Telephone rates fall in the evening and many people respond by deferring their calls. People with flexible hours commute to work earlier or later to miss the rush. My company’s website (and many others) does processing at night when load is low. If we use electricity at off-peak hours, the cost is less. And if enough people did this, we would actually use less energy overall to make the same amount of electricity.
How can that be?
Electricity demand varies greatly from month to month, day to day and hour to hour, especially as a result of extreme weather (more heating and cooling). There are two reasons it costs more to produce electricity at peak times. First, like any market, when demand is high, prices rise. That part is simple economics — this is a case of markets being efficient. But the other reason is simpler.
There needs to be enough capacity to supply the single moment in each year at which demand is highest. Perhaps a hot summer day. At the moment when demand is lowest (maybe a benign spring weekend morning), all that spare capacity needed for peak production is idle.
What happens to it? Well, some plants go off-line for maintenance. Others sit idling. No, not “off”, but idling (known as “spinning reserves”). Some just produce the small amount of power that is required. Just like cars idling, a plant designed to be efficient at 85% of capacity is not as efficient at full capacity, nor at low capacity. The difference between peak and valley is huge, and any time not in that sweet spot that the plants are tuned for is wasteful.
This is all managed by power plants with a goal of 100% uptime, much of which is required by laws. Famous recent black- and brown-outs notwithstanding, the power industry has a pretty good record of meeting this goal (at least in urban areas; some of my family lives in Deer Isle, Maine, where power outages are common — more on this in a moment).
So the thing is, all of this extra capacity is an incredible waste for two reasons:
- Plants are inefficient when under-utilized, which is as much as 75% of the time. so
- We build huge numbers of power plants that just to satisfy peak load, and then run them inefficiently
If you read the link above, you’ll see that utilities are trying market-based methods to mitigate these issues; shifting load to off-peak. This is something manufacturing facilities can do to some degree or other, but most of us need the lights on when it’s dark.
There are things you can do:
- Use the delay timers on dishwashers and dryers
Ok, there must be others, but mostly it’s not a real option for consumers.
(There is one thing you might consider: just don’t use it. When the lights go out at home, there is a brief and minor disruption if it is during supper time, but a few candles and kerosene lamps handle most cases. For longer ones, spare water in stored in the basement can flush the toilet a few times, and a secondary means of heating the house, like a fireplace or kerosene heater deals with most or all of the rest. Do all of the rest of us really need all this on-demand capacity? It is incredibly costly!)
One interesting aspect of plug-in hybrids and other battery-assisted vehicles is that their power gets drawn off the electrical grid at night, which is a good thing, or at least better than the alternative.
But the need to provide energy for peak usage is a strong argument for various renewable energy sources, notably solar. The obvious problem with solar power as a sole source of electricity is that it doesn’t do as well on cloudy days, or at night. But consider solar in a hybrid system, and the picture changes: solar can provide the boost a region needs at the very time it needs the boost.
While it is tempting to look at wind, solar, and various other variable sources of energy as sporadic and therefore of little use to our “I need it now” world, instead, we can think of these technologies as ways to help avoid building another coal plant, or taking an old, decrepit polluter out of service.