Harrold McGee indicates in On Food and Cooking that soaking brown rice for 20-30 minutes can speed the cooking. However, he doesn't give any specifics.
In looking to what I consider highly credible cooking web sites, I have not found any definitive answers.
Cook's Illustrated's recommended method for the fastest, best tasting brown rice (no link since it is probably on the pay site) is:
Boiling the rice for our brown rice recipe until it is almost tender
(about 30 minutes), draining it, then steaming it until done (another
five to 10 minutes) is by far the best stovetop method for brown rice.
Martha Stewart's recommended technique (50 minutes steaming, 10 minutes resting) is quite similar.
Alton Brown recommends baking technique which may be delicious but is almost certainly the one that will heat your house the most: putting rice in a casserole covered with boiling water, and baking at 375°F for 1 hour.
You have actually asked two different questions:
- What is the fastest way to cook rice (duration)?
- What is the most energy efficient way to cook rice (least heating of your house)?
These are not the same thing.
Something to consider: of all liquid non-metals (and I don't think any of us are going to cook in molten iron), water has the the highest capacity to transfer heat.
It is going to be very difficult to find a way to cook rice that is faster (at least for actual time cooking the rice, when not counting bringing water to the boil) than the traditional pasta method, as often employed in some parts of India: Bring water to a boil, add the rice, cook until done, and drain. However, the energy required to bring all of the surplus water to the boil and the enthalpy of vaporization will make this fast, but not efficient.
Your most energy efficient rice production method (and this is by the very laws of physics which govern our universe is also the one that will add the least heat to your home) is almost certainly a rice cooker, which will heat only until it senses the rice is done. (Of course, what the rice cookers are really measuring is the rise in temperature when the water is all absorbed or evaporated, and so the temperature can rise; therefore, starting with the correct ratio of rice to water is critical).
The bottom line: brown rice takes time to cook. Some rice cookers, however, let you set a timer so that the pot will have the rice ready when you come home. This might be your best bet.