Given that we're now moved into the new build and into the colder months, I'd like to monitor what fraction our space heaters are as a proportion of our total energy use.

Since we're all electric, I'm hoping this should be fairly straightforward with a couple of in-line sub meters. What I'm less sure on is whether there's any benefit to wiring these in permanently - I'm assuming this would be a bit more accurate than a clamp on the wire?

What do people recommend as a reliable make (i.e. fit and forget, then check up on it a few months later)..?

I don't really want to run these reporting to a permanent data logger as we tend to use the computer infrequently and only have a mobile broadband router so I'm thinking something like a domestic (dumb) power meter with a very basic kWh display, perhaps with the option to reset a second counter periodically (like a car odometer).

Thanks in advance.

I'd hope your space and water heaters are pretty much all your demand.

A 'revenue' meter is more accurate than a clamp (i.e. a CT or current transformer) but only because they spend more on the components. Revenue meters typically contain CTs, but certified, revenue-grade ones.

So yes, if you want accuracy, use revenue components, but why do you care about that level of accuracy?

Personally, I use an emoncms system, which has the flexibility and facilities I need. I'm presently integrating data from a neigbour's weather station into it.

Indeed, yes, but then you have to read them every day (or whenever) and what? Record them on paper and then get a piece of graph paper and plot a curve? Or get out a calculator and work out the average or standard deviation or gradient or whatever?

The Raspberry pi that that is part of my emoncms does all of that every ten seconds without me having to think about it.

I recommend for heating -elated data, daily readings, nominally at or close to local midnight (eg late evening), to work well with any HDD (heating-degree-day) analysis/normalisation.

Rgds

Damon

(Speaking as someone who has only just given up manually reading at least 6 meters per day!)

The decomissioned consumption meters typically have a LED flashing for every Wh consumed. These can be read out using a photodiode, which is also part of the openenergymonitor.org implementation. That way you have the best of both worlds: great accuracy, huge dynamic range and remote readout/logging capabilities, with complete galvanic isolation so intrinsically safe.

If you can't be bothered with running photodiode wires to all these meters, I once saw a solution using a LASCAR EL-USB battery operated logger coupled to a photodiode to store the time between flashes and extract consumption that way.

Having said that, my openenergymonitor.org based CT clamp & AC transformer DIY rig is only out by about 1% compared to the consumption meter.

I just got an old fashioned electric meter off Ebay for our GSHP. Not very slick but more than adequate for long term monitoring.

Wow, this went mad over the weekend!

To answer a few of the points above:

Posted By: djhI'd hope your space and water heaters are pretty much all your demand.

That's partly what I want to determine, but I've been amazed by the draw of 'unregulated' use items such as AV amplifiers, cookers etc. in the past.

Posted By: djhwhy do you care about that level of accuracy?

I don't, to be honest. Just interested in what that means in practical terms. If the current flow is small enough, would the readings be useless because the margin of error on any reading would outweigh the practical data? I'm guessing not, since these instruments are commercially available, but interested nonetheless.

Posted By: CWattersused an efergy clamp on meter for awhile. Seemed reasonable accurate

From all your answers above, I think a clamp-on system sounds perfectly adequate. Thank you all.