They are called either a “Transient Voltage Surge Suppressor (TVSS)” or "Surge Protective Device (SPD)” in technical bulletins, and here’s the important features to look for when shopping for a whole house surge protector:

1. UL 1449 Listed and UL logo - If the label says “UL 1449,” it means that Underwriters Lab has repeatedly subjected samples of the product to surges of different amperages to verify its integrity. The third edition of this spec requires passing a total of 21 surge tests for their approval.
2. Surge rating of 20,000 to 40,000 amps. 
3. Internal fuses and a failure-light that indicates the system is still functional when lit.

    The surge protector can be mounted in two open slots in the panel, like the Square D one shown at the top of the page, or on the side or bottom of a surface-mounted panel, or in the wall adjacent to the panel. Some models are also rated for exterior installation.

    But it should not be mounted so that the device obstructs full closure of the panel dead front, as in the photo below.    And, although mounting it inside the panel is allowed by the electrical code, the status light that tells you if it’s still functioning will become hidden and useless. 

    Cost runs between $200 and $500 installed by an electrician, depending on the specs you request. We recently had an Eaton “Ultra" Surge Protector added here in The Villages, Florida, for $315. This model is a “Type 2,” meaning that it is rated for installation after the main breaker and must be installed using a dedicated circuit breaker. A 50-amp breaker is recommended by the manufacturer, but only requires a #14 copper connecting wires because they do not carry load current. Instead, the wires only send short-duration currents that are associated with the transient surge event.

    An alternate solution is  “Type 1” SPD, which is rated for installation ahead of the main disconnect and a breaker is not required for installation. Some surge protectors are rated for either Type 1 or Type 2 installation.

    Also, because a surge protector will not function properly without a good ground connection, be sure your electrician verifies that there is low resistance to current flow to the ground.

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Here’s links to a collection of our other blog posts about ELECTRICAL WIRING:

• Which house appliances need a dedicated electrical circuit?

• Can a short circuit cause a high electric bill?

• What is the maximum spacing requirement for securing NM-cable (nonmetallic-sheathed cable)?

• Is it alright to just put wire nuts on the end of unused or abandoned NM-cable or wiring?

• What causes copper wires to turn green or black in an electric panel?  

• What are typical aluminum service entrance wire/cable sizes for the electrical service to a house?

• Why is it unsafe to bond neutral and ground wiring at subpanels?

• Should I get a lightning rod system to protect my house?

• Why is a strain relief clamp necessary for the cord connection to some electric appliances?  

• Does a wire nut connection need to be wrapped with electrical tape?

• What is the minimum clearance of overhead electric service drop wires above a house roof?

• What are the requirements for NM-cables entering an electric panel box?

• What is the color code for NM cable (Romex®) sheathing?

• Why is undersize electric wiring in a house dangerous? 

• What causes flickering or blinking lights in a house?

• Why are old electrical components not always "grandfathered" as acceptable by home inspectors?

• How can I find out the size of the electric service to a house?

• Can old electrical wiring go bad inside a wall? 

• What is an open electrical splice?

• What are the most common electrical defects found in a home inspection? 

• What is the life expectancy of electrical wiring in a house? 

• What is an "open junction box"? 

• How dangerous is old electrical wiring? 

• What is a ground wire? 

• I heard that aluminum wiring is bad. How do you check for aluminum wiring?  

    Visit our ELECTRICAL page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.