Outback FX-R Series Technical Note on Input Modes

Application Note

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form of a feed-in tariff program that can vary widely depending on the local state and utility

policies.

When the grid goes down, the main load panel (to the right of the inverter in Figure 3) will also

lose power but the critical loads panel (to the left of the inverter in Figure 3) will continue to

power loads from energy stored in the batteries and/or from the PV array. The batteries will

continue to power the loads throughout the night, and will recharge in the morning when the PV

array starts producing power to take over powering the critical loads while recharging the

batteries.

Specific settings for the Grid Tied input mode can be entered using the MATE3 user interface

Configuration Wizard, or can be done manually with guidance from the programming section of

the MATE3 Owner’s Manual.

While most site owners have opted for the more cost-effective grid-tie inverter, many have been

surprised when the PV panels are unable to produce power when the grid is down, since the

grid-tie inverter needs an AC source to synchronize to in order to produce power. As mentioned,

the grid/hybrid inverter produces its own AC source from energy stored in the batteries. It

isolates itself from the grid during a power outage using an internal transfer switch, and can

power critical loads connected to a backup subpanel panel while the power is out (panel on left

in Figure 3).

If it is known from the beginning that a site is subject to frequent or extended power outages, or

if there is a desire for secure power in areas that could experience extreme weather, then it is

more cost effective to add the grid/hybrid system from the beginning than to add in as a retrofit

later. More information on how to retrofit a grid-tied inverter system for storage can be found in

an application note titled, “AC Coupling Grid-Tie Inverters With OutBack Battery-Based

Inverters” on the OutBackPower.com website.

AVOIDING EXPENSIVE TIME OF USE SURCHARGES

Many utilities struggling with how to deliver enough energy during peak demand times have

turned to time of use (TOU) surcharges to discourage their customers from using unnecessary

loads during these peak usage times. Peak demand times usually include 4pm to 7pm or later

with per kilowatt charges running 200 to 300 percent of off-peak periods. Some utilities also

have a morning TOU surcharge, and may add weekend and seasonal peak periods as well.

As the solar peak typically runs from

about 10am to 4pm (more or less

depending on seasonal variation) adding

a local solar generation system will not

do much if anything to reduce TOU

charges without some kind of energy

storage system. As the solar peak

does not line up with peak demand

periods for many solar sites, the

Figure4 ‐ GridUseTimers