PULLMAN — As the long season of darkness sweeps over the country, it’s a natural time to think about lighting — and how dependent we are on electricity during this dim time of year.

You can heat your home with several different energy sources, including natural gas, heating oil or wood. But unless you’re living off-the-grid, the lights throughout your abode burn brightly because of electricity from the grid.

Yes, I have a couple of candles, a flashlight and two kerosene lamps in my household. But I don’t use them. Instead, like more than 99 percent of us, I just flip up a switch to turn on electric lights throughout my house.

Of course, people use electricity for many other purposes. We run all the equipment in emergency rooms on electricity — and when I’m trying to wake up in the morning I sometimes think it’s almost equally important that we run our coffee makers on electrical current, too.

It’s commonplace to note that the landscape of energy is changing in this country. But it’s harder to get agreement on where we should get our electricity in the coming years. People disagree about that, and for some good reasons. But no matter what you feel about our various energy options, some basic facts about solar energy are worth review.

We could start by noting that most of the energy we use is ultimately solar in origin. Fossil fuels, after all, represent solar energy that Mother Nature stored deep in the Earth over whole geological eras. One downside about fossil fuels is that once we use them, they’re gone.

Engineer Bob Olsen of Washington State University recently explained to me his view that we have quite a wonderful system of “renewable solar” energy in place, especially in the Western parts of the U.S. and around the region of the Tennessee Valley Authority (TVA).

“That’s the case not because of solar electric panels, but because of the world’s largest solar collector — seawater,” Olsen said.

Because we live on land, we don’t often think too clearly about the seas. But the oceans cover about two thirds of the planet. They absorb a lot of heat energy when light shines on them. Each day they soak up enormous quantities of energy from the sun, warming and evaporating as they do so. It’s evaporation from the seas that fills the sky with clouds. Water in the clouds comes down as rain or snow.

Olsen sees precipitation as the linchpin of renewable solar energy. That’s because the rains flow into major rivers across which we’ve built hydroelectric dams. By running the water behind the dam through turbines, we generate electricity. Electric utilities take that energy and move it from the dams to our kitchens and workplaces.

The dams have several good features. One is that they have the ability to cheaply store a great deal of energy. The vast reservoirs behind each dam are natural storage devices. Solar electric panels on a roof don’t have this feature unless linked to expensive batteries that degrade over time. Simply put, dams can easily produce electricity when the sun isn’t shining, a clear advantage in having them power the grid.

If we ever get a large slice of our electricity from windmills and solar panels, I think there will still be room for the dams. They — like fossil fuel and nuclear plants — are able to produce juice on a still night when the wind isn’t blowing and the sun isn’t shining. Because we want large amounts of electricity at our fingertips 24-7, windmills and solar panels cannot be our sole source of electricity.

Another positive attribute of the dams is that they make a lot of electricity without producing any greenhouse gases. And once the basic investment of constructing the dams is finished, they are economical to run because their “fuel” is freely supplied by Mother Nature. That’s essentially why those of us who live in regions of the country with dams have relatively cheap electric rates.

From where I sit, the hydroelectric dams are gifts that keep on giving — every time we switch on the lights.

* Dr. E. Kirsten Peters, a native of the rural Northwest, was trained as a geologist at Princeton and Harvard. Follow her on the web at rockdoc.wsu.edu and on Twitter @RockDocWSU. This column is a service of the College of Agricultural, Human, and Natural Resource Sciences at Washington State University.