Help Me Think

[wireform]

Have client with a non automation 5200 gallon AG pool that wants a heater. I can go either way NG or HP. Can't figure out from an efficiency point which would be better. The utility company is Orange & Rockland - Utility Company Serving Greater New York. Any help is greatly appreciated, Allan

 

[ajw22]

• Pentair has a Heat Pump Calculator to determine the appropriate size Heat Pump for your location. Pentair seems to do honest calculations based on the physics and efficiencies of each type of pump and energy source.
• Raypak also has a Heat Pump Heater Sizing App.
• Aquacal has a Heat Pump Sizing and Savings Calculator.
• To get the most accurate cost comparison, change the default electric kwh and natural gas to the actual O&R prices.

Consider also acquisition costs of the unit and gas line installation or electrical installation.

 

[PoolStored]

Heat pump 140K vs. 400K Gas heater. Assume daily demand of 5dF

24,000 x 8.3 = 58,000lbs of water.
58,000 / 140,000 = .4 hours to raise temp 1dF
.4 * 5dF = 2 hours of heating.
Heat pump Consumes about 5,000W/hour per 100,000 BTU. So 7,000W per hour for 140K unit.
2 hours, 7,000W, $.12/kWh = ~$1.68 / 5dF.

Gas heater
400,000 BTU * .8 efficiency =320K BTU
58,000 / 320,000 = .18 hours to raise 1dF
Gas heater consume 1g/h/100K BTU
Hourly consumption = 4g/h total
.18 * 5dF = .9 hours
.9 hours * 4g/H = 3.6g
3.6g/day * 82.62 = 297 cubic feet = .297 MCF
.297 MCF * $5.82/MCF = $1.73 / 5dF.

You can change your price per kWh and MCF to see what you get...

 

[Newdude]

Same as always up here. Do they want :

Substantially more season : gas heater
Warmer regular season : heat pump

If they want both, make them decide which of the two is more important and go that way. For example, they'd like a few more weeks of season but not 3 months, then go HP.

 

[JamesW]

Orange & Rockland's cost per kWh varies based on time of day and season, with summer rates (June-September) being 10.363 cents for less than 250 kWh and 12.960 cents for more, and other months at 10.363 cents for all kWh.

A 140,000 btu/hr heat pump uses about 7.2 kw to deliver 145,000 btu.

7.2 x $0.1296 = $0.933 per hour for 145,000 btu/hr.

That is $6.43 per 1 million btu.
______________________________________________________________________________________________________________________
In the Greater New York area, the average cost of utility (piped) gas per therm was $1.869 in December 2024.

1 therm = 100,000 btu.

A 400,000 btu/hr at 84% efficiency uses 4 Therms per hour and delivers 336,000 btu/hr.

4 therms x 1.869 = $7.476 per hour for 336,000 btu/hr.

That is $22.25 per 1 million btu.

22.25/6.43 = 3.46 times cost for natural gas.

 

[JamesW]

New York - Statewide​

Prices are dollars per thousand cubic feet ($/MCF).

	2024	2023	2022	2021	2020	2019	2018	2017	2016	2015	2014	2013	2012
January	14.55	17.20	13.83	11.21	11.37	12.28	9.51	9.86	10.30	10.51	11.18	11.27	11.67
February	14.75	16.57	13.09	10.87	11.62	11.44	11.23	11.04	9.45	9.79	11.32	10.80	11.69
March	15.46	16.08	14.15	11.53	11.93	10.86	12.09	10.81	9.64	9.34	11.78	11.41	12.99
April	15.04	15.08	14.84	13.84	12.07	12.09	11.29	11.09	9.88	10.19	12.49	12.65	13.06
May	18.13	16.70	17.61	15.02	11.56	13.99	14.19	14.45	10.99	12.68	14.55	15.73	15.13
June	21.38	19.70	24.59	17.55	16.03	17.06	19.32	16.28	14.69	16.26	17.99	18.16	18.00
July	23.22	21.74	26.20	21.25	19.34	19.86	20.10	19.14	16.64	17.09	18.99	19.25	17.40
August	23.29	22.69	26.17	23.11	19.82	20.14	20.83	19.06	17.86	17.30	18.88	18.99	18.78
September	23.46	20.97	28.22	22.19	19.24	19.97	20.15	18.12	17.34	17.50	17.86	18.42	18.16
October	22.31	19.97	21.93	N/A	16.08	16.89	17.15	17.17	14.87	14.24	15.99	16.12	15.26
November	19.61	16.28	19.28	17.29	13.67	12.45	12.18	13.07	10.95	12.26	12.27	12.27	11.35
December	15.34	14.69	16.75	14.65	12.15	10.75	11.64	10.52	9.60	11.43	10.66	10.50	11.97

One thousand cubic feet (1 MCF) of natural gas is equivalent to approximately 10.38 therms.

 

[JamesW]

5200 gallon = 43,368 lbs.

145,000 btu/hr = 3.34 degrees per hour.

336,000 btu/hr = 7.75 degrees per hour.

Based on the pool size, a heat pump will be the best deal as long as the air temp will be above about 60 degrees and the water temp will 85, or lower.

 

[JamesW]

Assuming a 15 foot round pool, the surface area is approximately 177 square feet.

If we use 210 btu/hr per sqft for the heat loss, that's 37,170 btu/hr lost.

A 140,000 btu/hr heat pump should be able to do about 90,000 btu/hr at 50, 63, 80..

At 50 air and 80 water, we can use 260 btu/her per sqft. for heat loss, which is 46,020 btu lost per hour.

So, even at 50 air temp, you should be able to maintain at least 80 degree water.

 

[JamesW]

$5.82/MCF

Where did you find that price?

In December 2024, the average cost of natural gas in New York was approximately $15.34 per MCF (thousand cubic feet) for residential customers and $11.12 per MCF for commercial customers.

$15.34/0.84 = $18.26 per 1 million btu. (Natural Gas).
_____________________________________________________________________________________________________

At a cost of $0.1884 per kwh and a C.O.P of 5.0, the cost per kwh delivered is $0.03768.

1 million btu = 293.1 kW h (kilowatt hours) = $11.04 per 1 million btu (Heat Pump).

https://cdne-dcxprod-sitecore.azureedge.net/-/media/files/oru/documents/saveenergyandmoney/shop-for-energy-money/how-to-choose-your-energy-service-company-esco/price-to-compare.pdf

 

[PoolStored]

You can change your price per kWh and MCF to see what you get...

 

[JamesW]

If we use 210 btu/hr per sqft for the heat loss, that's 37,170 btu/hr lost.

That is 892,080 btu per day or 27,152,685 btu/month.

Heat pump cost per month = $300.00.

Natural Gas cost per month = $500.00.

$11.04 per 1 million btu (Heat Pump).
$18.26 per 1 million btu. (Natural Gas).