The first question everybody has is “How much does this cost? There is no one answer to this question because it depends on what plants you wish to grow. The cost for growing low-light plants like lettuce or African violets is less than a high-light plant like tomatoes. Also, it requires less light to grow tomato starter plants in the spring than trying to harvest cherry tomatoes in January. Let’s consider the cost of growing 6 to10 cherry tomato plants for harvest in January as a worst-case scenario. To grow these plants to the fruiting stage requires a 400-watt HID fixture. If we consider the cost of electricity is $.8 per kilowatt-hour it will cost $.32 an hour or about $4.00 per day. The cost of the appropriate HID fixture ranges from $180.00 to $280.00. “Is this cost-effective”? The answer depends on what you wish to get out of your hobby. In many cases, it is cheaper to grow under lights than to heat a home greenhouse.
It is not economic to grow food under lights, but people concerned with what is being applied to the food they buy at the grocery may find some peace of mind growing their own food year-round. A gardener who purchases hundreds of dollars of plants each year only to have them die each winter may find the investment in lights worthwhile not just in terms of savings but having bigger and better plants the second year. The variety of plants seeds available far exceeds the live plants you can purchase. Being able to start healthy plants from seed gives you a wider variety to choose from. The fact is I have rarely heard gardeners maintain that their hobby is cost-effective. They get joy from growing plants. Using lights helps maintain that joy year-round.