[darkwater]

It's not a cost if you self-consume your energy, even if you get paid for what you inject. You are just amortizing differently the cost of the PV installation. But what you get for the energy you sell is not real money, it's just money you MIGHT consume as energy in other periods.

[danw1979]

I think this is the contentious point in this thread: in the UK you can get actual cash for exporting energy to the grid, at similar rates to import, with no strings attached.

Is the model you're describing (usage credits) in the European market somewhere ?

[dannyw]

Actually, saving $1 on something you would pay anyway is more valuable than earning $1 of taxable income.

I think that's just semantics -- unless you genuinely keep racking up non-redeemable energy bill credits for feed-in.

[darkwater]

You don't know if you are going to pay it anyway and depending on the retribution model you can loose them if you don't use them in time.

Cost is not the right mental model here, you can and should count them in the amortization plan of your installation (total cost / (projected generated kWh * lifetime)), so every kWh not used and injected is paying for it, while the kWh consumed should be discounted at the price you would pay for them at that specific moment.

> unless you genuinely keep racking up non-redeemable energy bill credits for feed-in.

I know many many cases of people with overdimensioned PV installations that at some point want to leave their current energy company because prices are changing and have hundreds or more of euros in the "virtual battery".

[nijave]

Opportunity cost

[IshKebab]

I have no idea what you're trying to say. With PV, if you consume one additional kWh your bank balance will be 20c lower than it would otherwise have been. You can argue semantics about whether that is a "cost" all you want, but practically the end result is the same and any financial decisions about whether to consume that kWh should have an identical result to what you'd decide if you bought the energy in for the same price.

[knollimar]

they're saying you might not use the extra energy if your PV runs year round. If you continuously had a year round surplus, you wouldn't have a need to buy any energy, so the credits would be monopoly money.

[IshKebab]

But unless you're off-grid you can always use extra PV energy by selling it to the grid.

[knollimar]

The grid doesn't give you money in these locations.

They give you credits for future consumption. You can only spend this on energy. If you always have a surplus, you will just rack up large amounts of credits.

[IshKebab]

What locations? In the UK they give you actual money. You can withdraw it.