"ransley" wrote

1 - At least one regular poster here continually mentions the
winter benefit of heat loss without regard to where the water
heater is located and totally ignores the AC impact in the summer.

Hi Mark,

The impact of standby loss with respect to added a/c demand is
generally very modest for three reasons:

1) with the exception of some of the southern most states, heating
degree days exceed those of cooling throughout most of North America,
in some cases by a factor of ten or more (e.g., Minneapolis MN).
Pittsburgh PA, a mid-eastern seaboard city, has 5,968 HDD and 654 CDD.
Even in San Diego CA, heating demands exceed those of cooling, i.e.,
1,256 HDD versus 984 CDD;

2) generally speaking, water heaters are located inside conditioned
spaces in colder regions due to the risk of freeze damage whereas they
are typically placed in non-conditioned spaces (e.g., attached
garages) in warmer climates -- located outside the home's thermal
envelope, there would be no impact on cooling demand;

3) for every kWh used, an air conditioner will remove three or more
kWh of heat. A 10 SEER air conditioner will purge 2.93 kWh of heat
for every one kWh consumed and a 13 SEER air conditioner (the current
minimum standard) will eliminate 3.8 kWh of heat. Thus, each kWh of
standby tank loss translates to 0.34 kWh of cooling demand at 10 SEER
and 0.26 kWh at 13 SEER.

Taken together, it's pretty clear the benefits in terms of heat gain
far outweigh any potential loss with respect to added cooling demand.

Cheers,
Paul