A calculator I have gives me the following
15 US brl (1760 litres) to cool at 1 deg C / hr requires about 2.2 kwh
Top heat cooling required = approx. 0.4434 kwh assuming 48 deg SG (12 deg P) over 60 hours)
1 kwh = approx. 1.341 HPh
So now you can mix and match the volumes at top heat and cooling to determine your peak loading. These values don't take into account any heat gain or loss due to (lack of) thermal insulation.