The graphic accompanying this text comes from page 16 of a university study by Charles Glassley, et al in 2014 which compared potential efficiency in all 16 of California’s climate zones between conventionally powered heating and cooling and that provided by a geothermal heat pump (GHP). The analysis was for a 2,000 square foot, conventional-framed home built to current Title-24 envelope standards.
The hot desert climate zone #15 was the only one of 16 where geothermal heat pumps failed to save energy.
However, it should be noted that the study did not include production of a heat pump’s de-superheater in the calculation. Therefore, it is questionable if the climate zone with the heaviest of cooling need in the state could fail to achieve efficiency parity with other zones by its providing such a high proportion of required, domestic hot water during heat pump cooling. A similar question could be raised in the case of climate zones 6-thru-10 in the southern California region. These areas have moderate air conditioning requirements.
Moderate air conditioning needs in the populated regions of southern California could still benefit society (even though the data in the Glassley study show only a 22-30% energy reduction by use of GHPs). Densely populated areas with conventional air conditioning boosts the “heat island” effect, raising the temperature in city neighborhoods and making condensers’ hot air discharge more difficult to accomplish. Neither does the study credit GHPs with the commonly known .7KW per ton reduction in electrical demand compared to conventional A/C.
This could reduce electrical generation needs within the South Coast Air Management District, where most of it remains as thermo-electric generation. Every megawatt reduction in generation lowers fossil emissions and steam cycle condenser heat rejection’s contribution to local temperature boost in the region.