I'll go through all the features of the Humm Duet Energy Monitor as I figure them out, but there's one that I'd like to highlight because it's a perfect example of usability and how a little improvement can go a long way.

The left half of the Duet is concerned with electricity. I want to focus on the "Speed Dial" on the top and the "Daily Counter" in the middle. The units can be £, kWh or Kg of CO2 - a click on the fascia buttons switches between the three modes.

As you will see in the first picture, the speed dial shows how "fast" you are using electricity. The more you are using, the more the dial lights up. A perfect metaphor for usage. There's an indicator in the middle of the dial which gives you a numeric representation of your speed

In the middle of the unit is a daily counter.  This shows how much you have used since midnight.  The above image shows monetary usage, this next image shows kWh usage - the actual amount of electricity.

Immediately two things are obvious - kWh are more precise and simultaneously harder to understand.

Perhaps the least useful of the three modes shows Kg of CO2 released due to energy usage.

Given that the duet doesn't know whether my electricity is being generated by coal burning or wind turbines, it's a slightly spurious figure.

As Joe Baguley points out in his article about the Humm Trio, understanding the read-out makes it easier to understand what's going on.

I now know my dishwasher costs 16p/cycle, compared to my washing machine at 7p, and that running it on the thermonuclear remove the spot-welded lasagne from the dish mode only takes it to 17p.

Money is highly conceptual.  You can't hold a kWh in your hand and most of us have never seen a Kg of CO2 - but we can all visualise the pennies trickling from our wallets.

The problem is that the monetary graph doesn't have enough precision in it; pennies are counted - not tenths of pennies.  Switching your oven on may generate a leap from 8p an hour to 50p an hour - but switching off your lights may only drop you from 8.8p to 8.1p - a change that you won't see on the dial.

I would make the following suggestions

• Where possible include as much prescision as possible.  There's space on the readout for fractions of pennies - make use of it.
• Allow the different readings to be displayed in separate units.  For example, the Speed Dial could be in kWh while the daily total could be in £.
• The Duet allows you to set your unit cost of electricity - perhaps it should allow you to set how green your tariff is to ensure the Kg CO2 count is correct?
• It's fascinating to watch the speedo jump when the oven switches on, or drop when the TV goes off - perhaps large events should be recorded on the SD card.  Currently it only has 30 minute precision.  Given a whole day of 30 minute readings takes ~50KB of a 2GB card - I wouldn't think it unreasonable to record either twich the amount of data or only where there have been significant changes in usage.

Overall, the speedo idea is neat - you don't need to understand everything that goes on to get a quick visualisation of how much energy you are using.

I'll go through all the features of the Humm Duet Energy Monitor as I figure them out, but there's one that I'd like to highlight because it's a perfect example...

After setting up the HummEnergy Duet electricity monitor yesterday, I was pleasantly surprised at how easy the gas monitor was to set up.

Pairing the device was easy and the manual was very clear as to which pipes need to be monitored. A velcro strap makes it really easy to attach the wires to the pipes.

Once it's all plugged in, this is what it looks like

The monitor now shows whether your hot water and radiators are on.  It will show whether the water is cool, heating up or hot.  It can optionally show how long the hot water has been heating.  All very swish.

There's only one slight problem with the set up - and it's our flat.  Rather than conventional hot water radiators, we have hot air.  The same boiler that heats are water has a fan which pipes hot air around out house.  We also use a gas hob to cook.

The Duet only monitors gas usage by hot water.  So I'm not sure how much use it will be for monitoring our gas usage.  In the last year, we used around 15,000kWh of gas.  Here's how our energy company recorded our usage.

To really monitor gas usage, I think we'll have to go with Alistair MacDonald's ersatz suggestion - stick a webcam by the meter, upload images every hour and use OCR to figure out what the reading is.

That won't tell you what appliance is using the gas, but it will give a more accurate reading of how much gas you use per hour.

I'm already becoming quite a pain - running around turning lights off. Might need to get our boiler thoroughly serviced and our pipes and hot water tank properly insulated to make sure it's as efficient as possible.

After setting up the HummEnergy Duet electricity monitor yesterday, I was pleasantly surprised at how easy the gas monitor was to set up. Pairing the device was easy and the...