NET METERING, a very simplified explanation.

For a one-paragraph explanation, check this link:

http://www.bmcsolar.com/Home_Page.html

Then navigate to the How Solar Works page. For those who want to understand the details, please read on.

In this article I am going to strictly focus on the residential aspect, although the term Net Metering does apply to both residential and commercial producers of solar electricity. OK, so what is Net Metering? Well, lets take things step by step.

The essence of a solar panel system is this: During the day, Solar PV (Photo Voltaics) panels convert sunlight to DC electricity, which in turn gets converted by an inverter to AC electricity, the kind we use in our homes.

What happens to this electricity? Well, the household appliances that are on during the day (fridge, digital clocks, computers, etc...) use what they need. However, solar PV systems are designed to produce much more than the daytime minimum. The excess electricity gets fed back to the utility grid system. Well call that the Grid with capital G.

As the electricity passes into the Grid through the house electric meter, that meter spins backwards. Lets pause for thought. A meter spinning backwards is pretty unusual. Normally, a meter spins forwards (left-to-right) as it uses electricity, tallying up the kilowatt-hours, (kWh is the way electricity usage is measured, just like a pound is a unit of weight.) At the end of the billing cycle, the utility company charges the homeowner for the number of kilo-watt-hours they used during that billing period.

Back to the backward-spinning meter. In this case, the utility company keeps track of how many kWh was fed back into the Grid by that homeowner, and uses that number as a credit. All this happened during the day, when the sun was out.

When night arrives, things change. Firstly, the PV panels dont produce anything, because there is no sunlight. Now the fridge, clocks, and computers have to get their juice from somewhere else, meaning the Grid. Then the lights and the TV and the microwave, and the garden lights, and the washing machine you get the picture, all get turned on. And now the house meter spins forwards, racking up the kWh used. For the non-solar user, the kWh total is what determines their bill. However, for the user who has a solar PV system, theres a difference. Yes, during non-daylight hours, they rack up the kWh too. However, they had built up a credit during the day. Now, they only have to pay the difference between their usage and their credit, in other words, the NET usage.

Youre getting the picture, but stay with me. For the solar panel system owner, there are kWhs being supplied to the Grid, and kWhs being used from the Grid on a daily basis. Utility companies are too busy to square-up daily. So they give the user a choice of squaring up on a monthly or yearly basis. Whatever the period, the customer pays the utility only for the NET kWh they used during that period. The household electric METER is what keeps track, either by spinning forwards sometimes, or spinning backwards at other times. Put the two together, and you have Net Metering!