Thursday, January 18, 2007

The Energy Star Efficiency Myth

For years the Federal Energy Star program has perpetuated the myth that if you buy appliances (or any electrical device) for the home that uses less energy, you'll see proportional savings in your monthly power bill. This is rarely the case.

Other eco-writers do similar simplistic math to calculate savings in money, energy and carbon. A recent example is Charles Fishman's September 2006 article in Fast Company magazine about WalMart's CFL project, "How Many Lightbulbs Does it Take to Change the World?".

The claim is made that if a single light bulb using 45 watts less is placed in 100 million homes, 6.57 billion Kilo-Watt-Hours will be saved. The fact is, unless you are cooling your home, there is ZERO savings. Charles focused on the bulb, but forgot about the home. His entire premise is based on a false assumption. The savings are grossly exaggerated.

"Wasted" energy takes the form of heat. And this heat helps heat your house, if only just a small amount. For most of America, for most of the year, that 45 watts will be automatically added back in by the home heating system to maintain the same level of comfort. If the home is heated with electricity, the savings in dollars, energy and carbon production is literally ZERO.

The only time energy is actually saved is when the air conditioning is running or you have the windows open to cool the house. With the air conditioning on, the savings can even be a little greater than 45 watts, but for most of America that's a small part of the year. What are the savings for the rest of the year?


If you are not cooling your home, EVERY light bulb and appliance is 100% efficient.

Here's why...

The second law of thermodynamics demonstrates that "wasted" energy tends to disperse evenly. And if this "wasted" energy is in your house, it simply keeps you warm. More importantly, it keeps your normal heat source from turning on. Let's see how it plays out in a real home and why saving energy by turning off the lights is mostly an illusion (pardon the pun).

If you have a home in the northern latitudes which is electrically heated much of the year, you are a net consumer of heat. And the nice thing about heat is that It doesn't matter where it comes from. And that's the key.

Take a light bulb that's only 10% efficient. That means 90% of it's energy is converted directly to heat. So what happens to that heat? It spreads out through your house and slightly delays your normal heating system from clicking on.

And what about the 10% of the energy in the form of visible light? Virtually all of it strikes objects in the house. It too is converted to heat. The ONLY ineffectiveness of a light bulb in a northern home in the winter is the light that escapes through the windows, which is a VERY small amount. Even THAT can be stopped with curtains. Which would make ANY light bulb 100% effective at producing heat. Here's how Wiki explains it... Efficiency versus Effectiveness.

Why do I qualify this with northern homes and winter? Because if you have to open the windows to be comfortable, you lose the advantage. And if you have to turn on the air conditioning, this "effectiveness" actually becomes a small liability. So those of you in Florida and south Texas, nevermind.

It's all about heat, where it moves and how we store it. But for most of America, much of the year, energy efficiency is very much an illusion. Effectiveness rules the day because we actually USE that "inefficient" heat.

And if your windows are closed but your heat is NOT turned on? Or not turned on until later at night? Those appliances are still 100% effective. That's because they are helping keep the house warm. They are one reasons your electric heat hasn't come on yet. If that heat doesn't come from one source, it has to come from another.

But what if you're a bit on the warm side in late afternoon but you haven't opened the windows? Again, it doesn't matter. This thermal intertia will delay heating later on. As long as you don't have to cool your house, everything is 100% effective. Let's take a couple more examples.

Electric blanket - 100% effective. If you turn it off, the electric wallboard heating will kick up 100 watts to compensate: net cost of blanket electricty for the same comfort level - zero.

TV, DVD & computer - Left on all the time? No problem, as long as the air conditioning doesn't kick on.

Hair dryer - 100% effective (and only used for short periods anyway), so get every hair in place.

Electric touthbrush - Yep. Even the charger is a perfect machine.

Refrigiator - 100% effective. This is one of my favorites. What does a refrigiator do? That's right. It compresses gas to pump heat from the inside to the outside of the ice box. Where does that heat go? It heats the kitchen! Even the compressor is 100% effective! Once again, it saves energy that would come from electric heat.

Why do I keep referring to electric heat instead of oil or gas? That's because in the past gas has been far cheaper than electricity per BTU. This made electrical devices a little less "effective" (and a little more expensive) in producing that "wasted" heat. Unfortunately, cheap gas is history. The price of oil and gas now approachs that of electricity. There's no big difference. Leaving your TV on is now almost as cost effective as buying natural gas.

This "effectiveness" creates the strange situation where you could turn EVERYTHING in the house off (except for the electric heat) and set in the dark for a winter month with no entertainment or hot food - and your power bill would be EXACTLY same. Try it sometime. You'll see.

This also means you could go out and buy the most efficient light bulbs you could find and all new Energy Star appliances; STLL the power bill would be EXACTLY same. So enjoy your gadgets and think twice before spending extra for "efficiency". Spend your money were it counts.

And where might that be? If there's little advantage to "efficient" appliances, how can we save energy and money? That's another blog post, but start by taking a look at the heat leaving your home through the walls or down the drain as hot water. Those two are your biggest loses.

Heat and air conditioning use 50% of home energy. Better insulation and sealing can save up to 25% of your energy cost for the typical home. But make sure the house still has reasonable ventilation - especially in radon areas. And hot water is about 13% of your energy use, so again, use it carefully. It's not effective to heat up the sewer drains.

Which brings up one important exception to this "effectiveness" rule - the clothes dryer. It blows it's heat outside and also brings in cold air - you lose. It's a good reason to get a clothes line. Or use the dryer sparingly.

There you have it. Now you can sleep better (and warmer) knowing your heat isn't as "wasted" as you thought.

OK. If you still want to know how much of that 65.7 KWH you would save by buying that bulb, multiply it by the ratio of cooling days over days in a year (365.25). The extra air conditioning load will be offset by less probable need for light in the summer. For me in Reno, Nevada that extra efficiency can be used about a quarter of the time (in the summer) which is probably about average for America. This makes WalMart's claim overstated by four times - you decide if that bulb still makes sense.

But why would Fast Company, WalMart and Energy Star not point this out? Simple. It would make the story less exciting, WalMart would sell fewer light bulbs and... and... I don't know what's wrong with the Federal government.

So from now on, don't let some slick magazine make you think a new light bulb will solve all your problems; don't expect WalMart to always save you money. And finally, don't expect the government to set them both straight. When you hear about efficiency, think also about effectiveness.

And quit worrying about your household appliances.

They are almost perfect machines much of the year..

No matter what their efficiency rating.

Please comment if I've missed something.


Anonymous Anonymous said...

Note that most homes heated by electricity use heat pumps. Heat pumps can be expected to put three Watts of heat into the house for every one Watt of electricity consumed. By comparison, One Watt of electricity consumed by a light bulb of any kind puts about one watt of heat into the house, assuming it is not in a porch or recessed fixture. Therefore it costs three times as much to heat with a light bulb, or any other electric appliance for that matter, than to use the house's heating system for heating. It is fairly rare to find a house that is exclusively heated with resistance heating, particularly in cold climates due to the high cost. The distinction that has to be made for what you wrote is applicable to resistance heated, versus electric in general, that includes heat pump systems. Electronic retrofit devices that can be added to old appliances improve perfomance and reduce energy consumption and work great, but they have not been promoted, and I think have been discontinued. The government and industry just want to sell new appliances because that is what can be taxed or profited from.

10:53 PM  
Blogger Sudden Disruption said...

Good point which was also brought up and addressed at...

>Paul M. Eldridge posted...
> Let me elaborate on my own situation, as it happens to be the one I
> know best. I heat my home with a heat pump that provides, on average,
> two and a half times more heat, per kWh, than electric resistance

You provide an excellent counter-example I hadn't considered. Heat pumps are wonderful and efficient machines and you show CFLs are indeed the way to go in your home.

But I think you would still agree, not ALL of the savings calculated
by Energy Star go into your pocket. Even though cost effective, your heat pump still has to replace that lost heat at the cost you've nicely defined.

Now if we could just convince 100 million home-owners to convert to
heat pump.

As noted, a heat pump helps but only reduces the error by two thirds under the best conditions. One third of the CFL savings are still missing.

And good point about the tax and profit motives...

Thanks for the comment.

Sudden Disruption

12:37 PM  

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