The Kansas City Royals had the best ERA by an AL team in 2013, with an ERA of 3.45.

	TEAM	ERA	SEASON	G	W%	W	L	GS	SO	CG	SHO	SV	IP	H	ER	R	HR	BB	HBP	IBB	TBF	WP	K/9	BB/9	K/BB	HR/9	K%	BB%	WHIP	BABIP	RA	H/9
1	Royals	3.45	2013	162	.531	86	76	162	1,208	5	2	52	1448.1	1,366	555	601	155	469	41	21	6,049	60	7.51	2.91	2.58	0.96	20.0	7.8	1.27	.290	3.73	8.49
2	Athletics	3.56	2013	162	.593	96	66	162	1,183	6	4	46	1452.0	1,339	574	625	163	428	35	23	6,069	56	7.33	2.65	2.76	1.01	19.5	7.1	1.22	.276	3.87	8.30
3	Tigers	3.61	2013	162	.574	93	69	162	1,428	3	1	39	1462.2	1,369	587	624	128	462	42	29	6,119	63	8.79	2.84	3.09	0.79	23.3	7.6	1.25	.306	3.84	8.42
4	Rangers	3.62	2013	163	.558	91	72	163	1,309	4	2	46	1463.1	1,370	589	636	157	498	48	35	6,146	68	8.05	3.06	2.63	0.97	21.3	8.1	1.28	.293	3.91	8.43
5	Rays	3.74	2013	163	.564	92	71	163	1,310	9	3	42	1464.0	1,315	608	646	153	482	52	38	6,083	69	8.05	2.96	2.72	0.94	21.5	7.9	1.23	.284	3.97	8.08
6	Red Sox	3.79	2013	162	.599	97	65	162	1,294	5	2	33	1454.0	1,366	613	656	156	524	47	10	6,143	47	8.01	3.24	2.47	0.97	21.1	8.5	1.30	.294	4.06	8.46
7	Indians	3.82	2013	162	.568	92	70	162	1,379	3	3	38	1441.1	1,359	611	662	147	554	58	26	6,154	71	8.61	3.46	2.49	0.92	22.4	9.0	1.33	.302	4.13	8.49
8	Yankees	3.94	2013	162	.525	85	77	162	1,233	7	3	49	1447.1	1,452	633	671	171	437	51	34	6,128	57	7.67	2.72	2.82	1.06	20.1	7.1	1.31	.302	4.17	9.03
9	White Sox	3.98	2013	162	.389	63	99	162	1,249	5	1	40	1455.0	1,424	643	723	182	509	60	24	6,214	62	7.73	3.15	2.45	1.13	20.1	8.2	1.33	.295	4.47	8.81
10	Orioles	4.20	2013	162	.525	85	77	162	1,169	2	1	57	1453.0	1,438	678	709	202	473	50	32	6,144	38	7.24	2.93	2.47	1.25	19.0	7.7	1.32	.291	4.39	8.91
11	Angels	4.23	2013	162	.481	78	84	162	1,200	4	2	41	1457.2	1,475	685	737	167	533	45	36	6,298	74	7.41	3.29	2.25	1.03	19.1	8.5	1.38	.300	4.55	9.11
12	Blue Jays	4.25	2013	162	.457	74	88	162	1,208	4	2	39	1452.0	1,451	685	756	195	500	65	33	6,250	54	7.49	3.10	2.42	1.21	19.3	8.0	1.34	.293	4.69	8.99
13	Mariners	4.31	2013	162	.438	71	91	162	1,297	4	2	43	1465.0	1,467	702	754	174	478	42	48	6,257	74	7.97	2.94	2.71	1.07	20.7	7.6	1.33	.303	4.63	9.01
14	Twins	4.55	2013	162	.407	66	96	162	985	1	1	40	1450.1	1,591	733	788	168	458	44	31	6,257	50	6.11	2.84	2.15	1.04	15.7	7.3	1.41	.309	4.89	9.87
15	Astros	4.79	2013	162	.315	51	111	162	1,084	2	1	32	1440.0	1,530	766	848	191	616	56	32	6,370	61	6.78	3.85	1.76	1.19	17.0	9.7	1.49	.303	5.30	9.56