Inverter question about overload ?

[JonRussell]

Hi,

Excuse the noob question, but I'm researching solar and off grid, for my house.

I've installed some power monitoring to understand my needs before I buy anything.

In the summer, my house runs below 4KW for 99% of the time, but for 1% of the time, it spikes at up to 8 or 9KW maybe more, if I have the washing machine, cooker, and dishwasher on at the same time.

I understand the technology of solar / battery / inverter. But all the stuff I've read talks about sizing the inverter for your needs. i.e. 4kw, 6kw, 8kw, etc.

Is there a product that monitors the power output and can switch the house from inverter back to the grid, if the power consumption exceed the rating of the inverter, rather than overloading the inverter. Or do I have no choice but to buy a 10 or 12KW inverter, just for the rare occasions when it might happen ?

I understand some inverters can survive a small surge, but I guess if my toaster, kettle and hair dryer all come on, it wont be a spike, it might be for quite a few minutes. I don't want the inverter popping all the time.

Thanks.

Jon.

[Mike90250]

Welcome, and you ask a tough question. Yes, a robust inverter can handle a spike, but 2 minutes for toast and pumping water, is going to overload it beyond what is considered a spike. Many inverters have a 1 second rating, and a 5 second rating. But they just are not designed to be overloaded.

Now if you have the "Grid" available, and can switch to it, then you really should not be thinking "off grid" unless you have gobs of extra money around to buy and replace batteries with, If you have grid, the economical thing is to have Grid-tie solar, get credit on your bill, and have a backup generator.

If you are in an area served by the grid, both the Utility and the City take a dim view of "Grid Abandonment" and try to take your house off grid. The building department will resist, and the Utility may charge you a huge fee.

So if you have Grid, you can get a grid tie connection and inverter, use as much power as needed, get credit for what you produce, and be in pretty fine shape.
You can even get a hybrid inverter, have batteries, and backfeed., As you exceed the inverter capacity, you will simply pull power from the grid. If there is a blackout, you have batteries for a couple hours, and a generator for longer.

In my case, being off-grid, this is why i have a 6Kw inverter, and my average load is 200 -250W. But if the toaster is on, and the pumps starts up, the power has to be met, or I black out, and have to walk outside and reset the inverter.

Hope this helps