What size heat mat should I buy?

[craigafrechette]

It's important to understand that heat mats aren't for ambient temps. They are there solely to provide a hot spot.

If your CHE isn't enough, your best bet is to use both (ALL heat sources regulated by a thermostat). Use the UTH for a hot spot and the CHE for ambient temps. If your current CHE isn't enough, you may need a higher wattage.

So, when using a thermostat you set it for a hot spot, not to heat the enclosure.