Inverters

4 min read Last updated March 1, 2026

Inverters

The inverter is the heart of your system. In DIY solar, “inverter” almost always means an all-in-one hybrid: a DC-to-AC inverter, an MPPT charge controller, and a transfer switch in one box. One set of connections, one interface, one thing to configure and understand.

Getting the spec right matters more here than anywhere else in your build. Here’s what you need to know.

Sizing for Continuous Output

Your inverter’s continuous watt rating needs to beat your realistic peak simultaneous load — with headroom.

The rule: multiply your expected peak by 1.25.

If your load profile tops out around 2,400 watts — fridge compressor running, furnace fan spinning, lights and router on — you need at least a 3,000W continuous inverter. Running any inverter at 100% capacity all the time stresses it and leaves no margin for anything unexpected that kicks on.

Sizing for Surge

Motor loads — fridges, freezers, pumps, furnace fans, AC units — pull 2-3x their running wattage for a fraction of a second when they start. Your inverter has to handle that spike without faulting out.

The worst case: two motors start at the same time. Fridge (800W surge) kicks on while the furnace fan (500W surge) is also starting. That’s 1,300W of surge on top of whatever base load is already running.

Inverters list both ratings. “3,000W continuous / 6,000W surge” means it can run 3,000W all day and absorb brief spikes up to 6,000W.

Solar Input: MPPT Specs

This is where panels and inverter have to match. Three specs matter:

Maximum PV input power (watts). The most solar the MPPT can process. Size your array near this number. Going slightly over is fine — the MPPT just limits intake. Going way over means you bought panels you can’t fully use.

MPPT voltage window (min to max VDC). The DC voltage range the MPPT can work within. Your string voltage must stay inside this window in all conditions — above the minimum at peak summer temperatures, below the maximum on the coldest winter morning. This spec drives your entire string design, and it varies enormously between units. A 12-150V window and a 120-500V window lead to completely different string configurations.

Maximum input current (amps). The most current the MPPT can accept. This matters when running parallel strings, which add current rather than voltage.

Consumer-path units (Bluetti, EcoFlow, Anker) typically have windows in the 12-150V range. Prosumer units based on SRNE and similar platforms run 120-500V. Neither is wrong — they lead to different string designs for different system sizes. See String Design for how to run the math.

120V vs. 240V

A 120V inverter covers most essential loads: fridge, freezer, lights, internet, furnace fan, window AC units, kitchen outlets. Simpler wiring, simpler transfer switch, lower cost.

A 240V (split-phase) inverter adds: clothes dryer, electric oven, well pump, mini-splits, EV charger. More capable, but adds wiring complexity, requires a different transfer switch configuration, and costs more.

Number of MPPT Inputs

Most inverters have one MPPT input. Some have two. Two MPPTs let you run independent strings — one facing south, one facing west, or one in full sun and one with afternoon shade. Each MPPT optimizes its string separately, so a shaded string doesn’t drag down the one in full sun.

If all your panels face the same direction with no shade issues, one MPPT is fine. If your layout is split or you have shading to manage, two MPPTs earn their cost.

Features That Matter

Generator input. If your inverter can charge from a generator, you have a backup plan for extended cloudy periods or winter. The inverter manages the generator — charges the battery, shuts it off when done.

Programmable charging schedules. Essential for time-of-use optimization. If you’re on a TOU rate plan, you want to control when the inverter charges from the grid (off-peak) and when it discharges (peak hours). See your rate context to find out whether this applies to your situation.

Monitoring and app. Knowing your battery state of charge from your phone is more useful than it sounds. At minimum you want battery level at a glance.

Transfer time. How fast the inverter switches from grid to battery when power drops. Most modern units switch fast enough that lights don’t flicker. Check the spec if you have sensitive equipment.

The Rebadge Reality

Many inverter brands are selling the same OEM hardware under different names. SRNE is a major OEM platform — their hardware shows up under a surprising number of brand labels with different firmware, different support, and different warranties.

This isn’t inherently bad. But it means you should research the actual hardware platform, not the brand name on the box.

DATA SOURCED FROM: Johnny Solarseed build guide, Section 3B (inverter specifications) and Section 3 (panel-inverter dance, consumer vs. prosumer MPPT window comparison). Individual results vary. Verify specifications against manufacturer data sheets before purchasing.