Once a month, your system sends you a report. A few numbers, maybe a
bar chart, a total in kilowatt-hours. If you’ve got a battery, there’s
probably a line about how much it charged and discharged too.

Most people skim it, see that it’s not zero, and move on. That’s fine
— nobody ever sat you down and taught you how to read the thing.

But that report is the closest thing you’ve got to a check-up on a
$30,000 investment. So let’s walk through what the numbers actually mean
— and just as important, what they don’t tell you.

Start with
kilowatt-hours (kWh) — your production total

The headline number is usually total kWh produced for the month. A
kilowatt-hour is just a unit of energy — the same unit your utility
bills you for.

On its own, it tells you the system made something. What it doesn’t
tell you is whether that something is enough. A number means nothing
without a fair comparison — which brings us to the most useful habit you
can build.

Compare
to the same month last year — not to last month

This is the single most important thing to understand about solar
data: it’s seasonal.

In Arizona, a system makes far more in May and June than it does in
December. Long days, high sun, clear skies. So if you compare June to
last December and panic that summer “dropped,” you’ve misread your own
report.

The right comparison is this June to last June. Same season, same sun
angle, roughly the same expected output. If this year is meaningfully
lower than last year for the same month — that’s a signal worth chasing
down.

Watch the shape, not just
the total

A healthy month of solar data has a shape you can recognize:
production rises through the morning, peaks around midday, eases off
toward evening, day after day after day.

Here’s what’s worth noticing:

• A sudden flat day, or a dead stretch in otherwise sunny weather.
  That’s not normal. Usually means something tripped or failed.
• A slow, steady decline over several weeks with no weather to explain
  it. Often dust and soiling. Sometimes a failing component.
• One panel or string reading way below the others, if your system
  reports down to that level. A single underperformer can quietly drag the
  whole array down.

If you’ve got a battery, it has its own shape worth a glance — it
should charge up during the day and discharge when you want it to, and
it should still show ready for backup or be offsetting Utility Demand
charges. A battery that stopped cycling, or stopped holding a charge,
won’t always announce itself. It just quietly stops doing the job you
paid it to do.

You don’t need to be an engineer to spot any of this. You just need
to actually look — and know that a clear-sky flat spot is the thing to
flag.

What the report does NOT tell
you

Here’s the honest part. Even a good monthly report has real blind
spots:

• It rarely tells you what “good” should be for your specific system,
  your roof, your shade. There’s no benchmark printed on it.
• It’s a month behind. A panel that failed on the 3rd might not show
  up as a problem you notice until the report lands weeks later. Same goes
  for a battery that quietly stopped holding its charge.
• It usually won’t diagnose the cause. It can show output dropped. It
  usually can’t tell you whether it was dust, a bad optimizer, an inverter
  fault, or just a cloudy week.

So the report is a smoke detector, not a diagnosis. It can hint that
something’s off. Figuring out what — and whether it’s costing you real
money — usually takes someone reading the detailed data sitting behind
it.

A quick monthly routine

If you want to keep an eye on things yourself, this usually takes a
few minutes:

1. Open your monitoring app on purpose, once a month.
2. Compare this month to the same month last year.
3. Scan the daily view for any flat spots or dead days in clear
   weather.
4. If you’ve got a battery, check that it’s still charging,
   discharging, and showing ready for backup or demand
   shaving/shifting.
5. If something looks off and the weather doesn’t explain it, don’t
   wait for the bill to confirm it.

When the numbers say
“get someone to look”

If your report shows a drop you can’t explain, or you’ve just never
been sure how to read it in the first place — that’s exactly the kind of
thing worth a professional set of eyes.

A $129 diagnostic brings you a certified local tech that can review
your data remotely or come out to your system if deemed needed. The
diagnostic typically covers a quick remote review and if needed the trip
to your home and the first 30 minutes on site. We pull the full
production data, check the hardware behind the numbers — panels,
inverter, battery if you’ve got one — and tell you straight whether your
system is working the way it should be working, or losing you power. If
we do come to site we typically charge our standard hourly rate after
the first 30 minutes if there’s real work to do.

We monitor and manage 500+ systems across Arizona, so we know what a
healthy system your size should be producing in any given month — the
benchmark your report leaves out.

SouthFace Solar & Electric has served metro Phoenix and the
Prescott Tri-City area since 2008. Locally owned, licensed, and happy to
work on systems we didn’t install. ROC #249187. 4.6 stars on Google.

Not sure how to read your production numbers? Call 480-405-6105 or
schedule a diagnostic — we’ll walk through what your system is actually
telling you.

📚 Part of our series on reading your solar data. Start with the overview: You Spent $30,000 on Solar. Do You Even Know If It’s Working?.