Q. My wife is a big tea drinker, so we have an electric kettle to keep her sipping her daily Darjeeling. Years ago I began using the hot water remaining from her pour for dishes, especially pots and pans to be hand washed. Waiting for the water to turn hot from the water heater definitely can be a big water waster. The instant hot water was so useful that in time I began to heat up some water in the kettle just for the purpose of cleaning pots and pans, knives, and wooden utensils. It works very well and saves water. On balance, considering both water and energy use, am I ahead, or am I using more energy to heat the water than any water savings justifies?

Larry C.
Pensacola, FL

A. Dearest Larry,

Our ancestors would surely find our modern kitchens remarkable, don’t you think? You need hot water, so you twist a little tap: almost instantly, bingo, hot water, no stoking a fire or stirring a cauldron required. They’d probably think it was a miracle.

But of course, hot water is no miracle. We burn quite a bit of energy – about 18 percent of our total home energy expenses – heating that water and then keeping it hot so it’s ready the moment we want to shower or wash the dishes. So you’re using resources (electricity, natural gas, or propane, depending on what kind of water heater you have) no matter which heating method you choose, Larry. The question is, how much? Or, put another way: Is it worth the extra time and hassle to heat water for doing the dishes in an electric kettle, instead of just twisting that magical tap?

Let’s take a look at our contenders. First, we have your water heater, which I presume is the common storage tank variety. These workhorses keep your water piping hot all the time; when you use some (by, say, doing laundry or bathing), the heater pulls in fresh cold water to replace it and promptly brings the contents back up to the proper temperature. A primary problem with this system, however, is something called standby heat loss: Inevitably, some of that hard-earned heat escapes into the air around the tank and pipes, forcing the heater to fire up again to keep the water at-the-ready hot.

You’ve already mentioned another primary problem: the potential for wasted water. Know how you have to wait a few moments — or, heaven forbid, a few minutes — for the water to get hot when you turn on the tap? That happens because the water that gets stranded in your home’s pipes (between the heater and the faucet) will lose its heat even more quickly; the next time you turn on the faucet, you first need to drain this now-cold water before the hot stuff from the water heater tank works its way to you. Many people just let that cold water pour straight down the drain.

In the other corner, we have the electric kettle. These little appliances beat out other common heating methods such as the microwave and the stovetop when it comes to efficiency, in part because their heating element is in direct contact with the water it needs to heat. And provided you only spark up enough water to meet your needs, there’s no standby heat loss or wasted water to worry about.

So who wins this matchup? I consulted Pat Remick, senior energy communications strategist at the Natural Resources Defense Council, and the answer is … the old, reliable, anticlimactic “It depends.”

As Remick explained via email, we can’t answer with precision without knowing what type of water heater you have and how efficient it is; the number of dishes you’re scrubbing at a time also plays a role. For example, a tankless or on-demand heater can be up to 34 percent more efficient than the usual tank variety, and a solar heater up to 50 percent better. Conventional water heaters, which it sounds like you have, also vary in terms of efficiency.

So, what can I tell you, Larry, without sneaking into your basement with a flashlight and a calculator? If you like using the kettle to get your dishwater a-boilin’, then go on using it. This efficient little heater will likely get the job done without costing too much in energy or water. To up your game, warm only the amount you need and use it promptly to avoid heat loss.

If you decide to switch to the tap, know that you don’t have to waste any water waiting for the hot stuff. Just catch the cold water in a bowl or jug and reuse it — rinse fruits and veggies, water your plants, use it for cleaning, or just drink it. And if you haven’t already, insulate your heater and pipes to slow the dratted standby loss. To eke out even more savings, consider turning the whole darn thing off at night, or when you’re not around. It takes a bit more planning, but you’re the kind of wonderful guy who cares enough to wait for a kettle to do his dishes. It might just be right up your alley.

Scaldingly,

Umbra