Heating and uv costs

[vikki]

Anybody have any idea whether it is cheaper to run a combi bulb or separate heat bulb and uv tube? Just wondering out of interest as I currently use Arcadia 100w d3 combi bulbs but will soon have had one for 12 months (although not in constant use over the summer) so just wondering if I will continue with that or swap - I like the the combi bulb and am happy with it but wondered if anyone knew of roughly what the cost comparisons might be. Also would a uv tube that was the length of the enclosure also provide light to the end away from the heat source - I currently have a small spot lights to provide light the end away from the d3 and wondered if this would still be needed?