# How Not to use your Air Conditioning

## By Mr. Money Mustache

## Mon, 18 Jul 2011 12:53:05 +0000

Happy July 18th. It sure is hot these days, isn’t it?

Statistically speaking, a good portion of the continental US and Canada has its hottest average day of the year right around now. So I thought it was a good time to share some thoughts on the modern household’s biggest energy consumer in July – the Air Conditioner.

See, normally I’d assume that we’re all adults and we’re able to decide for ourselves how to run our own appliances. But after being on my current summer vacation for over three weeks and visiting a large number of family and friends throughout the not-overly-hot Great Lakes region, I’ve noticed that most people leave their goddamned air conditioners running 24 hours a day, whether it is warm or cool outside, with their houses at a stupidly low temperature. Yes folks, it has become obvious that America and Canada both need a lesson from Mr. Money Mustache on how to use their Air Conditioners.

I recently measured the power consumption of the central A/C system in my own house. Mine is a “3-ton” (36,000 BTU/hr) system which dates back to about 1998, when my house was built. At the time, it was considered fairly efficient with a seasonal energy efficiency rating (SEER) of 10. Newer units, thanks to EPA rules, are now much better with ratings of 14 and higher – changes the SEER rating translate almost directly into similar percentage decreases in your cooling costs. When in full operation, my system uses 3,000 Watts (3kW) of electricity, about 500 of which is my furnace blower pumping the cool air around the house (and adding its 500 watts of heat back into the cool air stream, by the way).

For those without electrical engineering backgrounds, 3,000 watts is an Absolute Shitload of electricity. It’s enough to run 230 modern light bulbs simultaneously, and it’s equal to having about 15 monster-legged tour-de-France-level cyclists hooked up pumping at race level on bike generators continuously in your basement.

At the national average price for electricity of 12 cents/kWh, my air conditioning system burns 36 cents per hour, or $86 per month if used for 8 hours per day. With a three-month cooling season, this would compound to SEVERAL THOUSAND dollars of wasted electricity every ten years. Yet my TOTAL average electric bill in summer, despite an average daily high temperature of almost 90 degrees in Colorado, is really only about $35. How could this be?

The answer of course is that I have just cut out the waste, without sacrificing any real happiness or comfort.

Here’s how comfort works. Your body generates heat just by being alive. It needs to maintain its internal temperature at around 98 degrees F, and it depends on the skin surface temperature being lower than this to dump extra heat into the surrounding air. Producing sweat helps you cool the body faster, since the sweat sucks up heat as it evaporates. Humid air cannot evaporate your sweat as quickly, which is why it feels hotter. All basic elementary school science, right? This is why the Southeastern United States is a sucky place to be in summer even at 85 degrees F, while the desert states can feel quite comfy and invigorating at that temperature.

Finally, your body becomes more efficient at cooling itself the longer it spends at higher temperatures and humidities. Every summer as I drive from Colorado down into Nebraska and beyond, I break out into a great sweat and need to crank the car A/C. Even at midnight when the temperature drops into the sixties, I still can’t stand the humidity and need to continue the air conditioning. But within two days, I am comfortable with the higher humidity and I enjoy a regular Eastern summer with no difficulty. As July progresses and things get hotter, I am usually visiting a portion of my family with no A/C, so my body continues to adapt. There are a few days when the temperature is so high that I get uncomfortable, but then I spray myself with the garden hose and drink a gallon of water with ice cubes and all is well.

I also take advantage of the natural cycle of the environment. In the US Northeast and Canada, and even more in the Western desert areas, the temperature usually drops at night. So non-A/C users take advantage of this fact to open all their windows, and use large fans (100 watts) to exhaust heat and draw in cool air to chill the entire interior contents of their homes. A 100 watt fan blowing outwards from your highest window is pulling in night air from all other windows that is 10+ degrees cooler than your house. By sucking in thousands of cubic feet of cool air per minute, this fan is doing almost as much cooling as the 3,000 watt air conditioning unit that does the same job during the day time. The Naturally Cool crowd also makes a point of enjoying more outdoor food cooking and clothes drying on hot days, to further reduce indoor heat sources.

This is to be contrasted with the behavior of Air Conditioning addicts, who set their thermostats to a silly temperature below 80 and let that baby run, night or day. They might turn it off at night, but forget to open the windows, so they miss out on the free night-time cooling. I remember staying over at one friend’s house in June and heading out for a midnight errand. It was so cool outside that I needed a sweater. Yet his air conditioner was still running, pumping out the remaining heat from the 90-degree sunny day that had just passed. Meanwhile his body was not bothering adapt to summertime heat and humidity, because his house was always refrigerator-like inside. All of this is completely unnecessary!

The Mustachian Way is to think of Air Conditioning as a pleasant luxury to be used when all other efforts fail. Much like a car. It should be an exciting moment in your household, when every one is drinking their gallon-sized containers of icewater, wearing comfortable and summery outfits of bare feet and tanktops, and the ceiling fan is running, when you proclaim, “God Dammit it is hot today!! Let’s turn on the AIR CONDITIONING!! YEAH!!!!”

Then you run it for an hour or two, and the sun goes behind a tree, and you shut it back off again. And you open the windows that night and run the fan and go on with your lives.

If this sounds like too much hassle to you, grow some Frugality Muscles, punch yourself in the face, and try again. This is my Earth you are messing with, and your own Money Mustache you are burning off in the boiler of your local Coal-fired power plant.

Stay Cool!
love,
Mr. Money Mustache.