I sell solar stuff for a living (Portable Sun), but I'm not here to sell you anything. I’m just tired of seeing the same avoidable disasters.

I've been doing this for a while now and I swear some of these mistakes happen on repeat. Like, weekly. And they're not dumb people, I've seen engineers make some of these. It's just stuff you don't know until you know.

Figured I'd dump the big ones here so maybe someone avoids a $2k lesson.

Frying your inverter on a cold day

This one is so preventable.

People calculate their string voltage using Vmp (voltage at max power) from the spec sheet. But your inverter sees Voc (open circuit voltage) which is higher. AND voltage goes up when it's cold.

Had a guy call me last winter absolutely devastated. 10 panels, 49V Voc each. Single string. His inverter max was 500V so he figured he was golden with 490V. Nope. First real cold snap, voltage spiked past 540V. Cooked the inverter. That's a $2,400 mistake because he didn't account for temperature.

Just use a string sizing calculator and put in your actual coldest temps, not the 77°F "standard test conditions" on the spec sheet.

Cheaping out on wire gauge

Wire is expensive, I get it. But voltage drop is real, and ignoring heat will absolutely kill your system.

This usually bites guys doing low-voltage/high-current runs, or people who forget that wires get much hotter inside conduits.

Had a guy run 10 AWG about 150 feet from a parallel 48V ground mount to his charge controller. He was pushing about 30 Amps. 10 AWG is technically "rated" for 30A in perfect conditions, so he thought he was fine.

First problem: Voltage drop. 300 feet of round-trip 10 AWG wire has about 0.3 Ohms of resistance. Pushing 30A through that means he’s losing roughly 270 Watts to heat I²R. On a 1,800W array, that's a massive 15% drop. Almost an entire panel's worth of power just gone, every sunny hour of every day.

Second problem: Ampacity derating. Wires in a hot conduit sitting in the sun or crammed together lose their ability to shed heat. That 10 AWG wire wasn't actually safe for 30A anymore once it was baking in a PVC pipe outside.

Would've cost him a couple hundred bucks more to run proper 6-8 AWG. It would have cut that power loss down substantially and kept the wires running safely within spec.

When sizing wire, don't just look at a basic ampacity chart. You have to run the voltage drop math for your specific setup, and you have to derate the wires based on ambient temps and conduit fill. 3% max voltage drop is the goal, but safely handling the heat is the absolute requirement.

The rapid shutdown thing

This one happens often.

Someone finishes their roof mount install, calls for inspection, and fails because they didn't know about NEC rapid shutdown requirements. Now they're buying MLPEs or a rapid shutdown kit AND getting back on the roof to install it all.

One customer spent an extra $2k+ and probably around three weekends fixing this, just because he didn't check local code requirements first.

Not every jurisdiction requires it. Some have exemptions for ground mounts. But check BEFORE you order, not when the inspector comes.

Battery compatibility assumptions

"It says 48V, my inverter is 48V, should work right?"

No, because 48V nominal doesn't mean the same thing across brands. Charge profiles are different. Communication protocols are different. 

Had a customer buy some off-brand battery to save money on a Sol-Ark setup. Technically worked but only in "dumb" mode - no SOC readings, no proper charge management, basically just guessing at battery state.

He bought a proper compatible battery six months later. Expensive lesson.

If the battery isn't on the inverter manufacturer's compatibility list, assume it won't work right.

Skipping the grounding

This one's not exciting but it will absolutely ruin your day.

Guy skipped the grounding rods because "the system works fine without it." Lightning storm, nearby strike, surge came through and killed his inverter, charge controller, AND two batteries. Around $6k in damage. Insurance denied the claim because the install wasn't to code.

Grounding is like $150 in materials. Just do it.

Buying the "perfect fit" inverter

Meaning: sizing your inverter exactly to your current panel array with zero headroom.

Then two years later you buy an EV or add a heat pump or whatever and suddenly you need more capacity. But your inverter is maxed out. Now you're replacing the whole thing instead of just adding panels.

If you need 6kW now, buy an 8-10kW inverter. The price difference is nothing compared to replacing it later.

Not pulling permits

I know, I know. Permits are annoying.

But unpermitted systems can void your homeowner's insurance. Utilities won't give you interconnection. And if you ever sell your house it becomes a massive problem.

Had someone's home sale almost fall through because of this. Retroactive permits, failed inspections, modifications, two month delay. Cost him $4,500 and a lot of stress.

Just pull the permit, there are services that handle it, including us.

Not checking if the panels physically fit

It sounds unlikely, but it happens constantly.

A customer ordered 20 panels for a roof section. Didn't check dimensions. Turns out only 18 fit. Returned 2 (restocking fee), then decided the layout looked weird, ended up ordering different panels entirely to fill gaps. Wasted like $600 and three weeks.

700W panels are over 7 feet tall. They're not all the same size. Measure your space first.

Honestly, the fix for most of these is just getting someone to sanity check your plan before you order. Most suppliers will do it free because it's easier than dealing with returns and angry customers. I've talked people out of buying from us because their setup didn't make sense.

What else have people run into? Curious what I'm missing.

[Disclosure: I run a solar gear business (Portable Sun LLC), so I sell a lot of what this post talks about, and I'll reference our stuff where it's useful. I've been at this for years and I see people skip the essential steps that quietly hurt them down the line, which is why I wrote this. Fire any questions you've got in the comments.] 

I've watched a lot of people order their panels, racking, and inverter, get everything delivered, and then climb up on the roof on a Saturday only to realize they skipped the stuff that actually decides whether the system lasts 25 years or leaks into their attic by spring. The roof part isn't the exciting part and nobody brags about flashing, but it's the part that causes the expensive regrets, so here's what you want to lock down before the first panel goes up.

Can your roof even take it?

This is the step people skip and it's the most important one. Panels last 25 to 30 years, so the one thing you want to know before you start is how much life your roof has left, because if it's getting close to needing replacement, you're better off handling that as part of the project rather than mounting a 25-year array on a roof you'll want to redo in a few years. Here's the part people don't realize though: this usually isn't a reason to delay solar. Reroofing the section under a planned array is often a quick job, and to give you a sense of it, the ones we do on Michigan roofs are typically a single day, so an aging roof is usually a smaller hurdle than people assume. Get a roofer's read on it early and fold it into your timeline rather than letting it stall the whole project, because every season you put it off is a season of production you don't get back. 

The other half of this is load, and there's a common misunderstanding worth clearing up. A typical attached flush-mounted array often adds around 3 psf or less, and that rarely worries anyone, because building codes already require residential roofs to carry far more than that, so on a sound roof the added weight is well within the margins. Ballasted low-slope systems are the exception and can be heavier, so those need a separate structural look. The number that actually matters isn't the spread-out weight, it's the load at each attachment point  If your roof sags anywhere, has any history of water damage, or you're in heavy snow country, confirm the structure is sound before you trust those attachment points for the next couple of decades. In my experience the people who check whether the panels fit but never look at the structure underneath are asking the wrong question.

Wind uplift is the force people underestimate

This one doesn't get talked about enough, and for most roofs it's a bigger deal than the dead weight everyone fixates on. What tends to pull an array loose isn't the weight pressing down, it's wind getting underneath the panels and lifting up, and that uplift is exactly what your attachment spacing is engineered around. Your racking manufacturer publishes span tables that tell you how far apart your mounts can be based on your wind zone, your roof height, and your panel size, and those numbers exist for a reason, so spreading your rails out further than the table allows to save on a few brackets is how arrays end up in the neighbor's yard after the first real storm. Follow the span table for your wind zone rather than eyeballing it, because the engineering's already been done for you.

Before the roof, check where the power actually ties in

This is the most expensive thing people overlook, and it has nothing to do with the roof itself. Your roof might have room for twenty panels, but your main service panel may only legally accept a fraction of that, because there's a limit to how much solar you can backfeed into a panel based on its busbar rating and main breaker size, and that's the rule that quietly caps a lot of residential systems. If your system is big enough to exceed it, you're either doing a main panel upgrade, which is real money and its own permit, or tying in a different way, and either way it changes your plan and your budget. On top of that your utility has its own interconnection rules about system size and the disconnect they require. Sort this out before you order panels, because the cheapest version of this mistake is realizing your roof-sized system was never going to fit on your electrical service.

Your roof type changes everything about mounting

The surface you're working with decides your hardware and, more importantly, your leak risk. Asphalt shingle is the easiest and most common, and it uses lag bolts into the rafters with flashing over each penetration. Standing-seam metal is often the best case you can have because the mounts clamp directly onto the seams with no holes drilled into the roof at all, so there's nothing to leak later. 

Tile is the tricky one, and by that I mean clay and concrete tiles crack easily and need tile-specific hooks, so it's the surface I'd think hardest about before taking on. Flat or low-slope roofs are a different world again, since they use ballasted or tilt-up racking and you have to plan drainage carefully so you're not creating a pond up there. One thing worth knowing before you buy: your rails, clamps, and module are supposed to be a listed combination, because the fire rating and the bonding path are tested as an assembly rather than per part, so mixing cheap rails, random clamps, and a different module frame can fail inspection even when each piece looks like solar hardware on its own. Match your mounting hardware to your exact roof type and stick to combinations the racking maker actually lists.

Finding the rafters, and why flashing is the whole game

Here's the leak math that people underestimate. Every mount is a hole in your roof, and done right that hole is sealed for decades, but done wrong it's a slow leak you don't discover until it shows up as a stain on the ceiling two winters later.

[Through-flashing (left) vs. a caulk-only shortcut (right)]

Two things make or break this. First, for rafter-mounted systems, your attachments need to land in the structural rafters or trusses and not just the plywood sheathing underneath the shingles. Some products are engineered and approved for deck mounting, but only use that method if the racking manufacturer, your plan set, and your local AHJ allow it. I’ve seen plenty of arrays come loose because someone screwed into the deck and called it good, so use a stud finder, measure your rafter spacing, which is usually 16 or 24 inches on center, and confirm you’re hitting the structure required by your mounting system every time

 Second, every penetration needs proper flashing that tucks under the course of shingles above it so water sheds over the top and runs off the way it's supposed to. Now, there are purpose-built over-shingle mounts that seal with a manufacturer-engineered sealant rather than traditional flashing, and although they're less common, those are a legitimate option when you install them exactly as the maker specifies. What you want to avoid is the improvised version, meaning someone freehand gooping a generic mount down with a tube of caulk and calling it sealed, because that kind of sealant dries out and fails over a few years whereas a proper flashed or purpose-built sealed mount keeps working.  A tube of sealant runs about eight bucks and re-shingling a water-damaged section with the drywall repair underneath can run into five figures, so this is genuinely not the place to save money. 

A quick word on clamps

While you've got the hardware out: solar racking is soft extruded aluminum, so put the impact driver down when you're tightening panel clamps. Over-tighten and you'll strip the threads in the rail or stress the panel frame and glass, under-tighten and the panels work loose in the wind, and either way you want to clamp only in the spots the panel maker marks as approved. Follow the manufacturer's torque spec exactly rather than guessing, since a cheap torque wrench costs less than one cracked panel.

Layout, orientation, and leaving yourself room

In the northern hemisphere south-facing is ideal, and east or west loses you some production but is still perfectly workable. North-facing isn't the first option and it does produce less, but it can still generate a respectable amount, especially with today's panel prices, so it's often worth putting panels up there rather than leaving that roof space empty. Shading matters, though how much depends on your gear, because on a traditional string inverter shade on a single panel can drag down the whole string it's on, while microinverters and optimizers limit most of the damage to the shaded panel. They reduce shade losses, they don't erase them, so either way map how shade moves across your roof over a day and across the seasons before you commit to a layout. Trees grow, and the clear roof you have in winter isn't always the clear roof you have in July.

The other big one people miss is fire setbacks, and this one trips up a lot of layouts, so don't skip it. Setbacks come from your local fire and building code rather than the electrical code, which means they're a completely separate requirement from the rapid-shutdown stuff below even though people lump the two together. The codes generally want clear pathways around the array so firefighters can get up there and vent the roof, which commonly means keeping a setback around the ridge and along certain edges, though the exact dimensions vary by jurisdiction and code edition, so check with your local authority rather than trusting a fixed number off the internet. 

Your inspector will absolutely check this, and I've seen lots of layouts torn apart and redone when someone crammed in every last panel for maximum output and only found out about the setbacks at inspection.

Rapid shutdown and grounding

Even if you bring in a licensed electrician for the final connection, which most places require anyway, you still want to understand this part so you order the right gear up front rather than the wrong thing twice. Rapid shutdown is a code requirement meant to let firefighters quickly bring the system's conductors down to a safe voltage during a fire, and by that I mean it limits conductor voltage rather than literally switching the panels off, since a panel in sunlight always makes some voltage. In practice the limits are strict enough that most systems meet them with module-level electronics, meaning microinverters or DC optimizers, and if you've already got a string inverter you can add module-level rapid-shutdown receivers to each panel with a transmitter back at the inverter rather than throwing the inverter out. The thing to actually avoid is buying a plain string inverter without planning for any of this, because then you're back up on the roof retrofitting devices onto every module after the fact, which costs more than speccing it right the first time.

Grounding is the other piece, and it’s cheap insurance rather than a real expense. The whole array has to be bonded and grounded so all the metal is tied together electrically, and the reason matters more than people realize, because if a hot wire ever rubs through and contacts an unbonded frame, the fault may not clear the way it is supposed to, and exposed metal can remain energized. Use the proper listed hardware for this, meaning an equipment grounding conductor with lay-in lugs, bonding jumpers, and the washers designed to bite through the anodized coating on aluminum rails, rather than improvising with whatever wire and lugs are cheapest, since mismatched metals and unlisted parts cause both corrosion and inspection failures. It’s usually a modest amount in materials, and it’s what gives fault current a proper path back so protective equipment can do its job. Order your parts to your local code rather than to whatever the cheapest configuration you saw in a YouTube video happens to be, because jurisdictions vary and a video’s comment section is not your inspector. 

Wire management, because dangling wire fails inspection and fails early

This is a small thing that quietly causes big problems. The wires running between your panels and down off the roof can't just hang loose against the shingles, because of environmental factors (wind, debris, etc) causing wire abrasions. That is both a fault waiting to happen and a guaranteed inspection failure. Clip everything up off the roof with proper UV-rated clips, and while you're at it, mind your connectors: the quick-connect plugs on your panels only seal and conduct properly when both halves are the same connector type/manufacturer, or a combination specifically listed or approved as compatible**,** because mismatched 'compatible' plugs leave microscopic gaps that build resistance, heat up, and are a genuine fire cause over time. Last thing, the point where your wiring leaves the roof and enters the house is itself another penetration that needs flashing, so use a proper flashed roof entry rather than drilling a raw hole and gooping it with sealant, and don't seal everything else carefully only to leave that one spot raw.

Permits

I know permits are annoying, but pull them anyway. An unpermitted system can create headaches with your homeowner's insurance, your utility interconnection, and your resale down the line, because an unpermitted array is a red flag that kills deals or forces expensive retroactive permitting and re-inspection. The permit fee may be a few hundred dollars in many places, but the bigger issue is getting the plan set, utility interconnection, and inspection path right before you install .

Safety Measures

One last thing, and this is crucial: falls, not electrocution, are what actually hurt people on these jobs. People brace for the electrical side because it feels scary, but it's the roof itself that can send you to the hospital, and by that I mean a slip on a wet or dusty surface, a ladder that kicks out, or a wrong step near the edge while you're focused on the panel in your hands instead of where your feet are. A harness tied off to a proper anchor point is the single thing that turns a fall into a scare instead of a tragedy.

A few things that genuinely help: set your ladder up properly and tie it off so it can't shift, get your panels lifted up to the roof rather than carrying them up a ladder by hand, and watch out for the hazards that are easy to forget when you're concentrating, like skylights you could step through and roof edges that disappear from view once you're crouched over your work. If your roof is steep or you're not comfortable moving around up there safely, that's worth taking seriously rather than pushing through, because no amount of saved production is worth getting hurt over.

A pre-roof checklist worth saving

Before a single panel goes up, you want to have confirmed:

• Roof's remaining life checked early and, if needed, reroofing folded into the project rather than used as a reason to delay 
• Structure is sound enough to trust each attachment point for 25 years
• Service panel and utility interconnection can actually accept your system size
• Mounts spaced to the racking manufacturer's span table for your wind zone
• Mounting hardware matched to your roof type and listed as a system with your modules
• Rafter locations mapped, with flashed mounts ready to go
• A layout that respects fire setbacks and accounts for shade
• Rapid-shutdown and listed grounding parts ordered to local code
• Wire clips, matched connectors, and a flashed roof exit point planned
• Permit pulled and inspection scheduled
• A real fall-protection plan, meaning safe ladder access, a plan for lifting panels up rather than carrying them by hand, and guarded skylights and hatches

What we sell, and where it fits

We carry panels, racking and flashing kits matched to roof type, microinverters and rapid-shutdown gear, and grounding hardware, and we do free system planning for DIYers because honestly the planning is where most of these jobs are won or lost. If you want a second set of eyes on your layout, your parts list, or whether your service panel can take the system you're picturing, that's the most useful thing I can offer and I'm glad to do it whether or not you end up buying from us.

Ask me anything below. The single most useful detail is your roof type and a photo of your main service panel, since those two usually drive the whole plan, so if you share those I can help you think it through.

[Disclosure: I work at Portable Sun LLC. We sell solar equipment. I'm using our products as examples because I know them best, but this guide applies no matter where you buy. Happy to answer questions about competitors too.]

I've helped hundreds of people spec out DIY solar systems, and I see the same confusion over and over. People obsess over the wrong specs, overpay for features they don't need, or cheap out in places that cost them later.

This guide is what I wish everyone would read before buying their first panel.

The Only Specs That Actually Matter

1. Wattage (Power Output)

This is simple: higher watts = more power per panel = fewer panels needed.

Current sweet spots for DIY:

• Budget: 400-450W panels ($0.30-0.40/watt)
• Mid-range: 500-550W panels ($0.35-0.45/watt)
• High-output: 700W+ panels ($0.35-0.50/watt)

Real example: A Canadian Solar 445W TOPCon runs about $210 ($0.47/W). A CW Energy 410W bifacial is $139 ($0.34/W). The CW is better value per watt, but you'd need more panels for the same output.

What most people get wrong: Chasing the highest wattage without considering physical size. A 700W panel is massive (~7.5ft tall). Make sure it fits your roof/ground mount.

2. Panel Type

There are really only two choices worth considering in 2025:

Monocrystalline (Mono PERC or TOPCon)

• 20-23% efficiency
• Black appearance
• 25-30 year lifespan
• This is what you want for most installations

Bifacial

• Captures light from both sides
• 5-30% extra output depending on mounting
• Best for ground mounts with reflective surface underneath
• Overkill for roof mounts flush against shingles

Skip: Polycrystalline (outdated, worse efficiency for similar price) and thin-film (too inefficient unless you have unlimited space).

3. Temperature Coefficient

This is the spec everyone ignores but shouldn't.

Panels lose efficiency as they heat up. The temperature coefficient tells you how much. It's expressed as a percentage loss per degree Celsius above 25°C (77°F).

• Good: -0.30% to -0.35%/°C
• Average: -0.35% to -0.40%/°C
• Poor: -0.40%+/°C

If you're in Arizona, Texas, or anywhere hot, this matters a lot. A panel rated at 500W might only produce 425W on a 100°F day with a poor temp coefficient.

4. Warranty Terms

Two warranties matter:

Product warranty: Covers defects. Look for 12-25 years. Most tier-1 brands offer 25.

Performance warranty: Guarantees output over time. Standard is 80-85% output at year 25.

The catch: Warranty is only as good as the company behind it. A 25-year warranty from a brand that might not exist in 5 years is worthless. Stick with established manufacturers: Canadian Solar, Longi, Trina, REC, Q Cells, JA Solar.

Specs That Matter Less Than You Think

Efficiency percentage - A 22% efficient panel isn't meaningfully better than a 20% panel for most DIYers. The difference is physical size. If space is tight, pay attention. Otherwise, optimize for $/watt.

Brand prestige - A tier-1 panel from a lesser-known brand often outperforms an expensive "premium" brand. You're paying for marketing, not watts.

Aesthetics - Unless HOA requires it, all-black panels are a premium you don't need. Black frame + white backsheet works fine.

The Real Cost Breakdown

Panel pricing is confusing because there's huge variation. Here's what drives it:

Factor	Impact
Wattage	Higher = more expensive (but often better $/W)
Technology	TOPCon > PERC > Poly
Bifacial	10-20% premium over monofacial
Brand	15-30% premium for "name brands"
Quantity	Pallet pricing saves 10-25%

Real math:

For a 10kW system (typical whole-home), here's what panels alone cost:

• Budget route (24x TaleSun 445W @ $162): $3,888
• Mid-range (16x Canadian Solar 600W @ $278): $4,448
• High-output (15x Canadian Solar 710W bifacial @ $259): $3,885

The high-output bifacial is actually solid value here - fewer panels means less racking, less wiring, faster install.

Buying Individual Panels vs. Pallets

Individual panels make sense when:

• You need an odd number (filling out a small array)
• You're testing before committing
• Shipping a pallet isn't practical

Pallet pricing makes sense when:

• You're building 5kW+ (usually 12-36 panels)
• You have forklift/loading dock access or can arrange freight delivery
• You want the lowest $/watt

Most suppliers (us included) offer significant pallet discounts - often 15-25% off individual pricing.

Red Flags When Buying Panels

🚩 Too-good-to-be-true pricing - If someone's selling 500W panels for $80, they're either damaged, knockoffs, or about to take your money and vanish.

🚩 No brand name / "house brand" - Generic unbranded panels have no meaningful warranty backing.

🚩 "Clearance" panels with physical damage - Microcracks kill performance and spread over time. Not worth the savings.

🚩 No spec sheet available - Every legitimate panel has a downloadable datasheet. No datasheet = run.

🚩 Pressure tactics - "This price is only good today" is almost always BS. Solar equipment pricing is stable.

Matching Panels to Your Inverter

This is where most DIY mistakes happen.

Your inverter has three key specs that constrain panel selection:

1. Max PV input voltage - Don't exceed this. Add up the Voc (open circuit voltage) of your panels in series. Must stay under max even on cold days (voltage rises when cold).
2. MPPT voltage range - Your string voltage needs to land within this window for the inverter to work properly.
3. Max input current - Relevant when running strings in parallel.

Example: A Sol-Ark 15K has 500V max input and MPPT range of 120-450V. You could run 8x Canadian Solar 445W panels in series (8 × 51.9V Voc = 415V). That's safely within limits.

If this sounds complicated, most good suppliers offer free system design, and we offer it here. Use this service - it's worth it to avoid a $1,500 mistake.

Questions to Ask Before You Buy

1. Where is it shipping from? - Freight from across the country adds up. Local or regional suppliers save on shipping.
2. Who handles warranty claims? - Some retailers help facilitate claims. Others point you to the manufacturer and wish you luck.
3. Is there a restocking fee? - Mistakes happen. Know the return policy before ordering 30 panels.
4. Lead time? - In-stock vs. drop-shipped matters. Ask for the actual ship date, not "estimated delivery."

My Actual Recommendations

Best overall value (2025): TaleSun and Canadian Solar bifacial panels in the 400–550W range provide a great balance of performance and cost. You're getting modern tech at the price sweet spot.

Best for limited space: Highest wattage you can fit. 700W panels are pricey per panel but efficient per square foot.

Best for budget builds: Previous-gen mono PERC panels. Nothing wrong with them, they're just not the new shiny. Often 20%+ cheaper.

What We Sell (Full Transparency)

At Portable Sun, our current individual panel lineup:

• TaleSun 445W TOPCon Bifacial
• CW Energy 450W Bifacial
• Canadian Solar 600W TOPCon Bifacial
• Canadian Solar 705W Bifacial

We also carry pallets at lower per-panel pricing, plus full kits with inverters and batteries if you want a matched system. Browse everything here.

We're not the cheapest on everything. However, we try to compete on service - NABCEP-certified techs, free system planning, and actually answering the phone.

Ask me anything below. Happy to answer questions about competitor products too - I'd rather you get the right system than buy from us and be unhappy.

[Disclosure: I've been running a solar equipment business (Portable Sun LLC) for several years now and figured it was time to call out some of the myths that keep circulating, but cost money.]

I had three separate conversations this week with customers who had done their research, thought they had a solid plan, and were about to spend money based on advice that used to be true or was never true. 

"Installers always know best"

This one stings to say out loud because good installers are genuinely invaluable. However, "installer said so" is not a substitute for understanding your own system. I've seen installers upsell equipment that didn't fit the site, size systems with zero discussion of the homeowner's actual usage patterns, and recommend string inverters for roofs that clearly needed power optimizers.

Just ask why. If they can't explain it in plain terms, that's worth paying attention to. You don't need to be an engineer, you just need to understand what you're spending money on.

"Solar completely eliminates your electric bill"

"Eliminate" is a stretch. You'll likely still have a minimum service fee from your utility regardless of how much you produce. Seasonal variation means you'll probably pull from the grid during low-production months. And if your system was sized to your average usage rather than your peak, high-consumption months will still show a balance due.

"Dramatically lower" is the honest expectation. "Zero" is the exception, not the rule.

"You should wait because solar will get cheaper next year"

It might. It also might not, depending on tariffs, supply chain shifts, and incentive policy changes. This advice has been confidently recycled every year for about a decade. The people who acted on it in 2021 missed a rate environment where their payback period was significantly shorter. The people who waited for "cheaper panels" in 2022 got hit with supply disruptions instead.

Also the federal tax credit question is no longer an open one. The 30% residential solar tax credit expired for customer-owned systems on January 1, 2026. There was no phase-down … systems installed by December 31, 2025 qualified for the full 30% credit; systems installed after that date do not.

So … if your roof is ready and your usage is stable, the math is probably better now than the advice to wait suggests.

"Solar panels stop working after 25 years"

They don't stop, they degrade. Most quality solar panels lose roughly 0.25%–0.3% of output per year. The underlying point … a panel at year 25 is typically still producing a meaningful share of its original rated output.  The 25-year figure comes from performance warranty terms, not a hard expiration date.

Systems from the early 2000s are still running. Usually what gives out first is the inverter anyway, not the panels.

"Efficiency percentage is the most important spec"

It isn't. Efficiency just tells you how much power you get per sqare foot. If space isn't your constraint, you don't need to pay a premium for it. A 20% efficient panel at $0.33/watt and a 22% panel at $0.50/watt make identical electricity once they're on your roof. Optimize for $/watt, not the efficiency number.

"Any shade means you need microinverters"

Micros are great but they're not always necessary. One chimney throwing a shadow on one corner for an hour in the morning? A decent string inverter would handle that just fine. The blanket "any shade = micros" advice sells a lot of hardware that people don't need.

How much of your array is shaded, how often, and during peak production hours? Those are the actual questions. Not just “is there shade.”

"Poly panels are just as good, mono is overhyped"

This was sort of true in 2015. It's not true now. The price gap basically closed and mono PERC/TOPCon is just better across the board - efficiency, temperature coefficient, lifespan. For most new residential installs today, mono is the stronger recommendation. If you're still seeing that advice, check when it’s written.

"You should always size your system to cover 100% of your usage"

It sounds logical but it often isn't the right target. If your utility has decent net metering, oversizing slightly makes sense. If they've moved to avoided-cost buyback rates then producing more than you use just means cheap electricity going back to the grid at a loss. Size to your net metering terms, not some arbitrary round number. The payback math is usually better that way.

"You need batteries for solar to work"

You don't. Grid-tied solar without storage is a completely viable setup. Your panels produce power, that power offsets what you'd pull from the grid, and net metering handles the rest in most utility territories. One thing worth knowing … a standard grid-tied system without a battery will not keep your home running during a power outage. It shuts down by design to protect utility workers. That's a common assumption worth clearing up before you buy.

But … batteries have become useful in a way they weren't five years ago. If your utility has time-of-use rates, a solar battery can shift when you draw from the grid and influence your economics positively. And if your power goes out regularly, that changes the math too.

"Panel efficiency determines how much electricity your system makes"

Efficiency tells you how much power you get per square foot of panel. That's it. What actually determines how much electricity your system produces is the total wattage installed, your location's peak sun hours, shading, tilt, azimuth, and system losses from wiring and the inverter. 

A 400W panel at 19% efficiency and a 400W panel at 22% efficiency are rated for the same output … but real-world production still depends on all those other factors. The higher-efficiency panel just takes up less space to hit that wattage rating. Where efficiency genuinely matters is when roof space, layout, or available panel count is the limiting factor. 

In those cases, a higher efficiency rating translates directly to more power from the same footprint. If space isn't your constraint, chasing efficiency numbers is chasing a marketing spec, not real-world output.

"String sizing is pretty straightforward, you can just eyeball it"

Technically yes. In practice, the thing people consistently miss is that voltage goes up when it's cold. You need to calculate Voc at your actual coldest temps, not the 77°F standard test conditions on the spec sheet.

Just use a string sizing calculator and put in your actual coldest temps. Takes five minutes.

What other stuff have you guys seen floating around that turned out to be wrong? There's a lot of bad info from old YouTube videos still making the rounds.

FYI we do plan systems for free for DIYers