Heater Sizing Chart for 7 hour heating period per 24 hours with floating solar cover

(If floating solar blanket not used increase heater size by 50%)

Heater Size	Metric
	24°C		27°C		30°C
	M²	M³	M²	M³	M²	M³
3Kw	6	8	5	7	4	5
6kW	12	16	10	13	8	11
7.5kW	15	21	12	16	10	13
9kW	18	25	14	20	12	16
12kW	24	33	19	26	15	21
15kW	30	41	24	33	19	27
18kW	36	49	29	39	23	32
21kW	42	58	34	46	27	37
24kW	48	66	38	53	31	42
30kW	60	82	48	66	39	53
36kW	72	99	58	79	46	64
48kW	96	132	77	105	62	85
60kW	120	165	96	132	77	106
72kW	144	197	115	158	93	127
84kW	168	230	134	184	108	149
96kW	192	263	154	210	124	170
108kW	216	296	173	237	139	191
120kW	240	329	192	263	155	212

Model Ref	Imperial
	75°F		80°F		85°F
	SQ.FT.	GALLS.	SQ.FT.	GALLS.	SQ.FT.	GALLS.
12PHR/3	63	1750	50	1400	42	1170
12PHR/6	125	3500	100	2800	83	2340
12PHR/7.5	156	4370	125	3500	104	2920
12PHR/9	188	5250	150	4200	125	3500
12PHR/12	250	7000	200	5600	167	4670
24PHR/15	313	8750	250	7000	208	5840
24PHR/18	375	10500	300	8400	250	7000
24PHR/21	438	12250	350	9800	292	8170
24PHR/24	500	14000	400	11200	334	9340
36PHR/30	625	17500	500	14000	417	11670
36PHR/36	750	21000	600	16800	500	14000
72PHR/48	1000	28000	800	22400	667	18680
72PHR/60	1250	35000	1000	28000	834	23350
72PHR/72	1500	42000	1200	33600	1001	28020
120PHR/84	1750	49000	1400	39200	1167	32680
120PHR/96	2000	56000	1600	44800	1334	37350
120PHR/108	2250	63000	1800	50400	1501	42020
120PHR/120	2500	70000	2000	56000	1668	46690

The sizing chart is for outdoor pools in the South of England, running from the beginning of May until the end of september. For pools in the North, multiply the heater size by 1.3 - 1.5 depending on the exposure of the pool.

The figures shown for capacity of the pool - in gallons or M³ - are based upon an average depth of 4'6" (1.36m) and are provided as a guide when exact surface area is not known.

For indoor pools, provided the air temperature is maintained at least 1°C above the pool temperature by an alternative form of heating 24 hours per day, the heater size may be reduced by multiplying by 0.7, but since running costs are related to the size of the pool and the temperature required, not the size of the heater, we advise keeping to the table where possible.
In countries where off-peak electricity is not available, heaters sized at 1kW per 1000 gallons (4500 litres) with the heater operating 24 hours per day, will normally be adequate and will give an 8°F (4.4°C) rise in 24 hours assuming no losses.