Surge protector electricity

Surge protector buying guide

When it comes to protecting your electronics, do you need to break the bank or will cheap and cheerful do the job? We tested seven models including products from Belkin, Powerguard and Arlec to find out.

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Do you need a surge protector?

The next time you buy electronics from a big box retailer, there’s a fair chance the salesperson will suggest throwing in a surge protector to protect your pricey purchase. While it might sound like a good idea, it’s fair to wonder if you really need one.

New Zealand’s power supply is very stable and reliable compared to other parts of the world, so when you turn on a plug you can reliably expect 240V to come through the pipe. That said, small surges, which can slowly damage equipment, can still happen in your home, especially when electrical items with motors (such as skill saws) are switched on. Larger, destructive surges can still occur, usually when storms cause damage to the lines outside. These surges might only last milliseconds, but if they travel down the lines to your property a plug-in surge protector probably won’t protect your equipment. In a worst-case-scenario they can fry the electrical items.

What needs protecting

Electronics with internal, low-voltage gadgetry are the most susceptible to surge damage. It used to just be computers but now all sorts of items can contain microprocessors (anything with “smart” in the name is a dead giveaway). Your decision probably comes down to your device’s purchase price. You probably wouldn’t bother with a $15 jug, but it’s a different story for your expensive telly.

How do they work?

Surge protectors are like an energy sponge sitting between the power supply and your electronics. The main component all protectors have is a varistor, which absorbs any excess surge and prevents it from reaching your gear but, just like a sponge, it can only absorb a finite amount before it goes kaput. Once it’s reached this stage, it will no longer protect your device.

What to look for

  • Joule rating indicates the amount of energy the protector can absorb. The higher the rating, the more energy the surge protector can absorb and the greater its chance of protecting your devices from larger or multiple surges.
  • Clamping voltage is the amount of voltage the protector lets through before it cuts off. Look for a clamping voltage as close to 240V as possible to ensure maximum protection.
  • Response time is how long the protector allows a surge to run before stopping it. Anything indicating <1 nanosecond is best.
  • Indicator light will show if your devices are being protected. If it’s not lit, replace the surge protector.
  • USB connections allows smaller gadgets to charge while freeing up plug space.
  • TV aerial and phone line protection help keep modems and TVs safe, as surges can travel down these lines as well.

Connected equipment warranties

Many surge protectors offer cover for equipment damage – the most we saw was a whopping $250,000. It pays to read the fine print though. You aren’t covered unless everything is connected through a surge protector – this means your TV and computer would need all aerials and network cables plugged into a surge protector or the company won’t pay up. The Belkin website gives a timeline of eight to 10 weeks before a claim will be processed. In that time, Belkin does its own testing of your busted surge protector to see if it’s to blame. If satisfied, Belkin will pay the market value of the damaged equipment. However, with that timeframe and those restrictions, we think most people would just file a claim through their insurance company.

Our test and results

How we test

We plug each surge protector into a high-voltage pulse generator that fired off 1000V pulses. We monitored the voltage at the mains outlet of each surge protector and noted how much each let through and how quickly it cut off the surge.


Our testing showed cheaper models provided worse protection. There are two distinct groups – Group A cuts the surge off very quickly (less than 0.1 milliseconds), while Group B initially blunts the surge but lets it taper off rather than cutting it. All of Group B were purchased from either Bunnings or Mitre 10, with the most expensive costing $12.

If you really want to look after your equipment and cut off a surge completely then you’ll have to pony up at least $50 and buy something from Group A. The difference in performance, and price, comes down to the additional components within the protectors that help absorb and cut off the voltage.

Surge protector response

Best performers

Left to right: Belkin Pro 4000 - BV108130au3M; Belkin Surge Plus - single plug - BSV103au; Belkin Surge Plus - 4 way multi - BSV401au2M; Powerguard Charge protector black edition - PGAC345B
Left to right: Belkin Pro 4000 - BV108130au3M; Belkin Surge Plus - single plug - BSV103au; Belkin Surge Plus - 4 way multi - BSV401au2M; Powerguard Charge protector black edition - PGAC345B

By James le Page
Technical Writer