Q. Dear Umbra,

Is there a particular time of day that would be better for the environment to charge my phone and laptop? I know it’s probably a small difference, but I’m just curious.

Benjamin
New Haven, Conn.

A. Dearest Benjamin,

So much in life comes down to the proper timing: landing your dream job, falling in love, getting the high score in Whac-a-Mole. And so it is with electricity use. Though we might not notice it — every time we flick a light switch or run the washing machine, electricity is there waiting for us — when we choose to plug into the power grid does indeed matter. I can’t help much with the dream job or true love (or with your Whac-a-Mole skills, for that matter), but I can offer some insight into your charging query. It’s so nice to feel useful.

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The short answer is, some times are better than others for charging electronics. You’re right, Benjamin, that the difference is small, because smartphones and laptops use relatively tiny amounts of energy compared to household energy hogs like air conditioners and clothes dryers. But given the chance to do something better for the environment, well, why not take it? Besides, this question is just the tip of the iceberg: Under the water lies a hulking discussion about electricity supply and demand. Let’s nerd out!

Q: When’s the best time to juice up your phone and laptop? A: Anytime when overall demand for electricity is low, which generally tends to be evenings through early mornings and weekends. These are known as off-peak hours. Peak hours, on the other hand, occur when lots of people are using energy: turning on lights, printing useless documents, running laundry, cranking up the AC, etc. Anything you and I can do to reduce the peak energy demand on the grid is helpful, for a few reasons. (Need a refresher on the whole “grid” thing? Head over here.)

Background: We call on different kinds of power plants to meet our power needs. First, there are baseload plants, which run all the time so that we always have electricity ready to go. They’re expensive to turn on and off, so we typically just keep them humming. Then there are peaker (or peaking) plants, which are basically like the extra sandwich-maker who comes in for the lunch rush: They fire up when consumer demand for electricity surges, supplying extra power beyond what baseload plants typically provide.

But the electricity these two pump out isn’t created equally. This will vary a bit depending on the power sources used in any given community, but generally, baseload plants run on cleaner power sources, are more efficient power generators, and are cheaper to run. Peaker plants, on the other hand, almost always run on fossil fuels. So the less we need to call on those dirtier, more wasteful peaker plants, the better. One more reason to use power during off-peak times: The higher the demand, the more power is lost through transmission from the plants to your house.

So, will topping off your phone at 10 p.m. versus 6 p.m. really reduce New Haven’s reliance on a peaker plant? Eh, probably not. But you and a bunch of your neighbors shifting your use of washing machines, dryers, AC, heaters, electric-car chargers, and other power-hungry appliances to off-peak hours along with your electronics? Now we’re talking, Benjamin. Called demand flexibility or demand response, the idea of shifting our electricity use around enough to flatten out those peak power spikes can make a real difference. One recent report estimated this concept can shave 15 percent off grid costs — and up to 40 percent off your electric bill.

Some utility companies are so into this idea, they’re implementing time-of-use (TOU) or time-variant pricing, which simply charges customers less for the electricity they tap during off-peak hours. For these programs to really cook, we need smart-grid technology like appliance timers, fluctuating thermostats, and “smart meters” that let you know just when electricity demand dips and rises — and luckily, all of the above do exist. TOU incentives were enough to save New Jersey participants $150 or so per year, and an Oklahoma program found that they could skip building a new power plant if just 20 percent of customers got on board with the TOU plan. Yet another instance in which we see that, while green intentions are wonderful, nothing changes behavior like a whack to the ole pocketbook.

There’s one more thing to love about demand flexibility, Benjamin: It helps us fold renewable energy sources into the grid. Wind and solar power are notoriously variable and difficult to store, which can make it hard to take full advantage when the wind is blowing and the sun is shining. But with smart meters that are able to alert us when renewable energy is plentiful, we can target our power use to those times — making demand follow supply, in other words. As always, I encourage all my dearest readers to talk to your local utilities about this and other exciting energy- and cost-saving options.

You asked a simple question and I gave you a complex answer, but hey, I get a real charge out of these things. And now you’re even more plugged into the new frontier of home electricity. I’ll sign off now before I can think up a pun using TOU.

TOU late-ly,
Umbra