On-grid vs off-grid vs hybrid solar

Almost every rooftop enquiry comes down to one of three configurations. Getting this decision right at the first conversation saves everyone a redesign later, because the battery decision drives the entire cost of the system.

On-grid

The array feeds the load during daylight, and whatever is left over is exported to the utility under net metering. There is no battery. When the grid goes down, the inverter shuts down too — that is a safety requirement, not a fault, because linemen must not be working on a line that a rooftop inverter is back-feeding.

• Cost: the lowest per watt of the three, because there is no battery.
• Best for: homes, offices and factory sheds with a reliable supply, where the goal is to cut the bill.
• Watch for: net-metering rules, sanctioned load limits and approval timelines, which vary by state and utility.

Off-grid

The array charges a battery bank through a charge controller, and the loads run from the battery. The utility is not involved at all — often because there is no utility to involve.

• Cost: the highest per watt, because the battery bank is sized for the load plus days of autonomy, and batteries are the shortest-lived component in the system.
• Best for: farms, remote and border sites, telecom, surveillance and pumping.
• Watch for: sizing from the roof area instead of the load. Off-grid sizing starts from daily watt-hours and required autonomy, always.

Hybrid

Grid-connected and battery-backed at the same time. The array offsets the bill like an on-grid system, the battery carries essential loads through an outage, and surplus can still be exported where the utility permits it.

• Cost: between the two, and controllable — the battery is sized for essential circuits, not the whole building.
• Best for: homes and clinics in outage-prone areas, and anywhere currently running a diesel generator.
• Watch for: deciding which circuits are “essential” before quoting. That single decision sets the battery cost.

Three questions that settle it

1. Is there a grid at the site? No grid means off-grid. There is no second option, and the conversation moves straight to daily load.
2. Does the load have to survive an outage? If yes, the system needs a battery, which means hybrid. If no, on-grid delivers the same bill reduction for less money.
3. Is net metering available? Where it is, exporting surplus improves the economics of both on-grid and hybrid. Where it is not, size the array closer to the daytime load rather than the roof area.

What changes about the modules

Less than people expect. The same module can serve all three configurations; what changes is the string design and the voltage the system is built around. In practice:

• Small off-grid systems built around a 12V battery bank use 12V-class modules — the InnovaEDGE line.
• Rooftop, hybrid and larger off-grid systems use 24V-class modules — the InnovaMAX line — because fewer, larger modules cut the number of clamps, rails and cable runs, and rooftop labour is where the money goes.

A fuller breakdown of what goes into each configuration is on the rooftop solar page, and if you are quoting a live enquiry we will work the array, battery and controller sizing out with you.