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Homes today have more to protect than they used to. Furnaces, heat pumps, refrigerators, washers and ranges run on circuit boards, and so do the alarm panel, the network equipment and the EV charger in the garage. A surge can end a device's life in an instant or slowly wear down its electronics, and the damage isn't always visible.
This guide explains what causes surges, how panel-mounted devices and plug-in strips work together, what surge protection can't do, and why installing it at the panel is a job for a licensed electrician under a permit.
What causes a power surge: lightning, utility switching and large appliances
ESA describes a power surge as an unexpected increase in current or voltage in an electrical circuit, one that may damage electrical equipment in your home. Hydro One notes that these voltage fluctuations can come from outside, such as storms, or from the home's own electrical installation.
Outside sources include lightning striking the lines or the ground nearby, and the utility switching equipment on its network or restoring power after an outage. Inside the house, the motors and compressors in furnaces, air conditioners, heat pumps, well pumps and large appliances can create smaller spikes when they start and stop. Those spikes are much smaller than a lightning surge, but they recur every time the equipment cycles.
Whole-home surge protection at the panel vs plug-in surge protector strips
The two work as layers, not alternatives. Hydro One suggests considering whole-home surge protectors installed on your panel, and plugging sensitive or valuable electronics, such as televisions and computers, into a surge protector.
- A whole-home device mounts at or beside the panel and diverts surges arriving from the service before they spread through the house.
- It covers hardwired equipment that can't use a plug-in strip, such as the furnace, the heat pump, the range and an EV charger.
- Plug-in surge protectors form the second layer, placed where the most sensitive electronics sit, closer to spikes that start inside the home.
- Choose plug-in units that carry a recognized certification mark and are sold as surge protectors, since an ordinary power bar only adds outlets.
- Cable, antenna and phone lines can carry surges too, so some devices include protection for those connections.
- Neither layer lasts forever: many devices have an indicator that shows when the protection is used up, and a unit that has absorbed a large surge may need replacing.
How an electrician installs a whole-home surge protective device
- Assessment: the electrician looks at the panel, the service and the available space, and confirms which device suits them.
- Grounding and bonding: the ground connection at the service and the bonding of metal water and gas piping are checked, because a surge device can only divert energy through a sound grounding path.
- Placement: the device goes as close to the panel as the design allows, with short, direct connections, as manufacturers' instructions typically require.
- Connection: depending on the type, it connects through a breaker in the panel or on the supply side, with the power off while the work is done.
- Testing and labelling: the status indicator is checked, the panel directory is updated, and you're shown how to read the indicator.
- Paperwork: the notification or permit is closed, with an inspection where one is required.
What surge protection can't do: grounding problems, lightning protection and direct strikes
A surge protective device is only as good as the grounding behind it. It works by sending excess energy to ground, so a missing, corroded or loose ground connection, or piping that isn't properly bonded, leaves it with nowhere to send that energy. That is why the electrician checks grounding and bonding first, and why a surge device never replaces fixing a grounding problem.
It isn't lightning protection either. A lightning protection system, with rooftop air terminals and conductors running to ground, is designed to carry a direct strike safely around the building; a panel-mounted surge device limits the surge that reaches your wiring. Neither guarantees that nothing will be damaged, and Hydro One notes that protecting your electric and electronic devices is your responsibility and that it doesn't compensate for damage caused by lightning.
Surge protector installation permits: licensed electricians, ESA notification and CMEQ licensing
A whole-home surge device is connected at the electrical panel, which puts it squarely in licensed territory. In Ontario, the Licensed Electrical Contractor files a notification with ESA before starting; in Quebec, the installation goes to a contractor licensed through the CMEQ; in British Columbia, it needs an electrical installation permit from Technical Safety BC or the local government. The code edition in force in your province sets how the device is installed, and your electrician can tell you whether one is required for a new service or a panel replacement where you live. Plug-in protectors, by contrast, need no permit.
After a storm, a flood or a big surge: checking surge protection and safety devices
- ESA advises checking GFCIs, AFCIs and hardwired smoke and carbon monoxide alarms after a power surge, to make sure they still work.
- ESA also warns that you can't tell whether electronic devices are damaged by looking at them, so have anything that behaves oddly checked before relying on it.
- Look at the status indicator on the whole-home device and on plug-in protectors, and have any unit showing spent protection replaced.
- After a flood, the CMEQ's checklist calls for replacing surge protection devices that were submerged, along with breakers and wiring.
- Unplug valuable electronics before severe weather when you can, as Hydro One suggests, even with surge protection installed.
- Lights that flare and dim, a burning smell or a warm panel after a surge are reasons to call an electrician right away.
Surge Protection: frequently asked questions
Is a whole-home surge protector worth it?
It's worth considering if your home has appliances full of electronics, a heat pump or an EV charger, since hardwired equipment can't use a plug-in strip. Hydro One suggests considering a whole-home surge protector installed on the panel, alongside plug-in protectors for sensitive electronics.
Do I still need surge protector power bars with a whole-home device?
Yes, for sensitive or valuable electronics. The panel device handles surges arriving from outside, and a plug-in protector adds a second layer at the device itself, which Hydro One also recommends for televisions and computers.
Will a surge protector save my electronics from a lightning strike?
Not always. Surge protection limits the surges that reach your wiring, but it isn't a lightning protection system, and a strike on or near the house can overwhelm it. Unplug valuable electronics before severe weather when you can.
Can I install a whole-home surge protector myself?
No. It is connected at the electrical panel, which is work for a licensed electrician under a notification or permit, such as an ESA notification in Ontario or a CMEQ-licensed contractor in Quebec. The electrician also checks the grounding the device depends on.
How do I know if my surge protector still works?
Most whole-home devices and many plug-in protectors have an indicator light that shows whether protection is still active. If it's out or shows a fault, or after a major surge, have the unit checked and replaced as the manufacturer directs.
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Written by the LokalMatch editorial team. Reviewed by Zubair Afzal on September 10, 2026. How we write and check our guides