The average over this data set is 23.04% every 11.41 days so let's use that.
Date Difficulty Change Hash Rate
------------ ------------- ------ ---------------
Feb 28, 2014 3,815,723,799 21.92% 27,314,015 GH/s
Feb 17, 2014 3,129,573,175 19.39% 22,402,357 GH/s
Feb 05, 2014 2,621,404,453 19.49% 18,764,744 GH/s
Jan 24, 2014 2,193,847,870 22.59% 15,704,175 GH/s
Jan 13, 2014 1,789,546,951 26.16% 12,810,076 GH/s
Jan 02, 2014 1,418,481,395 20.12% 10,153,885 GH/s
Dec 21, 2013 1,180,923,195 30.01% 8,453,378 GH/s
Dec 10, 2013 908,350,862 28.41% 6,502,229 GH/s
Nov 29, 2013 707,408,283 16.07% 5,063,826 GH/s
Nov 17, 2013 609,482,680 19.29% 4,362,847 GH/s
Nov 05, 2013 510,929,738 30.70% 3,657,378 GH/s
Oct 26, 2013 390,928,788 46.02% 2,798,377 GH/s
Oct 16, 2013 267,731,249 41.45% 1,916,495 GH/s
Oct 06, 2013 189,281,249 27.19% 1,354,928 GH/s
Sep 25, 2013 148,819,200 32.13% 1,065,289 GH/s
Sep 14, 2013 112,628,549 29.56% 806,227 GH/s
Sep 04, 2013 86,933,018 32.22% 622,291 GH/s
Aug 24, 2013 65,750,060 29.40% 470,657 GH/s
Aug 13, 2013 50,810,339 35.88% 363,715 GH/s
Aug 03, 2013 37,392,766 19.63% 267,668 GH/s
Jul 22, 2013 31,256,961 19.47% 223,746 GH/s
Jul 11, 2013 26,162,876 22.63% 187,281 GH/s
Jun 29, 2013 21,335,329 10.32% 152,724 GH/s
Jun 16, 2013 19,339,258 23.92% 138,436 GH/s
Jun 05, 2013 15,605,633 28.41% 111,709 GH/s
May 25, 2013 12,153,412 8.64% 86,998 GH/s
May 12, 2013 11,187,257 11.03% 80,082 GH/s
Apr 30, 2013 10,076,293 12.28% 72,129 GH/s
Apr 17, 2013 8,974,296 16.96% 64,241 GH/s
Apr 05, 2013 7,673,000 14.59% 54,925 GH/s
Mar 24, 2013 6,695,826 38.13% 47,931 GH/s
Mar 14, 2013 4,847,647 10.98% 34,701 GH/s
Mar 01, 2013 4,367,876 19.63% 31,266 GH/s
Feb 18, 2013 3,651,012 11.47% 26,135 GH/s
Feb 05, 2013 3,275,465 10.33% 23,447 GH/s
So to make one Bitcoin a month that works out to:
Date Difficulty H/s
March 12, 2014 4,249,658,360 278E+009
March 23, 2014 5,228,779,646 342E+009
April 3, 2014 6,433,490,477 421E+009
April 15, 2014 7,915,766,682 518E+009
April 26, 2014 9,739,559,326 637E+009
May 8, 2014 11,983,553,795 784E+009
May 19, 2014 14,744,564,589 964E+009
May 30, 2014 18,141,712,270 1E+012
June 11, 2014 22,321,562,778 1E+012
June 22, 2014 27,464,450,841 2E+012
July 4, 2014 33,792,260,315 2E+012
July 15, 2014 41,577,997,092 3E+012
July 26, 2014 51,157,567,622 3E+012
August 7, 2014 62,944,271,202 4E+012
August 18, 2014 77,446,631,287 5E+012
August 30, 2014 95,290,335,136 6E+012
September 10, 2014 117,245,228,351 8E+012
September 21, 2014 144,258,528,963 9E+012
October 3, 2014 177,495,694,036 12E+012
October 14, 2014 218,390,701,942 14E+012
October 26, 2014 268,707,919,669 18E+012
November 6, 2014 330,618,224,361 22E+012
November 18, 2014 406,792,663,254 27E+012
November 29, 2014 500,517,692,868 33E+012
December 10, 2014 615,836,969,304 40E+012
December 22, 2014 757,725,807,032 50E+012
January 2, 2015 932,305,832,972 61E+012
January 14, 2015 1,147,109,096,889 75E+012
January 25, 2015 1,411,403,032,812 92E+012
February 5, 2015 1,736,590,291,572 114E+012
February 17, 2015 2,136,700,694,751 140E+012
February 28, 2015 2,628,996,534,821 172E+012
March 12, 2015 3,234,717,336,444 212E+012
March 23, 2015 3,979,996,210,761 260E+012
April 3, 2015 4,896,987,337,720 320E+012
April 15, 2015 6,025,253,220,331 394E+012
April 26, 2015 7,413,471,562,295 485E+012
May 8, 2015 9,121,535,410,248 597E+012
May 19, 2015 11,223,137,168,769 734E+012
May 30, 2015 13,808,947,972,453 903E+012
June 11, 2015 16,990,529,585,306 1E+015
June 22, 2015 20,905,147,601,761 1E+015
July 4, 2015 25,721,693,609,206 2E+015
July 15, 2015 31,647,971,816,767 2E+015
July 27, 2015 38,939,664,523,350 3E+015
August 7, 2015 47,911,363,229,530 3E+015
August 18, 2015 58,950,141,317,614 4E+015
August 30, 2015 72,532,253,877,192 5E+015
September 10, 2015 89,243,685,170,498 6E+015
September 22, 2015 109,805,430,233,780 7E+015
October 3, 2015 135,104,601,359,643 9E+015
October 14, 2015 166,232,701,512,905 11E+015
October 26, 2015 204,532,715,941,478 13E+015
November 6, 2015 251,657,053,694,395 16E+015
November 18, 2015 309,638,838,865,583 20E+015
November 29, 2015 380,979,627,340,214 25E+015
December 10, 2015 468,757,333,479,399 31E+015
December 22, 2015 576,759,023,113,052 38E+015
At 1W/GHs that works out to 38MW.
The datacenter that ran this would need a heavy industrial service similar to what is used to run a full sized pulp and paper mill or small city or town.