Comment by msandford | Hacker News Reader

Comment by msandford | Hacker News Reader

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Net metering is really, really smart when the installed base is small relative to the fossil fuel power plant capacity. But it doesn't scale forever. Once it gets up towards 20-40% of the fossil fuel capacity, it goes from an asset to a liability.

Suppose I have a 100MW gas turbine. And suppose there's 1MW of solar installed in my generation network. I don't really care if I sell 80MW at noon and 90MW around dinner time and 50MW through the night, or if instead it's 79MW at noon and 91MW at dinner and 51MW at night. The gas costs about the same irrespective of when I burn it so a bit of a fuel shift doesn't really matter.

But take that 1MW and turn it into 20MW and suddenly we go from 80MW at noon to 60MW at noon, 90MW at dinner to 110MW at dinner and uh oh. You see the problem? Whatever losses I endured at noon I don't get to make up for at dinner because my plant only goes up to 100MW and now we're not just shifting when we burn how much fuel, we're literally having to shift the power generation to a different plant.

Is this example precisely accurate? Absolutely not. But it helps you get a feel for the problem of net metering at scale. The grid can act as a battery for a few % of total generation, but by the time you hit some number, maybe 20% maybe 40% net metering turns from a cool math trick to a real cost on the grid.

Net metering only makes sense as a way to incentivize solar installations. Looking at the economics, it's not something any utility would offer willingly.

It's like if the grocery store let you give them milk for a credit at full price. (Let's ignore the sanitary/health/quality issues that would come up.) You decide to buy a cow and you drink that milk. Sometimes you need more than your cow can give so you buy extra from the store. Sometimes you need less and you sell the extra to the store. Long term, you use as much as your cow produces on average, so you pay the store nothing. But the store has provided a valuable services to you and has incurred expenses in doing so. They have to keep the lights on and maintain a building and pay workers to handle your transactions but they make no money from you. The only way it would work at all is if they made enough money from their non-cow-owning customers to make up for it, and that can only take you so far.

> It's like if the grocery store let you give them milk for a credit at full price.

I know of quite a few places where through net metering you don't get full price, you get the wholesale rate for your production which is significantly less.

Isn't that something other than net metering? Wikipedia calls that one "net purchase and sale."

Sure, I'm mentioning this because the number of places where you feed in at the retail rate is shrinking. It's great to get renewables on people's homes but as you get more of it, it becomes very expensive as fewer people pay for the base load

Not to be rude, but that's definitionally NOT net metering. Net metering is where you only get changed for your net consumption. If they're looking at your gross consumption and gross production separately, it just can't be net metering. You might still decide to sell solar to the grid for the wholesale price and get a reduction in your bill, but it's not net metering.

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