Like sho220 mentioned, ambient room temp does play a role in additional heating. Also, it depends what kind of enclosure you're working with and what wattage and how many or how big the heat panels you're using.

For example, I have an AP T12 (48x24x24). I have it split in half and each side has a RHP (one Pro Heat and one Reptile Basics) providing ambient temp. Then I have 12x24 heat tape in the middle providing a hot spot or belly heat for both sides. My whole setup is controlled by a herpstat 4.

Thankfully, with my setup now I don't have to worry about my room ambient temps. But before i split the T12, when I only had one RHP, with ambient room temps dropping as low as 65 in the winter, my T12 droped to 70 a couple of times.

Overall, there's a lot of factors invlolved so you should consider them all and adjust accordingly.

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