What Should Actually Be Connected to Your Solar Inverter?
You’ve decided to install solar.
The quotation arrives and somewhere among the panels, batteries, breakers and mysterious electrical terminology are two innocent-looking phrases:
Essential loads
Non-essential loads
It sounds straightforward.
The fridge is essential. The TV isn’t.
Except that’s not really what these terms mean.
When we talk about essential and non-essential loads in a solar or backup-power installation, we’re primarily deciding:
Which circuits should continue receiving power from the inverter when the grid goes down — and which shouldn’t?
Getting that decision right can make the difference between a backup system that comfortably carries your home through an outage and one that overloads, drains its batteries surprisingly quickly or costs far more than it needs to.
First: What Is an Essential Load?
An essential load is normally an electrical circuit or appliance that you deliberately want the inverter and battery system to continue powering when grid electricity is unavailable.
Typical examples might include:
- lights;
- fridge and freezer;
- Wi-Fi router and fibre ONT;
- alarm system;
- selected plug circuits;
- television;
- computers;
- security equipment; and
- garage-door or gate motors.
Notice something?
“Essential” doesn’t necessarily mean low power.
And it doesn’t necessarily mean something you literally cannot live without.
It means:
We’ve chosen to keep this powered from the backup system.
So What Is a Non-Essential Load?
These are normally high-consumption appliances or circuits that you don’t need the battery to support during a power failure.
Common examples include:
- electric geysers;
- electric ovens and hobs;
- pool pumps;
- underfloor heating;
- large air conditioners;
- electric heaters;
- some borehole pumps; and
- other heavy loads.
When the grid fails, these circuits can be allowed to switch off while the inverter concentrates its limited battery power on the things you actually want to keep running.
And that leads to an important idea:
Non-essential doesn’t mean unimportant. It means it doesn’t need battery backup.
Your geyser is obviously useful.
Your swimming pool still needs filtration.
Your oven still needs to cook dinner.
They simply don’t necessarily need to operate during a grid outage.
Why Not Just Put Everything on the Inverter?
This is where many solar-system expectations go wrong.
Suppose you’ve bought an 8 kW inverter.
It’s tempting to think:
“Excellent. My house can now use 8 kW whenever it likes.”
Not quite.
The inverter has a maximum output capability. Your battery has its own maximum charge and discharge rates. Your solar panels have variable production. And your battery contains a finite amount of stored energy.
These are related — but they’re not the same thing.
Power and Energy Are Different
This distinction is enormously useful when understanding solar.
kW (kilowatts) tells you how much power you’re using right now.
kWh (kilowatt-hours) tells you how much energy you’ve used over time.
Think of it like this:
kW is how fast the tap is running.
kWh is how much water is in the tank.
An inverter may be capable of supplying a large amount of power, but that doesn’t mean your battery can supply that power for very long.
A Simple Example
Imagine you have:
8 kW inverter
5 kWh battery
Now switch on a 3 kW geyser.
Ignoring losses and other technical factors for a moment, if that geyser ran continuously at 3 kW:
5 kWh ÷ 3 kW = about 1.7 hours
And that’s if the geyser were the only thing in the house using electricity and the full nominal battery capacity were usable.
Now add:
fridge, freezer, lights, TV, Wi-Fi, computers and a few other appliances.
Suddenly that battery isn’t looking quite so enormous.
That’s why:
A big inverter doesn’t automatically mean long backup time.
The inverter determines how much load the system can handle.
The battery largely determines how long it can keep handling it.
The Kettle Problem
Here’s an appliance that demonstrates another important point beautifully.
A kettle might use around 2 kW.
That sounds terrible for a backup system.
But perhaps it runs for only three minutes.
Very approximately:
2 kW × 3/60 hours = 0.1 kWh
So boiling the kettle once might consume around 0.1 kWh.
Compare that with a modest 500 W load running for eight hours:
0.5 kW × 8 hours = 4 kWh
The lower-power device has consumed 40 times as much energy.
This is why you can’t judge battery impact from watts alone.
High power for a few minutes can sometimes matter less than moderate power for hours.
Of course, the inverter and battery still need to be capable of supplying that kettle’s 2 kW instantaneous demand.
What Should Usually Be on the Essential Side?
There’s no universal answer, because every household is different.
But here’s a sensible starting point.
| Load | Typical Choice | Why |
|---|---|---|
| Fridge/freezer | Essential | Food preservation; modest average consumption |
| Fibre ONT/router | Essential | Communications; very low consumption |
| Lights | Essential | Low consumption, especially LED |
| Alarm/security | Essential | Security |
| TV | Usually essential | Relatively modest consumption |
| Computers | Depends | Important for work-from-home |
| Selected plugs | Essential | Useful, but requires sensible use |
| Kettle | Maybe | High power but short duration |
| Microwave | Maybe | High power but normally brief |
| Geyser | Usually non-essential | Large sustained load |
| Oven/hob | Usually non-essential | High power |
| Pool pump | Usually non-essential | Can normally wait |
| Underfloor heating | Non-essential | Very high energy demand |
| Electric heaters | Usually non-essential | Heavy continuous load |
| Air conditioning | Depends | Can be a substantial load |
| Washing machine | Depends | May be better scheduled for daytime solar |
| Dishwasher | Depends | Often better shifted to solar-production hours |
The word “depends” is important.
Solar isn’t about following somebody else’s list.
It’s about designing the system around your household.
But Here’s Where Solar Changes the Story
So far we’ve mostly been talking about backup power.
Solar introduces another possibility.
A device can be:
Non-essential during an outage…
but
Very useful when surplus solar is available.
The geyser is a perfect example.
You might deliberately exclude the geyser from battery backup so that it doesn’t flatten your batteries overnight.
But at midday, when the panels are producing strongly?
That’s an excellent time to heat water.
Likewise:
Pool pump: run during good solar production.
Dishwasher: start around midday.
Washing machine: use during daylight.
Geyser: heat water while PV production is high.
This is called load shifting.
Instead of asking:
“How much electricity can my solar system generate?”
start asking:
“How much of my electricity use can I move into the hours when my panels are generating?”
That’s one of the most powerful ways to get more value from a solar installation.
Your Geyser Can Be Non-Essential and Still Use Solar
This point is worth emphasising because it initially sounds contradictory.
A properly designed system may allow certain non-essential loads to operate when the grid is available and/or when sufficient solar generation exists, while preventing them from draining backup batteries when the grid fails.
Exactly how this is implemented depends on the inverter, wiring, control equipment and installation design.
So:
Non-essential ≠ never powered by solar.
It usually means:
We don’t want the battery responsible for keeping this running during an outage.
That is a very different thing.
Be Careful With “Essential Plug Circuits”
Here’s another trap.
The electrician puts your lounge plugs onto the essential circuit.
Wonderful.
Except the inverter doesn’t know what’s plugged into them.
Today it’s:
TV + router + laptop.
Tomorrow someone plugs in:
2 kW fan heater.
The socket hasn’t changed.
But the load certainly has.
The same applies to hairdryers, kettles, irons, portable heaters and other high-power appliances.
That’s why everyone in the household should understand which plugs are backed up and what shouldn’t be connected to them during an outage.
A little label saying INVERTER SUPPLY can be surprisingly useful.
The Battery Percentage Trap
Suppose the grid goes down at 18:00.
Your battery says:
100%
Excellent.
Then the geyser, heater, oven and kettle all start operating.
A short while later:
76%
Then:
58%
Then you begin wondering whether something is wrong with the battery.
Probably not.
You simply asked a relatively small energy store to power very large loads.
A battery percentage means little without knowing how quickly you’re consuming it.
This is why many inverter monitoring apps show both:
State of Charge (SOC)
and
Current Load
Learn to watch both.
A battery at 50% supporting a 300 W house load is in a very different situation from a battery at 50% supporting 5 kW.
Solar Panels Don’t Always Produce Their Sticker Rating
This also matters when deciding what to run during the day.
A 6 kWp solar array doesn’t continuously produce 6 kW from sunrise to sunset.
Output changes with:
- time of day;
- season;
- cloud cover;
- panel temperature;
- shading;
- panel orientation;
- inverter limitations; and
- system design.
So don’t schedule every heavy appliance to start at exactly 12:00 simply because “that’s when the solar is working.”
Watch your system.
Learn its production pattern.
Then stagger loads accordingly.
For example:
10:00 — washing machine
11:30 — geyser
13:00 — dishwasher
14:00 — pool pump
The actual times aren’t important.
The principle is:
Use electricity when you have electricity.
How to Decide What’s Essential in Your Home
Here’s a very simple exercise.
Imagine the grid is going to be off for six hours tonight.
Now walk around your house and ask:
“Would I genuinely want my battery powering this for those six hours?”
Fridge?
Yes.
Internet?
Probably.
Lights?
Definitely.
Pool pump?
Probably not.
Geyser?
Perhaps you heat the water beforehand instead.
Underfloor heating?
Your battery has just quietly left the room.
Once you’ve done that exercise, you’ve essentially started designing your essential-load strategy.
Then Ask a Second Question
Now imagine it’s a sunny Saturday at midday and your batteries are already full.
Ask:
“What can I switch on now instead of buying electricity later?”
Now the answers change.
Geyser?
Yes.
Pool pump?
Absolutely.
Dishwasher?
Good idea.
Washing machine?
Go for it.
That’s the difference between merely owning solar panels and using solar intelligently.
Essentially: The TL;DR
Essential loads are the circuits you choose to keep powered by your inverter/battery when grid power disappears.
Non-essential loads are generally circuits you’re prepared to let switch off rather than unnecessarily drain or overload the backup system.
A larger inverter does not automatically mean longer backup time.
Remember:
kW = how much power you’re using now.
kWh = how much energy you have/use over time.
Heavy loads such as geysers, ovens, heaters and pool pumps don’t necessarily need to be forbidden from using solar.
Instead:
Keep them off the battery when appropriate — and move their use into periods of surplus solar production.
And perhaps the most useful rule of all:
“Don’t design your solar system around what your house can consume. Design it around what you actually need when the grid is gone.”
— Essentially
