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How Much Can I Save With Solar?

Almost every family can benefit from solar, no matter how large or small their house, or how old. We can help you determine how much solar electricity can be produced on your roof.

How Much Electricity Does Your Family Use?

While every house and family are different, typical electric consumption for a single family house built in Central Florida during the past 15 years is 7 to 9 kilowatt-hours per square foot of air conditioned living area per year.

For example, a house built to the current building code with 2,400 square feet of living area, newer energy efficient appliances, a 3 ton 14 SEER/8 HSPF heat pump air conditioner and three occupants should use about 8 kilowatt-hours of electricity per year. 2,400 square feet × 8 kilowatt-hours = 19,200 kilowatt-hours a year.

What are some major factors that can change annual electricity consumption, compared to the example above?

  • Family size.  The primary impact of family size is in the amount of electricity used for water heating. For an all-electric home in North Florida, each person more or less than the three assumed in the example above will change the amount of electricity used for water heating by about 1,376 kilowatt-hours a year.1
  • Swimming pool.  A 1-1/2 horsepower swimming pool pump running an average of 6.7 hours a day (4 hours a day from November to February and 8 hours a day the rest of the year) will add 2,733 kilowatt-hours a year.
  • Landscape lighting.  Six 100-watt outdoor floodlights for landscape lighting, turned on for 10 hours each night, will add 2,190 kilowatt-hours a year.
  • Second refrigerator.  A second refrigerator can add between 600 and 1,500 kilowatt-hours a year, depending upon the unit’s size and age.

Older homes with less attic insulation and less efficient air conditioning systems use a lot more electricity than newer homes. If the house described in the example above was built in the 1970s and had a 10 SEER air conditioning system, we would expect the annual electricity consumption to increase to at least 10 kilowatt-hours per square foot per year, just based upon the air conditioning system alone. Poor insulation and leaky air conditioning ducts could make the situation even worse.

Check your electric bills.  Compare the information above to the number of kilowatt-hours you are actually using by looking at your electric bills for the past year. To make the job easier, most electric utility company websites now have a billing history feature that lets you see your monthly power consumption for the previous 12 to 24 months.

So How Many Solar Panels Does It Take?

The goal of a solar power system is to achieve net zero annual power consumption. Net zero means your solar power system’s annual electricity production equals your annual household electricity consumption. In other words, Solar kilowatt-hours produced − household kilowatt-hours consumed = 0.

An easy rule of thumb for how large your solar power system must be to achieve net zero in Central Florida is to divide your annual household electricity consumption by 1.5.

For example, if your annual electricity consumption for the last 12 months was
19,200 kilowatt-hours, you would need 19,200 kWh ÷ 1.5  =  a 12.8 kW system to reach net zero

How many panels is that? Well, for one of our premium solar panels with a nameplate power output of 320 watts, you would need 12.8 kilowatts × 1,000 watts/kilowatt ÷ 320 watts = 40 panels.

And how much roof area do 40 panels cover? A premium efficiency 320 watt solar panel has a sun-facing surface area of about 17.6 square feet. So you would need about 40 panels × 17.6 square feet per panel = 704 square feet of roof area to get to net zero energy consumption for a house using 19,200 kilowatt-hours of electricity per year. Note that this is for solar panels installed on a south-facing roof. For an east- or west-facing roof, the required roof area would increase to 819 and 809 square feet, respectively.

Important Note. These performance figures are for premium solar panels with an efficiency of 19% or better at standard testing conditions. Lower quality solar panels, or solar panels manufactured and sold before 2016, may have efficiencies in the 14% to 16% range and require more roof area to produce the same results.

A heat pump water heater can reduce the number of solar panels you need to get to net zero.  A hybrid electric heat pump water heater (HPWH) can reduce the number of solar panels needed by 0.64 kilowatts of system size per household occupant. For our example 320 watt solar panel, we can reduce the net zero system size by two solar panels for each family member. So if the example house above had three occupants, we could reduce the 40 panel system to 34 panels—by replacing a conventional electric water heater with a HPWH—and still get to net zero.

The Key Point to Understand

While not every Florida house has enough usable roof area to achieve net zero, most have enough usable roof area to get rid of a huge chunk of the annual electric bill with solar power. For most Florida homes, at least 70% of the annual electric bill can be eliminated with solar.

We Can Custom Design a System Just For You

Our solar power system design software uses satellite and aerial imagery to custom design solar panel roof layouts. But our solar design experts are also critical to getting the best layout. Each roof is unique, and automated roof layout applications of the sort you may find online aren’t very good at adjusting for hips and valleys on roofs, tree shading, or roof obstructions like plumbing and clothes dryer exhaust vents, attic fans, dormers and fireplace chimneys. The automated online programs also aren’t very good at determining the most attractive location and layout for your house.

There is absolutely no cost or obligation for using our custom solar roof layout design services.

Take the Next Step

Let us determine how many solar panels can be attractively and effectively installed on your roof. At no cost to you. We’ll also be happy to sit down with you at your convenience, to explore your home energy use and answer all your questions. The first step is to complete and send the short form below.

Get Your Free Solar Quote

Get your FREE quote by completing this brief form. We’ll estimate your annual electricity consumption, use satellite imagery to design a custom solar power system for your roof, then get in touch with you to arrange a convenient time to review your electrical service panel location and capacity, explain your quote and answer all your questions. There’s absolutely no obligation.

Notes

  1. Household hot water consumption usually averages about 20 gallons per person per day. Average groundwater temperature for North Florida is 71°F and electric resistance heating element efficiency is 90%. We assume a water heater thermostat setting of 130°F and 15% added energy to offset standby heat loss from the hot water storage tank. Active households with heavy laundry use, more automatic dishwasher loads, and/or frequent long showers for hair shampooing can average as much as 25 to 28 gallons per person per day. A 130°F minimum water heater thermostat setting is strongly recommended to prevent legionella bacteria formation in the water heater tank. An anti-scald valve should be installed on the the water heater “hot water out” line to the house plumbing.