TL;DR: A solar panel makes DC power. Your house runs on AC power. A microinverter converts one to the other and pushes the result into your wall outlet. Utah’s 1,200W limit is on the inverter’s AC output — you can have more panel wattage on the DC side. The kit you buy from us picks the right combination so you don’t have to do this math yourself.

This page is for the curious. You don’t need any of it to use a kit, but if you’ve ever wondered what’s actually happening when sunlight becomes electricity in your living room, here’s the whole story.

The basic flow

Five components, one direction:

Everything below is the detail behind those five steps.

Why DC and AC even exist

Solar panels are made of silicon. When a photon hits a silicon cell, it knocks an electron loose. Electrons flowing in one direction is direct current — DC. It’s clean, simple, and doesn’t change polarity over time.

Your house runs on alternating current, AC. The voltage in your wall outlet swings between +170V and -170V sixty times a second (that’s where 120V “RMS” comes from — it’s the effective average). The grid runs on AC because AC is easy to step up and down with transformers, which is how power gets pushed across long distances efficiently.

Panels make DC. Houses use AC. Something has to translate. That something is the inverter.

What a microinverter does

An inverter is a small electronic box that takes DC in and pushes AC out. A microinverter is just an inverter sized for one or two panels, small, weatherproof, and bolted directly to the panel frame.

Inside, fast electronic switches flip the DC current back and forth thousands of times per second, then a filter smooths it into a clean 60-hertz sine wave that matches the grid exactly in voltage, frequency, and phase.

That sine wave is what comes out of the inverter and into your wall outlet. Once it’s there, it behaves exactly like grid power — because that’s the point.

Watts — volts, and amps

Three numbers describe any electrical thing. They’re related by a single equation:

Volts × Amps = Watts

Volts are pressure. How hard the electrons are being pushed.
Amps are flow rate. How many electrons per second.
Watts are power. The actual work being done.

A microinverter that outputs 120 volts at 10 amps is producing 120 × 10 = 1,200 watts. That’s also the maximum your kit can push into the grid:

Why does that fit any normal household outlet? Because residential outlets are rated for 15 amps or 20 amps. A 1,200W inverter pulls 10 amps maximum, well under either ceiling, with headroom for whatever else might share the circuit. That’s the engineering reason plug-in solar is allowed at all.

Why Utah caps it at 1,200W

HB 340 limits the AC output of the inverter to 1,200 watts. Not the panel wattage. Not the DC side. Specifically the AC side, because that’s what determines how much current flows into your home wiring.

This number wasn’t picked at random. It’s the highest power level that can safely run through a standard 15A/20A residential circuit without risk of overloading shared loads. Push more than that and you start needing engineered circuits, dedicated breakers, and the full interconnection paperwork. The 1,200W cap is the line between “appliance-class” and “system-class” — appliance-class skips the paperwork.

Panel oversizing — and why it makes kits more efficient

Here’s the part most people miss.

Panels are rated under Standard Test Conditions — bright sun, 25°C, perfect angle. Real panels in real Utah weather almost never hit their rated wattage. Cloudy, hazy, hot, sun-not-overhead, every condition derates the actual output below the spec sheet.

So if you put exactly 1,200W of panels on a 1,200W inverter, you’ll only see 1,200W out for a tiny fraction of the year. Most of the time you’re under-utilizing the inverter.

The fix is DC oversizing — putting more panel wattage on a smaller inverter. Three 460W DMEGC bifacial panels (1,380W DC) feeding a 1,200W AC inverter still respects the law (the AC output is capped). For the much larger fraction of the year when the panels are producing at, say, 70% of rated capacity, you’re now hitting the inverter’s full output instead of just 70% of it.

The Utah cap is on what comes out of the inverter, so this is fully legal. It’s just smart engineering, the kits we sell are sized this way on purpose so you get the most kWh per year possible while staying within the 1,200W AC ceiling.

Where the electricity goes

When the inverter pushes 1,200W out the wall outlet, that power doesn’t sit there. Electricity always flows toward whatever is using it. Here’s the order of priority:

Whatever’s plugged in on the same circuit consumes it first — but that’s rarely much, since the kit is on an outdoor outlet.
The rest of your home, your fridge, your AC, your computer, lights, anything drawing power right now — pulls from the same neighborhood electrical network. Solar power flows backward through your panel and supplies whatever loads are running.
If you’re producing more than your home is using, the excess flows out through your meter and into the grid. Your neighbor’s house is now running on your sun.

That last step is the one that needs the smart meter.

Why a smart meter matters (one more time — with the physics)

Old-style mechanical meters spin the same way for power flowing in either direction. They literally can’t tell which way it’s moving, they just count revolutions. So if you push 200W out to the grid for an hour, the old meter records 200Wh of “consumption,” and you get billed for power you generated yourself.

A bidirectional smart meter has separate counters for delivered energy (grid → you) and received energy (you → grid). It charges you for the first, and under HB 340, ignores the second. That’s exactly what you want.

If you have an older grandfathered net metering agreement with RMP (pre-2020), the smart meter actually credits your received energy at near-retail rate. Plug-in kits don’t qualify for those agreements on their own — but if you already have one from an existing rooftop system, the situation gets specific. Call RMP and confirm.

The certification side

Microinverters can’t legally connect to a US power grid without certification. The big one is UL 1741 / UL 1741-SA, it’s the safety standard that mandates anti-islanding (the inverter shuts off automatically when grid power drops, so it can’t electrify a downed line) and grid-quality voltage and frequency output.

There’s also NEC 2023 compliance — the National Electrical Code that governs how everything wires together, and FCC Part 15 for electromagnetic interference. Every microinverter we ship has all three.

Cheap unbranded inverters off Alibaba often have certification stickers but no actual testing behind them. Under HB 340 they’re not legal in Utah. The kits we sell carry the real certifications.

Choosing panels and inverters

In principle, any solar panel from any reputable manufacturer works. Most modern residential-class panels output 300W to 500W and run at 30–40 volts DC at maximum power. A microinverter is matched to a voltage range and a wattage range; if your panels fit, they work.

In practice, getting it right means matching:

Panel voltage range to inverter MPPT (maximum power point tracker) input range
Panel current to inverter input current limit
Panel wattage total to inverter AC output (with reasonable oversizing — typically 10–30%)
Connector type (almost always MC4)
Cable length (longer runs = more loss)

Get any of those wrong and the inverter under-produces or refuses to start. The kits we sell are pre-matched to take this off your plate. The 3 Panel configuration pairs the NEP BDM-1200-LV microinverter with three 460W DMEGC bifacial panels, 1,380W DC into a 1,200W AC inverter. ~15% DC oversizing, full inverter utilization for more hours of the year, optimal price-per-watt at the legal ceiling.

The 2 Panel configuration pairs the APsystems EZ1 (900W AC) with two 460W DMEGC bifacial panels — 920W DC into a 900W AC inverter. Same matching logic, smaller scale.

If you want to build your own, you absolutely can. Just keep the AC output under 1,200W, make sure everything is UL-certified, and make sure the math works on the DC side. The economics usually don’t beat a kit because we buy components by the pallet, but the option is there.

What about batteries?

Plug-in solar kits are grid-tied without storage. The microinverter requires the grid to be present to operate (that’s part of UL 1741), when the grid goes out, the inverter shuts off, even if the sun is shining. So a basic plug-in kit doesn’t keep your fridge running during an outage.

If you want backup, that’s a separate decision: a portable battery like an EcoFlow Delta or Bluetti AC300 can be charged from a plug-in kit and provide outage backup independently. RMP also runs a Wattsmart Battery program with a $400/kW incentive (capped at $2,000) for AC-coupled batteries on time-of-use rates — but that’s a more complex install and lives outside the simple plug-in story.

You don’t need to know any of this to use a kit

The short version: panels make DC, the inverter converts it to AC, the AC pushes through your outlet into the rest of your home, and a smart meter keeps the accounting straight.

For the setup steps, read how it works. For the safety detail, see the safety guide. For the law in plain English, see HB 340 explained.