By Mark Eckert, PE
With solar panels getting more efficient and less expensive every year, you may be considering installing solar panels on your home. There can be many benefits to a household solar array, like reduced utility bills and consistent energy prices. However, solar systems also present what can be a dizzying array of factors that can cause confusion and affect the payback time. We will concentrate on seven of the most important factors that should be investigated when considering a residential solar system.
1. What are your goals for installing a solar array?
Whether it be to go “off grid”, to reduce your carbon footprint, or just to save money on your electric bill, you must determine why you want a solar array in the first place. Once the goals have been laid out, the array sizing can begin, and potential locations can be identified. Typically, I recommend eliminating or minimizing your electric bill annually, so your net electric bill is zero. To do this we look at each month’s electric usage, and the available property to determine the size of the solar array for this breakeven point.
2. Understand net-metering in your state.
Net-metering is set up under state laws to govern how the billing between the utilities and customers operate. This allows the homeowner to get an electric meter that operates in both directions so that during the day, when the array is generating more electricity than the residence is using, the homeowner gets credits from the utility. When the array is generating more, the homeowner is effectively selling electricity to the grid, and when the array isn’t generating, the homeowner buys from the grid. Net-metering allows the homeowner to store energy “in the grid”. The trick is sizing the array large enough to offset the normal electric bill but not so large that you are generating excess electricity annually. You want the annual net to be close to zero in order to maximize your return on investment and minimize array installation costs.
3. Check out your utility’s “price to compare” for net-metering.
The price to compare is the price that the utility pays you for the excess generation your solar array produces. This price ends up falling near the generation rate on your utility bill, since utility companies do not pay you the transmission and distribution portions. Say your utility bill works out to be $0.12/kWh, the price to compare may only be $0.08/kWh. If you oversize the array, then you are only getting paid the price to compare, not offsetting the power you are consuming. When the price to compare is greater than your cost of generation, then it makes sense to oversize. This may lead to issues with income taxes and possible utility restrictions.
4. Investigate Permitting and Inspection
As with any building project, building permits may be required, so it is best to check with your municipality, and possibly county. Some areas may not have any experience or guidance for solar installations, so it is always best to work with a contractor that knows the building and electrical codes pertinent to your location. A final inspection of the installation may need to be conducted by your local government, and possibly the interconnected utility, before the system is turned on. Engaging the services of an experienced solar contractor/designer can alleviate some of the delays involved with permitting.
5. Location, Location, Location
Potential locations for solar arrays may seem to be everywhere, but there are a few caveats that need to be checked out. With any solar system, shading must be considered, and minimized as much as possible. Locating the array in an area that eliminates shading may be impossible with the available property. Sometimes the shading can be so extreme that solar photovoltaic (electric) may not be practical, but solar thermal to produce hot water may. Engaging the services of an engineer that understands solar shading can go a long way in maximizing the productivity of your array while keeping costs under control. Modelling software exists for exactly this reason and can be used to drive better payback periods on the system.
6. Roof mount, ground mount, or pole mount
Unless you have a property with extra space, a ground or pole mount may not be a good fit. If you have plenty of roof space that faces south with very little shading, then you are in luck. The metal framework on the market, called racking, has been designed to hold the panels slightly above your roofing. This space between the panels and roof allows air to travel through and cool the panels, which prevents efficiency degradation. Solar panels can be removed when it is time to replace the roof, but it adds to the cost, so it is best to ensure the roof is new(er) before installing an array.
7. Check for tax credits.
Tax credits and incentives may be getting far and few between as solar prices decline, but some are still available. Usually, there is a federal tax credit for many energy or energy efficiency projects for homeowners. Solar Renewable Energy Credits (SRECs) are another source of income from panels, but the price can vary significantly. Incentives are not a necessity when installing a solar array, but they do help with up-front costs. Working with a reputable solar designer/installer who understands the current credit market is important as any credits can make the payback time, and therefore the project, more attractive. Go to www.dsireusa.org and check out your state’s incentives.
If you are considering a solar array for your home, begin by thinking about the reasons you would want solar. Then pull together a couple of years of electric bills, check out your property and roof, and then contact someone in the solar field. Usually a quick energy audit and a simple layout can shed light on the feasibility, and payback time, of solar for your location. Just remember the basics of designing a system outlined above. When I design a system, my goal is match up the client’s goals with the best system that will maximize the return on the investment.
Mark Eckert is a Project Engineer at JHA Companies and works on an array of projects ranging from water & wastewater to energy development. He brings experience from the energy generation and transportation sectors, and his degree in Alternative Energy Engineering provides a background in multiple sources of energy. Mark lives in Northeastern Pennsylvania with his wife April, three dogs, and April’s menagerie of reptiles from her biology classroom.