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The Miracles of Self Consumption

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Over the years, you may have continually heard me rabbiting on about how to get the most value out of your solar system you have to self consume as much of the energy you produce as you can.

So let’s talk about the difference about export, import and self consumption.

For starters, with most solar systems,  as soon as the sun hits the panels from the first thing of a morning until the sun sets in the evening, it just makes energy and doesn’t overly care where it goes. It either used by the house or it goes to the grid.

Exported Energy

This is the energy produced by the solar system which is surplus to the site or houses requirements and this goes out to the street. This energy is sold to your energy retailer and sits as a credit on your account. The amount you receive for this is around 8.4 cents per kWh (though 1st Energy  in Tasmanian will give 13.4 cents but only for the first 12 months). It’s basically an enticement to sign up with those guys. The rate is called the FIT which stands for ‘Feed In Tariff’. The FIT rate is set by the average of the wholesale price of electricity over the previous 12 months and the rate is announced on the 1st of July every year.

This is low value energy.

Imported Energy

This is energy you buy from the grid. So, of a night time when obviously solar is not working or cloudy days when the site or houses requirements exceed the solar systems energy output. You will pay for this energy at whatever rate that the tariff you’re connected to costs. Obviously, we want to minimise the amount we import from the grid as this costs us money but also the credits we accrue from any energy we sell come off this amount when bill is tallied up at the end of 90 days.

Self Consumption

This is the important bit. This is the energy your solar system has produced that is running your site or house. This is energy you haven’t had to buy and its worth whatever you would have had to pay for it if you didn’t have a solar system.

On tariff 31 that would be around 27 cents per kWh on off peak on Tariff 93 that’s around 15 cents per kWh and on the peak period on Tariff 93 around 32 cents per kWh.

One thing to note is that all of those rates are significantly higher than 8.4 cents that you would have got if you sold the energy. So, self consumption is what we call high value energy.

How do we go about maximising self consumption?

In simple language, use that power. For many of our customers, we use a timer on a hot water cylinder to allow it to come on between the hours of 10 am and 4 pm this means your solar system is heating your hot water for free. Think of this as the world’s cheapest battery. We can dump that energy into the cylinder and store it as hot water to use later. If you have one of our LG Heat Pumps, you can have a look at how your solar is performing (and remotely) via the LG phone app, you can turn on your heat pump (or as they are really called your reverse cycle air conditioner or split system) to use that energy as opposed to selling it for 8.4 cents per unit. So you can preheat or pre-cool our home during the day.

I personally use the timer function on my dishwasher and washing machine to come on during the day so my solar system energises those appliances and it doesn’t cost me anything. I also use my slow cooker a lot. I’m always looking for ways to increase my self consumption and I would be interested in hearing ways people out there have came up with increasing their solar systems value.

Also, system design is important array orientations favouring East and West orientations spreads your available power to self consume earlier and later in the day. This flattening of the power curve means yes your system will make a bit less in a year than an all northern array but will greatly improve your ability to harvest and convert that energy into high value power by actually using it instead of selling it in the middle of the day when homes are often empty.

Let’s just have a look at some numbers really quickly. These are just loose number but it gives you the idea of the importance of self consumption and these based on a typical 6kW solar systems summer performance with the home connected to T93:

If you used 100% of your solar energy and some of our customer especially commercial customers do. 100% of self consumption would save you $405 for 90 days.

If you self consumed 50% of your energy and sold 50% the savings would be $315 for 90 days

If you only self consumed 25% and sold 75% the saving would be $271 for 90 days.

Lastly if you sold it all and self consumed nothing you would only save $226 for 90 days.

The numbers don’t lie and the more you use, the more value it is.

Okay this week’s interesting energy factoid

How fast is electrical energy? From the time you turn the light switch on to the time the energy reaches the light in a typical house is pretty quick.

About 80% to 90% the speed of light quick or around 300 million metres per second quick.

So that the energy travel as an electromagnetic wave but the electrons themselves are moving much, much slower. The difference between the 2 is called drift velocity. This in a copper wire can be as slow as 8cm per hour.

A layman’s version of imagining this as lining up a row of billiard balls so that are all touching and hitting one end of the line with the cue ball. The energy passes through those balls and only the far end one moves any real distance while the majority of the line of balls stays stationary. This is the best way I can describe what is happening.

DMS Energy is the North West Coast of Tasmania’s busiest solar installers and as the name implies, we know a lot about anything energy related. From power points, wiring up or heating and cooling homes or putting your very own power station on your roof. DMS Energy has you covered.

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