I found out my solar system was wired in a way that breaks Span’s monitoring features after I’d already bought the Span panel and had it installed. The Span app showed all my consumption circuits, but solar production was nowhere in the picture. A call to Span support confirmed what I’d started to suspect: my Tesla inverter was wired to the service entrance, upstream of the panel, and Span simply couldn’t see it.
I’d never heard of “load-side vs. line-side” inverter connections before that conversation. Nobody mentioned it during the solar installation, nobody mentioned it during the Span installation, and nothing in Span’s marketing materials flagged it as something to check. I learned about it the hard way.
If you have solar and you’re considering a smart panel like Span — or if you already have Span and you’re puzzled by the same missing data — this guide will walk you through how to check your wiring, what you’re looking at, and what it takes to change it.
The Two Wiring Options, Explained Simply
When a solar installer wires your grid-tied inverter to your home’s electrical system, they have two valid connection points.
Option 1: Load-side connection (into the breaker panel) The inverter output connects to a dedicated breaker inside your main panel. You’d see a breaker labeled “Solar,” “PV,” or something similar, usually toward the bottom of the panel. Power from the inverter flows through that breaker onto the panel’s main busbar, where it mixes with grid power and feeds your circuits.
Smart panels like Span monitor everything that happens at the busbar level. When solar comes in through a panel breaker, Span sees it as a power source and can track production, offset per circuit, and net flow in real time.
Option 2: Line-side connection (service entrance) The inverter output connects to the wiring between your utility meter and your main breaker — what electricians call the service entrance or supply side. This is physically upstream of the panel. Power still flows into your home and works exactly the same from a usage standpoint, but it never passes through the panel’s internal monitoring.
Span monitors circuits inside the panel. Anything that comes in before the main breaker is invisible to it. A line-side solar connection means Span has no idea solar exists.
Both are code-compliant under NEC 705. Electrically, your lights don’t care which method was used. But for smart panel monitoring purposes, they are very different.
How to Check Which Method Your Installer Used
You can figure this out yourself without any electrical knowledge beyond basic panel reading. Here’s the process.
Step 1: Look at your main breaker panel.
Find your electrical panel — usually in a garage, utility room, basement, or exterior wall. Open the cover. You’re looking at a column (or two columns) of breakers, each labeled for a circuit in your house.
Step 2: Look for a solar breaker.
Scan the breakers for anything labeled “Solar,” “Solar PV,” “Photovoltaic,” “PV,” or a similar label. It might also just say the inverter brand — “SolarEdge” or “Tesla” or “Enphase.” In panels where a load-side solar connection was used, there will be a dedicated breaker for the solar input, typically at the bottom of the panel (NEC code requires backfed breakers to be positioned near the bottom, though the exact rules depend on your panel manufacturer).
If you see a solar breaker inside the panel: you likely have a load-side connection. This is the configuration that supports smart panel monitoring. If you have Span and this breaker exists, check the Span app — solar should be visible as a source.
If you don’t see any solar-labeled breaker: your inverter is almost certainly wired to the service entrance, outside the panel. This is the configuration that makes solar invisible to Span.
Step 3: Check the service entrance area (optional, more definitive).
If you can safely view the top of the panel or the conduit coming into it, look for additional wiring that isn’t from the utility feed. A line-side connection will have a conduit from the inverter meeting the service entrance wiring above or alongside the main breaker, not inside the panel body. This requires opening the outer cover of the panel (the one with the breaker labels) and looking at where conduits enter — not touching anything inside the panel itself. If you’re not comfortable doing this, don’t. The breaker inventory in step 2 is sufficient for most homeowners.
Easier alternative: just ask your installer.
Pull out your original solar installation contract or permit paperwork and look for the term “load-side” or “line-side” connection. Or call your installer and ask: “Is my inverter connected via a breaker inside the main panel, or via a line-side tap at the service entrance?” Any competent installer can answer this immediately.
What to Ask Before Installing Solar
If you’re pre-installation and considering Span, raise this question before your installer runs a single wire.
Ask your installer: “I have a Span smart panel and want it to monitor solar production. Can you wire the inverter output to a breaker inside the panel rather than to the service entrance?”
Most installers can do this. The reasons installers default to line-side connections include: avoiding the complexity of working inside an energized panel, avoiding the NEC 120% busbar rule (more on that below), or simply force of habit because it’s what they’ve always done. When you specify load-side wiring upfront, a professional installer will accommodate the request.
Get the answer in writing, or at minimum confirm what you see when the installation is done — look for that solar breaker before the installer leaves.
The 120% rule caveat: NEC 705.12(B) limits how much solar can backfeed into a panel via a breaker. The formula is: (main breaker amps + solar breaker amps) must be ≤ 120% of the busbar rating. For a 200A panel with a 200A busbar, you can have a main breaker up to 200A plus a solar breaker up to 40A (200 × 1.2 = 240; 240 - 200 = 40). If your solar system is large enough that this math doesn’t work out, your installer may not be able to do a load-side connection without a panel upgrade. This is a legitimate constraint, not an excuse — ask them to show you the math.
Can You Rewire It After Installation?
Yes. It’s not a trivial job, but it’s a standard electrician task. What you’re paying for is:
- Disconnecting the inverter output from the service entrance connection
- Running new conduit and wiring from the inverter to a dedicated breaker inside the panel
- Installing the solar breaker inside the panel
- Inspecting and permitting the new connection (required in most jurisdictions)
The typical cost range I’ve encountered is $500 to $1,500. Variables that push toward the higher end: distance between the inverter and panel, whether conduit needs to be routed through finished walls, how full your panel is, and whether the 120% rule creates complications.
If your panel doesn’t have a free breaker slot, the electrician may need to use a tandem (slimline) breaker or address the capacity issue first. If your busbar rating is too close to the limit for a load-side solar connection, a panel upgrade is the alternative — that’s a more significant expense ($1,500-$3,000 depending on scope).
Call your original solar installer first. Depending on how the installation was scoped and whether the contract specified monitoring requirements, they may perform the rewire as a correction. Frame it as: “My smart panel can’t see solar because of the service entrance connection — can we move the inverter connection to a panel breaker?” If they push back, get a quote from an independent licensed electrician.
Questions to Ask Before Buying a Span Panel If You Have Solar
These are the exact questions I wish I’d asked before signing the Span installation contract:
1. How is my inverter currently wired — load-side (panel breaker) or line-side (service entrance)? This single question determines whether Span will see your solar production.
2. If it’s line-side, can it be rewired before Span installation? Logistically, it makes sense to fix the wiring before putting Span in, not after.
3. Does my panel have available capacity for a solar breaker under the 120% rule? If not, you need a different plan.
4. Does Span support monitoring for my inverter brand natively? Even with correct wiring, Span’s solar monitoring works by reading the inverter’s output at the panel level. Confirm with Span’s support that your specific inverter will be recognized.
5. Is there a solar breaker inside my panel right now? If yes, Span should be able to see production with minimal additional configuration.
What You Can Still Do Without Rewiring
If you already have Span and your inverter is line-side, your options short of rewiring are:
Use your inverter’s native monitoring app for production data. Tesla Solar gives you full production visibility in the Tesla app — daily, monthly, and historical. SolarEdge has its monitoring portal. Enphase has Enlighten. These pull data directly from the inverter and are unaffected by where the output is wired.
Track net usage manually. Span shows total consumption. Your inverter app shows total production. Production minus consumption tells you whether you’re net exporting or net importing at any moment. It’s two apps instead of one, but all the data is there.
If you have a utility smart meter, some utilities offer interval data download (usually 15-minute increments) that shows net grid usage. Combined with production data from your inverter app, this gives you a reasonably complete picture — just not inside Span.
The Bigger Takeaway
The wiring question is something that falls through the cracks during solar and smart panel installations because the people doing each job are focused on their piece, not the system as a whole. Your solar installer knows about inverter connections and production. Your panel electrician knows about circuit monitoring. Nobody is automatically thinking about how the two interact until after you notice the solar data is missing.
Asking one specific question — “Where exactly does the inverter output connect: to a breaker inside my panel, or to the service entrance?” — would have saved me the frustration of discovering the blind spot after the fact. Ask it before either installation, and you’ll have the information you need to make the right choice.