Help working out energy efficiency

lolhandy

My other (better) half has asked (instructed) me to install something to stop our bathroom mirror steaming up when someone has a shower/bath.

We have tried the old remedies - smearing potato, vaseline, etc over the mirror but this only works for a week or so before returning to its previous state.

I have looked online and have come across various heated mirror pads.

However, what i am concerned about is how much power these things actually use. On the information sheet on the above link further down the page it shows "200w/sq m". But what does this mean in real terms? Say someone is in the bathroom for 20 mins with the light on, how much is this actually going to cost? Can someone with some electrical knowledge give me a real world idea - is this the same as boiling a kettle of water?

Any helps for a DIY handy chap but without electrical skills appreciated.

fwor

Not a very greenfingered question! But I'll have a go:

If for example the mirror's heated area is 600mm square, then it should take 72W while on.

How much that would cost to run depends on your electricity tariff, but I reckon that would cost me less than a penny an hour to run.

lolhandy

Many thanks for your reply. I know, its not green-fingered and I couldn't find a more appropriate forum to put it in and as it did consider some form of energy efficiency i thought this was the best place. I'll check the size of the pad we need and try and work out the cost based on your calculations. Thanks for your help.

forgotmyname

I find switching the extractor fan on and having the shaving mirror on above the light before i start showering and it stays clear.

Probably wont if you have the temperature at 90 degrees or spend an hour in the shower. But works for me.

WestonDave

Might be better on the DIY or green/ethical board. However we don't have a direct mirror heater but have the mirror mounted on the wall above the radiator/towel rail. The rising heat off the towel rail is enough to clear the mirror - it struggles a bit whilst the shower is actually on but you don't need the mirror at that point and it clears quickly once the shower is off.

WestonDave

One other thing to try - if you look in the pound shops you can sometimes find the "rainclear" type stuff that is sold for car windscreens. That on the mirror might work for longer - I bought some last winter to make it easier to scrape the ice off and it did seem to last a few weeks per application even though I was scraping ice off it and using the windscreen wipers on it.