King Electric, a family-owned business in Seattle, has been thriving to provide smart comfort solutions for American households. Inspired by the needs of their customers they have been manufacturing industrial, Commercial, and Residential Electric Heaters and Thermostats, Hydronic Heaters, Electric Heating Cables and Accessories since 1958.

Here we are reviewing one of its thermostats namely the KING ESP programmable thermostat.

The KING ESP thermostat comes in two variants: 120V and 240V thermostats. One of the highlights of this thermostat is that it is a 7-day programmable where we can program a different schedule for each day.  For each day you can set 4 different temperatures for four different time periods.

Also, with its accurate electronic temperature sensors, you can save upto 28% for 240V Variant and 15% for 120V variant on the energy bills. The King ESP max 22 is available in 120V or 208/240V.

You can use it with 120V or 240V baseboard heater. The large LCD digital display is readable and has a backlight which can be illuminated with an ON/OFF button.

The line-powered KING ESP programmable thermostat comes with 3 wires for installation.

For extra comfort, the temperature swings have been reduced with a 3-minute cycle rate.

These were some of the key specifications of this thermostat in a nutshell. To know more about these in detail, read on.


The KING ESP (120V and 240V) has been given a contemporary style design. The King ESP120 and ESP240 both look like a small rectangular boxes with dimensions 4.9 x 3.1 x 2 inches(LXWXH).  This shallow design allows more wiring room inside the full electrical box. The thermostat has a large LCD display and a Temperature UP/DOWN control button at the front. The program control buttons are placed inside the front cover, safely secured from wandering hands and unauthorized access.

The display backlight and the system can be controlled with their respective ON/OFF switches placed at the bottom of the product. This single pole thermostat comes with three wires; the third one is for the power supply.  The red LED indicator tells you when the heater is ON. One drawback in its design is that you will have to snap off the front cover to access the control buttons. Taking it off and placing somewhere near may lead to its unintentional loss. All in all, it has a simple yet classy look.  


The digital LCD display of the 120V/240V King ESP thermostat takes up the most room on its front panel. The colored backlight of the display changes when the temperature changes. It has a blue backlight at 60 Degrees F and a red backlight at 75 Degrees F. The display shows vital information like the day of the week, room temperature, set temperature, time, the mode selected, and the programming period in action.

The illumination of the screen can be controlled with ON/OFF button at the bottom of the thermostat.


The maximum wattage rating for ESP120V is 2640Watts and that for ESP240V is 5280 Watts

Both the variants 120V and 240 V thermostats are suitable to be used for the line electric heaters such as baseboard, fan-forced, and others. Both models are 22-amp thermostats and can be used if you have a 2-wire system at your house.

NOTE: These units cannot control cooling; they have been designed to be used with heaters only.


One of the features of this thermostat that sets it apart from other 7-day programmable models is that it has 7 individual-day programmabilities. This means you can set a different schedule for each day. For every day, you can set 4 temperatures for the 4 periods.

The temperature set point ranges from 44°F to 95°F. It is powered with memory backup in case of power outages.

The default set temperature will be the one that you have programmed. That means after a power outage the thermostat will retain the set program. This negates the need to reprogram after every power failure.

Temperature Swings

One of the features of a “good” thermostat is a low-temperature swing. The temperature swing in this thermostat has been reduced by the delay provided between cycles. A 3 min delay has been provided that minimizes the temperature swings to give maximum comfort. This means when the program shifts from a cycle say the morning cycle(where temperature is set at 70oF) to the day cycle where the temperature set is say 680F, there will be 3 min delay.  During this delay, the thermostat will shut off and will wait for the room temperature to cool down.  


The electronic thermistor sensor of this product takes temperature samples every 60 seconds, for better accuracy and efficiency. The 22 amp 240V model has a test accuracy of 1.5oF. The 30 amp snap action relay works efficiently to control the heater. This reduces the energy consumption of your heaters and saves you a lot of bucks on energy bills.


This thermostat comes with 3 wires for installation, instead of the usual 2 wires for a single pole thermostat. The third wire is connected to the display for its backlight. The installation is quite simple and fuss-free. There is no need of a neutral wire for this unit to operate. An experienced professional can take only few minutes to install this product. The installation manual guides you through the process.

Power Source

This KING ESP 120V/240V programmable thermostat is a line-powered thermostat and requires 120V or 240V 50-60Hz power supply. It does not require any batteries for operation. However, there is a provision of battery backup.

These were some of the important features of this thermostat in detail. These specifications meet the necessary energy requirements. Before concluding, let me give you a gist of the pros and cons of this unit.


  • Large illuminated LCD Display
  • The backlight of the display can be controlled with ON/OFF switch placed at the bottom of the unit.
  • Compatible with all electric line heaters including baseboard , fan-forced heaters
  • Program control buttons protected from wandering hands
  • 7 individual day programmability, 4 times a day
  • 3 minute delay between the cycles reduces the temperature swing.
  • 30 Amp Snap action relay improves the efficiency
  • Accurate electronic temperature sensors
  • Battery backup, so you won’t lose the program in case of a power outage
  • Easy installation


  • The front cover needs to be snapped off completely to get access to the program control buttons
  • Does not work for both air conditioning and heating systems; works only for heaters
  • Does not have a lock feature

So, these were some of the important features you need to know about the KINGS ESP 120/240V thermostats before buying them.

Remember to check with your heating system and your requirements if it supports this thermostat.

Cost wise this thermostat works efficiently to save you great bucks on your electricity bills. All you need to do is ace the programming and you are good to go!


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