Update in 2016: Following publishing this article, we’ve noticed there are many similar “kettle vs microwave face-offs” online, and not all results are the same as ours. Also, please note our in-home study doesn’t take into account the quality of the tea made… :)

I’d like to introduce one of my favourite parts of science (and of law among physics) with a simple hot-water-for-a-cup-of-tea scenario. In our part of the world, most homes will have: hot water through taps, a kettle and a microwave. This is what occurs based on these various energy systems:

1.      Hot water by tap. Regardless of how your water is heated (burning oil, electricity or another source), you are condemned to replace a large stored volume of heat in your household water tank any time you finally get the hot temperature you wanted in the small volume you requested at your tap (this also applies to washing hands at your sink). The remaining portion of unused heated water, in case you thought the heat would dissipate usefully, remains in your pipes in areas that are unoccupied.

Result (scientifically speaking): a 3000-4500 watts heater running for approximately 20-30 minutes totals an energy input of 1-2.25kWh (kilo-Watt-hours).

2.      Hot water by kettle. Our kettle at home uses 1500 watts (BTW, true watts as it is strictly a resistive load – another topic for later) and will boil cold, tap water in 5-10 minutes depending on the volume and time of year (BTW, incoming water temperature changes drastically through the year – this will be another topic as we speak about ‘Delta T’).

Result: 1500watts running for approximately 5-10minutes = 0.125-0.250kWh, or one-tenth (1/10th) of example #1.

3.      Hot water by microwave. Our microwave uses 1500 watts (BTW, a microwave is not a purely resistive load and you actually only get about 750 watts of usable energy into the items inside it – which technically makes it about 50% efficient). We can boil a cup of cold tap water in 1-2 minutes.

Result: 1500watts for 1-2 minutes = 0.025-0.050kWh, or one one-hundredth (1/100th) of example #1.

The moral is that the tighter and more efficiently you can transfer energy, the less energy it will take to accomplish a task (such as heating a cup of water).

Regardless of your current energy set-up, SAGE Energy Inc. supports sustainable options and offers sales, installation & service by using cleaner technologies and true natural resources such as sun, wind and water. We always welcome questions and comments.