It can be done but it's not that practical since you need a huge insulated tank and if you're also using the water you it's even less practical to store heat in

It can be done but it's not that practical since you need a huge insulated tank and if you're also using the water you it's even less practical to store heat in it. One can use a pool as a heat sink during summer though. Water stores 1.16 kWh/m³K. The heat capacity could be increased with phase changing materials.