Hi Mike
For cost per watt you use
metal halide or
high pressure sodium. 400 watt or even better 1000 watt.
Greenhouse tomatoes are indeterminate which means they grow and produce fruits continually so they aren't affected by getting to much light. I would turn the
lights on whenever it got to cool in the greenhouse like at night or on a cloudy day. The lights would do double duty. Give the plants light and heat.
Ron