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Calculate cost of running recirculation system

Taco recirculation systems  
Taco

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General manual
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Grundfos recirculation systems
Grundfos UP series

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Replacement crossover valve
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watts recirculation systems
Watts

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grundfos super brute
Grundfos UP series
Grundfos circulation pump for baseboard heating or water heater recirculation
Requires flange set
Use for whole house... install on 3/4" pipe or 1"

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UP15 circulator timer
grundfos bushings
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Load calculation for pump:
1 horsepower = 756 watts.
1/25 Hp motor = 30.6 watts  
30.6 watts divided by 120 volts = .255 amp
Laing recirculation systems
Laing

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Laing recirculation systems

Resource:
Autocurc manual
ACT 909 manual
E10 autocirc manual
Laing thermotech
Troubleshoot laing pump
3 factors affect cost:
Factor 1) Wattage of pump. Wattage appears on pump label.
Factor 2) Number of hours pump runs each day. This can be estimated if pump runs via thermostat, or known for certain if a timer is used or a Kwh meter is used.
Factor 3) Water heater cost from re-heating water ... cannot be known for sure unless a gas meter or electric meter are installed on heater.

Note also that a pipe with lots of elbows vs straight run can cause the pump to work harder. Unknown how much heat loss that slow circulation would add.
Example 30 watt pump
a) Pump runs full time > yearly cost $26 + reheat water $10 = $36 per year
b) Timer runs 2 half-hour periods per day > yearly cost $2 + reheat water $1 = $3 per year

Calculation for Full time
Pump uses approx 30 Watts = .030 Kw (30 watts divided by 1000 = Kw kilowatt)
Full time calculation: .03Kw x 24 hours = .72 Kwh per day
.72 Kwh per day x 365 days = 262.8 Kwh (kilowatthour)
262.8 Kwh x 10¢ per Kwh = $26.28 per year

Calculation for two 1/2 hour periods a day
Pump uses approx 30 Watts = .030 Kw (30 watts divided by 1000 = Kw kilowatt)
Pump runs 1 hour per day = .030 Kwh per day
.030 Kwh x 365 days = 10.95 Kwh per year
10.95 Kwh x Todays Rate 10¢ per Kwh = $1.95 per year
Water heater cost from re-heating water ... cannot be known for sure unless a gas meter or electric meter are installed on water heater.
Circulating pump does not cause new cold water to enter tank via the cold water inlet.
Instead the recirculated water cools down after leaving tank, so when the water arrives back at tank, it is cooler than when it left and needs to be re-heated.
Factors that affect how much the water cools include pipe insulation, length of pipe, ambient house temperature, and length of time water spends inside the recirculation loop.
Factors that affect how much it costs to reheat circulated water include efficiency of heater and cost of energy (gas or electric), with gas costing less than electric.
Estimate cost for extra water heating
Let's say circulating loop is 100' of 1/2" pipe and the water temperature drops by 10°F during recirculation.
This means 1.2 gallons of water weighing 10 lbs must be reheated to thermostat set point. (2.2 gallons for 3/4" pipe)
See calculations to right.

It takes 1 BTU to raise 1 lb of water by 1°F
If you have gas heater and run pump two 1/2 hour cycles per day
10 lbs of water x 10°F = 100 BTU per day x 365 days = 3650 BTU per year.
Use this figure and estimate from gas bill. Probably 50¢.

If you have electric water heater and run pump two 1/2 hour cycles per day
It takes .000293 Kwh to raise 1 pound of water 1° F
It takes .00293 Kwh to raise 10 lbs water 1°F
It takes .0293 Kwh to raise 10 lbs water by 10°
10 lbs of water per day must be raise by 10° ... so .0293 Kwh x 365 days = 10.69 Kwh x .10 per Kwh = $1.06 per year if pump runs two 1/2 hour cycles per day

For full time pump, we might guess it takes 10 times more energy than two 1/2 hour cycles per day??
 maybe $10-15 per year for electric, $6-9 for gas

Calculate gallons inside 100' pipe:
1 gallon = 231 cu inches
Inner diameter of 1/2 pipe .54" so r radius = .27"
Area = πr²


A = 3.14 x .27 x .27 = .229 sq in
100 ft = 1200 in
1200 in x .229 sq in = 274 cu in
274 cu in ÷ 231 cu in per gallon = 1.2 gal
1.2 gallons = 8.34 x 1.2 = 10 lbs

3/4" pipe: r radius .37"
A = 3.14 x .37 x .37 = .429 sq in
100 ft = 1200 in
1200 in x .429 sq in = 514 cu in
514 cu in ÷ 231 cu in per gallon = 2.2 gal

Kevin emails question Dec 2020
Woods 59366 timer''I have a heat pump water heater with a 44 watt recirculation system.
My pump plugs into an outlet with a timer so it doesn't run during the night. 
My plumber thinks that's nuts because he says it just costs pennies a day to operate, and he says that it's harder on the pump to go on/off as opposed to continually on.

We have a dedicated return line on the recirculation system that is about 60 ft. long and it is insulated the whole way.  It's also in a conditioned basement.
Energy Prices: Where we live, the price is about $0.0785 per kWh.
So, given all of that, I'm coming up with about $41 per year to run that pump 24/7.  Am I missing anything?
Resource:
Plug in timers
Gene answers with calculation
44 watt pump x 24 hours per day = 1056 watts, divided by 1000 = 1.056 Kwh per day ... or .083¢ per day .... less than 1¢ per day
1.056 Kwh per day x 365 days per year = 385.44 Kwh per year
385.44 x $.0785 per Kwh = $30.24 + tax and other charges if applicable

Heat pump water heaters are efficient but are slow to reheat  ... taking up to 4-6+ hours for 80 gallon  ... plus they use ambient room temperature to reheat water (they consume power from your HVAC)
Since the water heater is running more, causing HVAC to run more, and there is a tax on your electric prices, then add those cost to the $30.24, and $41 is probably about right
Resource: Best  when set to efficiency mode water heater
Gene answers with more detail
A high-priced plumber might think $.08 per day is ok in the era of global warming, and that $41 per year is better than having a timer that reduces cost to $20.50 per year.

The pump is only part of the cost of pulling hot water out of tank ...
the tank runs more//// how much more? I don't know for sure. Esimate might be $10 or more.

Your pump has FLA 44 watts ... so it consumes 44 watts when running, with slight surge more amps when starting up each morning...
If you run it 24-7 then that's like leaving a 40 watt light bulb running all the time. I say turn it off and save energy.
For reasons of economics and planetary responsibility, a recirc pump should be on a timer or switch in my opinion.

Kill a watt meterRemember too, that most small residential recirculating pumps come with a built-in crossover valve thermostat that cycles pump on-off based on temperature ... and nobody thinks about pump lifespan with that system ... and pumps last for decades.

I suggest you plug the pump into a Kwh meter ... to arrive at real answer.
Buy:
Energy Kwh meters

You can also add another meter to water heater ...  ... might be revealing and help solve what is best decision.
Resource:
How-to-install-electric-meter-on-240Volt-water-heater
Kill a watt meter120Volt meter for refrigerator, pump, microwave, TV, computer etc
Test any 120 volt appliance

Resources:
Kill a watt Instruction .pdf

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Energy meters
Meter on water heater
The Kwh meter is din rail mounted inside enclosure.
Records billable power usage in Kwh. Multiply by rate you pay per Kwh to get monthly/ yearly cost of running electric water heater.

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240 volt pass through Kwh  meter
2T2502GA beige plastic enclosure
2T2500GA grey plastic enclosure

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How to install electric meter on 240Volt water heater
How to meter 240Volt water heaterHardwired, 120 and 240 volt Hour meters
Example shows 240 volt Hour meter installed on pressure valve for 1 HP 2-person residential water well with light usage.

After 12 days, the hour meter reading showed 3.5 hours
1 Hp pump, 735 Watts (start up amperage not included)
735 watts X 3.5 hours = 2572 wh = 2.572 Kwh per 12 days
Extrapolate for 1 year = 78 kwh per year @ 12 cents = $9.39 to operate pump for 1 year

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UWZ48E-240V AC hour meter at Amazon
Intermatic bezel to support UWZ hour meter
Intermatic ac hour meters at Amazon

Resource:
Square D pressure switch .pdf
gas meter on gas water heater Install meter on Gas water heater
Record exact usage of BTU of gas appliances.
3/4" pipe thread connections. Use yellow teflon tape or gas-approved sealant.
No excess tape or sealant inside pipe. Use black pipe or yellow flex line. Keep pipes clean during assembly.
Install in vertical position with inlets pointing up as illustrated.
12.2" Tall x 8.5" Wide x 11.2" Deep
No power source required
Digital readout in cubic feet
Remote Readable option (pulse output) using EKM-25IDS

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EKM gas meter
Approved gas pipe sealant
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