Every solar quote in this market includes a production estimate. Almost none of them are ever checked against what the system actually did, and most homeowners have no idea how to check.
This is what a solar system in Camas realistically produces across a year, how to estimate it for your own roof before you buy, and how to tell whether the one you already own is underperforming.
Why local numbers matter more than national ones
National solar calculators are built on averages that include Arizona. Camas sits in a specific climate with a specific problem: a genuinely excellent summer and a genuinely poor November through January. Annual totals in the Pacific Northwest are respectable. The monthly distribution is dramatic, and that distribution is what confuses people in their first winter.
How to estimate output for your roof
There is no single figure that fits every roof — system size, orientation and shading each move the number. Here is how to get a real one for your own address, rather than a marketing average.
The most reliable way to estimate a specific roof is NREL’s PVWatts calculator, which is free, public, and built on decades of measured weather data for this region rather than on a national average. Put in your address, your array size, your tilt and your azimuth and it will give you a monthly and annual figure. It is the same underlying dataset most installers model from.
Two things to know before you trust the output. PVWatts does not know about your trees — it assumes an unshaded array, so on a typical Camas lot with mature conifers the real number will be lower, sometimes considerably. And it uses a default system loss figure that a real design may beat or miss.
The better question to ask an installer is not “how much will it produce” but “what did you model, what shading did you account for, and what did you assume for losses?” Two quotes for the same roof can differ by a fifth purely on assumptions.
What orientation actually costs you
South is best. That is not news. The useful question is how much you give up when south is not available, because a lot of Camas roofs are not oriented conveniently and the honest answer decides whether a project is worth doing at all.
South is best, and that is not news. The useful part is what you give up when south is not available, because plenty of Camas roofs are not oriented conveniently and the answer decides whether a project is worth doing at all.
- South — the benchmark. Maximum annual output for a given array size.
- South-east and south-west — a modest reduction. Rarely enough to change a decision.
- West — less overall, but produced later in the day, which lines up better with when most households actually use power.
- East — less overall, weighted to the morning.
- North — generally not worth doing on a pitched roof in this latitude.
Two things we can say without any caveat. An east-and-west split array is often a better outcome than forcing everything onto a small south face, because the total usable roof area goes up. And on a shaded lot, the orientation question matters far less than the shading question — fix that first.
Two things we can say without any data caveat. A west-facing array produces less overall but produces it later in the day, which lines up better with when most households actually use power. And an east-and-west split array is often a better outcome than forcing everything onto a small south face, because the total usable roof area goes up.
The monthly shape of a Camas solar year
If you take one thing from this page, take this: your system will produce several times more in July than in December, and that is normal and expected rather than a fault. Net metering exists precisely because of this shape. Summer surplus is banked as credit and drawn down in winter.
The shape is dramatic and it is normal. A system here will produce several times more in July than in December. That is a function of daylight hours and sun angle at this latitude, not a fault, and not something a better panel fixes.
Net metering exists precisely because of this shape. Your summer surplus is banked as credit and drawn down through the winter, which is why annual totals matter and monthly ones mostly do not. The practical consequence is that a system sized against your annual usage will feel wildly overproductive in July and wildly underproductive in December, and still be sized correctly.
Checking your system against its estimate
The comparison that matters most is not whether the numbers are big, but whether they matched what was promised. A modelled estimate that consistently comes in above reality is a sales tool, not an engineering one.
This is the comparison worth making, and you can make it yourself. Find the production estimate in your original proposal — it should be there as an annual kWh figure — and compare it against a full twelve months from your monitoring app.
Compare full years, not months, and compare the same month against the same month in a previous year rather than against last month. A single weak August tells you about wildfire smoke, not about your system.
If your actual output is coming in meaningfully below the modelled estimate year after year, that is worth raising with whoever installed it. A modelled estimate that consistently overshoots reality is a sales tool rather than an engineering one, and you are entitled to ask which assumptions produced it.
What makes a real system underperform its model
- Tree growth. A shade study is accurate the day it is taken; Douglas firs do not stop.
- Soiling in the dry months, then a moss and needle problem in the wet ones, particularly on low-pitch roofs under trees.
- Wildfire smoke, which has measurably reduced late-summer output in this region in recent years.
- Snow cover, which is brief at Camas elevations but not zero.
- An inverter or optimiser fault that nobody noticed, which is the argument for actually looking at your monitoring app.
How much solar power can you actually get in Camas, WA?
Enough to make solar work financially. The Pacific Northwest has a strong summer that offsets a weak winter, annual totals matter far more than any single month, and net metering is what lets summer surplus cover winter use.
Does solar work in the Pacific Northwest with all the rain?
Yes. Panels produce on overcast days at reduced output, and cool temperatures actually improve panel efficiency. Long summer daylight hours at this latitude do more for annual production than rainfall does against it.
Do I need a south-facing roof?
No, but orientation changes the economics. West and east-facing arrays produce less per installed kW than south, and the right response is usually to size the system for the roof you have rather than to skip solar entirely.
Why does my system produce so little in December?
Short days, a low sun angle and heavy cloud. A large summer-to-winter swing is normal in this climate and is exactly what net metering is designed to smooth out across the year.
How do I know if my system is underperforming?
Compare against the same month in a previous year rather than against last month, and check your monitoring for a single panel or string that has dropped relative to the others. Shading from tree growth is the most common gradual cause.
Do solar panels lose output over time?
Yes, slowly. Modern panels are typically warranted to retain the large majority of their rated output after 25 years, and the annual decline is small enough that seasonal variation dwarfs it.
Want a production estimate for your roof built on local data rather than a national average? Call us at 360-313-7190 or request a free quote.
