I was curious how quickly water would heat up on top of a "Candlelier" (3-candle candle lantern) so I put a cup of water in a Snow Peak titanium cup and placed it on top of a Candlelier.

Within 10 minutes the one cup of water was warm. Within 20 minutes the water was cocoa-toasty. After 40 minutes the water was not boiling but it was painful to dip a finger in and tiny bubbles were forming on the bottom of the cup -- plenty hot enough for mixing with Mountain House freeze-dried meals.

With these candles still burning I emptied out the water, cooled the cup and started over with 2 cups of water. This time I put the pot set's "frying pan" over the cup as a lid. The time-line is about the same -- cocoa-toasty after 20 minutes, Mt. House-ready in 40 minutes (water not quite boiling but bubbles forming). Around 50 minutes it was boiling.

I've been carrying a single-candle candle lantern but this makes me think the 3-candle is worth carrying in the car. For this experiment I used the standard 9-hour UCO candles that come in packages of three ($3) and that are nearly burned out.

Candlelier (these are $29 at Campmor)
http://www.rei.com/product/624320

REI and Campmor also carry a Beeswax version of the candles that last 12-15 hours. They are three times as expensive ($10 for three) but in addition to lasting significantly longer, they generate less smoke. Seems worthwhile for a stranded car situation. Light + heat in one package that you can use inside the vehicle.

Beeswax UCO candles
http://www.rei.com/product/737330

I just ordered three packs of the Beeswax candles, from Amazon, for $9.84 each and free shipping with the Prime membership. Should receive them in two days and they'll be going in the car along with a Candlelier that's been sitting in a box. I went Candlelier-crazy in the 90s after a power outage.

Fortunately, camp gear lasts if stored well and sometimes sees much more use later on in a different application. I'd bought them for ambience.

The titanium cookset I'm using:
http://www.llbean.com/llb/shop/41366?feat=506856-GN2