Is Your House Suitable for Solar?
For most homes in Southern California, there are really only four characteristics that could make solar impractical. Still, it's worth starting by checking these four, because if your house suffers from any of these solar handicaps, you should know at the beginning of your shopping process.
Depending on the house and the severity of its solar handicap, most of these problems are solvable. However, they will either add to the costs of a solar-PV (photo-voltaic) system or subtract from what it can save you. How much can only be determined through a site inspection from a thoroughly qualified installer.
But for most homeowners who get their electricity from SCE, none of these handicaps will be likely to have a significant economic effect on your overall solar savings. Here are the four characteristics:
(All the calculations below are from PV Watts, the highly respected NREL calculator.*)
Depending on the house and the severity of its solar handicap, most of these problems are solvable. However, they will either add to the costs of a solar-PV (photo-voltaic) system or subtract from what it can save you. How much can only be determined through a site inspection from a thoroughly qualified installer.
But for most homeowners who get their electricity from SCE, none of these handicaps will be likely to have a significant economic effect on your overall solar savings. Here are the four characteristics:
- Roof space suitable for the panels (often called the "array")
- Solar-panel facing direction (azimuth)
- Solar-panel shading
- Roof condition
(All the calculations below are from PV Watts, the highly respected NREL calculator.*)
Roof Space Suitable for Solar Panels
How much roof space do you have for a solar panels? For example, a typical house might need 22 high-efficiency panels occupying 386 sq.ft. or 82 low-efficiency panels occupying 1,140 sq.ft. The low-efficiency panels would take up almost 3 times as much space. Adding space for clearance and walkway around the sides of the system, this low-efficiency system would be at least 39 feet long and 38 feet wide, free of chimneys and vents. Your roof might not be big enough.
Therefore, if you're short of suitable roof space, the first decision to make is to get efficient panels. That saves quite a bit more money than using less-efficient, cheaper panels and mounting some of them on less-desirable roof surfaces, which decreases their output. It also leaves room for possible future expansion if, say you expand your home or get an
electric car.
If even high efficiency panels won't fit, you can mount the system on multiple roof surfaces. If still more are needed, they can be ground-mounted. As a last resort, you can settle for a system that produces less than 100% of your electricity needs, which is still worthwhile. So, one way or another, lack of suitable space is usually manageable.
Therefore, if you're short of suitable roof space, the first decision to make is to get efficient panels. That saves quite a bit more money than using less-efficient, cheaper panels and mounting some of them on less-desirable roof surfaces, which decreases their output. It also leaves room for possible future expansion if, say you expand your home or get an
electric car.
If even high efficiency panels won't fit, you can mount the system on multiple roof surfaces. If still more are needed, they can be ground-mounted. As a last resort, you can settle for a system that produces less than 100% of your electricity needs, which is still worthwhile. So, one way or another, lack of suitable space is usually manageable.
Solar-Panel Facing Direction (Azimuth)
Although arrays that face roughly south produce the most energy, any direction other than within 45º of due north may work just fine in Southern California. An array facing between 160º and 210° outputs almost as much as one facing 180° (due south). Outside this range, output declines by about 1.5% per 10° of azimuth in Southern California.
For example, an array facing 270° (due west) would output about 10% less than one facing due south. To offset this facing, you would just get an array that is 11% larger. That would probably increase system cost by less than 10%, and not lower your 20-year savings much.
For example, an array facing 270° (due west) would output about 10% less than one facing due south. To offset this facing, you would just get an array that is 11% larger. That would probably increase system cost by less than 10%, and not lower your 20-year savings much.
Solar-Panel Shading
Any shading of the PV panels definitely cuts output. But this doesn't mean solar never makes sense unless the panels are 100% shade-free. The average percentage lost of annual energy is about equal to the percentage of annual shading, but this can be reduced for partial shade by using specially-designed string inverters or micro inverters. And even what is called "severe shading" (25% or more) will rarely reduce savings to the point that solar isn't worthwhile.
You can try this out for yourself on our Solar Panel Cost & Savings Calculator. Just enter your monthly average bill (plus your annual usage, if you can find it) and you will immediately see your costs and savings in the short, medium, and long term. Then you can adjust those numbers for your shading by following the brief instructions below the results.
So unless you have extensive shading of all the suitable roof surfaces and ground-mount areas, and you can't or don't want to prune it enough to reduce shading to below 50%, shading will probably be manageable.
You can try this out for yourself on our Solar Panel Cost & Savings Calculator. Just enter your monthly average bill (plus your annual usage, if you can find it) and you will immediately see your costs and savings in the short, medium, and long term. Then you can adjust those numbers for your shading by following the brief instructions below the results.
So unless you have extensive shading of all the suitable roof surfaces and ground-mount areas, and you can't or don't want to prune it enough to reduce shading to below 50%, shading will probably be manageable.
Roof Condition
Solar panels can be mounted on nearly any type of roof, although some types are more expensive to install on than others.
If your roof has seen better days, you can replace just the part of it that will be under the solar array. This will add a few thousand dollars to the cost of the system, but is more cost-effective than later removing and reinstalling the system to repair or replace that part of the roof in the future. Your savings over time will remain about the same, since you'd soon have expenses for that part of the roof anyway.
It does increase the importance of having a fully qualified installer, however, to make sure your roofing work is done properly. Of course, you can instead replace the whole roof while the solar is being installed, possibly saving some money by doing both at the same time.
If your roof has seen better days, you can replace just the part of it that will be under the solar array. This will add a few thousand dollars to the cost of the system, but is more cost-effective than later removing and reinstalling the system to repair or replace that part of the roof in the future. Your savings over time will remain about the same, since you'd soon have expenses for that part of the roof anyway.
It does increase the importance of having a fully qualified installer, however, to make sure your roofing work is done properly. Of course, you can instead replace the whole roof while the solar is being installed, possibly saving some money by doing both at the same time.
The Decision About the Suitability of Your House for Solar
The decision to make for this issue is simply whether there's anything about your house that makes clearly unsuitable for solar, and there's nothing you can or want to do about it. If the answer is yes, there's obviously no need to continue. For most homeowners who are customers of SCE, the answer is that the house is probably suitable, even if not ideal.
For a complete guide that walks you quickly through all the factors to consider to decide whether solar makes sense for you, please see our Solar Buying Guide - Step 1.
*National Renewable Energy Laboratory (NREL), “PV Watts Calculator,” updated 4/22/16.
For a complete guide that walks you quickly through all the factors to consider to decide whether solar makes sense for you, please see our Solar Buying Guide - Step 1.
*National Renewable Energy Laboratory (NREL), “PV Watts Calculator,” updated 4/22/16.
