Hot-h2o-ked

Estimating the energy cost and hot water usage for Miller Farm turned out to be an involved process. In attempting to produce a reasonable estimate, we used multiple online hot water cost and energy usage resources, online manufacturer provided equipment model information, experimental data collection, and our best guesses.

We began with a list of hot water considerations:

• What fixtures use hot water at Miller Farm?
• How often are these fixtures used?
• What is the averge hot water consumption for each use?
• What is the daily peak hot water use?
• Can the current water heater accomidate the peak use (i.e. is all hot water used fully heated)?
• How much energy is needed to provide the averge daily hot water used?
• What is the monthly cost of heating water at Miller Farm?

The next logical step is data collection. This proceeded in a piecemeal fasion as we worked. Special thanks to Kate for finding the online model information for the hot water heater and to Dan for the online Washing Machine model info.

Miller Farm Water Fixtures (w/ hot water):

• (2) Showers
• (3) Bathroom Sinks
• (1) Kitchen Sink
• (1) Washing Machine

Applience Information:

• Water Heater AO Smith ProMax ECT-52
  • Element Wattage: 4500 Watts
  • R-rating: 16
  • Storage Capcity: 50 gal.
  • Tempeature Setting: 125 degrees Farenheit (as per thermastat)
  • Energy Efficiency Factor: .91
  • First Hours Rating: 58-62 gallons
  • Recovery Rate: 21 gallons by 90 degees F in one hour

• Clothes Washer Maytag model MAT12PDBAW
  • Total Average Water Used per Load: 31.5 gal.
  • Average Hot Water Used per Load: 6.5 gal.

Armed with the hard data on the water heater and the washer, we proceeded to address the question of how much hot water is used at Miller Farm. Unfortunatly, without installing a water meter on the hot water line (might not be a bad idea), the hot water usage data will be approximate at best. We began with online hot water heater sizing tables to get an idea of the average hot water use of everyday activities.

Average Hot Water Usage Sources:

• Gainesville Regional Utilities
• DOE Water Heater Fact Sheet
• DOE Consumer Guide

All three sources have different hot water use estimates for given activities (even the two tables from the same DOE department). The averages of the three tables were calculated and are as follows

Hot Water Usage Estimates from Online Sources:

• Showering: 20 gal. (only the GRU table listed their number based on a 10 min. shower at 2.5 gal./min)
• Shaving: 2 gal.
• Washing Hands and Face: 2.6 gal.
• Shampooing Hair: 4 gal.
• Hand Dishwashing: 3.6 gal. (seems low)
• Clothes Washing: 25 gal. (only GRU listed usage for various washer settings, note that this number does not corrolate to the model information)
• Food Preparation: 5 gal. (DOE listings)

founds:

• in Miller Farm shower
  • average shower temp is 106.3F
  • ~2 gallons of water are used per minute
  • ~1 gallon of cold water is used for every 4 gallons of hot water (July 10th 2006)