While purchasing solar panels you may also be looking at getting some other green energy appliances at the same time such as a power diverter or a solar battery.

Those two choices offer competing ideas for how to get the most out of solar panels by finding a use for any electricity which is not being consumed right at that time.

But which is a better choice of investment in the long run, a solar battery or a power diverter?

Before going into the pros and cons of the two devices let’s explain what a solar battery and a power diverter are first so people can understand the difference in what they offer.

A solar battery is simply a large scale battery system meant to store excess power generated by solar panels which would otherwise be sent to the grid. 

This stored power can then be used later when the panels are not producing electricity, either powering your home or for another use such as charging an electric vehicle.

A solar power diverter, also called an immersion diverter, is a device which uses solar energy to generate hot water by powering the immersion.

To do this it measures if your solar panels are currently generating excess electricity not being used in the house. If there is any surplus to work with, it diverts that power to the immersion heater rather than letting it be exported.

There are multiple pros and cons to getting a solar battery or power diverter, all of which will have to be looked at in the context of your solar PV system and your power usage.

Factors which will affect the value of either appliance include:

Both of them rely on having enough solar electricity from your solar panels which would otherwise be exported to the grid. If you have a small solar PV system, or if there are people at home all day using the power being generated, there may not be much or any excess electricity.

Solar batteries are definitely a more expensive option than a power diverter. A battery is a far more substantial investment since it is a larger and more complex product, needing to store large amounts of energy rather than simply telling it where to go.

These are average prices, and some high end battery systems may cost more than this, going up to the region of €3,000.

Both solar batteries and power diverters have a much shorter expected lifespan than the solar panels they are attached to, and will need to be replaced at least once. 

Power diverters should be able to stay operational as long as they are well maintained, but they come with a shorter warranty. This may reflect they expectation they will break.

Solar batteries have come a long way, with their lifespans extended dramatically in just a few years. This is especially true of modern Lithium Ion Phosphate (LiFePO4) batteries which are becoming the industry standard.

This growth in the technology is reflected in their longer warranty periods. However, a battery will inevitably wear out with each cycle of charging and discharging.

Solar batteries definitely have the edge in terms of the different uses they can be put to compared with power diverters.

A solar power diverter is used for a single task, powering the immersion heater. If you don’t need that, then it has no function.

Energy stored in a solar battery can be used to power your home, EV charging in the evening, sold the grid if it is not needed, or even used to power the immersion just like a diverter.

A solar battery can even be charged using cheaper electricity at night to be used the following day. This use creates savings even without involving solar panels.

Using a battery or power diverter is about replacing some paid energy use with free solar power, whether that is electricity, gas, or oil. 

In the case of a battery, this means reducing the amount of electricity being purchased from the grid, which can have great savings if you have enough surplus. A solar battery can easily increase the amount of your PV system’s power which is used in the home by 30%.

In the case of a power diverter, this depends on what you primarily use for hot water. If you use the immersion heater frequently then you will be saving a considerable amount of money. 

However, if you get most of your hot water from gas or electricity then savings will be smaller as they can be as little as a third of the price of electricity per unit.

This won’t apply to all or even the majority of households, but an increasing number of homes have heat pumps installed, which are a very efficient way to make hot water with electricity.

A heat pump can generate two to three units of heat for every unit of electricity consumed while operating. This is more efficient than the immersion, and having a heat pump reduces the relative value of a power diverter.

There is nothing stopping anyone from getting a power diverter and solar battery installed on their home if they can afford the cost. 

They will, however, be competing for the same surplus of electricity from the solar PV array. If your system is large enough then it could well be generating enough power for both. There is also the option of charging the battery from the grid using cheap night rates.

If we had to recommend a single purchase it would be to invest in a solar battery. But anyone getting solar panels installed should talk this over with their installer.

Whether you wish to get a solar battery or power diverter will depend on factors such as your budget and how you intend to use any surplus electricity. 

If you live in a household that uses a lot of hot water then a diverter might be worth the cost. 

However, in almost all instances the solar battery is the better long term investment. While the upfront cost is higher it can pay for itself in a fraction of its lifespan by significantly increasing the amount of energy being used from your solar panels.

The multiple uses of battery storage such as free EV charging, charging from the grid, or its potential for blackout protection just increase its value further.