Your Know Your Numbers math gave you a wattage target. Now let’s turn it into an actual panel spec — and understand how panels and inverters work together before you spend a dollar.
Your roof. Your land. Your decision. Let’s make a good one.
The residential panel market has settled on 400 watts as the practical sweet spot. Panels range from 300W to 550W+, but 400W panels hit the best balance of output, cost, physical size, and availability. They’re what most DIY builds use and what most quality inverters are designed for.
Lower wattage panels (100-200W) require more of everything — more mounts, more wire runs, more connections. Fine for portable setups. Not a smart call for a permanent home system.
Higher wattage panels (500W+) are bigger and heavier. A 500W panel on a rooftop with two people is manageable. One person will have a bad time.
A 400W panel is roughly 6.8’ x 3.4’ — about 22 square feet, 45-55 lbs. Two people can handle one on a roof. One person will struggle.
Before you commit to a panel count, sketch out your actual mounting surface. Measure it. Account for:
An actual sketch with tape-measure numbers is worth more than any app. Don’t guess — measure.
The formula from Know Your Numbers:
Daily kWh ÷ PSH ÷ 0.70 ÷ panel watts = minimum panel count
That’s your floor. Buy more if you have the space and budget. Panels are the cheapest component per watt in a solar system. More panels mean faster battery charging, more cushion on cloudy days, and room to grow.
Here’s the practical reality: shipping panels is expensive. Adding two extra to your initial order costs a fraction of what it costs to order two panels separately later.
Three main ways to mount solar panels, and each has its place.
Roof mount is the most common. Panels attach to rails, which anchor into your rafters through the roof. Done right with proper flashing, this 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 flashing hardware. Most problems come from cutting corners, not from the approach itself.
Ground mount uses a rack structure at grade or slightly elevated. Easier to install, easier to maintain, easier to adjust the angle. Trade-offs: you’re using yard space and running longer wire runs back to your equipment.
Shed or pergola mount is a smart middle-ground option. You’re not touching your house roof, the structure is accessible, and it can do double duty as covered outdoor space. Worth considering if your main roof is a poor candidate.
The right tilt for most of the continental U.S. is roughly 30-45 degrees from horizontal. Steeper favors winter production; shallower favors summer. Most residential roofs already fall in this range.
Shade is the silent production killer. And in a series-wired string — which is how most systems are built — it hits harder than people expect.
One shaded panel drags down the whole string. Not just its own output — the entire string. If one panel in a four-panel string is producing at half capacity due to shade, your whole string takes a hit. It’s not one bad link. It’s a bad chain.
What you can do:
See String Design for how to set up separate MPPT strings.
Here’s something most tutorials skip: you can’t fully spec your panels without knowing your inverter, and you can’t fully spec your inverter without knowing your panels. This isn’t a flaw in the process — it’s just how it works.
Two paths in the market:
Consumer path (Bluetti, Anker, EcoFlow): All-in-one units, easier setup, lower MPPT voltage windows (12-150VDC typical). Good for modest systems. Ceiling: MPPT input capacity limits how large your array can go.
Prosumer path (SRNE-based and similar): Higher input capacity, wider MPPT voltage windows (120-500VDC), more configuration, steeper learning curve. Better for larger systems and long-term expandability.
The design loop:
Work this out on paper before buying anything. It’s free to iterate on a spreadsheet. It’s expensive to swap hardware.
The Inverters page covers the specs. String Design covers the voltage math. The 200W starter system shows a complete example on the consumer path.
Ready to run your numbers? Get your free energy audit and see what your specific roof and location can produce.
DATA SOURCED FROM: Panel dimensions and weight from manufacturer datasheets (standard 400W mono PERC specifications). Production derating factor (0.70) based on NREL PVWatts system losses methodology (nrel.gov). Consumer/prosumer inverter specifications based on published product datasheets. Individual results vary based on location, roof orientation, and shading conditions.