the variables weren’t related at all. Based on that, we can’t confidently claim that higher IMDb ratings correlate with higher opening weekend box office revenues.

Why aren’t these variables more correlated? I had a few theories:

  • Opening weekend box office revenue is probably more related to how much the production company spent on marketing and advertising for the movie beforehand. You’re probably not going to go see a movie that you’ve never heard of, right? I’ll investigate this further below. Note I would have liked to use total box office revenue instead of just opening weekend box office revenue, however it wouldn’t have been fair since several of these movies are still in theaters.
  • More people want go to the movies around certain holidays or peak seasons (like Halloween or Valentine’s Day), even if the movies aren’t that great. For example, Brittany and I went to see the horror movie “Five Nights at Freddy’s” around Halloween and the romantic comedy “Anyone But You” around Valentine’s Day, even though we weren’t particularly excited about either film.
  • Reviews are a lagging indicator. I’ve noticed that a movie’s IMDb rating tends to start out very high and gradually decrease over time. For example, if you go see a movie on opening night, you probably already know that you were going to like the movie before it even started. But as more people go see a movie, the rating usually decreases closer to it’s truer and long-term average. Since these movies all came out at different times, this probably isn’t a fair dataset. Or maybe IMDb is just rigged.

Just like politics, it’s all about the money. Higher movie budgets don’t lead to better reviews (r=.089, r=0.55), but they do lead to higher opening weekend box office revenue (r=0.467, p=.001).

The chart on the left is all over the place, driving home the point that higher budgets don’t correlate with higher IMDb ratings. The r value indicates a weak correlation, however even if that were true, the p-value of 0.55 indicates that there’s a 55% chance that the observed data could occur even if budget and IMDb were totally unrelated. Therefore, we conclude that there’s no significant evidence that higher budgets lead to higher IMDb ratings.

On the other hand, the chart on the right indicates that higher budgets do lead to higher opening weekend box office. This isn’t a surprise. With more money, studios will bring in more famous actors, hire better producers, and spend more money on advertising. The r-value of .467 suggests a moderately positive correlation between a movie’s budget and opening weekend box office revenue, and the p value of .001 gives us high confidence that the correlation is statistically significant. The slope of the trend line (m=.202) suggests that for every additional million dollars in a movie’s budget, the opening weekend box office revenue is expected to increase by approximately $0.202 million (or $202,000).

So what does all this mean?

Our sample size is too small to reach any major conclusions other than we’ve had a great time on our 46 date nights at the movies. We’re looking forward to more movies coming up (Joker 2, Wicked, Bettlejuice, etc.), which may turn into more blog insights, but until then, check out my last movie blog where I’m “Reviewing Movie Reviewers.”