In my previous articles in this series on solar power basics, we've looked at solar energy options including a basic overview of how a system works, renewable energy rebates, grid connect, solar panels and deep cycle batteries. In this article, we'll take a look at two other crucial components in a system; the regulator and inverter; both of which sit between the solar panels and your appliances or battery bank - depending on the type of system you have.

What is a solar regulator?

A solar regulator (sometimes referred to as a charge controller) is used in conjunction with a stand alone system, or a grid connect solar power system with a battery bank for backup. For a grid connect system without a battery bank, a solar regulator is not required, just a power inverter which we'll look at shortly.

A solar regulator is a small box situated between the solar panel and your batteries. Its role is to control the amount of charge coming from the panel that enters into the battery bank to ensure that it doesn't overcharge the batteries. A regulator can also offer a direct connection to load; i.e. you can run appliances directly from it, bypassing the battery bank; but the batteries will continue to be charged.

The solar regulators of today are highly efficient. A few years ago, I spent $350 on a whizz bang 3 phase mains powered battery recharger for charging my batteries when I was back in the 'burbs (before I had the panel) and it performs nowhere near as well as the solar regulator I now have which cost less. The regulator is able to cram far more juice into my battery.

Regulator hookup in the back of my minivan
(Solar regulator from Energy Matters)

To calculate the size regulator you'll need, add up the amp ratings of your solar panels - or you can use this solar energy system builder tool which will calculate the size you'll need based on various component selection.

I have a 130 watt panel, which is rated to around 7.8 amps. Considering I'll add another panel in the future, that means the regulator I needed had to be able to handle at least 16 amps, and just to be safe, I bought a 20 amp solar regulator. That's an important point - to take into account your future needs which will save you money as you upgrade your system.

A solar regulator is maintenance-free; you just need to check the connections regularly and ensure where you have it situated there's air flow and it's not placed in direct sunlight. While they are quite robust, extreme summer heat can affect a solar regulator's performance and shorten the serviceable life.

Another tip - always place an appropriately rated fuse between the solar panel and the regulator to help reduce fire risk, protect your batteries, regulator and any appliances you're running.

What is a power inverter?

As mentioned in my articles on solar power basics and solar panels, the current produced by a panel (and consequently from a deep cycle battery) is DC (Direct Current). While there's many appliances available that will run directly from DC; most household appliances that you plug into an ordinary wall socket require AC (Alternating Current). In order to switch the current type, you'll need a power inverter.

The inverter sits between the solar panels and your mains wiring in a mains grid connect system, or between the batteries and your appliances in a stand alone power setup.

In the case of grid connect, the inverter feeds any surplus power your panel has generated directly into the power grid for use by other customers - no; the utility doesn't get it for free - you get a credit for the electricity you've contributed, and in some countries you'll even get paid extra! 

Inverter used in mains grid connect system
(Image courtesy of Energy Matters Australia)

Tip - cheap inverters do not seem to like ac adaptors running off them, such as those used for power supplies for notebooks. The inverter gets quite warm, to the point of tripping out if it's a hot day. That heat is also just wasted energy.

The size of the inverter you'll need will depend upon your peak load; i.e. the total number of watts you might be using at any given point in time. For example, if you'll be wanting to watch TV while the washing machine is going, lights are on etc.; you'll need to add up the watts of all those appliances and select an inverter rated to that wattage.

It doesn't hurt to go a little larger too in case you need the extra power at some stage and also, electrical appliances can consume far more than their rating when they are first switched on.

As with a solar regulator an inverter is maintenance free.

You can learn a little more about power inverters here or check out my other articles in the solar power series below!