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When living in a rental, if solar panels are hooked up in the traditional way they become part of the property, and have to be left behind when leaving the rental.

When placing solar panels, how could I connect those to the grid in a detachable way?

The problem I'm facing is that, from what I understand, both sides are live. A plug is not allowed to be live.

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  • With a rental, you probably need the approval of the landlord first. Would make an written(lawyer checked) agreement to take them with you with the landlord if you are paying for them out of your own pocket.
    – crip659
    Jun 25, 2022 at 15:09
  • The problem here is, depending upon local codes, but generally you need not only the solar panels, but the inverter, disconnect switches, possibly production meter base, all hard wired....as in permanent. Not easily transportable. So, that said, have you approached your landlord about this? Perhaps he/she might pay for everything in exchange for a higher rate of rent. This would increase the value of their property and get higher rents in the future. And it would meet your goal of saving on your electric bill. Jun 25, 2022 at 15:20

2 Answers 2

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You don't.

The reason is, well aside from entitlement issues...

The electric meter may not cooperate. Meters are not necessarily designed to detect current flow bidirectionally. The old ones' discs may spin backwards, but that doesn't mean their digits will roll backwards - they may have a ratchet to disallow that. Smart meters aren't designed to, or are designed to not to. The newest meters can turn that function on, but only if the power company commands it remotely.

So, if you push 1000W onto the grid for 8 hours, you expect your electric bill to be 8 KWH less... actually, it will be 8 KWH more, because the meter has no idea you were the source of that. Whoops!

Any backfeeding onto the grid will require the assent of the power company, so they can fit a more sophisticated meter.

So in a rental, it isn't going to happen.

"But my solar won't exceed my usage, so my meter won't roll backwards". Nope, that fails too. The problem is, the meter only cares about your instantaneous usage vs generation. Your solar panel might make 500W consistently all day. However, your house's load jumps all over the place! Usage is intermittent - when you turn on a light, or when a heater or dehumidifier cycles on. The only constant load is the "vampire loads" from TV, cable box, computer, wall charger blocks, etc. which might amount to 30 watts at most.

So you need to expect that your meter will be needing to roll backwards, a lot. There are gadgets that can throttle the solar generation so that it never rolls the meter backwards, but they need to be hard-wired, so we're back to your landlord's permission.

If you want to support green power, buy into a co-op solar installation. If you want power when the AC grid is down, grid-tied solar is incapable of that, so that's the wrong tech anyway. You need a battery/inverter solution, which can be augmented with portable solar.

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    Meters are 100% capable of detecting the difference between power import and export, although many have a mechanical or software block to prevent this happening, or count in another register. It's simply an extension of the existing requirement to multiply the instantaneous voltage and current to determine actual power regardless of power factor. You get a negative output, and that applies a torque to the disc in the opposite direction. Jun 26, 2022 at 1:51
  • @SomeoneSomewhereSupportsMonica But that's designed for transients of a millisecond (fraction of a cycle), not an hour of backfeeding. After awhile, the meter will lose its frame of reference to distinguish the continuous backfeed from the normal direction. Jun 26, 2022 at 1:57
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    I am trying to find the video I originally saw (this one is close), but old-school mechanical meters are essentially a stalled single-phase induction motor. A voltage coil designed to produce 90* phase shift provides part of the magnetic field. A current coil provides the second part of the field. If there is no current, then the voltage coil field alone provides no torque. If there is both current and voltage, then the strengths and relative phase angles provide proportional torque. A brake magnet ensures speed is proportional to torque. Jun 26, 2022 at 2:02
  • So-called 'four quadrant' smart meters allow measuring and separate calculation of each of the four phase quadrants - leading PF import, lagging PF import, leading PF export, lagging PF export. Many even have little arrows/indicators on the display indicating exactly which direction they're counting. edmi-meters.com/wordpress/wp-content/uploads/2018/03/… Jun 26, 2022 at 2:06
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    @Someone you've got me really interested now! The answer I'm seeing over and over is, it varies... a lot. Old mechanical meters tend to run backwards particularly when the pan is wired upside down. Basic smart meters tend to "bill in both directions" as I say. More advanced smart meters are solar savvy, but refuse to roll backwards unless the power company signals them to do so. Jun 26, 2022 at 2:31
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There are modular systems that will plug in to a standard socket and once connected feed back power into the grid.

They comprise a solar panel and a small inverter, the wiring between panel and inverter comprises a plug that is oriented so it only fits one way.

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  • Do they require some type of extra lock out to prevent power being fed to the grid during power outage, or is that built into the inverter?
    – crip659
    Jun 25, 2022 at 16:11
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    @crip659 all built in (islanding etc all catered for) and seen them in use in several countries. Perhaps they may be on sale in your location?
    – Solar Mike
    Jun 25, 2022 at 16:34
  • Do these have a name on which I should search and find them? Jun 26, 2022 at 8:02
  • @DaniëlvandenBerg names vary but modular solar systems can be a start. Check out those who sell pv equipment…
    – Solar Mike
    Jun 26, 2022 at 8:23

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