How to Boil Water ... Efficiently, That Is

| 9/9/2010 9:23:08 AM

“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. 

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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