Let ’ s start with the union Residential Energy Efficient Property Credit. Currently, the tax credit is 26 % of the solar exponent undertaking ’ s total price. In the font of a 4,000W system ( which, when priced at around $ 3/watt represents a $ 12,000 purchase ), the 26 % citation would reduce the solar project ’ s cost by $ 3,120. The following piece of the calculation – net metering – can get building complex in some states. If you happen to live in a state where your final metered solar electricity is 100 % compensated, then that ’ s an easy calculation. All of the electricity your solar panels export will be worth precisely the lapp as what you use immediately. If you live in a state where web metered electricity exports are priced lower than the electricity that you buy from the grid, then you ’ ll indigence to estimate the dispute. This international relations and security network ’ t easy to pin down without specialize hardware in station ( like a solar inverter ). historical averages have shown that close to half of solar generation will be used instantaneously, while the other half will likely be credited to your account, offsetting future use. Multiply the 50 % that is used immediately by your full electricity rate, and the other 50 % by the net meter rate offered in your express. The sum of those two numbers represents the come of money that you will save on your electricity beak over the adjacent few decades, assuming that your country ’ s net meter agreement remains in locate.

Keep in mind that your solar power arrangement will degrade over clock time, lowering its electricity output. On modal, solar abasement rates are 1-3 % in the first year, and 0.5 % in late years. That means that by class 25, your solar system will probably be operating at 85 % of its master output . The solar control panel you buy will have a guarantee that specifically references its abasement rate and expected life. now, for our last calculation, state incentives. Each express is unlike. In Massachusetts, you get paid a bonus for each kilowatt-hour generated. In Rhode Island, you ’ re paid a fixed dollar amount, based on system size, that is disbursed immediately after the system connects to the ability power system. If you ’ ra golden enough to live in a state with incentives, you ’ re going to have to do a short homework to know the claim method to calculate the dollar come. Our guide to country incentives is a commodity starting rate to research these differences. Most contractors will provide something like the graph below, which combines all the variables likely to affect your solar system ’ s prospective vengeance period. But now that you understand the mathematics, you may want to create your own spreadsheet. After all, confidence, but verify .

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here ’ s how it works. Start with the total cost of the system, then subtract the one-off items like the federal tax citation and state incentive. following, divide by the estimated annual net-metered savings ( plus any electric potential submit incentives that we sorted out earlier ), and voila ! – that ’ s your vengeance period. Your calculations should look a short less complicated than the vengeance postpone for a Massachusetts farmer ( above ). But with a little fortune, the column on the far good – which adds up all savings, incentives, and gross – will shift from red to black sooner than you may have expected. This content is protected by copyright and may not be reused. If you want to cooperate with us and would like to reuse some of our contentedness, please reach : editors @ pv-magazine.com .