Best Way to Boil Water

When it comes to home energy use, we often find that conventional wisdom is wrong, uselessly vague, or outdated. So, we recently set out to put a bit of experimental rigor into the question of making our morning cup of tea.

Here are some questions we wanted to answer:

1. What’s the best (i.e. least energy intensive) way to boil water?
2. Is the answer different for 1 cup of water vs. 4 cups? What about 2 quarts?
3. Most importantly, if I’m doing it wrong, is it worth changing the way I do things already?

We carried out 13 tests on a typical microwave (1.3 kw), a popular electric stove (1.5 kw element), and a standard electric kettle (1.5 kw). The results were a bit surprising. The electric kettle (unsurprisingly) performed great. The microwave, on the other hand, was shockingly inefficient while the stove performed surprisingly well (considering all of the wasted heat it dumps into the kitchen).

Question 1: What’s the best way to boil water?
Answer: The electric kettle won hands down. The real advantage with the kettle is on the first cup. It boils in half the time as the first cup boiled in either the microwave or the stove. Since (at 1450 Watts) it uses about the same amount of power as the others, halving the time halves the energy. Thereafter, the energy requirement for boiling larger volumes of water is nicely predicted by a linear function. Each additional cup requires an additional 25 Watt-hours of energy and about a minute of additional time. The stove had similar performance except that the first cup required twice the energy (and time) of the kettle’s first cup.


Question 2: Does the answer change based on the volume of water boiled?
Answer: For the first quart of water, the answer is surprisingly unchanged. The only thing that really changes is that the microwave performance degrades much more rapidly than the other two. So, while the decision to boil one cup of water in the microwave isn’t much worse than using the stove top, using the microwave to heat up 4 cups of water is a bad choice (from the energy and time perspective).

Question 3: Is it worth changing my behavior?
Answer: In the grand scheme of home energy usage, it turns out the savings you could gain by changing your habits on this one aren’t huge. In fact, even if you boiled a quart of water every day, the cost difference between the best performer (the electric kettle) and the worst performer (the microwave) would only be about $4 per year. But, what if we extend this lesson into other realms? We might consider reheating our soup in the kettle rather than the microwave or adding an electric kettle to the office kitchen for all of those cup-o-noodles (after all, the kettle is faster too). Furthermore, this is one of those rare energy decisions that can save time, money, and energy. Electric kettles are cheap, fast and efficient. Microwave ovens are expensive, slow and inefficient (for heating water).
The relative strength of the stove can also be seen as great news. If you size your pot appropriately the stove can almost rival the kettle… not bad.

*- To heat 8 cups in the microwave or electric kettle would take two batches. You can therefore approximate the time (and energy) by doubling the time it takes for 4 cups. The savings are small enough though that you might as well just use the stove for volumes greater than your electric kettle capacity.

How to Be an Energy Efficiency Hero

Some truths transcend their original context. In Jim Collins' modern classic, Good to Great, he classifies the qualities of businesses with exceptionally high growth rates over sustained periods of time. The findings sound a lot like timeless common sense, and one quality struck me as particularly applicable to energy consumption.

If you’ve read our blog before, you know our mantra, “You can’t manage what you don’t measure.” But sometimes measurement feels uncomfortable and painful. Fear of the unknown thwarts us from wanting to discover what ugly truth may lie behind door #1. Maybe it’s a test result that will have implications for our health or an auto tune-up that reveals this may be a more expensive bill than we’d planned on. That feeling of unknowing can be terrible.

And yet, Collins finds that truly excellent businesses, the ones that have gone from mediocre to awesome, share the quality of confronting the brutal facts. They don’t stop there, though. They possess the rare combination of confronting the facts while also having an unwavering faith that they will prevail in the end, regardless of the difficulties. Collins calls it the “Stockdale Paradox,” but for the purposes of this post, I’ll call it the heroic combination.

The second element, unwavering faith that you’ll prevail, can be difficult. The challenges of global warming or even the thought of having to change our behavior can make us want to throw up our hands. “This is too hard, too tedious, too hopeless,” we say. “I don’t want to know how bad it is.” But our greatest heroes are those who face the facts and press on with the faith that they will prevail.

Our goal at PlotWatt is to give you rich information about what’s happening in your home… which appliances are consuming the most energy and how much energy you’re consuming on a day-to-day basis. Sound scary? It may be, at first. Remember the heroic combination though. Armed with the facts, you can prevail to make far-reaching, sustainable reductions to save you money and prevent tons of energy from being generated. Then, you’ll be an energy efficiency hero. And who knows, maybe tomorrow you’ll fly around the planet so fast that you reverse time to save the world. With heroism, you’ve got to start somewhere.

http://www.flickr.com/photos/bohman/ / CC BY 2.0

Upstream Watt Multiplier (1 Watt Saved > 1 Watt Generated)

In the world of “clean energy,” projects fall into one of two categories: increasing clean energy generation (supply) or decreasing energy consumption (demand). The energy generation side is developing technologies aimed at displacing the power plants we already have and building additional capacity for our ever-increasing energy appetites. Cool. On the other side, there are those of us focusing on more efficiently using the energy produced, no matter what the source. In this post, I’ll describe why these aren’t just two sides of the same coin.

This is really important: energy saved can have multiplicative upstream impacts. A unit of energy (e.g. a kilowatt-hour) consumed by your television has much more impact than the same unit of energy produced by your local power plant. This is a consequence both of inefficiencies in our system and of the laws and limitations of physics.

Inefficiency in the Home
Let’s look at the power it takes to illuminate a light bulb. We’ll start with a new term, the lumen. A lumen is a unit of measurement used to express the amount of useful (visible) light produced by a light bulb. It is important that we start there because lumens (not Watts) are what we want from our light bulbs. We’ll begin at the lumens and follow the electricity back to the power plant where we’ll discover just how much energy a light bulb wastes along the way.
Let’s say we want to create 1700 lumens of visible light. If we had a perfectly efficient light bulb, it would take about 2 Watts of electricity to produce 1700 lumens. Incandescent bulbs are far from being perfectly efficient. They are about 2% efficient at producing useful light. That means for every 1 Watt worth of useful light produced, 50 Watts are wasted on things like heat and invisible light. For incandescent light 1700 lumens requires a 100W bulb (i.e. 98% of the energy is wasted).

Transmission Inefficiency
Next up, we have transmission losses. This is energy lost between the power plant and our homes (usually the loss takes the form of heat). In the US, our average transmission losses are about 7%. So, a 100W bulb, which makes 2 Watts worth of light, requires 107W of power from the power plant.

Power Generation Inefficiency
Finally, we have power plant losses. Extracting energy from just about any fuel source is an inefficient business. We generally burn a fuel and then use the heat generated to turn a turbine. In the US, across all electricity sources, we’re about 32% efficient (i.e. 68% wasted). So 107W requires 334W of input. All-in-all, it takes 334 W to make 2 W worth of useful light. From coal mine to illuminated living room, we are wasting 99.4% of the energy. Yikes.

So what?
The repercussions of our gross inefficiencies are oft-neglected when it comes to clean energy thinking. We think that adding generation to the grid has the same impact as removing demand from the grid. In reality though, doing without the 2W worth of light is equivalent to removing the upstream need for 334 W worth of input or 107 W worth of generation. Similarly, increasing the end-use efficiency from 2% to 8% like we can do with CFLs, has huge upstream repercussions. Now, we’re still creating 1700 lumens of light, but it only takes a 25 W bulb, 27W of generation, and 84W of input.

Adopt a Home and Live Net Zero

A lot of the readers of this blog are energy-savvy “ecogeeks.” Most of you share our enthusiasm for energy efficient, conservation-oriented living. We love you for that. In this post I’m going to frame our individual efforts in the big picture and encourage you to spread the energy-saving love.

We humans are a self-serving species. There are few places where this is more apparent than environmentally-oriented purchasing. We will go to great lengths to make our individual lives eco-pristine. Photovoltaic solar anyone? We will squeeze every ounce of energy waste out of our homes and we often do so at great monetary expense. The first 10, 20, even 50% might be easy, and then it starts to get costly. We start to rationalize things like 20-30 year payback periods.

At the point where we start looking at home improvements that take a decade or more to pay for themselves, we should all ask ourselves a question: “Why am I doing this?” Your answer to that question is important. If your goal is to stimulate innovation by pumping money into bleeding edge technologies, that’s awesome. If your goal is to have the most eco-bling on the block, that’s fine too (I guess). But, if your goal is to reduce the need for dirty power plants, fight climate change, end mountain top removal, pursue energy independence, or take up any other clean energy goal requiring collective improvement, I’d like to suggest an alternative to the big capital investments. The alternative is to adopt a friend or family member’s house. Help them save 10% and then adopt another.

Keep in mind, 10% of a serious consumer’s energy might amount to your home’s entire energy bill. When it comes to overall energy reduction, personal percentage reductions really aren’t important. This is a bit like the MPG Illusion. Our friends live in homes that burn energy like a Hummer with flat tires. Meanwhile we are giving ourselves a pat on the back for upgrading from a Toyota Corolla to a Prius. We are unplugging cell phone chargers to save watt-hours when we could be helping others to save kilowatt-hours. We need to reduce the total number of kilowatt hours used. For that McMansion your brother-in-law lives in with the landscape lighting running at all hours, a simple timer might be worth a thousand times its weight in coal. So, let’s get off of our high horses, stop trying to get our own electric bills to zero and start going after the big opportunities.
Please don’t mistake my plea as presentation of a false dilemma. There is lots of room for a “both and” approach rather than an “either or” approach. Often, you can shave the watt-hours from your bill AND help your neighbor with the kilowatt-hours. If you’re thinking about spending the big bucks though, please do so with your eyes wide-open, acknowledging that you could almost certainly achieve the same end with much less capital and bit of friendly outreach.

Want to see how we tackle energy waste? Sign up for our mailing list at plotwatt.com to learn about becoming a pilot home.

Images from:

http://www.flickr.com/photos/auntylaurie/ / CC BY 2.0 & http://www.flickr.com/photos/landschaft/ / CC BY 2.0

1 Watt Rule of Thumb

In the spirit of sanity checking my energy saving decisions, I like to keep simple technical estimations in mind. In this post, I’ll discuss one of the most useful. If you’re not in the mood for math, here’s the bottom line: 1 Watt of energy reduction equates to approximately $1 of electric bill savings per year. So, eliminating 10 Watts of phantom load from your house will save you about $10 per year, 100 Watts produces $100 of annual savings…
Disclaimer:
This is a gross estimation. As such, this rule should only be used for getting a ballpark idea of savings potential.
Let’s Practice:
If 1 Watt of energy reduction produces $1 of savings per year, replacing a 60 Watt incandescent bulb with an equivalent 13 W compact fluorescent could provide as much as $47 (60-13=47) of annual electricity bill savings. BUT, most of us don’t keep our lights turned on 24/7. So, instead let’s say that that same bulb is turned on only 2.5 hours per day. Since 2.5 hours is about 1/10th of a day, our savings have dwindled to $4.70 per year. If it’s on just 15 min per day (1/100th of a day), the annual savings fall to 47 cents per year. (More on CFL's here and here.)
Let’s look at another example. A typical cell phone charger has a phantom load of about 2 Watts. If you leave it plugged in all the time the charger will waste $2 per year. S0, religiously unplugging it after charging your phone will save you about $2 per year. Cool. But if you forget to plug the charger back in just once you might find yourself with a dead cell phone (and that might cause > $2 of frustration). For that reason, I prefer to target the less risky phantom loads, like that TV in the guest room. A TV might use as much as 15 Watts of energy when it is turned off but in standby mode. Unplug the TV’s you seldom use (or learn a slick new use for a holiday light timer here) and save as much as $15 per year per TV.
Here’s the math:
As you might recall from a previous post, one kilowatt-hour is the amount of energy used by 1000 Watts running for one hour or 1 Watt running for 1000 hours. There are 8760 hours in a year (24 hours per day x 365 days = 8760). So, if an appliance uses 1 Watt of electricity constantly (24 x 7 x 365) it uses a total of 8760 Watt-hours or 8.76 kilowatt-hours of electricity in a year. With me?
The average cost of a kilowatt hour in the US is between 9 and 10 cents. We’ll round up and call it 10 cents. So, if one watt burns up 8.76 kwh in a year, it will cost you 87.6 cents on your electric bill every year. In the spirit of gross estimation (and in anticipation of rising electricity costs), I round that up to $1.
The graphic shows the approximate distribution of electricity rates around the country. The 1 Watt rule of thumb is close enough for most of us. If you’re in Hawaii though, where electricity is more than 20 cents per kwh, this estimation should be closer to $2 per Watt.
Happy energy saving!

Vocab Lesson: On-Peak, Off-Peak

Through recent industry events and conversations with consumers it has come to my attention that there are some electricity grid fundamentals that the industry insiders take for granted and we consumers never even consider. One such fundamental is that of baseload generation and its counterpart, peaking generation. In this post I’ll outline these principles and touch on what they mean to you, as a consumer of electricity.


First, the basics:
When we look at energy consumption curves, they reveal particular times of the day when we tend to use lots of energy, and other times of the day when we use very little energy. For instance, in the winter months here in South, where lots of people have electric furnaces, there is a spike in energy use at around 7 or 8 AM when lots of the furnaces come on to warm up homes and offices after a cool night. Then, as the day warms, energy use subsides as the furnaces are used less. Again in the evening, as it gets cold there might be another spike. The periods of high energy demand are called “on-peak hours” and the low-energy use periods are “off-peak.” As you might imagine there are lots of different ways to characterize these periods. Some utility companies have off-peak, medium-peak, and high-peak periods for instance. The basic premise remains the same: our collective energy use over any given day is not a flat line. And the peak and off-peak hours change with the seasons and even with the day of the week (weekends being different than weekdays).


Why does it matter?
It turns out that certain sources of energy are best suited to meet certain types of demand.

If we are painting with a fat brush, our electricity generation pie looks like this:

What the pie fails to represent is the temporal characteristics of various fuels’ usage. It turns out that coal plants are very difficult to start and stop. Furthermore, they are happiest when plugging along at a constant output. Think of a coal power plant as a campfire. Keep shoveling in the coal, and it keeps pumping out the power. Like a campfire though, it’s tough to quickly turn down, turn off or crank up a coal plant. For that reason, coal power plants are best suited to meet the minimum, mostly constant, baseline power needs of the grid, aka baseload power. Nuclear plants are similarly suited to baseload generation. Hydroelectric is also usually considered a baseload.

Natural Gas plants, on the other hand, run like a car engine. In the case of a gas plant, when you turn on an electric appliance, the power plant instantly responds by pumping out more energy. Turning on an appliance is like stepping on a car’s accelerator, the power plant just works a little harder and burns more fuel to power the appliance. This relative nimbleness makes natural gas plants ideal for on-peak generation. Such power plants are called peaking or peaker plants. As you can probably imagine, these peaking power plants tend to be much more expensive to operate than the baseload plants so they are only used when needed. This cost discrepancy is the basis for utilities offering time of use billing plans… more on that in a future post.

What does this mean for you?
The implications for you depend in part on your goals. If you want to save money on your electric bills, shifting your energy usage to off-peak hours can save you serious cash. This gets into time of use billing plans (once again the subject of a future post) but I can hit the key points here. Time of use billing is already available in some parts of the country. If you can handle the inconvenience of shifting your demand to your utility’s off-peak hours, opting in to time-of-use billing can be great. In my case, by shifting my demand to off-peak hours I pay about 30% less per kwh than I would if I were on a standard billing plan. If TOU billing isn’t available to you, shifting your demand to off-peak hours still helps your utility to run more efficiently and theoretically keep your bills low.

If you’re more interested in environmental concerns, simply shifting demand to off-peak hours may not help the cause. In fact, if such a shift means more coal and less natural gas you may actually be doing more harm than good! Natural gas plants after all emit about half the CO2, one-third the NOx and almost no SOx and Mercury. I suspect there is a win-win opportunity here to shift our demand to those off-peak hours that are best met by renewable sources. Does your area have lots of solar power? If so, consuming in the few hours on both sides of noon makes good environmental sense. Do you live near wind turbines? Perhaps you should try and run your dishwasher when it’s windy. In truth, this type of demand shift might encourage renewable generation as much as paying extra for it on your electric bill.

In theory, if we all shift demand properly, utilities will run more efficiently, and we’ll all get lower rates and maybe some cleaner power too!

A Letter to Dr. Steven Chu (the next Secretary of Energy):

My faithful blog readers, I apologize for the lapse. If you are not already using an RSS reader or the “Subscribe via Email” feature on this blog, please consider doing so. It will obviate the need to check in on the blog to see if there is a new post. And now, back to our irregularly scheduled post…

Dear Dr. Chu,

As a “cleantech” entrepreneur, I’m really excited by President Elect Obama’s decision to appoint you the next Energy Secretary. Based on the tremendous breadth of energy research that you have overseen in your time at Lawrence Berkeley National Labs, I believe that you may be one of the best equipped scientist-administrators to take on the challenge of American energy policy. It has been my experience that this sector needs a healthy dose of perspective. We all get lost in the weeds of our particular technology and become myopic. Those who can afford it hire lobbyists to spread their myopia in Washington where any and all things nominally pro-environment are seemingly being promoted with reckless abandon. If your project Helios lecture is any indicator, I think you will be able to help Washington to get out of the weeds and properly prioritize our research and short-term energy priorities.

However, I do have some warnings and observations to share. The rest of this post will be devoted to the critical observation that when it comes to energy policy, California (your home state) may not be the shining example of sustainable consumption success that its politicians like to claim. You rightly have pointed out that while America’s average per capita energy consumption has been rising since the industrial revolution, California’s per capita consumption leveled off around 1970 and has remained the same since. Way to go California! But wait a second… Is “per capita energy consumption” really the right metric?

At VisibleEnergy we are big fans of using meaningful metrics (see the Cheeseburger Calculator and the Gallons per Mile posts). When it comes to metrics that are intended to assess our energy sustainability, “per capita use” isn’t very helpful. This metric fails to consider some very important characteristics like population growth and energy source. If the population is growing and the per capita energy consumption is flat, the total energy use still grows. When it comes to resource sustainability, our finite resources don’t care whether our average consumption is low. Sustainability is much more a concern of aggregate or total consumption. So what does California’s total energy use look like? Not so great. That is not to say that per capita consumption is a useless metric altogether, just not an adequate measure of sustainability.

The following series of graphs illustrate different ways to look at the same data. You tell me, where should we be investing our attention? Making the country more like California or figuring out what on earth is going on in Alaska?

This first graph shows a zoomed-in picture of the per capita energy consumption in all 50 states and the total per capita energy consumption for the US. I've highlighted some stand-outs. Nice work Rhode Island!To make things comparable in this second plot I scaled all of the values to be a percentage of the total consumption in 1970. So, you can see for instance that America's energy use is now about 150% of what it was in 1970.This plot reveals that California doesn't look so great when compared to the US if total consumption is the metric of choice. Since the per capita consumption is relatively flat, the population must have grown.The following graph shows the zoomed-out perspective on the first graph. From this perspective the worst offenders are Alaska, Wyoming, Lousiana, and North Dakota.And finally, a zoomed out picture of total consumption for Alaska, California and the US.Thoreau wrote: “In the long run, men hit only what they aim at." (Walden)
Let's find something good to aim at.

Best of Luck Dr. Chu!

- The data for all of these charts can be found through the Energy Information Administration (eia.doe.gov) -