Off grid type setup that is on grid?

[jflorey2]

So , my question is, can you design a system that the house will run off the solar system and when all electricity is depleted from batteries or at night will switch to grid power?

Sure. Outback inverters have a mode called "HBX mode" that does this. It will be pricey, though, as others have pointed out.

[rsilvers]

How about a low-voltage battery disconnect?

[SunEagle]

Is it the cost of buying the batteries that keep costs up? So should I take it that even if you could make enough electricity to go off grid that it would not be worth it?

Until the price of solar & battery equipment comes down more it will cost more to generate your own power then to just purchase it from your POCO. A solar grid tie system can pay for itself. IMO since you pay a high price for electricity depending on what the cost to install a pv grid tie system you should see a payback much quicker then someone paying only 10 cents/ kWh.

[ButchDeal]

Is it the cost of buying the batteries that keep costs up? So should I take it that even if you could make enough electricity to go off grid that it would not be worth it?

no that is a part of the added costs.
The inverters that handle batteries costs more
there are Charge controllers that add cost
there is different wiring and more labor that adds costs
to provide the same amount of power, the system must be larger, adds costs

[JapanDave]

Is it the cost of buying the batteries that keep costs up? So should I take it that even if you could make enough electricity to go off grid that it would not be worth it?

[SunEagle]

Electricity where I am is about 28-30 cents for a Kilowatt hour. Would you still say that it is not worth it?

Most solar battery systems can cost above $1/kWh. So yes I would say it is not worth it.

Now a hybrid grid tie system may help someone with that type of electric rates but even in Hawaii where it can get to ~ 50 cents / kWh a battery is hard to justify.

[JapanDave]

Electricity where I am is about 28-30 cents for a Kilowatt hour. Would you still say that it is not worth it?

[ButchDeal]

Maybe you can use an automatic transfer switch and set it up so that your "off-grid" solar system is the primary power source. As long as it has power, the switch will use it to power your home. When it no longer has stable power, the transfer switch will change to utility power.

http://www.electricgeneratorsdirect....er-Switch.html

I think you will lose power every day though. In real use, it would probably have issues to keep it from being practical.

This system would kill the batteries rather quickly, basically fully draining the batteries before switching every time.

If your goal is to save money then the best bet is a legal grid tie system.
There are bimodal systems that can be configured to not feed into the grid but they would requier similar permits but not necisarily an interconnect agreement.

[SunEagle]

Unfortunately any type of off grid system with batteries will end up costing more to generate a kWh than what you can purchase it from your electric utility.

The best way to get solar to pay for itself is to install a legal grid tie system. Whenever you add a battery you pretty much are spending more money than just using your grid power.

[rsilvers]

Maybe you can use an automatic transfer switch and set it up so that your "off-grid" solar system is the primary power source. As long as it has power, the switch will use it to power your home. When it no longer has stable power, the transfer switch will change to utility power.

http://www.electricgeneratorsdirect....er-Switch.html

I think you will lose power every day though. In real use, it would probably have issues to keep it from being practical.

[JapanDave]

Sorry, new to solar and I am still in the research stage. I know the title sounds strange, but please let me explain.

I live in Japan and we have to go through registered dealers to sell electricity back to the grid. So a DIY setup will not be approved. What I wanted to do was build my own system and store any excess electricity made during the day (no one is at home during the day and electricity use is very minimal) in batteries for use in the evenings and night. Problem is with space being an issue going off my calculations I won't be able to make enough power to go completely off grid.

So , my question is, can you design a system that the house will run off the solar system and when all electricity is depleted from batteries or at night will switch to grid power?