Energy Monitor

[Wowbagger]

We've just borrowed one from the library. It's quite an eye-opener.

We have a fairly high base consumption anyway because we have a fileserver whirring away 24 hours a day - even at night it seems we are using about 200w/h.

However, yesterday was the first day for months that the solar panel has failed to provide us with a tank-full of scalding water so Mrs. Wow is in the downstairs (electric) shower. This is a fairly basic, cheap & cheerful shower running at mains pressure and it's knocked our rate up to 5 kw/h, or £665 a month!

She's out now and we are down to 500w/h again.

Too many computers...

[tonycollinet]

I've just bought one.

Things to be wary of - they only measure current - so in fact are only telling you VA which may be different for actual watts for some items. For example - our garage fridge (just found out it is a power hog) takes about 1.5A when running the compressor, so at the assumed voltage of 230V the monitor is telling us about 340W. The real power is actually about 150W due to the power factor of the motor.

Plus the units they are giving you is meaningless - watts per hour doesn't actually mean anything. The units are actully watts. Or Watt hours per hour which is the same thing.

[Wowbagger]

Sorry, don't understand any of that.

[rae]

Why do you need to get into all this complexity?  If gets hot, then it is using power.  The hotter it gets, the more power it is using.

[border-rider]

I've just bought one.

Things to be wary of - they only measure current - so in fact are only telling you VA which may be different for actual watts for some items. For example - our garage fridge (just found out it is a power hog) takes about 1.5A when running the compressor, so at the assumed voltage of 230V the monitor is telling us about 340W. The real power is actually about 150W due to the power factor of the motor.

But a crazy power factor loads the generator, and they still have to produce the requisite reactive power.  This why commercial operations get charged for reactive power and why they use power factor correction.  It's almost always inductive; the power companies would probably thank you for a capacitive power factor.

[tonycollinet]

Correct

But *I* dont' get charged for it, and my meter doesn't show it.

And as I understand it - it doesn't load the generator (it is not actual power), except in the extra losses in the transmission lines due to higher currents.

[rogerzilla]

But a crazy power factor loads the generator, and they still have to produce the requisite reactive power.  This why commercial operations get charged for reactive power and why they use power factor correction.  It's almost always inductive; the power companies would probably thank you for a capacitive power factor.

And they *hate* CFLs, which have a terrible power factor.

[tonycollinet]

Sorry, don't understand any of that.

PS - sorry, sometimes I get carried away. Ignore everything I said, it really doesn't matter. The monitor gives you a pretty good estimate of how much power you are using, and how much each device uses if you switch it on and off - assuming it uses enough power to register on the monitor.

[border-rider]

And as I understand it - it doesn't load the generator (it is not actual power), except in the extra losses in the transmission lines due to higher currents.

And increased generator losses.  And the requirement to run more generator plant.

But *I* dont' get charged for it, and my meter doesn't show it.

Probably so.  The issue only really exists if you're concerned about energy generation wastage.

[tonycollinet]

Yes and no

The point I think I am making is that the energy costs of the reactive current in my fridge are a tiny fraction of the energy costs which would result if it were power generating current.

Which is why I don't get charged for it.

[border-rider]

It's going to be some small percentage overall, especially when the need to run extra generating plant is considered.  But it adds up.

[fred the great]

So how can I check the extra cost of running three independant air conditioning units which are only switched on when needed.

Currently, I just look at the monthly invoice and break out in a sweat

[border-rider]

Read from the label on the aircons, or in the manual, what the power consumption is.  You should know how much your electricity costs you.  Get them all into compatible units (eg kW and cost per kWh) and you then know how much the units cost to run per hour/day.