PS. This is a brand new installation. Guess my questions are: is the heat sufficient to heat the house on the coldest days (probably gets to low 30s, sometimes 20s)? How energy efficient are the heat strips?

Heat strips are not energy efficient and are expensive to operate. Is this a new home? You will be unhappy with your electric bill in the winter mths using straight heat strips. If this is new home, I would ask that outside AC condenser be replaced with like HP model.

IMO

I would say that it depends
on the cost of replacement verses the cost of energy. While heat strips are not
nearly as efficient as a heat pump they’re still 100% efficient. Another
consideration might be comfort. If this is an attic installation with all the
supplies being ceiling mounted, the higher heat temperature supplied by the
heat strips, verses the lower temperature supplied by the heat pump, might feel more comfortable to you since supplied
heat with strips will penetrate to a lower level before rising.

While ceiling supplies are
ideal for air-conditioning are not ideal for heating. Heating supplies should
be at or near floor level.

‘Staged’ heat strip
operation would be preferable to full ‘On’ only.

IMPO

SR

To the novice homeowner. I always get a little concerned when someone says heat strips are 100% efficient which is absolutely true but can be entirely misleading to the OP's situation. The condenser should be changed out to the HP model regardless where ductwork and supply registers are located.

IMO

If you define efficiency as the ratio of input over output, then heat strips are 99+% efficient. The only loss is the heat lost in resistance of the wiring. Many people ask if a system is efficient when they really if the system is economical. Resistance heating is the most efficient but it is also the most expensive. An air sourced heat pump can be 2.5 - 3.5 times more efficient in providing the same amount of heat.

Two 5KW heat strips will provide about 32K BTUs. I am not sure if this will be enough to heat a 1400 sq. foot house in the winter. The design temperature for San Antonio is 29 degrees. I suggest doing a load calculation at 20 degrees with an indoor temperature at 72 degrees to see if you heat strips need to be increased. My thinking is it is not enough for very cold nights.

If the heat pump and heat strips are providing the same amount of heat then I don't see why one would be feel more comfortable than the other.

Thank you both! My understanding is that heat strips give 1 unit of heat per unit of electricity (thus 100% efficient which is indeed misleading), but that heat pumps give 2.5 to 3.5 units of heat per unit of electricity. Would you agree with that? "Staged heat strip operation would be preferable to full On only"...does that mean what's preferable is working like an electric furnace where strips cycle on and off, controlled by a 'brain', as opposed to just being either on or off? This is a redo of an old home—nice insulation in attic and walls but none in crawl space; ducts are in ceiling. A heat pump thermostat is installed; it has to be turned to 'emergency' to get heat. I thought it needed a heat pump switched out for the AC only but good to hear a pro say it :) I think the bills with the strip heat are going to be exorbitant.

And thank you Mike...apparently we were posting at the same time!

Staged heat strips means the two strips in the system are controlled by the room thermostat such that only one energizes when the room temp isn't too far-off from the setpoint so lower wattage attempts to maintain or attain the target. The 2nd activates if the room temp drops further below the setpoint (one strip can't handle the load).
Full-on refers to both strips always being activated whenever the thermostat calls for heat.

Got it, thanks...is it likely that auxillary heat designed for a heat pump would be staged heat strips or full on? I'm guessing full on.

Some higher-end systems can stage the strips for auxiliary (which is an excellent feature). Depends on the thermostat involved and capabilities of the system.

Good good. Thanks.

hot humid La. here.
very pleased with my heat pump
and fwiw, I only hooked up half
of my heat strips.
worked too hard making this
house efficient to spin it away
on elec strip heat. the most expensive
way to heat a house.

invest in the heat pump, stage
the heat strips.
you'll be glad you did when we
have a cold winter!

best of luck.

My understanding is that heat strips give 1 unit of heat per unit of electricity (thus 100% efficient which is indeed misleading), but that heat pumps give 2.5 to 3.5 units of heat per unit of electricity. Would you agree with that? "

Put another way, you bills will be approximately three times higher with heat strips vs heat pump. Divide the annual difference into the cost of a heatpump condenser and you will get the payback time in years.

Are you living in San Antonio now, or just planning to move there? The weather is definitely hot, but humidity is usually moderate. You will need heat in the winter, but temps in the 20's are very unusual, and its not often that you even have to deal with 30-35 degree temps for more than a few hours.

Natural gas is also available in most neighborhoods in the city, so most systems either use a heat pump or they use a natural gas furnace. I think that using only heat strips would be fairly unusual in new construction, since its much more costly to run when you do need heat.

Bruce

Take a look at the outside unit, could be a heat pump.