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Old 29-04-2016, 09:47   #1
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Unused boat solar to commercial grid?

Home solar installations are all the rage. I've got one on my floating home. about 300 watts worth. I'm fortunate to keep that home behind my shore home. Has anyone experience with sending the boat's unused daily solar power back into the grid to lower one's home bill? Why waste it?

Let's say I make 200W a day for a week which is 1400W. That's 5.6kw a month. Not much compared to what the AC sucks up but it's something.

Anyone tried this?

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Old 29-04-2016, 09:56   #2
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Re: Unused boat solar to commercial grid?

You would need a grid tie inverter that met utility standards to sync the phase and provide a disconnect when shore power is off. Enphase makes a micro inverter that is only $160. but it's for 60 cell panels and may not meet utility requirements.

5KW a month would be somewhere between 50 cents and 85 cents a month so payback on the inverter would be 15 to 26 years. Less expensive to not do a grid tie for most boats.

I'm sure the utilities and marinas would have issues with a single boat on a grid tie.

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Old 29-04-2016, 09:59   #3
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Re: Unused boat solar to commercial grid?

Say you get 200W unused for 5 hours a day (5 hours would be generous for typical boat solar installation). That's 1kWh/day, or 30kWh/month. FPL charges about $0.10/kWh (for usage < 1000kWh/month), so you make about $3/month worth of electricity.

To put that back into the grid you'll need a grid-tied inverter. If you go the micro inverter route (easiest for that wattage) you're looking at $150, so your payback is 5 years or so. And that doesn't count interconnection fees, or permit fees, or upgrades to your dock/wiring, or....

Could it be done, yes. Is it worth it? YMMV.
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Old 30-04-2016, 20:31   #4
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Re: Unused boat solar to commercial grid?

If you have a smart meter on your house, it does not measure direction of current.
Without another meter to measure solar generation, if and when your original meter is "turning backwards" you would be PAYING for that as USAGE.

We have a grid tie 4kw.
Emphase inverters with transfer switch home brew MAGNUM 4kw Sinewave inverterLiFeP04 backup.
The main reason besides reducing electrical bill is independence during power outages as we live on an island.
"I have never understood why it is "greed" to want to keep the money you have earned,
but not greed to want to take somebody else's money"

-Thomas Sowell
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Old 30-04-2016, 21:40   #5
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Re: Unused boat solar to commercial grid?

Way more hassle than it's worth.

Do it yourself and you are probably talking a decade or more to payback. Figure life cycle of some of the parts and after that decade in a salty marine environment and it may never pay back.

If you have to pay someone to wire it up for you, it just gets silly.

PS: you are talking about watt-hours or kilowatt-hrs. Watts is an instantaneous measurement. The power company charges based on kilowatt-hrs.
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