Battery use during mains power cut

Hello. In November ‘24 we had 16 panels and a battery installed, so we’re new to the world of solar. This is a really basic question, so please be kind!
We live in a hamlet in the middle of Salisbury Plain and most winters have a power cut ranging from a couple of hours to a couple of days. The kit is 16 panels, 1 inverter, 1 battery. It’s all on and in a big shed at the top of the garden, joined to the house by a wire as our Wi-Fi signal isn’t good enough to go wireless. I don’t know anything really technical about the system. It works and it is saving us some money, that’s enough knowledge for us so far. We already had solar water panel and air source heat pump (no gas supply out here). That’s it.
So my very simple question, based on a half-remembered convo with our installer, is:
if there’s a power cut,, can the house run off the battery until it’s depleted??
Thinking about it, we don’t see how it can, but as I said earlier, we know nothing!!
A simple yes or no would suffice, but a slightly more detailed answer would be interesting. Thanks.

Chrystal if there’s a power cut,, can the house run off the battery until it’s depleted??

I think that will depend on

• Your set-up - e.g. what type of battery did you get and,

• Whether or not your system has the ability to isolate itself from the grid (known as Islanding)

The latter point is very important, because if you are not able to isolate the house from the grid, there is a real risk of sending power back through the wires and electrocuting somebody working on the powerlines to fix the problem. All systems are designed to "stop" if a grid outage is detected.

The Givenergy AIO (Tesla powerwall etc.) have the ability to isolate the house from the grid, and then the GE kit certainly will simulate the grid voltage/frequency etc to allow the solar to continue to produce if required.

If you don't have that option, your system may have an EPS setup (Emergency Power Supply) whereby the inverter can supply power to a dedicated socket that you could plug some devices into for example (and I think this would be a totally seperate wiring from the house to prevent power going back to the grid)

HTH

CW Whether or not your system has the ability to isolate itself from the grid (known as Islanding)

All systems have this ability - its the law (or wiring regs which in this case is much the same).

If it's a standard install, the answer is almost certainly NO.

However it can be done, but may be difficult, expensive, potentially dangerous (ok, all electricity is potentially dangerous), and requires additional knowledge on your part to operate safely.

Some info here https://givenergymonitor.wixsite.com/tutorials/emergency-power

Chrystal I wouldn’t put it as negative as some of the answers you have been given, and CW makes some good points.

Can you run your house off the battery until it runs out. The answer to that is yes BUT there are some limitations and it depends on how the kit has been installed relative to your fusebox and mains grid supply.

All the GE kit, AIO’s and older hybrid/AC coupled inverters have the ability to provide EPS (emergency power supply) capability. You are however limited to the discharge rate of the inverter; so if you have an AIO then its 6kW, if its a hybrid inverter its 3.6kW so running your heat pump and say the oven could well push it over the limit and the inverter will shutdown.

However, for the inverter to work like this your house circuits need to be connected onto the EPS connections on the inverter. If your grid supply to your house comes in via the shed where the solar/battery equipment is then this is relatively easy, if its not and your solar/battery is in an outbuilding that feeds the house you’d need two sets of cables running to it, one to feed the house fusebox from the EPS and one from the grid supply.

And bear in mind that a heat pump chews electricity so your battery wouldn’t run your home for that long.
You could do something simpler, have an EPS socket on your inverter and then run an extension lead to the house to power a few lights, the TV, etc

Thank you all for your replies, we’re grateful. I wasn’t thinking of trying to heat the house, that uses way too much battery. It was more for lights, tv and charging phones. Luckily we have log burner for heat and calor gas hob for cooking. Simple works best for me and as we already have wires running from house to shed I think that’s what we’ll investigate. I must say since we’ve had the solar kit and I can see how much the house needs, I’ve got very mean about having the heating on during the day!

Chrystal If your installation engineer didn’t wire up anything to the EPS output on your inverter, this can be done after the event. Its a straightforward wiring job but it does require a givenergy engineer to enable to EPS function on your inverter (for your warranty). I had to get my engineer back to do this for me as it wasn’t part of my original install.

Sorting out the house fusebox, splitting low load circuits into one fusebox and higher load like the hot tub took a bit more effort beforehand. There are several options for how automatic you make the changeover from grid supplied to inverter EPS supplied, have a look at the installation manual for your inverter.

Thanks [unknown] I’ll check with our installer and find out what, if anything, he’s done.

geoffreycoan thanks, I’ll have a chat with our installer

geoffreycoan it does require a givenergy engineer to enable to EPS function on your inverter

It doesn't & hasn't for more than a year now. EPS can be enabled/disabled on the portal. Whether this is sensible or not is another matter.

Nobody seems to have mentioned the most important thing though - an earth spike is compulsory for EPS operation and the OP would probably know if one had been fitted.

I think there's two separate settings?

Enable EPS which is in the portal

And enable fast switching which is on request? E.g. true UPS style cut over.

We had the EPS fitted and enabled at install, with an earth spike to allow 'islanding' i.e. supply EPS power during a grid failure to a double socket indoors. It takes a few seconds to start the EPS and we plug-in reading lights, CH pump (we do have gas) and the internet router. Have survived several four hour outages so far. Obviously the lower the load the longer it lasts. With a bad storm forecast we try to make sure the battery is charged. For those unforeseen outages its more hit or miss (hit so far). Good luck.