Tea boiler energy use

Cup of hot drink on the table

Everyone is a creature of habit. One of my habits is to go round switching off lights. Sometimes I can be a bit over zealous about this and hear an angry voice from the office toilets as I “do my rounds”. The Decerna offices have the latest energy efficient LED lights but the controls haven’t yet been upgraded by our landlord so if I’m the last one out of the office I pick up my cycle helmet from the kitchen area, switch off the lights and any other appliances and head for home. Recently though, something’s been bothering me : the tea boiler.

With a 2.8kW heating element and 10 litres of stored hot water, this is perhaps our most heavily used piece of equipment in Decerna. It really does get some hammer! But it’s left on all night and this got me wondering how much energy could be saved if I were to turn it off at night. And how long would it take to reheat when the first of my caffeine addicted colleagues arrives the next morning?

Checking the datasheet I found no mention of energy consumption so I hooked up our spare Loxone energy monitoring kit. This neat smart home system is quick to set up and can be used to control appliances plugged into it and remotely access the data. A couple of days later I was studying the graphs and had to come clean to my colleagues about why morning coffee had been somewhat tepid the day before!

So what did I learn? Left to its own devices, the boiler used approximately 1027Wh overnight just to keep the water hot. And by turning it off at 5.30pm and back on the following morning. it took 16 minutes to warm up and consumed 747Wh electricity in the process, a waste of 280Wh per day. That works out to about 100kWh per year. Doesn’t sound like much but you try generating 100kWh of electricity – it’s much harder than you think!

About 10 years ago I read the book Sustainable Energy Without The Hot Air by the late great David MacKay. One of the chapters in this excellent free book is entitled “Every BIG helps”.  I remember reading that If you leave your mobile phone charger plugged in, it uses one quarter of one percent of your home’s electricity. You could say that switching off the tea boiler is just like “fiddling while Rome burns” but I reject that argument – we all need to be more energy conscious in our lives. Fly less, eat less meat, cycle to work, walk to the shops. And switch off the lights.

Alex Savidis is a renewable energy technical specialist at Decerna. He’s currently working on delivering energy efficiency advice to local businesses through the ERDF funded BEST project as well as delivering consultancy on energy storage and renewables to a variety of private and public sector clients.

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