Heating water is more expensive than you might think.
img src EDIT_IMAGES_label-preview.jpg width 150 height 200 alt Typical Electric Water Heater Energy Guide
Many homeowners are surprised to learn that water heating is the second biggest yearly energy use in a typical Florida home, after the central air conditioning system.
Floridians see their electric bills go through the roof during July, August and September and don’t need to be told that air conditioning uses a lot of electricity. But while you may use hardly any air conditioning during March, April and November, those two big 4,500-watt heating elements in your water heater are burning away every day of the year. At today’s typical Florida electric rates (including fuel surcharges and utility taxes) of around 12—14 cents per kilowatt hour, water heating can easily cost $800 to $1,200 each year for a three to five person household. In Central Florida, a solar water heater can substantially eliminate this portion of your electric bill.
Solar energy is clean and free.
You could travel 12,000 miles on the energy needed to heat your water with electricity for one year. Yes, that’s right: A mid-sized car driven 12,000 miles, averaging 22 miles per gallon, and an electric water heater supplying 80 gallons of heated water per day each require about 11 barrels of oil over the course of a year. And over the solar system’s 30-year expected life, you will eliminate about 37,000 pounds of powerplant carbon dioxide emissions.
Propane and natural gas prices have doubled and tripled over the last few years. Electricity rates are up by as much as 50 percent. You may not be able to escape the high price of gasoline, but you can take a big chunk out of your home utility bills!
Other benefits include:
- Tax-free savings pay for system within two to four years
- Exempt from Florida state sales tax
- $500 State solar rebate
- Plus $450 Progress Energy rebate
- Plus a 30 percent Federal income tax credit
- Protects you against future utility rate increases
- Reduces your dependence on fossil fuels and foreign oil
- 30-year equipment life
- Increases your property value
- Clean and renewable energy source
- Low to zero maintenance cost
Using the sun to heat water is nothing new
img src EDIT_IMAGES_day-night-solar-heater.jpg width 300 height 245 title Day and Night Solar Water Heater Illustration
Back in the early 1900s, solar waters were common in California and Florida. Thousands of “Day & Night” solar water heating systems (shown in the illustration at right) were installed in Los Angeles during the early 1900s, before the discovery of vast natural gas fields in the Los Angeles basin.
This 1918 advertisement shows a typical residential “Day & Night” model solar water heating installation. This system had a tank in the attic, at a point higher than the solar collector. The coldest water from the storage tank sank down into the bottom of the solar collector, where it was heated. The heated water flowed up through the collector and back into the storage tank by natural convection. This natural circulation process, which requires no circulating pump, is called thermosyphoning.
As the price of electricity dropped during the second half of the 20th century and electric power became more widely available, people started using it to heat their hot water. However, skyrocketing electric rates are making solar water heating very attractive once again. Today’s solar water heating systems are far more efficient than the systems of the late 1800s and early 1900s.
Floridians see their electric bills go through the roof during July, August and September and don’t need to be told that air conditioning uses a lot of electricity. On the other hand, while you may use hardly any air conditioning during March, April and November, that big 3,500 to 4,500-watt heating element in your water heater is burning away every day of the year. (Some high-recovery models have two heating elements.) At today’s electric rates (including fuel surcharges and utility taxes) of around 14 to 15 cents per kilowatt hour, water heating can easily cost $800 to $1,200 each year for a three to five person household. In Florida, a solar water heater can almost completely eliminate this portion of your electric bill.
Solar water heaters offer many extra benefits.
Naturally, switching to solar water heating means going green in a big way. but you might also be surprised to learn that solar water heating gives you benefits that improve upon conventional electric or gas water heaters:
- More hot water. Most electric water heaters hold enough hot water for about 20 minutes of continuous use. Then the electric element reheats another tankful. You can run out of hot water if two people are showering at the same time, or if you take a shower after the clothes washer or dishwasher have been running. Solar storage tanks are sized to store an entire 24 hour’s worth of hot water because there is no sunshine at night. But this gives you the added benefit that you are less likely to run out of hot water when there are multiple uses at the same time.
- Hotter water. The water delivered by a solar collector panel can be hotter than the thermostat setting on your electric water heater. This means you will have hotter water for the dishwasher and for showers if you you want it. (A mixing valve on the storage tank protects you against scalding.)
- Plenty of hot water during emergencies. With a passive solar water heater, or a system with a solar-powered circulating pump, you will have your customary supply of hot water even during electric power outages. This is an important feature even if you have a standby power generator, because standby generators are not typically sized to handle the power consumption (4,500 to 9,000 watts) of a conventional electric water heater.
Which home energy uses are the most expensive?
The pie chart above shows where the money goes in a typical Florida family’s annual electric bill. The chart is based upon an electric power consumption study by the U.S. Department of Energy’s Lawrence Berkeley National Laboratory. The “typical” Florida household and energy use pattern shown above is based upon these factors:
- Florida home built in 1990 with 2,400 square feet of living area
- 9.5 SEER air conditioner with thermostat set at 81°F during day and 78°F at night
- cold weather thermostat setting of 64°F during day and 68°F at night
- two adults and two children in household
- 80 gallons of hot water per day
- 14 cents per kilowatt-hour electric cost (including fuel surcharge and utility taxes)
Is your hot water use average?
Actually, an active American family of four is probably closer to 100 gallons per average day and just over $1,000 per year at 14 cents per kilowatt-hour. Here is an example that shows how a four-person household can easily use 100 gallons of hot water per day:
- three people take an eight-minute shower every day; the fourth showers 12 minutes for a longer shampoo and rinse: (4 showers x 2 gallons per minute x 8 minutes x 80% hot water) + (1 shower x 2 gallons per minute x 4 extra minutes x 80% hot water) = 57 gallons per day
- five loads of laundry per week; for example, one load each of whites, darks, towels, sheets, and blue jeans: 5 clotheswasher loads x 32 gallons per load / 7 days = 23 gallons per average day
- At least four face and hand washings x 1 gallon per minute x 4 minutes each x 80% hot water = 13 gallons per day
- few sit-down meals because everyone is constantly on the run, so the automatic dishwasher is only run twice per week: 2 automatic dishwasher loads x 14 gallons per load / 7 days = 4 gallons per average day
- One shave x 1 gallon per minute x 2 minutes = 2 gallons per day
- Hand-rinse dishes once a day x 1 gallon per minute = 1 gallon per day
If you happen to have small children, each bath averages about three gallons less hot water than a shower. However, if you happen to have two active teenagers, each taking two showers a day and perhaps creating two or three extra loads of laundry per week, the total can easily jump to over 120 gallons per day.
Heating 120 gallons per day from 72°F to 140°F, at 15 cents per kilowatt-hour, costs about $115 per month.
Because incoming solar radiation—called insolation—is often interrupted by cloudy or rainy weather and fluctuates in intensity with seasonal changes in the sun’s position in the sky, solar water heating systems are usually sized to collect and store an entire 24 hours or more worth of energy to meet hot water demand. A modern solar water heating system storage tank will usually have a backup electric heating element to meet unusual peaks in hot water use or extended periods of very cloudy or rainy weather.
While solar thermal water heating systems are viewed as “pre-heating” systems in many regions of North America, the sunbelt states enjoy solar insolation levels that allow solar potable water heating systems to economically meet 85 to 90 percent of the annual hot water need.
Hot water facts
Energy guzzler. Water heating is the second largest energy user in the average home. Only central air conditioning uses more energy.
History. Miami had 60,000 solar water heaters during the 1940s. What happened? Really cheap electricity and utility company “All-Electric Living” promotions. Some utility companies gave away electric water heaters, just to get homeowners to switch from natural gas.
Carbon bigfoot. Everyone is concerned about their carbon “footprint” these days. Well, a home water heater’s carbon footprint is a whopper.
How big, you ask? Using electricity from an electric utility powerplant to heat 80 gallons of water from 72°F to 140°F each day for one year sends almost four tons of carbon dioxide1 emissions into Earth’s atmosphere. Yes, really.
Solar water heaters are a proven green strategy and should be on every rooftop.
- According to the U.S. Energy Information Administration, the average U.S. electric utility powerplant sends about 1.36 pounds of carbon dioxide emissions into the atmosphere for every kilowatt-hour (kWh) of electricity delivered to an end-use. If an average family of four uses 80 gallons of hot water per day, this requires 5,581 kWh per year, assuming a temperature rise of 68 degrees (from 72°F to 140°F) and a 15 percent added energy factor for maintaining the temperature of stored hot water. 5,581 kWh x 1.36 pounds of carbon dioxide per kWh = 7,590 pounds. 7,590 pounds / 2,000 pounds per ton = 3.8 tons of atmospheric carbon dioxide emissions per year.