I was wondering how much running a Kindle as an always-on, underpowered Debian box was costing me in terms of electricity. So I plugged it into one of the Energycount 3000 devices and monitored its power consumption over the last 4 days. This took into account the power consumption of the Kindle as well as the efficiency of a small Nokia cell phone charger I'm using to power it.
ec3k reported an average power of 1.0 W (and maximum 2.6 W). Dividing the watt-seconds count with time also yielded 1 W to three decimal places. This nice round number makes me suspect that it's due to limited precision of the measurement, but let's consider it accurate for the moment.
1 W is equal to 0.72 kWh per month. With the current prices I'm paying for electricity this costs me 0.083 € per month. For comparison, a cup of synthetic-tasting coffee from a machine at work costs around twice as much and running my desktop machine all the time would be around a hundred times as expensive.