There is no added insulation to our Modpools outside of our interior and exterior liner that helps distribute the heat and does not let it escape as fast as if it were just water against steel.
To use your pool all year round, you need to set an ambient temperature above freezing on your thermostat and make sure it is in "pool" mode, ensuring the water temperature will not drop below freezing (if your water freezes, it can damage the pool, pipes and pumps). If your pool has a cover, it retains heat exceptionally well, so you can maintain the temperature consistently without too much cost. Electric heaters will typically cost much more in the long term, depending on the size of your pool and the frequency of its use.
If you have the spa seating feature in your unit, it will have a removable divider wall that you must either leave out all winter or remove every night to make sure the warm water is moving throughout the unit. When using the spa seating in the wintertime time, you can have the wall in place, put the unit into "spa" mode and heat it to your desired temperature; you can also close the cover (if you have one) to the divider wall so just the spa section is available.
You also have the option to drain the Modpool and not use it over winter. If you choose to do that, you can follow these linked steps to protect your Modpool: Winterizing Steps.