The watt-hour (Wh) is a unit of energy that measures the amount of electricity consumed or generated over time. It is the energy equivalent to one watt of power consumed for one hour. While electricity bills commonly display kilowatt-hours (kWh), understanding watt-hours can give you clearer insights into the energy efficiency of your household. For instance, a 60-watt incandescent light bulb running for one hour uses 60 watt-hours of electricity, while an energy-efficient LED bulb might only use around 10 watt-hours for the same illumination.
Interestingly, the concept of the watt-hour helps in comprehending renewable energy systems. Solar panels, for example, are rated in watts, but their output over time is often expressed in watt-hours or kilowatt-hours. Knowing this can help you assess how much energy your solar array could generate or your battery storage can hold, emphasizing the real value of alternative energy sources.
The kilojoule, abbreviated as kJ, is a unit of energy in the International System of Units. While it may not be as commonly recognized as calories in everyday conversation, the kilojoule is actually the standard metric unit for quantifying energy. Fascinatingly, 1 kilojoule is equivalent to 0.239 calories, making it a handy unit for converting nutritional information, especially in countries that primarily use the metric system.
Interestingly, the term “joule” is named after the English physicist James Prescott Joule, who studied the nature of heat and discovered its relationship to mechanical work. This unit has applications far beyond nutrition, including physics, chemistry, and engineering, where it measures various types of energy transformations, from kinetic to thermal. Understanding kilojoules can deepen our appreciation of energy, highlighting the intricate balances that power our world and our bodies.
| Watt-hours | Kilojoules |
|---|---|
0
Wh
|
0
kJ
|
10
Wh
|
36
kJ
|
20
Wh
|
72
kJ
|
30
Wh
|
108
kJ
|
40
Wh
|
144
kJ
|
50
Wh
|
180
kJ
|
60
Wh
|
216
kJ
|
70
Wh
|
252
kJ
|
80
Wh
|
288
kJ
|
90
Wh
|
324
kJ
|
100
Wh
|
360
kJ
|
110
Wh
|
396
kJ
|
120
Wh
|
432
kJ
|
130
Wh
|
468
kJ
|
140
Wh
|
504
kJ
|
150
Wh
|
540
kJ
|
160
Wh
|
576
kJ
|
170
Wh
|
612
kJ
|
180
Wh
|
648
kJ
|
190
Wh
|
684
kJ
|
200
Wh
|
720
kJ
|
210
Wh
|
756
kJ
|
220
Wh
|
792
kJ
|
230
Wh
|
828
kJ
|
240
Wh
|
864
kJ
|
250
Wh
|
900
kJ
|
260
Wh
|
936
kJ
|
270
Wh
|
972
kJ
|
280
Wh
|
1008
kJ
|
290
Wh
|
1044
kJ
|
300
Wh
|
1080
kJ
|
310
Wh
|
1116
kJ
|
320
Wh
|
1152
kJ
|
330
Wh
|
1188
kJ
|
340
Wh
|
1224
kJ
|
350
Wh
|
1260
kJ
|
360
Wh
|
1296
kJ
|
370
Wh
|
1332
kJ
|
380
Wh
|
1368
kJ
|
390
Wh
|
1404
kJ
|
400
Wh
|
1440
kJ
|
410
Wh
|
1476
kJ
|
420
Wh
|
1512
kJ
|
430
Wh
|
1548
kJ
|
440
Wh
|
1584
kJ
|
450
Wh
|
1620
kJ
|
460
Wh
|
1656
kJ
|
470
Wh
|
1692
kJ
|
480
Wh
|
1728
kJ
|
490
Wh
|
1764
kJ
|
500
Wh
|
1800
kJ
|
510
Wh
|
1836
kJ
|
520
Wh
|
1872
kJ
|
530
Wh
|
1908
kJ
|
540
Wh
|
1944
kJ
|
550
Wh
|
1980
kJ
|
560
Wh
|
2016
kJ
|
570
Wh
|
2052
kJ
|
580
Wh
|
2088
kJ
|
590
Wh
|
2124
kJ
|
600
Wh
|
2160
kJ
|
610
Wh
|
2196
kJ
|
620
Wh
|
2232
kJ
|
630
Wh
|
2268
kJ
|
640
Wh
|
2304
kJ
|
650
Wh
|
2340
kJ
|
660
Wh
|
2376
kJ
|
670
Wh
|
2412
kJ
|
680
Wh
|
2448
kJ
|
690
Wh
|
2484
kJ
|
700
Wh
|
2520
kJ
|
710
Wh
|
2556
kJ
|
720
Wh
|
2592
kJ
|
730
Wh
|
2628
kJ
|
740
Wh
|
2664
kJ
|
750
Wh
|
2700
kJ
|
760
Wh
|
2736
kJ
|
770
Wh
|
2772
kJ
|
780
Wh
|
2808
kJ
|
790
Wh
|
2844
kJ
|
800
Wh
|
2880
kJ
|
810
Wh
|
2916
kJ
|
820
Wh
|
2952
kJ
|
830
Wh
|
2988
kJ
|
840
Wh
|
3024
kJ
|
850
Wh
|
3060
kJ
|
860
Wh
|
3096
kJ
|
870
Wh
|
3132
kJ
|
880
Wh
|
3168
kJ
|
890
Wh
|
3204
kJ
|
900
Wh
|
3240
kJ
|
910
Wh
|
3276
kJ
|
920
Wh
|
3312
kJ
|
930
Wh
|
3348
kJ
|
940
Wh
|
3384
kJ
|
950
Wh
|
3420
kJ
|
960
Wh
|
3456
kJ
|
970
Wh
|
3492
kJ
|
980
Wh
|
3528
kJ
|
990
Wh
|
3564
kJ
|
1000
Wh
|
3600
kJ
|
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