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How many 9s of reliability do you want to pay for? Speaking only regarding residential energy: In North America, other than Hawaii as of a couple weeks ago, so

by ghouse 11y ago

How many 9s of reliability do you want to pay for? Speaking only regarding residential energy: In North America, other than Hawaii as of a couple weeks ago, solar generation banks credit for electricity exported to the grid. In effect, a 100% efficient, and free, battery. In Austrlia, exported power receives credit only equal to the offset generation -- less than 1/3 of the total price of electricity. In those cases, there is an economic evaluation. Otherwise, batteries are for reliability. And apparently there are more residential backup generators in the US than there are residential rooftop solar.

jacquesm 11y ago
Going off-grid when the grid is present and reliable is dumb. Even without net-metering being 100% as long as you cover your own use 90% of the time it is still much cheaper than battery power (charge/discharge costs more than what power from the grid costs, batteries have a life-span). So in that situation you try to cut your consumption when you generate little power or you take the hit by paying for grid power. The larger chunk of your bill in that case will be the termination fees, the electricity bill typically has two components, one where you pay a fixed fee for the connection whether you use it or not and another you pay per used KWh. The first component can handily outstrip the second making those very expensive KWs, especially when you're close to running of your own power most of the time. Still, if you think of it as a replacement for both your genset and your very large battery it may make economic sense to do this anyway. It all depends on the location and reliability of the grid. Where I lived our PV system was many times more reliable than the local grid so we ended up ditching the hookup but that's a very exceptional situation.
- chris_wot 11y ago
  That's what this doesn't take into account. If you install batteries, you use them for only part of the time to make up for times the PV doesn't generate electricity. This offsets costs of drawing from the grid. But when you need to draw from the grid, you do so.

by ghouse 11y ago

jacquesm 11y ago

Going off-grid when the grid is present and reliable is dumb. Even without net-metering being 100% as long as you cover your own use 90% of the time it is still much cheaper than battery power (charge/discharge costs more than what power from the grid costs, batteries have a life-span). So in that situation you try to cut your consumption when you generate little power or you take the hit by paying for grid power. The larger chunk of your bill in that case will be the termination fees, the electricity bill typically has two components, one where you pay a fixed fee for the connection whether you use it or not and another you pay per used KWh. The first component can handily outstrip the second making those very expensive KWs, especially when you're close to running of your own power most of the time. Still, if you think of it as a replacement for both your genset and your very large battery it may make economic sense to do this anyway. It all depends on the location and reliability of the grid. Where I lived our PV system was many times more reliable than the local grid so we ended up ditching the hookup but that's a very exceptional situation.

chris_wot 11y ago
That's what this doesn't take into account. If you install batteries, you use them for only part of the time to make up for times the PV doesn't generate electricity. This offsets costs of drawing from the grid. But when you need to draw from the grid, you do so.