Send your question to Umbra! We are in the midst of a heat wave. I have a window unit air conditioner in my tiny apartment. There is an “energy saver” option that shuts down once the temp reaches the desired setting (generally 79 degrees), then starts back up again when the mercury rises. It’s been so hot that it seems to only take a few minutes till it fires back up. Is this really saving energy? With hope, the heat will have broken by the time you read this. But we all know it will rise again, and we’ll have plenty more days when we can hear the entire country lean back in its chair, wipe its brow, and mumble, “Hot enough for ya?” Except here in Seattle, where we get approximately one hot day a year, usually the third Tuesday in September. Before we get to your question, a few eye-opening facts about America’s love of indoor climate control: In the late 1970s, 23 percent of American homes had some form of air conditioning; today, 87 percent do. We have become so addicted that 9 out of 10 new homes are built with central air.

We spend $40 billion a year air-conditioning our buildings, says the EPA, and cooling our homes accounts for 17 percent of household energy use. In return, we get — well, I’ll let author Stan Cox say it: “Air-conditioning buildings and cars in the U.S. has the climate impact of half a billion metric tons of carbon dioxide a year. That exceeds the total annual carbon dioxide emissions of any one of these nations: Australia, France, Brazil, or Indonesia.” Wait, you mean the thing we use to get through the record heat is … helping to cause the record heat? I believe that is what the kids call ironic. So my first piece of advice is, when you can stand to go without the AC, please do. Keep your blinds closed against the sun, use a fan, unplug appliances that generate heat, eat popsicles, drink water, place wet washcloths upon your fevered brow, sleep naked. When you use the AC, please set it at a reasonable temperature (your 79 is very civilized) and do not — do not — crank it all day while you are gone, people.

Your dining room set does not need to be comfortable. Emily, you’ve perhaps passed out while waiting for me to get to your actual question. I have experienced “energy-saving” mode, and I’ll admit I find it rather annoying. The mechanical hum stops. Your brain adjusts to the quiet. And then — ga-glunk — it starts up again. It can’t seem to decide.indoor floor ac unit Here’s what is actually happening: Air conditioners remove heat and moisture from your air by passing it over coils filled with refrigerants. york ac unit commercialIn a window unit, a compressor moves the refrigerants through the coils, and fans move the air where it needs to go. ac heater unit costIn energy-saver mode, the compressor shuts off when, as you say, the desired temperature is achieved.

The fans turn off too, but they come back on every so often to check in on you, see whether you need any lemonade, etc. When the fans find air that’s too warm, the compressor comes back on. So what you might be hearing every few minutes is the fans turning on and off, while the compressor is laying low. According to the EPA, this mode uses about 10 percent less energy than the conventional “cool”mode, so that saves you a little money. I’ve had trouble getting more detail than that from several manufacturers I contacted, none of whom could provide specifics on power savings by my deadline. Some even seemed a bit stymied. Generally I can count on geeky online chats to yield at least one insanely detailed calculation in these situations, but here, too, they all just shrug and say, “Eh, doesn’t save you much.” I guess even the geeks are feeling hot. If I do get more details, I’ll add an update here. Meanwhile, I can tell you that choosing a unit that’s the right size for your dwelling is the real key to efficiency and comfort.

Make sure your home is properly insulated, too — that will keep you comfy in summer and when the now-unimaginable chill of winter descends. From keeping the freezer door open while you pick your ice cream to leaving the lights on, let’s face it, we all have bad energy habits – ClearlyEnergy has field-tested the impact of seven of the most common ways we waste electricity, and discovered which ones matter to your wallet. Read on to find out what habits are worth trying to shake. We all have bad energy habits, from hanging out in front of the open freezer door letting all the cold out, to falling asleep in front of the TV, to the classic leaving the lights on all day when nobody’s in the house…but since appliances and gadgets all use different amounts of electricity, it’s tough to say which habits we should feel guilty about and which really don’t affect our wallet.So we collected seven of our own pet peeves and field tested them using an in-home electricity monitor..

Here’s what we found*: 1. The old favorite leaving the lights on depends on what kind of light you’re leaving on – and, obviously, how many. A “normal” incandescent bulb costs about 0.75cents per hour, and LEDs or CFLs cost only one-sixth of that – so leaving the lights on (either overnight or while you’re at work for the day, say both are about 8 hours) costs you roughly 6 cents for a normal light and a bit over 1 cent for modern bulbs. Obviously this isn’t going to break the bank 2. Falling asleep with the TV on is another classic: it’s so cozy on the couch…before you know it, it’s 3 a.m. and your TV has been broadcasting to no-one for 4 hours. It turns out that doesn’t cost you too much, thanks to modern TVs: current EnergyStar models use only 30-60Watts for a 40" TV, so those 4 hours asleep cost you about 2 cents.If you have an old TV, however, it can consume as much as 400W - in that case your nap costs you about 15c. Again, it matters how often your bad habit happens: if falling asleep in front of your TV is your nightly ritual, it pays to get a new energy-efficient TV because you’ve been wasting $55 per year.

3. Like to clean? If you are so eager to get dust-busting that you start vacuuming before moving the furniture, and then leave the vacuum running while you shove the couch away from the wall or remove the dining room chairs, you are wasting lots of power – right? Turns out despite their loud noise, vacuums only use about 1200 Watts – so spending 5 minutes moving furniture while the thing sucks air in the corner only costs you about an extra penny. That’s not a lot to pay for an extra-clean house. 4. How about this one: standing in front of the open fridge or freezer trying to figure out what to eat? Our home energy monitor showed us that leaving the freezer open for 2 minutes wastes about as much as leaving the fridge open for 4 minutes. The former is about enough time to pick an ice cream flavor and scoop it, while the latter is the time it takes to figure out which sandwich ingredients to use while the bread is toasting and to put everything back. But it turns out, it’s a habit that isn’t costing us too much: the door open situations drew about as much as leaving two CFL's on for an hour or so.

If you repeat your bad habit once a day for a year, it only costs $1.50. However, leaving the fridge door inadvertently open a crack means the appliance is working overtime for hours. So instead of kicking yourself for having left the door open, make sure you really close it tight! 5. We all know that it doesn’t waste much power to leave our cell phones plugged in after they’re done charging…but shouldn’t we try to unplug stuff to avoid the famous “phantom load” adding extra bucks to our energy bills? It turns out once gadgets are done charging, they suck only a miniscule amount of juice – one professor even tested how much exactly, using 4 laptops, 2 cell phones, 2 iPads, a Nook, a Nexus, and an iPod. When all of these were fully charged but still connected to their chargers in sleep mode, they collectively used only 8 Watts – less than half an energy efficient light bulb! So even if you had every one of these appliances charging in vain 8 hours a day every day for a year, it would amount to roughly $2.50.

A lot of folks pay more for their morning coffee. 6. After finding out that all those bad habits actually don’t waste a lot of power, we came across one that really does cost more than you think: an old stereo (the kind you typically have in your living room) uses a whopping 70 Watts in standby mode, which is what people normally leave it in for weeks at a time! All of us at ClearlyEnergy have some type of older stereo equipment at home that we didn’t realize is a silent sucker of electricity when not playing music – leaving those in standby all day can cost $67 per year. We all went home and turned ours off! 7. And now for the bad habit that really makes a difference: leaving the air conditioning on! Whether you have a central system or a window unit, air conditioners are powered solely by electricity – and they use lots of it. Leaving central the a/c on while nobody’s home (for instance the 8 hours you’re at work) can add up to a couple hundred dollars per season, depending on how hot and long your summers are.