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How to Boil Water ... Efficiently, That Is

9/9/2010 9:23:08 AM

Tags: energy, efficiency, off-grid, Cam Mather

“So what’s it going to be today Cam, gas or electric?” This is the question that my wife Michelle asks me as she contemplates boiling a kettle of water. Have you ever wondered what’s the most efficient way to boil water? Is it more efficient to use an electric kettle or a propane or natural gas stove? I’ve wondered about this. And spent a lot of time thinking about it. Oh it’s not something I’m proud of, but somehow living off the electricity grid has set me on a journey of exploration to always search out the most efficient way to do things … lots of things … everything in my house that uses energy!

Many people don’t have a choice about how to boil water. They have an electric stove. They should probably use an electric kettle because that just means the heating element is actually in the water making sure that all of the electrical energy that flows in gets converted to hot water. An electric kettle is actually 100 percent efficient. It uses 100 percent of the energy that it gets to heat the water. None is wasted.

The problem is that electricity isn’t really a primary energy source; it’s a secondary energy. Fossil fuels were used to create it. For much of the electricity used in North America, coal was burned at a power plant. The coal was used to heat water and once the water was hot enough the steam was used to power a turbine to create electricity. But for every unit of electricity produced this way, three units of energy are wasted as heat. In the case of nuclear plants, huge amounts of cold water are used to keep things under control and then this wastewater gets dumped into lakes and rivers, heating them up. So even though all the electricity that went into your kettle went directly to heat the water, if you look at how much energy was used to create that secondary energy, and transmit it to your home, it’s really not as efficient as using natural gas.

When you use grid power from any of the traditional centralized power plants only one third of the fuel source energy … coal, uranium, natural gas or oil … actually reaches your house as electricity. The rest is wasted as heat at the plant and in generation losses and transmission losses as it travels through all those wires to your home.

Now natural gas isn’t perfect either, because much of the heat that is generated when it’s burned actually flows around the kettle and dissipates into the air. It’s a bit more efficient than electricity, but still wastes heat. And if you look at the energy used to drill for natural gas and pipe it a long distance to your home, it isn’t perfect either. If you look at its impact on the environment and the people who live near the wells, it has a real negative impact.

The Rocky Mountain Institute has a great chart which shows the losses inherent in traditional centralized power generation. It was published in an article, More Profit with Less Carbon, in Scientific American. 

So how can you boil water or use energy more efficiently? By making the energy at your house with solar panels, wind turbines and/or micro hydro, and putting that energy right into your kettle. Then you dispense with all the waste in the burning of fossil fuels and shipping the secondary electricity over long distances. It is elegantly efficient … and very cool.

This is why I love living off the electricity grid. When I make a cup of tea, I know that I am using the most efficient method of boiling the water. There is no waste. The sun hits my panels, they make electricity, and the electric kettle converts that into heat in the water. There is nothing as comforting as a cup of tea made by solar power. I just love it.

Kettle on propane stove or electric kettle?

Now I can’t pretend that my system is perfect. If we have too many days of cloud here I have to be more careful about using electricity. I sometimes even resort to boiling my hot water on my propane stove and using fossil fuels. But for the most part I use solar power to boil my water, and after 12 years of living off the grid, I still marvel at the wonder of it all. The nearest utility pole is 4 miles away and yet I am still able to enjoy the same comforts as other North Americans — I just use my solar panels to create that marvelous electricity that so enhances my life.

At this point I am going to admit to being obsessed with efficiency to the point where I probably spend way too much time playing with water. I’m not content to just use my efficient solar-powered electric kettle to heat my water. I know that if I boil the electric kettle having started with cold water, it’s going to take longer than if I started with hot water. So on sunny days I use our solar oven. I leave a black kettle full of water in the solar oven and it reaches about 300 degrees Fahrenheit on a sunny day. After a couple of hours in full sun, the water is almost fully boiled. So I bring that into the house, pour it into the electric kettle and finish it off in there. This minimizes how much electricity I use, even though I’ve got lots.

Black kettle in the solar oven

Michelle thinks I obsess about electricity. She is correct. But I absolutely love it. I love knowing where it comes from and what went into making it. Right now when we have friends over for breakfast, I’m a whirling dervish going from electric appliance to electric appliance cooking everything in a well-choreographed sequence to make sure that I don’t overload the inverter. Then we end up with a zero-carbon breakfast. No fossil fuels were burned to make it. I find it insanely gratifying. If my wife’s biggest complaint about me is that I spend too much time trying to figure out how not to spend money on propane, I can take that. Anyone reading this blog knows that probably isn’t the worst thing Michelle has to put up with.


Photos by Cam Mather 

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Post a comment below.


9/22/2010 3:17:06 PM
"So on sunny days I use our solar oven. I leave a black kettle full of water in the solar oven and it reaches about 300 degrees Fahrenheit on a sunny day" Um... No... liquid Water anywhere near atmospheric pressure CANNOT reach 300 deg F... Only 212... Before it can go any higher temperature it must change state to vapor So maybe typo and should read 200 deg F?

9/14/2010 11:32:45 AM
Cam- I share your journey to always search out the most efficient way of doing things with what you have. Boiling water really is a big deal to off -gridders and should be for us all. IMHO Electric stoves are the worst. (BTW- What kind of stove is in the photo? It’s “kicken”! will it burn methane too?) Glass-top electric stoves being the worst of all. It became very obvious to me when I was canning on a glass-top electric. I reverted to pulling in the propane tank and using the Coleman stove. I was canning peppers and after boiling the pint bottles, I removed them and filled them with peppers, boiling water, and spices. The canning water was boiling all this time, until I submerged the pint bottles in the water. The temp. of the pint bottles dropped the water from boiling. It took a good five minutes to reach boiling again. This is not good when the recipe calls for only five minutes of boiling. Whatever you are canning looses its crunch and becomes soft. With the flame of the Coleman stove I was able to keep the water boiling. I have also noticed that many off grid neighbors up here pull out the propane and tripod burner for tasks like canning and butchering. Reboot2009

9/13/2010 1:49:00 PM
I like this kind of practice, but I know it is far from zero impact because of the materials burned and used to make these solar products. I just want to make sure this is realized. However I know it is a huge step and commitment in the right direction. I often wander though what is the actual initial foot print of these applications (I say initial because of course the footprint is reduced over time and continued use) Any insight to this let me know!


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