Re: Have power usage data - now what (Excel question ?)

["Paul Robinson" <ukcueman@xxxxxxxxxxx>]

Excel should work well.

Multiply the current (amps) the device gives you by voltage (around
230-240) to give the
wattage [1]. Assuming the current is constant over each minute, then
current*voltage gives
you a number of watt-minutes. Convert this to watt-hours by dividing by 60
and convert to
kWh by dividiing by a further 1000.

So the number of kWh used each minute is current*voltage/60000

To find out the number of kWh used in a day, just add up the kWh used each
minute.

If you're feeling adventurous, and you have (or can have) a column showing
the date, then
you could use a pivot table to sum the electricity usage for you, so it
would show you a
table of usage by day.

HTH
Paul

[1] For AC, current*voltage does not quite give the wattage. I don't know
if there's a
rule-of-thumb conversion that is better than the one I've given, but this
is a good first
estimate. It will probably depend on how they've calculate the current
anyway.

----- Original Message -----
From: "David Chapman" <david@xxxxxxx>
To: <ukha_d@xxxxxxx>
Sent: Wednesday, September 21, 2005 10:48 AM
Subject: [ukha_d] Have power usage data - now what (Excel question ?)


> I'm using the excellent MAS345 multimeter with PC output and I now
have a
> .csv file that records every minute the power consumption of the
house.
>
> It's in a time / value (amps)  format:
>
> 10:00    1.8
> 10:01    1.9
> 10:02    9.6
>
> Example above kettle went on at 10:02. During the day I'm using just
under 2
> amps most of the time which climbs to about 5 in the evening with all
the
> lights on.
>
> But - how do I make it into something useful ? I thought I'd done the
> difficult bit ! Have been playing with Excel to try and get it to show
total
> consumption - I think to do that I total the 60 values for each hour
and
> then divide those by 60 to give me an average kWh for that hour - or
does
> that give me the total kW in that hour ? Ideally I want to know how
much I'm
> using between midnight and 7 and the rest of the day so I can do the
Economy
> 7 sums.
>
> Anyone already built the macros to display this sort of stuff ? Or
should I
> not be using Excel ? Maybe there is something else that can do a
better job
> of displaying the raw data ?
>
> David C






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