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What's it going to cost me to go solar?
NOTE: These steps are designed for systems tied to a power grid. For off-grid systems, roll up an estimated watt-hours calculation using a system sizing worksheet (available from Gaiam Real Goods Solar).
To estimate the cost of a solar power system for your home:
1. Find your daily utility usage by dividing the kilowatt-hours (kWh) used on an average month’s utility bill by 30.
2. Divide that number by 5 (the average number of peak sun hours in the U.S.) and multiply by 1.43 to account for system losses. This is the size of the solar system, in kilowatts, that you will need to take care of 100% of your electrical needs.
3. Multiply that number by $9,000 ($9/watt installed) for a good ballpark estimate of the gross installed cost.
1. Can state rebate incentives take a chunk out of the cost estimate I come up with here? Go to www.dsireusa.org to find out what grants or incentives are available in your state. For instance, in California, you can multiply your gross installed cost by 0.65 to account for rebates and tax credits. In New York or New Jersey, multiply by 0.5.
2. What ongoing savings can I expect? Whatever you’re paying your utility company for electricity now could change to $0 (service charges will still apply), depending on your system design, how much sun you get where you live, and what percentage of your total electricity usage is offset by your solar system's output. Many Gaiam Real Goods Solar customers have seen in the neighborhood of 75% savings off their previous electric bills.
3. How can I shave dollars off the cost of the solar system I'll need? Your first step should be reducing your load — the amount of power your household uses. Conservation comes first, for more reasons than one. In the case of off-grid solar, it pays for itself by a factor of five. That is, every dollar you spend to conserve will save you $5 in system costs. The cost to purchase an off-the-grid solar system is about $3.20 per watt or $3,200 per kWh (kilowatt-hour). At $3.20/kWh, a solar electric system for an off-grid American home with average electricity usage of 18 kWh would be $58,000 before rebates, incentives and tax credits.
But by reducing the load your solar system has to produce, you can reduce your cost to solarize and do your part for resource conservation at the same time. Let's take light bulbs as an example. If you replace 30 of the 60-watt incandescent bulbs in your home with more efficient compact fluorescent bulbs that run for an average of five hours per day and use only 15 watts each (but put out as much light as a 60-watt incandescent), you’ll save 6,750 watts per day (45 watts each x 30 bulbs x 5 hours), which equates to a $21,600 savings on your solar system.
You can also lighten your power load in many other ways in an existing home, including:
• Add insulation and/or heat barrier in your attic
• Choose more energy efficient appliances
• Replace or repair drafty windows
• Be diligent about maintaining calking and seals around windows and doors
• Dry laundry on a line outside vs. in an electric dryer whenever possible.
The point is: always conserve first and build your renewable energy system second. The money you save by shrinking your solar-system output requirements will more than pay for longer-lasting, energy-efficient appliances!