Saving power around the house with an EnviR

We took delivery of an EnviR from CurrentCost a week back, we’ve been measuring power usage around the house since then. The unit itself is super easy to install – the LCD panel sits on a window sill and the measurement unit clips to the electric meter (it has a 30m range).

Here’s what we measured (kW is kilo Watts, W is Watts, I’m not writing ‘per hour’ for each entry):

  • Kettle boiling – 2.9kW/hr (for about 5 minutes)
  • Electric oven – 2kW/hr at 220 degrees C (used 30-60 minutes per day)
  • 800W Microwave running – 1kW
  • Washing machine – 300W
  • Electric clothes drier – 282W (used for 2 hours every few days)
  • Dehumidifier – 200W (used 1 hour each day)
  • Widescreen LCD TV – 90W-140W
  • Kitchen downlighters (5) – 112W
  • Fridge and freezer running – 94W (turns on and off throughout the day)
  • Media PC on and playing a video – 100W
  • Media PC on but idle – 40W
  • Macbook charger – 40W
  • Amplifier on media PC – 20W (idle most of the day)
  • Power saving lights – 9W-24W each
  • Microwave on standby – 4W
  • Dishwasher running – ??
  • Toaster running – ??
  • DECT phone, broadband router, standby power for media PC – 3W
  • The following readings are guestimates – 1W seems to be the lowest reading the EnviR can make
  • Coffee grinder on standby – 1W
  • Toaster on standby – 1W
  • Widescreen LCD TV – 1W
  • Electric oven and extractor fan on standby – 1W

Has it changed our behaviour? We’ve started turning off the media PC when not in use (saving 40W/hr overnight). We also turn off the microwave and coffee grinder (saving 5W/hr 23 hours a day) – it is trivial but the grinder gets warm, turning them on just to use them is easy.

We’ve also stopped turning off the TV at night (it uses at most 1W/hr on standby) and turning off the toaster (again 1W/hr at most). I had wondered if the TV consumed a lot of standby power, the toaster has a set of LEDs – both use a trivial amount of power so I’ll ignore them for now.

I had no idea that the kitchen lights were so expensive – we won’t leave them on when not in use any more. I was really surprised by the oven – 2kW/hr  swamps the usage of everything else! We really ought to use the outside line for some wet clothes too (but we don’t have back access to the tiny garden so getting there is a bit of a faff…).

The Economist has a nice Watts Up article looking at how people underestimate the expense of some items (I certainly did!) and overestimate the savings they get from turning off things like lightbulbs.

Now the meter sits on a window ledge facing the sofa – we can monitor the house’s power usage and over time we’ll learn to play the game of keeping the numbers as low as seems reasonable. Feedback is a powerful thing!

Ian is a Chief Interim Data Scientist via his Mor Consulting. Sign-up for Data Science tutorials in London and to hear about his data science thoughts and jobs. He lives in London, is walked by his high energy Springer Spaniel and is a consumer of fine coffees.


  • Miles Sabin
    Interesting ... How did you measure the contributions of individual appliances? Taking a whole-supply reading with them on vs. with them off? How accurate is that?
  • We turned everything off and got to a base of about 25W (we're not sure what that was - it'll be the unit's LCD, the boiler's clock and we're not sure what else). Then we turned on one item at a time, let it stabilise, then turned it off. It took about an hour to do everything. I'm not worried about absolute accuracy, a rough reading is good enough to tell me what's super-hungry.