How to measure how much power your gadgets are using -- and wasting

If you're anything like me, chances are that you have a lot of gadgets in your home or office. But how much power are these gadgets using -- and wasting? How much are your gadgets and devices costing you in power? And how much carbon dioxide is their use releasing into the atmosphere?
Written by Adrian Kingsley-Hughes, Senior Contributing Editor

A common question I get asked relates to how I go about measuring power consumption for devices. Some people are coming at this from a perspective of pure curiosity, others are looking so save money, while an increasing number are concerned about their environmental impact.

I've been monitoring and measuring the power consumption of gadgets for many years now and the tool I use is the HOPI HP-9800 20A energy monitor. I picked mine up from eBay for under $50.

I first came across "the HOPI" (as I like to call it) when it was featured on the Big Clive YouTube channel (not familiar with Big Clive's channel? If you're technical, I highly recommend you check him out). The HOPI is a bit rough and ready, it has things I don't like, and it's not "certified" in any way, but I've found it to be very reliable and accurate.

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HOPI HP-9800 20A energy monitor

The good

  • Accurate - I've tested this against much more expensive bits of kit and it's accurate enough for what I do!
  • Cheap - It's under $50!
  • Easy to use - The manual is in Chinese so it's a good thing that the HOPI is little more than plug-in-and-it-works. Apparently, there's some way to connect it to a PC but I've never investigated this.

The bad

  • No certification - Might be important for some.
  • The manual - Chinese only I'm afraid!
  • Flicker - The display does flicker. It's not visible to the eye, but can mess up photography (I had to use a neutral density filter to photograph the HOPI's display in action).

The ugly

  • Safety - That front plug offers no safety in the event of screws falling (or little fingers) going in and touching live metalwork.
  • More safety - There are two speaker-type jacks on the front that are live and can block some style plugs, such as UK plugs (if you are technically inclined, it is easy to "delete" this feature if you want to).

Bottom line: It's a very useful tool, and for the price offers something that is very usable. It's not something I'd leave plugged in unattended, and be aware that it doesn't feature the safety interlocks that might be present on more expensive hardware.

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That said, I've been using one for years and never had a problem. Just be aware when around it.

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