Monitoring office energy usage

By David Mytton,
CEO & Founder of Server Density.

Published on the 6th November, 2012.

It’s been a year since we started construction of our London office, which we moved into in February this year. One of the design goals was to optimise energy usage which we implemented through our choice of lighting and heating. We wanted to see the impact of that, so we recently started monitoring our electricity usage.


After some research, we started using an Efergy wireless electricity monitor. This simply requires you to set up a measuring device onto one of the cables from your meter and it then transmits the real time usage to a monitoring device you can set up somewhere. They clip onto the outside of the wiring so there’s no danger or electrician required. Input your supplier cost per unit and it then gives you a live cost per hour output.

That’s great for “what’s happening now?” but it doesn’t record data over time. For that we use Efergy Engage where you buy another device which taps into the wireless signals from the measuring devices and reports them over the web to a hosted service which graphs your usage.

From this we can see the patterns when people arrive in the office, when lunch starts (we all eat the same time) and when things like the microwave are in use. Everyone has a Macbook + Cinema Display and from the data it looks like each person uses 0.20kWH, which costs about £0.03 per hour. This is with a single overhead spotlight per desk and no air con (it’s winter now), which is quite a bit more expensive.

As soon as we started measuring and checking out the graphs, we realised we were using a lot of power out of working hours. Thinking about what could be running, we realised that our network switches remain running 24/7. So we bought some simple timers which turn everything on at 8am and switch things off at 9pm. That saves almost half the day of electricity usage where no packets need routing!

As we build up more data on the system, we’ll be able to see how things change throughout the year and with the weather. There are also plans to try and track down that last 0.20kWH that’s being used throughout the night…possibly the router (which has to stay running for the data to be reported!).

Just 3 people in the office

Just 3 people in the office

Full office with drop during lunch

Full office with drop during lunch

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