a few folks have asked for pictures of my set-up for using 7W night lights to provide supplemental heat during the winter.
When I use to use SBB, I would build them with enough space between the screen and the insert to allow for a 1" PVC fixture that I made.
Here is one of the SBB with fixture and insert in place.
Here is a closeup of the fixture, it is just a 1" PVC 'T' and a few straight pieces. I soldered both lights to a common cord and hot glued the sockets into the pipe. I also hot glues a piece of metal flashing over the sockets so that wax and other hive debris didn't cause the bulbs to get stuck in the sockets.
Now that I no longer use SBB, I have even a simpler design. Two sockets on a common cord hot glues together with a small piece of flashing glues & tie wrapped on.
This just slips under the slatted rack and then the lower entrance is completely closed off.
I provide a small upper entrance for cleansing flights and for moisture to escape.
For less than $3 I have a hive heater. You can probably get away with just one light, but I prefer 2 so when one goes bad there is still some heat. I don't want to try and pull everything apart in the middle of the winter to replace a bulb. In previous years when I had been using wooded brood boxes, I had the lights set to come on when the outside temperature fell below 30 degrees. This year I have switched to polystyrene hives which will hold the heat much better, so I am setting it up to control the lights based upon the internal hive temperature.
The main benefit of the heaters are in February when I turn them on full time. This really helps them raise more brood as the added heat from the bulbs allows the bees to spread out and cover more brood. The queen moves right down above the bulbs and lays eggs.
I use my home automation system and X-10 controls to turn them on and off automagically based on the set temperature.