There are great advantages to grow seedlings indoor in the start of the year. As soon as risk of frost is over, you are ready to plant the seedlings outdoor. That way you can harvest one or two months earlier.
When you sow in the dark months, you will need light. Otherwise, plants get weak and leggy. Until LED lamps were invented it could be a costly affair. You will need light for 16 hours a day until the sun and the light outside takes over. LED lamps only use very little electricity.
Heat is neaded too. For the seeds to germinate they need about 25 degrees. The exception is lettuce seeds. It does not germinate properly at temperatures more than 18-20 degrees.
Once the seeds have germinated, you must turn down heat when it comes to anything but chili peppers, some types of herbs and some summer flowers. Otherwise the plants grow too quickly and become weak. Temperature should preferably be about 18 degrees.
Typically you sow new seeds while you have plants already growing too. Then you need different temperatures in the same room. Here, an electric heat mat might come to help. It raises the temperature 5-10 degrees in the pots, but it is not powerful enough to raise the temperature throughout the whole room. The heating mat can also be used in the greenhouse or in the GrowCamp in springtime when frost comes on unexpected visit.
GrowCamp offers a complete set of LED grow light with a rack. It fits into GrowCamp plant trays with under watering. When spring comes the plant trays can be moved directly into the GrowCamp where it is used as an additional floor. Here they can be used for growing seedlings in the warm season.