A new national real estate report card has rated Houston top of the class for housing demand and affordability.

Realtor.com's first-ever Metro Affordability & Homebuilding Report Card compared the 100 largest metropolitan areas in the U.S. based on two scores that measured the most important factors for potential home buyers: an "Affordability Components" score that examined the current affordability of housing for residents, and a "Homebuilding Components" score that analyzed the rate of new home construction to meet future demand. Both scores were then used to calculate the final score and assigned a letter grade.

Including Houston, 10 total U.S. metros received grades in the "A" range — A+, A, A- — representing the most balanced locales for "favorable current affordability conditions and healthy future inventory growth to sustain them."

"Homebuilding and affordability are inseparable, and if we want to improve affordability in a lasting way, we need to build more homes," said Realtor.com chief economist Danielle Hale. "The metros at the top of these rankings show that buyers benefit most when communities pair homes that are attainable for today's local earners with enough new construction to support tomorrow's demand."

Only two metros earned "A+" grades with a total score of 77.5 or higher: De Moines-West DeMoines, Idaho (83.4 points) and Raleigh-Cary, North Carolina (82.8 points).

Houston was rated "A" overall with an "Affordability Components" score of 64.4 points and a "Homebuying Components" score of 85.2 points. The only other metros that earned an "A" for affordability and homebuilding were Columbia, South Carolina and Indianapolis, Indiana.

Realtor.com's report said the Houston metro has median household income of $78,845, and home listings have a median price of $363,106. The report's findings also show that newly built homes in the region cost 6.9 percent more than existing homes on the market.

Houston has a 1.88 housing permit-to population ratio, meaning the metro permits 88 percent more new homes than what would be considered typical based on the metro's population and national average construction levels.

Houston's "Realtors Affordability Score," or the share of for-sale inventory affordable to households at different income levels, is 0.691, just slightly higher the national average of 0.675.

Housing market grades across other Texas metros
Austin-Round Rock-San Marcos was the only other Texas metro to earn a grade in the "A" range. It is rated "A-" with a combined score of 72.5 points.

Unlike many other U.S. metros, newly built homes in the Austin area are actually more affordable than existing homes on the market. Austin has a negative new construction premium, where new build homes are 6 percent cheaper than existing ones.

The Austin metro also has a permit-to-population ratio of 2.37. Combined with the negative new construction premium, these factors signal that "builders are delivering homes at a rate well above the metro's population share — and at prices slightly below existing homes."

This is a snapshot of the factors that impacted Austin's grade:

• Realtors Affordability Score: 0.639
• Median listing price: $501,200
• Median household income: $102,412

The top 10 U.S. metros with the highest-performing housing markets are:

• No. 1 – De Moines-West Demoines, Idaho (A+)
• No. 2 – Ralgieh-Cary, North Carolina (A+)
• No. 3 – Columbia, South Carolina (A)
• No. 4 – Houston, Texas (A)
• No. 5 – Indianapolis, Indiana (A)
• No. 6 – Austin-Round Rock-San Marcos, Texas (A-)
• No. 7 – Jacksonville, Florida (A-)
• No. 8 – Oklahoma City, Oklahoma (A-)
• No. 9 – Palm Bay-Melbourne, Florida (A-)
• No. 10 – Columbus, Ohio (A-)