seven pence, seems very expensive! 37 x 10=370watts cost of out the meter
per unit if unit is 2.5kw or 2500watts. Only use 370watts of is higher percentage (+50%) of unused units; the rest its up to you.
Should add for the prim and proper, consumption (370watts) of non-inclusive of waste of from leds or components giving off heat ect, add halve penny, no worries. :0)