Measured System Power Consumption

Following discussion elsewhere about the cost of leaving systems on etc., I finally got round to measuring my system’s consumption. For your interest (if any) and comparison, I offer my data below:

  • Measurements taken between 0900-1000, 2nd April 2022 in Wiltshire, UK.
  • Supply Voltage measured at 240±1 V.
  • System: CDX2/NAPSC/200/202/NACA5 into B&W 804S. The 202 and 200 were serviced at Naim HQ within the last 12 months.
  • Measurements taken using Prodigit 2000MU and Radio Shack SPL meter, both with system quiescent and playing at steady 80-85 dBC


  • Quiescent: 15W, 22VA
  • Playing: 17W, 26VA (though pressing Play and Stop made it peak at about 20W, 29VA, presumably as the transport action pulled more current)


  • Quiescent: 4W, 7VA
  • Playing: no discernible difference, probably as expected!

200 (which is also powering the analogue side of the 202)

  • Quiescent: 10W, 18VA (manual states 11W, so reasonably close!)
  • Playing: 30-45W, 45-65VA (the refresh rate of the meter is about 2Hz, so this will be an approximation as the system deals with transients etc.)

My system’s total quiescent consumption is therefore 29W or 47VA. Off the top of my head, I can’t remember (nor can I get a straight answer from Google) about whether we’re charged for Watts or Volt-Amps. I’m sure someone out there has a better memory than me.


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Billing everwhere is in Kilowatt hours AFAIK.

Quite a few wattmeters let you plug in the average hourly rate and they’ll tell you how much something cost for the duration of the test or for a 24hr period.

I did an exercise a month or two back on everything in the home. 80% was blown on heating/cooling. Followed by office equipment, then washing machine and Telly, Then hifi. Finally, modern LED lighting costs next to nothing. Heating and cooling were true shockers though. Trying to make a dent in the ballooning monthly energy bill, the only meaningful impact was lowering the thermostat. Minor changes there had massive impact. Chasing my wife around nagging her to turn off lights or doing full shutdown of the workstation was barely a rounding error.

Out of curiosity, why did you measure the sound level using C weighting, rather than the conventional dB(A) normally used for measuring music sound level?

From dBA vs dBC — The Production Academy

“A-weighted decibel readings only really work at lower volumes and don’t take into account the loud low-end frequencies we have at a lot of shows. C-weighted measurements include more of the low frequencies. When we get up to loud volumes, this is actually closer to how we hear it.”

Interesting, as different from my learning and practice, with which these are consistent:


A-weighted decibel
Decibels with the sound pressure scale adjusted to conform with the frequency response of the human ear. A sound level meter that measures A-weighted decibels has an electrical circuit that allows the meter to have the same sensitivity to sound at different frequencies as the average human ear. There are also B-weighted and C-weighted scales, but the A-weighted scale is the one most commonly used for measuring loud noise.


Frequency Weightings - A-Weighted, C-Weighted or Z-Weighted
The human ear responds more to frequencies between 500 Hz and 8 kHz and is less sensitive to very low-pitch or high-pitch noises. The frequency weightings used in sound level meters are often related to the response of the human ear, to ensure that the meter is measuring pretty much what you actually hear. It is extremely important that sound level measurements are made using the correct frequency weighting - usually A-weighting. For example, measuring a tonal noise of around 31 Hz could result in a 40 dB error if using C-weighting instead of A-weighting.

A Weighting
*The most common weighting that is used in noise measurement is A-Weighting. Like the human ear, this effectively cuts off the lower and higher frequencies that the average person cannot hear. Defined in the sound level meter standards (IEC 60651, IEC 60804, IEC 61672, ANSI S1.4), a graph of the frequency response can be seen to the right.

C Weighting
The response of the human ear varies with the sound level. At higher levels, 100 dB and above, the ear’s response is flatter, as shown in the C-Weighted Response to the right. Although the A-Weighted response is used for most applications, C-Weighting is also available on many sound level meters. C Weighting is usually used for Peak measurements and also in some entertainment noise measurement, where the transmission of bass noise can be a problem.

Perhaps it is a matter of what one means by loud, Elsewhere I have seen references to C Weighting being used for extremely loud noises such as explosions though don’t recall where. That is rather louder than most hifi use (other than for peak measurement playing the Telarc 24 bit recording of Tchaikovsky’s 1812 through speakers with sufficient power capability…!)…

Either way, I very much doubt it’ll affect the power consumption data I gathered!


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