Yeah, I have a 8' HO unit in the garage and it works pretty well even in the winter. Even the 0°F rated instant start T8s fare ok in the winter if it's not too cold. Make sure you get the full wattage/outdoor rated HO lamps though. The energy saver HO lamps don't work that well in the cold.
You might be able to find either a 4' or 8' HO unit at the Restore. HID is another option you could use if you tend to keep the lights on for longer periods.
That would work but I would like to keep these fixtures because they work well in the summer and they look nice. Maybe I should try other lamps because most of these are from the 90s and seem mercury starved. I am hesitant about HID due to colour temp. I have no clue how I would move an 8 foot fixture. Thanks for advice.