Heat pump or propane for 20x40 inground gunite pool in Massachusetts

[Pavlin]

Hi, new member here . I'm in process of getting a quote on 40x20 (maybe 36x18, yet to be tetermined) inground gunite pool.
I'm pretty much all decided on all opitions and features except one. Don't know which way to go on the pool heter.

The property doesn't have NG so heat pump or propane are the only options. Currently have 500gl inground propane tank that serves standby generator and tankless water heater in the house
The goal is to keep pool at constant 85-ish degree temp. For the entire season. The pool will have auto cover. The pool location will have about 9-10 hours per day of direct sun.
So the questions are:
1. Will 500 gal tank suffice to heat the pool and support stand by gen and tankless water heater and how much propane will i use per month to maintain 85-ish degree temp?
2. If I go heat pump route by how much my monthly elctric bill will increase?

I'm ready to eat reasonable one time higher installation costs if I have to. The main goal is lower operational costs down the road.
Would like to hear real electric/propane monthly $ bill numbers from owners of both systems. I know technical pros and cons of HP vs propane but would like to know which one would be cheaper to run in my case?
Thanks

 

[PoolStored]

Assuming a 30K gallon pool. 140K heat pump., 400K propane heater. Further assume 5dF demand daily (may be off, but just an assumption)

Heat Pump.
30,000 x 8.3 = 249,000lbs of water.
249,000 / 140,000 = 1.77 hours to raise temp 1dFF ( this will be wildly optimistic for a heat pump, heat pump efficiency varies dramatically with the air temperature, only reaching the listed BTU number when the air is quite warm)...but let's roll with it.
1.77 * 5dF = 8.85hours of heating. Because of the optimism above, let's say 10hours
Heat pump Consumes about 5,000W/hour per 100,000 BTU. So 7,000W per hour for 140K unit.
10 hours, 7,000W, $.15/kWh = $10/day.

Gas heater
400,000 BTU * .8 efficiency =320K BTU
249,000 / 320,000 = .78 hours to raise 1dF
Gas heater consume 1g/h/100K BTU
Hourly consumption = 4g/h total
.78 *5dF = 3.9 hours
3.9 hours * 4g/H = 16g/day
Don't know your gas prices, but average for MA in July is $3.62 Weekly Massachusetts Propane Residential Price (Dollars per Gallon)
16g/day * $3.62 = $58/day
Deplete the tank in a month.

Maybe my numbers are off, and if they are someone will come along and correct me.

Given your situation, and the fact you want to keep your temp level, looks like the heat pump is the way to go.

All of these numbers are based on assumptions. You likely won't have 5dF demand in June, July and Aug. Doesn't include the water heating the walls etc, reducing efficiency, the HP numbers are likely very optimistic on the run times. YMMV

 

[pygmy1]

Hi. I'm a pool designer in Massachusetts. We install a number of Electric Heat pumps on our Pool Only installs. This the best way to maintain a desired temperature even know that heat rise takes more time than Propane or Natural Gas. If you are installing a motorized Automatic Cover and are aggressive by closing it when not in use, this will give you the most efficiency in terms of operating costs. I would recommend a 140,000 BTU Electric Heat pump and design the pool equipment to be in that sunny area you mention because that aids in the fan taking in the air which has heat to the scroll compressors. I'd be happy to discuss this with you if you would like.
Mark
Removed Email. Use Start Conversation. TFP Mod

 

[Pavlin]

Assuming a 30K gallon pool. 140K heat pump., 400K propane heater. Further assume 5dF demand daily (may be off, but just an assumption)

Heat Pump.
30,000 x 8.3 = 249,000lbs of water.
249,000 / 140,000 = 1.77 hours to raise temp 1dFF ( this will be wildly optimistic for a heat pump, heat pump efficiency varies dramatically with the air temperature, only reaching the listed BTU number when the air is quite warm)...but let's roll with it.
1.77 * 5dF = 8.85hours of heating. Because of the optimism above, let's say 10hours
Heat pump Consumes about 5,000W/hour per 100,000 BTU. So 7,000W per hour for 140K unit.
10 hours, 7,000W, $.15/kWh = $10/day.

Gas heater
400,000 BTU * .8 efficiency =320K BTU
249,000 / 320,000 = .78 hours to raise 1dF
Gas heater consume 4g/h/100K BTU
Hourly consumption = 16g/h total
.78 *5dF = 3.9 hours
3.9 hours * 16g/H = 62.4g/day
Don't know your gas prices, but average for MA in July is $3.62 Weekly Massachusetts Propane Residential Price (Dollars per Gallon)
62.4g/day * $3.62 = $225/day
Deplete the tank in a week.

Maybe my numbers are off, and if they are someone will come along and correct me.

Given your situation, and the fact you want to keep your temp level, looks like the heat pump is the way to go.

All of these numbers are based on assumptions. You likely won't have 5dF demand in June, July and Aug. Doesn't include the water heating the walls etc, reducing efficiency, the HP numbers are likely very optimistic on the run times. YMMV

Thanks a lot for braking it down for me. So looks like even thou some of the HP numbers are on the optimistic side the running cost is day and night difference compared to LP.
What's the best 140K BTU HP on the market today?

 

[1poolman1]

Assuming a 30K gallon pool. 140K heat pump., 400K propane heater. Further assume 5dF demand daily (may be off, but just an assumption)

Heat Pump.
30,000 x 8.3 = 249,000lbs of water.
249,000 / 140,000 = 1.77 hours to raise temp 1dFF ( this will be wildly optimistic for a heat pump, heat pump efficiency varies dramatically with the air temperature, only reaching the listed BTU number when the air is quite warm)...but let's roll with it.
1.77 * 5dF = 8.85hours of heating. Because of the optimism above, let's say 10hours
Heat pump Consumes about 5,000W/hour per 100,000 BTU. So 7,000W per hour for 140K unit.
10 hours, 7,000W, $.15/kWh = $10/day.

Gas heater
400,000 BTU * .8 efficiency =320K BTU
249,000 / 320,000 = .78 hours to raise 1dF
Gas heater consume 4g/h/100K BTU
Hourly consumption = 16g/h total
.78 *5dF = 3.9 hours
3.9 hours * 16g/H = 62.4g/day
Don't know your gas prices, but average for MA in July is $3.62 Weekly Massachusetts Propane Residential Price (Dollars per Gallon)
62.4g/day * $3.62 = $225/day
Deplete the tank in a week.

Maybe my numbers are off, and if they are someone will come along and correct me.

Given your situation, and the fact you want to keep your temp level, looks like the heat pump is the way to go.

All of these numbers are based on assumptions. You likely won't have 5dF demand in June, July and Aug. Doesn't include the water heating the walls etc, reducing efficiency, the HP numbers are likely very optimistic on the run times. YMMV

A propane heater will use about 1 gallon/100K BTU. There are 91,500+/- BTU per gallon. A 400K heater will use 4+/- gallons per hour.

BTU per Gallon of Propane: The Ultimate Guide to Energy Efficiency

Discover the science behind propane gas. Learn about propane BTU per gallon of propane and how it can power your home or business.

www.amerigas.com

 

[ajw22]

What's the best 140K BTU HP on the market today?

The better question is what 140K HP can you get service and warranty support locally?

Many folks have found they have orphaned HPs as many companies whop sell them do not service them. And then they have trouble finding anyone to repair the HP as many HVAC companies will not work on pool HPs.

Pentair UltraTemp, Aquacal, Gulfstream, Built Right all seem good. I would not get a Hayward or Jandy HP.

 

[Bill1974]

Not sure on the cost of propane in Mass, but I recall doing the math for comparing a HP vs NG and the HP was pretty much half the cost of NG. With a cover the HP should be the most efficient. Beginning and end of the season it might be a challenge to keep of depending on the air temps. Cost if going to change throughout the season. Beginning and end it's going to be the highest, middle it may not even run. I'm on Long Island and just the sun keeps mine around 85 for most of July and August.

 

[PoolStored]

A propane heater will use about 1 gallon/100K BTU.

Got my 4s mixed up. Fixed it...