It takes about four hours to roast a 16 pound turkey, which means if you put it in a 350-degree oven at 8 a.m. you should be asleep by 3 p.m. That's fairly simply Thanksgiving math, but a far more tricky question is: How much electricity did it take to roast that turkey? 

Before we try to track down the answer, let's just point out that from a utility-perspective the holidays really are a relaxing time of year. Perhaps not for you — your household power bill might be higher as you crank the oven for hours and fill the house with crazy aunts and uncles — but overall loads decline on the holidays.

“Demand for electricity on Thanksgiving Day is generally lower than on a typical week day,” said NYSEG spokesman Clayton Ellis, “because the largest users of electricity are closed for the holiday.”

Commercial businesses tend to close (at least until Black Friday) and manufacturing shuts down. Even if your holiday lights aren't LED, massive heating, ventilation, cooling, and lighting loads are offline. So when utilities are pushing energy efficiency, they aren't worried about peak load so much as customer bottom lines.

So, about that turkey …

The most direct answer comes from TXU Energy, which estimates it takes roughly 8 kWh to cook your average turkey – an electric oven drawing 2 kW, running for four hours. And with about 46 million turkeys roasted each Thanksgiving (a fact they authoritatively sourced from the National Turkey Federation), that's a lot of energy.

But not all households use electricity for cooking. The California Energy Commission estimates about  58% of American homes have electric stoves rather than gas, which means about 26 million turkeys cooked in electric ovens – or 213 million kWh used, according to TXU.

“When you translate that to dollars spent on electricity for the day, it’s nowhere near what’s spent for holiday meal ingredients, but it still adds up,” the utility said. “Based on the most recent federal electricity pricing data, it also means that roughly $25 million may be spent on the electricity used to roast turkeys across the nation this Turkey Day.”

That's one answer, but TXU isn't the only source to try and dig into the power consumption behind the gravy boat and cranberry sauce.

A lot of blogs have dipped into the question: Over at Green Explored, they assume an oven using .4 kWh would cook the average bird in four hours using 1.6 kWh — or 48 million kWh across the United States. Go Green Solar assumed a 4.4 kWh oven for a total of 17.6 kWh per turkey and came up with 792 million kWh used around the country to cook turkey (but they assumed a large bird and all electric ovens).

Back in 2013, Wired — being Wired, of course — tried to figure out how many batteries it would take to cook a turkey. They came up with 151 D cells, unless you tried to cook it fast, and then it was 263. The magazine's tests showed that to cook a 10 pound turkey in an hour you would need almost 200 watts.

About the only thing these estimates have in common is cook time, which is hugely variable since opening the oven door once can drop the temperature by 25 degrees. And who can resist?

But the coolest answer comes from a blog post a few years ago at Home Energy Pros, which is a network aimed at home energy professionals and is partly funded by the Department of Energy. Using data from the Phased Deep Retrofit project at the Florida Solar Energy Center, an analyst compared Thanksgiving 2012 load with the previous week's Thursday in fairly small sample of 30 homes.

For the day, holiday loads averaged 2.76 kWh while the week before was just .73 kWh. While the post focused on all-day power use (including cooking the full meal), the basic estimate is about 2 kWh to feed the family. And that result was largely in line with another Florida project completed more than a decade before, which estimated Thanksgiving cooking at 2.5 kWh. Check out the graphical representation of load, dropping off right after the Macy's Thanksgiving Day Parade.

Stop opening the oven. Yes, you.

Any way you cut it, it takes a lot of energy to cook a Thanksgiving meal. A lot of electricity, too.

Utilities are increasingly looking for ways to engage their customers, and holiday efficiency tips have become a staple of the season. So unless you're cooking with gas or stocked up on Duracells, here are a few suggestions from around the power industry:

• Consolidated Edison is using turkey season to put energy savings in terms of pizza. Maybe they figure there's only so many leftovers you can eat? The utility says an average string of LED lights costs 47 cents to run for a month, so six strings add up to just under $3 -- "a little more than the cost of an NYC slice of pizza," ConEd notes. "Non-LED lights can cost you up to 10 times the amount to power, so get rid of the old lights and go enjoy the whole pie." They're serious about the pizza and have included a video. Watch until the end.
• Stop peeking: Florida Power & Light notes that ovens "lose a lot of heat when opened and require significant energy to heat back up to the appropriate temperature." What doesn't use a lot of energy? The oven light and window.
• Edison Electric Institute is running a virtual culinary efficiency school with 10 cooking tips, including: "Use the microwave instead of your regular oven whenever possible. Microwave ovens draw less than half the power of your regular oven, and they cook for a much shorter period of time."
• And the California Energy Commission's Consumer Energy Center makes a point about right-sizing your pan to heating element. "More heat will get to the pan and less will be lost to the surrounding air," the agency notes. Using a six-inch pan on an eight-inch burner will waste more than 40% of the energy.