Should I Add More Solar Panels or a Bigger Battery?

It is one of the most useful questions a homeowner can ask before upgrading an existing solar system: Should I add more solar panels or get a bigger battery?

The answer depends on where the energy gap is occurring. A battery stores electricity. It does not generate it. Solar panels generate electricity. They do not automatically make that electricity available after sunset. So before investing in either upgrade, you need to understand what your existing solar system is doing throughout the day.

Additional solar panels can make sense when your home simply does not generate enough electricity. You might consider expanding your solar system if:

• your existing solar system is relatively small
• daytime household consumption has increased
• you have added air conditioning or a pool
• you are moving from gas to electric appliances
• you have bought or plan to buy an EV
• your battery regularly struggles to reach full charge
• you have suitable unused roof space
• you expect household electricity consumption to keep increasing

If your battery is regularly undercharged because there is not enough surplus solar available, installing even more battery capacity may not solve the underlying problem. You may need more generation first.

Additional battery capacity becomes more interesting when you are already generating surplus electricity but cannot store enough of it.

Signs can include:

• significant solar exports during the day
• your battery reaching full charge early
• your battery emptying well before morning
• high grid imports during evening peak periods
• increased overnight electricity consumption
• wanting greater blackout backup
• planning to charge an EV outside solar-production hours

In those situations, increasing battery storage may allow you to retain more of your own solar rather than exporting it.

Add more battery storage to an existing solar system

This is a simple way to think about it.

If you are short of energy: You probably need more solar generation.

If you have plenty of excess energy but nowhere to keep it: You may need more battery storage.

If both are happening: A combined solar and battery upgrade may make more sense.

That distinction can prevent homeowners from spending money on the wrong part of their system.

Maybe. Exporting solar does not automatically mean your system is oversized. The important question is how much you export and when. For example, your system may export substantial electricity around midday but still fail to generate enough in the morning, late afternoon or during winter. That is why smart-meter and inverter data can be valuable when planning an upgrade. Rather than looking only at an electricity bill, the team at MPV Solar can look at the pattern of generation, exports and household consumption.

Again, it depends when those imports occur. If you are importing significant electricity overnight while exporting large amounts of solar during the day, additional battery capacity may help shift more of your own electricity into the evening.

But if you are importing electricity throughout the day because your solar system cannot keep up with household demand, more storage alone is unlikely to fix the problem. You first need electricity available to store.

An EV can change the equation significantly. If your vehicle is regularly parked at home during daylight hours, increasing solar generation may allow you to direct more excess rooftop solar straight into the car.

Learn more about charging an EV with solar panels.

If your EV is away during the day and normally charges at night, battery storage may become more valuable. However, home batteries and EV batteries have very different jobs, and using a residential battery to completely recharge an EV every night may not be the best system strategy.

Find out How much battery storage do I need for an EV? 

Often, but several factors need to be assessed. These include:

• existing inverter capacity
• roof space and orientation
• panel compatibility
• age of the existing installation
• electrical configuration
• switchboard capacity
• network requirements
• whether adding a separate system may make more sense

Sometimes existing equipment can be retained. In other cases, an inverter or broader system upgrade may provide a better long-term solution.

Potentially. Some battery systems can be expanded with additional modules, while others may require a separate battery or system redesign. Compatibility can depend on:

• battery make and model
• battery age
• inverter compatibility
• existing battery capacity
• battery management system
• manufacturer requirements
• installation standards

Your inverter is critical to both options.

If you want more solar panels, the inverter must be assessed to determine whether it has sufficient capacity or whether an additional or replacement inverter is required.

If you want battery storage, the existing inverter may already support a compatible battery, or an AC-coupled battery with its own inverter may be possible.

Instead of choosing based on a generic package, look at:

Solar generation: How much electricity does the rooftop system produce?

Solar exports: How much surplus electricity is currently being sent to the grid?

Grid imports: When are you still buying electricity?

Battery behaviour: When does the battery become full and when does it run out?

Future consumption: Are you adding an EV, electric hot water, induction cooking or other major loads?

Your objective: Are you trying to minimise bills, increase self-consumption, improve backup or prepare for home electrification? The answers will reveal whether your next dollar is better spent generating more electricity, storing more electricity or doing both.

Solar systems should evolve as households change.

A system that suited your home five years ago may not suit an EV, larger family, home office, heat pump and increasing electrical loads today.

MPV Solar can assess your existing panels, inverter, battery, switchboard, solar generation and household consumption before recommending what actually needs upgrading.

More solar? More battery? Or both? We can help you work it out before you spend.