[Greenbuilding] Geothermal (ground source) Heat Pump question

[Reuben Deumling]

a local group is proposing to build a district energy system that utilizes
the following components:

A large PV array on top of a centrally located building;

A ground source heat pump with 300 ft wells connecting to an aquifer that
ostensibly supplies 54F water;

A backup boiler fired with some form of renewable fuel;

Large diameter pipes to carry hot water under the streets and into people's
houses where a heat exchanger would heat domestic water and provide space
heat.

My question is whether there is a simple way to calculate (approximate) the
electrical needs of this system in the winter when no PV power is expected.
We can assume for now that the system will supply 100 residences. I have
felt that this system, since it will be substituting for natural gas heat,
will exacerbate our winter electrical peak. The system's proponents say it
won't use any electricity from the grid in the winter--that the heat comes
out of the ground.

Thanks.

Reuben Deumling