Currently, there are various electric cars on the market that offer the ability to feed energy back into the power grid, also known as vehicle-to-grid (V2G) technology. Although V2G is not yet widespread, there are some car models that support this functionality. Some examples include:

1. Nissan Leaf: The Nissan Leaf is a popular electric car that offers V2G capabilities. With the use of a special V2G charging cable and a V2G-compatible charging station, the Nissan Leaf can feed electricity back into the grid, thus contributing to the stability of the power grid.

2. Mitsubishi Outlander PHEV: The Mitsubishi Outlander PHEV (Plug-in Hybrid Electric Vehicle) is a hybrid SUV that also supports V2G functionality. With the right equipment, the Outlander PHEV can be used to deliver energy back to the grid.

3. BMW i3: The BMW i3, a compact fully electric car, has the ability to participate in V2G programs. With the appropriate V2G equipment, the BMW i3 can feed electricity back into the grid.

It's important to note that the V2G functionality is often optional and that specific equipment and charging infrastructure are required to make it possible. Additionally, the availability and compatibility of V2G technology may vary depending on the country and specific market.

If you're interested in using V2G technology, it's advisable to contact car manufacturers or charging infrastructure suppliers to inquire about the possibilities and availability of V2G functionality for specific car models.