Growing tomatoes indoors is more expensive than growing outdoors because indoor vegetable gardens require grow lights. This increases the cost to start the indoor garden as well as the cost of upkeep because of the energy the lights use.
As of 2015, grow lights can cost around $200 to $400, depending on the number of tomato plants growing and the type of grow lights purchased. In addition to the initial cost of growing tomato plants indoors, the amount of power needed to run the grow lights every day can increase a home's energy bills by $30 to $50 per month, depending on the location of the home. The cost of other materials needed to grow tomatoes, such as pots, soil, seeds and water, are about the same for growing indoors or outdoors.