I get a lot of questions about thermostats. A lot of people ask if proportional thermostats are better than non-proportional ones and which brand or model of thermostat they should use, so I'm going to talk a little bit about both types and the pros and cons of each type, and also share my experiences with the various thermostats we use.  Except for the Helix brand, I own at least one of each that I list on this page.

Traditional On/Off (Non-Proportional) Thermostats 

 Before we talk about proportional thermostats, you need to have a basic understanding of how a regular thermostat works.

In a nutshell, a typical thermotat will monitor the temperature using a thermocouple or probe attached by a wire. When the probe tells the thermostat that the temperature has reached one degree (or whatever the case may be) above the desired temperature, the thermostat will cut power to the heating device, turning it off.  When the temperature drops back down below the desired temperature, the thermostat will turn power back on to the heating device.   It's a very simple idea - if the temperature needs to go up, power to the heating device is turned on. Once the desired temperature is met or exceeded, it is turned back off.  That being the case, the heating device is either getting full power or no power at all.  This type of thermostat is best suited for heating devices that work in a strictly on/off fashion.

Proportional Thermostats

Similar to a traditional thermostat, a proportional thermostat has a probe that tells it when heat needs to be applied or turned off. Unlike a traditional thermostat, a proportional thermostat works like a dimmer in that it can adjust the amount of voltage being applied to the heating device. But it's better than a dimmer because it can measure the temperature and it knows exactly how much power needs to be applied to the heating device to maintain the desired temperature.

As a general rule of thumb, if a heating device works in a strictly on-or-off fashion, it will not run without a set amount of voltage.  As such, proportional thermostats cannot operate things like the furnace in your home, or even a space heater, because those devices need full power from the wall outlet in order to function. However, heating devices that we commonly use in the reptile hobby, like heat pads, heat panels, heat rope/cable, heat tape, ceramic heat emitters and even incandescent light bulbs,  can be operated by a proportional thermostat.  With these types of heating devices, a proportional thermostat may be your best option.

Pros...

Gentle Warmth
By applying just enough voltage to the heating device, you're providing a more uniform, gentle warmth.  This is because the heating element (tape, pad, cable, etc.) is constantly running right at the desired temperature, rather than bouncing back and forth between full power and no power. 

Longer Lived Heating Devices
With an on/off thermostat, the constant on/off action causes more wear and tear on devices meant to be run on dimmers like heat pads, heat tape, heat cables and especially light bulbs.

Cons...

Proportional thermostats will not run a furnace, space heater, etc.
The only downside to pr oportional thermostats is that because they work by applying varying amounts of electricity to the device they're controlling, they generally will not run certain types of heating devices.    

*Remember, I said MOST...
Spyder Robotics makes an entire line of proportional thermostats that also have a "Non-Proportional" setting which allows them to be used as a standard "on/off" thermostat.    These units are quickly becoming my thermostat of choice for python enclosures...industry leading technology and still competitively priced.  Apples to apples, these things are a steal.

Popular Thermostats 

The "Made in China" Special  (ALife, Big Apple, Newtek, Zilla, etc.) - On/Off
It's all the same $30-40 on/off thermostat being sold under several different brand names. I don't know much about electronics, but these things seem to work pretty well. I do still have my doubts about quality, I do own several of these units and use them as backups when a thermostat probe goes bad, or when I need to set up a new cage or rack in a hurry.   I probably have close to ten of these things around the shop, and have yet to see one fail. That said,  I do tend to use these with setups where the heating device would not cause a disaster if it were left on at full power - for example to control an internally regulated heating device like the T-Rex Cobra Heat Mats on our Tokay cages. 

 They say these units will run up to 1,000 watts, but I've never used them to control more than 300 to 400 watts. cheap enough...why push my luck?

Ranco and Johnson Controls - On/Off
These are two different brands of industrial grade heavy-duty on/off units that are very popular in the industry.   Either of these thermostats work great for running things like space heaters, air conditioners, etc.  We use these to control several racks and cages in the facility, but I would like to eventually phase them out.  For most applications, this type of thermostat is probably just fine, but I prefer proportional whenever possible.

Capacity on these units is 750 watts and I have pushed them pretty close to maximum wattage.

Big Apple Herp Power - Proportional
This unit works well, but is a 15+ year old design. It has an analog temperature dial, which means there's a lot of waiting and adjusting involved to get the cage to the temperature you want.

I have one of these units that I bought in 2002 and it's still working today. a night drop feature, but it's a little red knob on the bottom of the housing, with no numbers or markings to help you set the desired night time temperature - meaning you have to guess and measure it in a few hours.  The night drop feature also requires you to plug a household timer into it...more cords and junk.  Overall, this is a solid thermostat, but it's an obsolete design - in other words, there are much better units on the m arket for the money.

Max output is only 300 watts.

Helix DBS-1000 - Proportional
These are popular, but they had some problems about a decade ago that caused me to steer clear of them for a long time.   From what I know, these problems are long gone, but I've never owned one, so I don't feel comfortable saying anything about them....other than they're popular, they're out there and they are popular.  One thing I will say - contrary to what the model number suggests, this unit is capable of 500 watts of output. 

Spyder Robotics - Proportional or On/Off - HIGHLY RECOMMENDED 

No BS Disclaimer: Yes, this product line is getting a great review - and no, I'm not getting anything out of it!  I'm giving them two thumbs up because they're the best temperature control products on the market, in my opinion.  I have done the research, I have used just about everything out there and looked at literally everything, and this is the company getting my money until something better comes along...the only loyalty I have is to my animals and my customers, and honestly...if I could think of a complaint, I would put it here just to make this review sound a little more balanced. lol

Spyder Robotics products are designed and manufactured in the USA specifically for use with reptile housing and incubation. Being designed for our intended use, they sport a whooole lot of relevant features that I've never seen on another thermostat.  These units are not only full of features, but they're versatile...they even have a setting to allow them to be used as an on/off thermostat, should you find yourself in the situation where a proportional won't work. ool features include a built in alarm clock (remind you to mist cages, check water, etc), high/low temperature alarms, the ability to TEXT or Email you when temperatures aren't right (Herpstat II and PRO with USB connector), built-in "night drop" feature on all but the most basic model, the ability to keep a small amount of power applied to heatind devices where a coil is used, the ability to upgrade the internal firmware (should a new feature be developed, you can update it), the ability to replace the probe without disassembling the unit (good luck with that on a lot of the other units out there), the list goes on. 

I currently own several Herpstat II units. two thermostats in one case - each capable of outputting 700 wats.  For the amount of caging I can control with one unit, these things are worth twice what they cost ($229 factory direct).

Another popular model is the Herpstat PRO, which is basically four thermostats in one case.  This model is only good for 400 watts per channel - great for controlling multiple zones or cage/rack sizes.

There are a few resellers, but I can highly recommend ordering factory direct. About six months back I ordered two replacement probes for one of my Herpstat II units (I literally bent and smashed the cords - they didn't fail) and I received the replacements in less than a week. I ordered two more Herpstat II units direct from the factory - Ordered them on a Sunday and I got them on Wednesday.