Passive solar homes are constructed in a way that maximizes solar heating potential.
In the Northern Hemisphere, the sun shines into south-facing windows. In the winter months, the low-angle of the sun allows the sun to shine through the windows and heat up a floor or wall with high thermal mass.
These high-thermal-mass materials, including concrete, stone, and tile, retain the sun's heat and slowly release it throughout the day, helping to keep the house warm.
In the summer, the sun is in the sky at higher angles. A roof overhang blocks the summer sun, preventing the interior of the house from getting too hot. Note that the overhang doesn't prevent the sun's rays from penetrating the windows in the winter, when the warmth is desired.
The home layout can be designed to maximize the flow of air. Fans and ducts can also be used.
Active solar technologies capture and convert solar energy for another use, such as heating water or producing electricity.
Solar hot-water heaters are the solar technology with the quickest payback for the average homeowner. Sunlight heats a fluid in pipes, which then heats water in a tank to be used in the home.
Photovoltaic panels capture sunlight and convert it to electricity that can be used by the homeowner or fed back to the grid and sold to the local utility.