Power Measurements

I spent $2.51 on parts at Home Despot and built something that looks like a normal U.S. power outlet but which i'm calling a PET ("Power Estimating Tool"). So with the PET, i can use a normal multimeter to measure the amps pulled by whatever i plug into the PET.

Measurements below are the number of amps something uses at ~120 volts, alternating current.

Please be aware that i have been advised by someone (Hi Bob!) who understands A/C power theory much better than i, that the method i am using to measure current is not accurate, especially for the "switching" power supplies commonly found in computers. Some of the reasons leading to the inaccuracy of my method seem to be explained on this page, though i can't say for certain, because i really don't fully comprehend that information. (I am not an electrical engineer, or anything even resembling one.) There's probably some hairy calculations that would enable me to supply better numbers, but for the moment, that is beyond my meager abilities.

Computers

Manufacturer Model CPUs Hard Drives1 Status Amps Watts kWh used in 30 days2 Cost in 30 days3
Apple Computer PowerBook G3
"Pismo" 		(1) 400 MHz G4
(PowerPC 750) 		(1) 6GB Asleep 0.02 2.4 1.728 $0.15
" " " " Awake but Idle 0.11 13.2 9.504 $0.80
" " " " CPU 100% 0.15 18.0 12.960 $1.10
" " " " Heavy Disk I/O 0.16 19.2 13.824 $1.17
Apple Computer G4 Cube
(CPU upgraded)
incl. power for Apple CRT Studio Display 		(1) 1200 MHz G4 (1) 20GB Off, but plugged in 0.28 33.6 24.192 $2.04
" " " " Idle, monitor asleep 0.60 72.0 51.840 $4.38
" " " " idle, montior on 1.70 204.0 146.880 $12.41
" " " " Busy (ripping DVD) 1.80 216.0 155.520 $13.14
Compaq DS 10 (1) 466 21264-4 (Alpha) (2) IBM, DDYS-T09170N Off, but plugged in 0.09 10.8 7.776 $0.66
" " " " idle 2.06 247.2 177.984 $15.04
" " " " compiling 2.05 246.0 177.120 $14.97
Sun Microsystems GDM-20E20 (20 in. Color Monitor) - In Use 0.71 85.2 61.344 $5.18
" " - - Asleep -OR- Off 0.08 9.6 6.912 $0.58
" GDM-20D10 (20 in. Color Monitor) - In Use 0.68 81.6 58.752 $4.96
" SPARCstation 2 (1) 40 MHz CY7C601 None Idle 0.18 21.6 15.552 $1.31
" SPARCstation 5 (1) 170 MHz microSPARC-II None Idle 0.24 28.8 20.736 $1.75
" " " (2) ST32171W Idle 0.42 50.4 36.288 $3.07
" " " " heavy I/O (one disk) 0.45 54.0 38.880 $3.29
" " " " heavy I/O (two disks) 0.47 56.4 40.608 $3.43
" SPARCstation 20 (2) 50 MHz mircoSPARC (TI,TMS390Z50) WDIGTL (2.1GB)
IBM DCAS32160 (2.1GB) 		Idle 0.51 61.2 44.064 $3.72
" SPARCstation IPC (1) 25 MHz LSI L64801 or Fujitsu MB86901A None Idle 0.14 16.8 12.906 $1.02
" Ultra 30 (1) 300 MHz UltraSPARC-II IBM DMVS36D (32 GB)
Seagate ST34371 (4.2GB) 		Off 0.14 16.8 12.906 $1.02
" " " " Idle 1.00 120.0 86.400 $7.30
" " " " CPU 100% busy
(no disk I/O) 		1.01 121.2 87.264 $7.37
" " " " heavy I/O (two disks) 1.03 123.6 88.992 $7.52
" Netra X-1 (1) 400 MHz UltraSPARC-IIe ST320413A
WDC WD1000BB-32CCB0 		Off 0.02 2.4 1.728 $0.15
" " " " Idle 0.31 37.2 26.784 $2.26
" " (1) 500 MHz UltraSPARC-IIe ST340016A x 2 off 0.04 4.8 3.456 $0.29
" " " " Idle 0.42 50.4 36.288 $3.07
" " " " heavy disk I/O or compiling 0.44 52.8 38.016 $3.21

Household Appliances

Manufacturer Model Function Status Amps Watts kWh used in 30 days2 Cost in 30 days3
Black & Decker 2200TY1 Toaster oven Off 0.00 0.0 0.000 $0.00
" " " On 12.11 1453.2 1046.304 $88.41
Capresso #437 Coffee Maker Idle 0.03 3.6 2.592 $0.22
" " " Brewing 6.82 818.4 589.248 $49.79
Denon AVR 2802 AV amp/tuner Off 0.00 0.0 0.000 $0.00
" " " On4 >= 0.35 >= 42.0 >= 30.240 >= $2.56
GE JES1231 Microwave Idle 0.02 2.4 1.728 $0.15
" " " In Use. 13.85 1662.0 1196.640 $101.12
" ASP08ACS1 Air Conditioner (window) Fan only 0.89 106.8 76.896 $6.50
" " " Fan and compressor ~5.00 ~600.0 ~432.000 ~$36.50
" ACV05LAB2 Air Conditioner (window) Fan low 0.47 56.4 40.608 $3.43
" " Air Conditioner (window) Fan High 0.63 75.6 54.432 $4.60
" " " Fan and compressor ~3.40 ~408.0 ~293.760 ~$24.82
Kenmore Like 20-30 years old. Refrigerator On 3.20 384.0 276.480 $23.36
Lakewood ? Box Fan "High" Speed 2.07 248.4 178.848 $15.11
" " " "Low" Speed 1.06 127.2 91.584 $7.74
Living Air XL Air Purifier (ionizer) fan:low, purify:100 0.21 25.2 18.144 $1.53
" " " fan:low, purify:1500 0.25 30.0 21.600 $1.83
" " " fan:low, purify:3000 0.34 40.8 29.376 $2.48
" " " fan:med, purify:100 0.24 28.8 20.736 $1.75
" " " fan:med, purify:1500 0.29 34.8 25.056 $2.12
" " " fan:med, purify:3000 0.38 45.6 32.832 $2.77
" " " fan:high, purify:100 0.34 40.8 29.376 $2.48
" " " fan:high, purify:1500 0.39 46.8 33.696 $2.85
" " " fan:high, purify:3000 0.48 57.6 41.472 $3.50
Panasonic KX-FPC95 combo fax/cordless phone Standby 0.03 3.6 2.592 $0.22
" " " Phone in use 0.04 4.8 3.456 $0.29
" CW-XC82YU Window Air Conditioner Off 0.01 1.2 0.864 $0.07
" " " Fan: Low 0.50 60.0 43.200 $3.65
" " " Fan: Medium 0.59 70.8 50.976 $4.31
" " " Fan: High 0.66 79.2 57.024 $4.82
" " " Compressor, Fan: Low 4.45 534.0 384.480 $32.49
Patton PWF2198 Window Fan Off 0.12 14.4 10.368 $0.88
" " " "Low" Speed 0.41 49.2 35.424 $2.99
" " " "Med" Speed 0.44 52.8 38.016 $3.21
" " " "Hi" Speed 0.48 57.6 41.472 $3.50
Roper ? Refrigerator not running 0.00 0 0 $0
" " " Door open 0.33 39.6 28.512 $2.41
" " " Running 1.97 236.4 170.208 $14.38
Rotel RDV 985 DVD player Off 0.01 1.2 0.864 $0.07
" " " Playing DVD 0.10 12.0 8.640 $0.73
Sony KV27V42 27 in. Color TV Off 0.01 1.2 0.864 $0.07
" " " On 0.47 56.4 40.608 $3.43
" SCPH-3001R PlayStation 2 Off 0.00 0.0 0.000 $0.00
" " " On 0.23 27.6 19.872 $1.68
TMK 510cp Small Color TV/radio Off 0.02 2.4 1.728 $0.15
" " " Radio On 0.03 3.6 2.592 $0.22
" " " TV On 0.15 18.0 12.960 $1.10

1Internal 3.5 in. drives, spun up, but not under I/O.

2kWh (Kilowatt hours) used if left in the designated Status for 24 hours a day.
(Amps * 120 V * 24 hours * 30 days / 1000 = kWh for 30 days)

3 Assuming a cost of 8.45 cents (US currency) per kWh.
(kWh * 0.0845 = $ cost per 30 days)

4 The stereo amp consumes more power as its volume is increased. The figure indicated is the minimum the amp will use. (Amp on, but speakers turned off)

Other Notes:

  1. Electricity does not including cooling costs. (I.e. Air conditioning)
  2. Of course, numbers are approximate.
  3. Interestingly, the Ultra-30 pulls 0.14 Amps (as much as a SPARC IPC) when it's switched Off! (But still plugged in.)

$Id: power.html,v 1.19 2008/07/08 07:25:35 johan Exp $