Your Know Your Numbers math gave you a wattage target. Now let’s turn that into REAL panels mounted on YOUR roof, producing YOUR electricity, and cutting the cord from the utility monopoly that’s been charging you EVERY month with ZERO competition.

YOUR roof. YOUR land. YOUR God-given right to generate your own power. Let’s use it.

Wattage: The Answer Is 400W

The market has spoken. 400-watt panels are the volume standard for residential solar — best cost per watt, widest availability, most compatible with quality inverters. That’s where the competition is fiercest and where YOU get the best deal.

Lower wattage (100-200W)? More hardware, more connections, more labor, higher cost per watt of capacity. Pass.

Higher wattage (500W+)? Bigger, heavier, harder to handle on a roof. Not worth the premium unless your inverter specifically calls for it.

Physical Sizing: Know Your Roof

A 400W panel is about 6.8’ x 3.4’ — 22 square feet, 45-55 lbs. Two people can handle one on a roof. One person shouldn’t try it.

Before you commit to anything, get out a tape measure. Sketch your mounting surface. Account for:

  • Inter-panel gaps for mounting hardware (1-2 inches)
  • Edge clearance — no overhanging panels
  • Airflow underneath — hot panels produce less; clearance helps
  • Obstructions: vents, chimneys, stacks, skylights — anything that takes space or throws shade

A real sketch with real measurements beats any app. Measure your roof. THEN commit to a count.

How Many? More Than You Think.

The formula from Know Your Numbers:

Daily kWh ÷ PSH ÷ 0.70 ÷ panel watts = minimum panel count

That’s the minimum. HERE’S THE TRUTH: panels are the cheapest component per watt in your entire system. More panels means faster battery charging, more production on cloudy days, and room to expand. And shipping? Adding two extra panels to your initial order costs FAR LESS than ordering two panels separately later. The monopoly loves small systems. Don’t give them that satisfaction.

Mounting: YOUR Roof, YOUR Rules

Three ways to mount panels. Each has its place.

Roof mount is the most common. Panels attach to rails anchored through the roof into your rafters. Done right with proper flashing kits and sealant — it doesn’t leak. If the idea of making penetrations in your roof gives you pause, that’s reasonable! Take your time, watch several installation videos, and use quality hardware. The problems come from cutting corners, not from the approach.

Ground mount uses a rack structure at grade. Easier to install, easier to access for maintenance, easier to set the angle. Trade-off: longer wire runs and yard space. May need its own permit in some states — check yours.

Shed or pergola mount is a strong middle-ground choice. No penetrations in your main roof, lower and more accessible, can serve double duty as covered outdoor space. Excellent option if your house roof has problems.

Tilt: Get It Close, Then Stop Thinking About It

Optimal tilt for most of the continental U.S. is 30-45 degrees from horizontal. Steeper favors winter. Shallower favors summer. Most residential roofs already fall in this range. If you’re ground mounting, you can set it exactly.

Shade: The Silent Killer

Shade is the #1 performance killer in a solar system — and it’s WORSE than most people realize.

In a series-wired string — which is how most systems are built — the WEAKEST panel controls the WHOLE string. One shaded panel doesn’t just lose its own output. It DRAGS DOWN every panel in the string with it. One bad link. Whole chain.

The utility monopoly doesn’t tell you this. Now YOU know.

What to do about it:

  • AVOID IT. Position panels for maximum unobstructed sun. Your best move, costs nothing.
  • Separate MPPT strings. Put shaded panels on their own MPPT input. A shaded string won’t drag down an unshaded one. String Design covers this.
  • REMOVE THE SOURCE. Trimming a tree branch is cheaper than buying extra panels to compensate for its shadow. A chainsaw costs less than two extra panels.
  • OVERSIZE. If 20% shade loss is unavoidable, build in 20% extra capacity. Beat the loss with volume.

The Panel-Inverter Loop

HERE’S WHAT THE TUTORIALS DON’T TELL YOU: panels and inverters are linked specs. You can’t fully design one without the other. Most guides tell you to pick panels, then pick an inverter — as if it’s a straight line. It’s NOT. It’s a loop. And that’s fine.

Two paths in the market:

Consumer path (Bluetti, Anker, EcoFlow): Plug-and-play all-in-one units. Lower voltage MPPT windows (12-150VDC). Good for modest systems. Ceiling: input capacity limits your array size.

Prosumer path (SRNE-platform and similar): Higher input capacity, wider MPPT voltage windows (120-500VDC), more configuration, more learning required. Right tool for larger systems.

The loop:

  1. Available roof space estimates your maximum panel count
  2. Panel count points to required inverter MPPT input capacity
  3. Inverter MPPT voltage window determines valid string configurations
  4. String voltage math may require adjusting the panel count or string design
  5. Repeat until it all fits

Do this on PAPER before you spend a dollar. Iteration is free. Wrong hardware is not.

Inverters covers the specs. String Design covers the string math. The 200W starter system shows a complete worked example.

YOUR Next Move

You know the specs. You know the math. You know what shade does to a string and why 400W is the right starting point. Now it’s time to see what YOUR specific roof and location can actually produce.

Get your FREE energy audit — see the real numbers for YOUR home. No salesperson. No pressure. Just data.

The monopoly has been charging you for DECADES. How much longer?

DATA SOURCED FROM: We’re using THEIR data against them. Panel dimensions and weight from manufacturer datasheets (standard 400W mono PERC). Production derating factor (0.70) based on NREL PVWatts system losses methodology (nrel.gov). Consumer/prosumer inverter specifications from published product datasheets. Individual results vary based on location, roof orientation, and shading conditions.