Solar inverters: the part that makes solar usable in an outage
We research products from makers' specs, manuals and safety agencies; we do not run hands-on tests. Links to Amazon may earn us a commission at no cost to you. How this works.
Quick answer
A solar inverter turns the direct current (DC) from panels and batteries into the alternating current (AC) your home uses. For outages, the type matters. The U.S. Department of Energy says solar-plus-battery systems rely on advanced inverters to run without the grid, if they are designed to. An off-grid all-in-one inverter like the EG4 6000XP combines solar charging, battery charging and 120/240 V output in one box: 6,000 W rated, 8,000 W of usable solar. It also draws about 50 W idling on battery, which adds up overnight.
What an inverter does
The Department of Energy calls the inverter one of the most important pieces of equipment in a solar system. Panels produce DC, current that flows one way at a constant voltage. Your outlets and appliances use AC, where the voltage swings between positive and negative. The inverter converts one to the other. DOE adds that modern inverters can also monitor the system and connect it to the internet.
Types of solar inverter
| Type | How it works | Trade-off |
|---|---|---|
| String inverter | One inverter converts a whole string of panels | DOE says shading or a problem on one panel reduces the whole string's output |
| Microinverter | A small inverter on every panel | Shading on one panel does not drag down the others, but DOE notes they can cost more |
| Off-grid or hybrid all-in-one | Inverter, solar charge controller and battery charger in one unit | Built to run from batteries without the grid |
DOE adds that solar can charge a battery directly over DC or after a conversion to AC, depending on how the system is designed.
Will my solar work in a power outage?
Not automatically. DOE says solar-plus-battery systems rely on advanced inverters to operate without any support from the grid in an outage, if they are designed to do so. It explains that traditional grid-following inverters need a signal from the grid to produce their AC sine wave. So a basic grid-tied system with no battery and no backup-capable inverter may not supply your home during a blackout, even on a sunny day. If backup is a goal, design for it: a battery, plus an inverter rated for off-grid or backup operation.
Inside an off-grid all-in-one: EG4 6000XP
EG4's spec sheet for the 6000XP shows what to look for in a backup-ready inverter:
- Output: 6,000 W rated at 120/240 V split phase, with a surge of 12 kW for about 3.5 seconds or 11 kW for about 5 seconds.
- Solar: two MPPT inputs and 8,000 W maximum usable solar, 4,000 W per MPPT. The DC input range is 100 to 480 V, with an MPP operating range of 120 to 385 V.
- Battery: 48 V nominal, lead-acid or lithium, 125 A maximum charge and 140 A maximum discharge.
- Power quality and switching: under 3% voltage THD, and under 15 ms switching time as a single unit.
- Grid or generator input: 50 A grid bypass, 30 A generator bypass, and up to 9,000 W AC input for charging.
- Scale: up to 16 units in parallel for 96 kW. 5 year warranty.
One spec trips people up. The sheet lists 6,000 W rated output but a maximum continuous line wattage of 3,000 W. That suggests each 120 V leg tops out at half the total, so have your electrician balance loads across both legs.
Idle draw: the hidden battery drain
Inverters use power just being on. EG4 lists idle consumption for the 6000XP at about 50 W on battery, under 30 W with solar and under 50 W with AC. At 50 W, a full day of idling uses about 1,200 Wh (50 times 24). That is nearly all of a single 12.8 V, 100 Ah LiFePO4 battery's 1,280 Wh. Size your battery bank for your loads plus the inverter's own draw. EG4 lists battery charging and discharging efficiency at 93% each, so some energy is lost both ways.
What to look for when you buy
48 V off-grid all-in-one inverter (example: EG4 6000XP)
Best for: A home or cabin battery-backup system with solar, and generator charging
EG4 lists 6,000 W at 120/240 V, 8,000 W usable solar on two MPPTs, a 48 V battery input, a generator input, under 15 ms switching and a 5 year warranty.
Watch out: It draws about 50 W idling on battery, and the max continuous line wattage is 3,000 W per the sheet. Have it installed by an electrician.
See options on Amazon (opens Amazon in a new tab)Microinverters for a grid-tied array
Best for: Roof arrays with partial shade
DOE says microinverters keep shade or damage on one panel from cutting the power drawn from the others.
Watch out: Grid-tied systems need a backup-capable design and battery to run during an outage.
See options on Amazon (opens Amazon in a new tab)Pure sine wave inverter for a 12 V battery bank
Best for: Small DIY systems built on 12 V LiFePO4 batteries
A 12 V battery bank needs an inverter to run AC devices. Look for a low-distortion pure sine output like the 6000XP's under 3% THD spec.
Watch out: Match the inverter's continuous watts to your loads and fuse the battery cables correctly.
See options on Amazon (opens Amazon in a new tab)Questions people ask
- Do solar panels work during a power outage?
- Only if the system is designed for it. DOE says solar-plus-battery systems use advanced inverters to run without the grid when designed to. Grid-following inverters need a grid signal.
- What is the difference between a string inverter and a microinverter?
- A string inverter serves a whole string of panels, so shading one panel lowers the string's output. Microinverters sit on each panel, so one shaded panel does not affect the others, per DOE.
- How much power does an inverter use when idle?
- It varies by model. EG4 lists its 6000XP at about 50 W idling on battery, which is about 1,200 Wh over a day.
- What is a hybrid or all-in-one solar inverter?
- One unit that combines the inverter, solar charge controller and battery charger, and can usually take grid or generator power too, like the EG4 6000XP.
Sources
- Solar Integration: Inverters and Grid Services Basics, U.S. Department of Energy
- EG4 6000XP Off-Grid Inverter Specification Sheet v1.2.1, EG4 Electronics
- LiTime 12V 100Ah LiFePO4 Lithium Battery (specifications), LiTime