Too Cold in grow tent

If you can move your grow tent into an already heated space you would not need a heater but if you are planning on keeping them in cold temperatures you do need to switch to an hps fixture or add a heater because plants don't grow very fast in the cold. You basically need to move the grow tent or stop gardening in the winter time when its more expensive and that does mean that sunlight is free but LED lights are not that expensive per month in electricity costs and neither is a heater if it is a small space. Heaters get expensive when you move beyond 3x3 and 4x4 spaces into larger spaces.

Yeah couple of blankets over the tent might help a bit. I usually just Increase the light intensity and raise the light up . The excess heat from the driver on the light heats the tent up for me.

Dimplex wardrobe heater 40watt. Works fine for a small tent, but insulation around the tent is essential if it's winter temps it's exposed to.