Well runs out of water

[Speedbump]

I'm glad Bob NH finally put the cost of a dime part at the end. Now I understand all that math better. I know there is not a lot of cost involved in operating a 3/4hp sub for a normal residence. And also that irrigating alfalfa could be quite costly. Here the fish farmers are the one's that cry about the cost of operating circulating pumps.

Can anyone put together an average cost of lets say a 3/4hp motor giving the average homeowner's household needs minus sprinkling the grass in normal america with normal water levels and normal electric power costs per day, week, month? I think this would be a great selling feature for homeowners looking for the difference in operating a well over buying water from the government. I realize repair costs would have to be estimated as well.

bob...

 

[Bob NH]

"Can anyone put together an average cost of lets say a 3/4hp motor giving the average homeowner's household needs minus sprinkling the grass in normal america with normal water levels and normal electric power costs per day, week, month? I think this would be a great selling feature for homeowners looking for the difference in operating a well over buying water from the government. "

That is why I calculated the kWHr per 1000 gallons at 200 ft of head. That is a reasonable head for a well where the water rises to within 60 ft of the surface and you are trying to get 50 psi in the tank, with the pump operating near its nominal flow rate (not throttled).

If the pump you need is operating at 300 ft of head at the nominal flow rate, multiply the 1.4 kWHr/1000 gallons by 300/200=1.5, so you get 2.1 kWHr per 1000 gallons.

It makes absolutely no difference what the horsepower of the motor is if you have the correct motor and the correct pump. You are working with total water pumped and the bigger pump uses more power and produces more water.

A typical homeowner may use about 100,000 gallons per year, and where I live the cost of municipal water is about $3.00 per 1000 gallons and we are paying about $0.12/kWHr for electricity. Therefore the electrical cost per 1000 gallons would be 1.4x0.12=$0.168, so the municipal water costs about 18 times as much as your pumping power. The one costs $300 per year and the other costs $16.80.

It takes 6233 gallons to put an inch of water on 10,000 square feet, or 27,150 per acre-inch. For the rates given above it will cost about $1.05 of pumping power to put an inch of water on your 10,000 sq ft lawn, or about $4.50 for an inch on an acre of your alfalfa. Everyone can scale electicity rate and usage numbers to fit their situation.

The above doesn't apply if you are operating a jet pump or are throttling your submersible.

Horsepower doesn't matter if you do the math based on how much water is being pumped.

 

[Sponsor]

 

[Rshackleford]

If you strictly have irrigation pump, horsepower is less of a consideration. You start the system up and it runs and runs and runs at a consistent flow rate. In this case it is easy to calculate power or energy, its just physics.

However, in a household there will always be throttling. You take a shower and as you deplete the storage reservoir the pump will turn on. In my house the pump might continue to run while I shower. In your house it might cycle on and off several times during the shower. In both cases the pumps are moving all over the pump curve and therefore the efficiency is also all over the place. Also to play the devil’s advocate the water level in the well is changing. Again my well might drawdown 300’ and yours only 2’; this would also affect the efficiency and energy use. It is for this reason that I took the pump horsepower and length of time operated approach.

BobNH, I agree that the method you purposed would provide a good estimate of energy use and I guess all we are looking for is a good estimate. Perhaps the only good way to get a better estimate on power usage for household water systems would be to perform a study on a group of homes. The sounds like an excellent academic study and it would be useful to the consumer.

 

[Speedbump]

I'm sorry Bob Nh, I don't follow your math, but I do like the part of the 18 times more for the city water than the electric to run the pump.That's what I was after and the fact that it would cost on average $300.00 per year for normal city water usage and $16.80 for the well pump.

I have customers here that have city water and are spending more than $500.00 per month just to use in the home and water the lawn. (These folks may be a little fanatical about their grass but still, that's a little ridiculous.)

Thanks,

bob...

 

[Speedbump]

Ok Shack,

Does this mean your volunteering? I like your idea.

bob...