Posted by: Alex MacPhee | January 12, 2012

Plug-in Mains Power and Energy Monitor (Maplin Electronics)

Energy monitor

Conscious of rapidly rising energy prices, and wanting to cut costs, I was skeptical of the suggestion that I could save more by changing my usage patterns, than by changing my supplier on one of those price comparison web sites.
I am glad I didn’t hold on to that mistake for too long. Instead, I bought this electricity monitor to look at which appliances were the biggest drain on my income, and it has been a revelation.

There are two kinds of electricity monitor : one that measures total household consumption, and one that measures consumption of individual appliances. This monitor is of the second type. Using it is simple : plug it in to a wall socket, then plug the appliance in to it in turn. The LCD will display a range of measurements by pushing an appropriate button, including voltage, wattage, current draw, and perhaps most usefully, consumption in kiloWattHours. It also has a clock display to tell you how long the appliance has been connected. These different displays are useful for different kinds of appliance ; for example, some take electricity as long as they are connected and in use, such as a vacuum cleaner or steam iron or fridge, others use a certain amount of electricity for a fixed job, such as a washing machine or kettle or toaster, which have automatic switch off.

Using the monitor, it becomes easy to estimate the cost of running any appliance, either per job or per hour, and in this way you can build up a table or, in my case, a spreadsheet, of every appliance in the household, for analysing usage patterns and costs. I now know how much it costs to run my kettle, iron, toaster, grill, oven, laundry, computer, printers, radios, television, Sky box, freezer, aquarium, in short, everything.

There are some appliances that you can’t measure with this monitor, such as domestic showers, where they don’t have a socket connexion, but are wired directly. I also had difficulty trying to measure my microwave oven, as it continually tripped the RCD protection circuit at the mains every time I tried. However, such were the savings to be made merely by having the information, that I also bought one of the ‘total consumption’ monitors, which measure consumption at the mains supply instead. Whilst you can’t measure individual appliance consumption with this type, you can usually work out the difference made by switching one on by the increment in total consumption, and doing this, I found that both monitors were in remarkably good agreement. So I now have reliable figures for the microwave, grill, oven, and the shower. Reassuringly, the manufacturers’ ratings were born out by the monitor right across the spectrum of makes and types, giving confidence in its readings.

Several surprises came out of this exercise. For example, in my household, the single most expensive item to run per annum was not, as I’d expected, the washing machine or the electric oven. It was the fish tank. The washing machine (Bosch) turned out to be very conservative indeed. I have Economy7 tariff and used to put it on overnight for the cheap rate, but this in fact saves very little money indeed, as almost all the cost of a washing load turns out to be the detergent. The tumble drier, on the other hand, sucks electricity out of the socket at a terrifying rate, up to ten times that of the washing machine. (Somewhat annoyingly, my tumble drier has an electronic on-off switch, meaning it cannot be started using a timer switch for overnight runs. So I just wait until half past midnight for things that benefit from tumble drying, such as towels, but now generally air dry instead.)

This monitor lacks any backup battery, so that the displayed readings are lost when you switch off the supply. This can make it difficult if the socket for your appliance is in an awkward place, such as at the back of a kitchen fitting (sockets for my washine machine and dishwasher, for example, are behind the plumbing). The way round this is to have a short extension cable to bring the monitor out and connect it and the appliance to the end of the extension where you can see it. Sometimes I have accidentally pulled it out of the socket before noting the readings, so now I have a small sticker on the front reminding me not to do this. A battery-backed display would be a convenience, but its lack shouldn’t be a deterrent to acquiring such a useful device as this.
This has been one of the most helpful little gadgets I have bought in some time. It has changed my energy consumption patterns and saved me far more than its cost. Moreover, it’s helped make me energy aware, and has brought down my household bills significantly.


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