What is on the FlexBOSS21 spec sheet?
The FlexBOSS21 Hybrid Inverter is a split-phase hybrid inverter from EG4 Electronics, rated for 16000 W of continuous AC output at 240 V. EG4 Electronics recommends a solar array of at most 21000 W. Keep these ratings apart when you plan: 16000 W is what it puts out, and 21000 W is the most panel power the maker recommends feeding it.
Its CEC efficiency is 97 %, according to EG4 Electronics. The spec sheet lists UL1741, SA, SB certifications and a warranty of 10 years. On the spec sheet, grid sell back is a yes, and so is rapid shutdown.
| Power and capacity | |
|---|---|
| Continuous AC output | 16000 W |
| Surge output | 24000 W |
| UPS switchover (max) | 20 ms |
| Size and moving it | |
| Width | 22.28 in |
| Height | 30.43 in |
| Weight | 121 lb |
| Temperature and warranty | |
| Warranty | 10 years |
| Product | Best current price | Watts per dollar | Value rank |
|---|---|---|---|
| EG4 Electronics FlexBOSS21 Hybrid Inverter | $4,390.34 at A1 SolarStore | 3.64 W/$ | #1 of 5 |
| Sol-Ark Limitless 15K-2P-N Hybrid Inverter | $6,099.15 at A1 SolarStore | 2.46 W/$ | #5 of 5 |
| Sol-Ark Limitless 18K-2P-LV Hybrid Inverter | $6,999.32 at A1 SolarStore | 2.57 W/$ | #3 of 5 |
| EG4 Electronics FlexBOSS18 Hybrid Inverter | $3,879.57 at A1 SolarStore | 3.35 W/$ | #2 of 5 |
| EG4 Electronics 18kPV Hybrid Inverter | $4,699.08 at A1 SolarStore | 2.55 W/$ | #4 of 5 |
How big and heavy is the FlexBOSS21?
The FlexBOSS21 Hybrid Inverter weighs 121 lb, which puts it in the heavy (over 50 lb) class. It stands 30.43 in tall, 22.28 in wide and 11.22 in deep. Heavy equipment usually needs more than one person and a mount rated for its weight.
The enclosure is rated NEMA 4X. A NEMA type rates an enclosure against outside conditions such as water, dust and ice. EG4 Electronics gives an operating temperature low of -25 C and a high of 60 C.
How much solar can it take?
The maker recommends at most 21000 W of panels on this inverter. It has 3 MPPT inputs. Panels facing different ways are usually put on different MPPT inputs.
The MPPT voltage minimum is 120 V and the maximum is 440 V. PV input voltage is capped at 600 V. Panel voltage climbs on cold mornings, so leave room under any voltage cap when you size a string.
What battery bank does the FlexBOSS21 expect?
The FlexBOSS21 Hybrid Inverter has a nominal battery voltage of 51.2 V. Battery voltage has a minimum of 40 V and a maximum of 60 V.
Charge and discharge current each top out at 250 A. Check the battery's own current limit against the 250 A figure.
What happens when the grid goes down?
EG4 Electronics lists a UPS switchover time of at most 20 ms. That places it in the site's 20 ms or less group. EG4 Electronics rates continuous AC output at 12000 W from the battery alone, against 16000 W overall.
Compare the battery-only rating with the loads you need in an outage. Surge is 24000 W for 0.5 s. The spec sheet includes a statement about starting air conditioners, giving 5 tons.
The site groups it as 2000 W or more of continuous AC output.
How much power does the FlexBOSS21 give per dollar?
At A1 SolarStore the FlexBOSS21 Hybrid Inverter costs $4,390.34 for 16000 W of continuous AC output, and the site lists it at 3.64 W/$. Among the inverters in this article, it ranks #1 of 5 on value.
Watts per dollar leaves out wiring and labor, so add those to the budget.
Where does it lead, and where does it trail?
It leads on value at #1 of 5, ahead of the FlexBOSS18 Hybrid Inverter at #2 of 5. It trails on switchover: its at most 20 ms is longer than the 5 ms Sol-Ark lists for the Limitless 15K-2P-N Hybrid Inverter.
Its surge of 24000 W lasts 0.5 s, while the Limitless 18K-2P-LV Hybrid Inverter lists 36000 W for 10 s. Surge ratings matter for loads that pull hard as they start, such as well pumps and other motors.
How does the FlexBOSS18 Hybrid Inverter differ?
The FlexBOSS18 Hybrid Inverter costs less at $3,879.57, against $4,390.34 for the FlexBOSS21 Hybrid Inverter. It is rated for 13000 W continuous and 10000 W from the battery alone, against 16000 W and 12000 W on the FlexBOSS21 Hybrid Inverter. It has 2 MPPT inputs instead of 3, and the recommended array is at most 18000 W.
Its 3.35 W/$ places it #2 of 5. The case is the same height on paper, 30.43 in, and it weighs 115 lb.
Where does the Sol-Ark Limitless 15K-2P-N differ?
Sol-Ark lists a switchover of at most 5 ms for the Limitless 15K-2P-N Hybrid Inverter, against 20 ms on the FlexBOSS21 Hybrid Inverter. It is rated for 15000 W continuous, and generator input is a yes. Sol-Ark gives separate solar figures: a max solar input of 19500 W and a recommended array of at most 23400 W.
The enclosure is rated IP65 / NEMA 3R, and the unit weighs 135 lb. At A1 SolarStore it costs $6,099.15, which puts it at 2.46 W/$ and #5 of 5.
What does the Limitless 18K-2P-LV Hybrid Inverter add?
Sol-Ark rates the Limitless 18K-2P-LV Hybrid Inverter at 18000 W continuous, above the 16000 W of the FlexBOSS21 Hybrid Inverter. Its recommended array is at most 32400 W, against 21000 W for the FlexBOSS21 Hybrid Inverter. Sol-Ark also lists a max solar input of 28800 W.
Sol-Ark lists an operating low of -40 C. It weighs 137 lb and stands 34 in tall. At $6,999.32, its value is 2.57 W/$, rank #3 of 5.
Which batteries does the 18kPV Hybrid Inverter list?
EG4 Electronics lists the 18kPV Hybrid Inverter for lead-acid or lithium batteries, with a 48 V nominal bank. Its surge rating is 15500 W for 300 s, against 24000 W for 0.5 s on the FlexBOSS21 Hybrid Inverter.
Generator input is listed as a yes. Continuous output is 12000 W, and the price is $4,699.08, for 2.55 W/$ and #4 of 5 on value.
How do you pick between these inverters?
Start with the loads you must keep running in an outage, and compare battery-only output first. If more panels may come later, compare the recommended array size as well as output.
Match the battery voltage and current limits to the bank you own or plan to buy. Ask your installer and utility which listings they need before you order.