Running from solar during a powercut
Requirements to be able to run your house from a solar panel system during a power cut / power outage in Ireland
Yes, you have a solar panel system running your home during a power cut.
This has additional requirements compared to a standard system, but yes it is very possible.
By default, all solar panel systems and batteries will shut down during a power cut. But, systems that include batteries can be set up to run off-grid by adding a changeover switch. With that setup, you'll be able to flick over to work off-grid and run your house from solar & solar batteries when there is no mains power.
Why do standard solar systems shut down during an outage?
This is to protect the ESB Network crews working on the lines. ESB Networks require that the solar system cannot supply electricity back out to the grid during a power cut, as this could cause risk to people working on the grid to fix the lines. So the default action of all household solar systems is to shut down during a power cut.
Once the external grid turns back on, a standard solar panel system will start up automatically on its own.
System requirements to run your house in a power cut from solar
There are number of changes needed to be able to run your house from solar during a power cut / outage.
Requirement #1: Battery system
Firstly, you need a battery system, which also requires a "hybrid" inverter (they are the inverters that take input from both batteries and solar panels simultaneously).
Requirement #2: Changeover switch
This fully disconnects your house from the outside grid, so that you can then draw power from your batteries and panels without the risk of sending that outside your house to the public lines (and potentially zapping any workpeople trying to fix the broken lines).
Firstly you need a battery system, which also requires a "hybrid" inverter (they are the inverters that take input from both batteries and solar panels simultaneously).
Requirement #3: Inverter brand with "off-grid" feature
Most brands of hybrid inverters offer this "off-grid" feature, but not all. Do let us know when inquiring if you would like a change-over switch, and we can make sure we install a brand that has this feature.
Costs for a changeover switch
Adding a changeover switch normally adds around €1000 to the price of a household solar installation, though it does vary from project to project. This is assuming it is installed at the same time as the rest of the solar installation.
Can a changeover switch be retrofitted later on?
Yes, but please note it's more expensive to add later on.
This would also be on the assumption that your original inverter supports this feature, your fuseboard is okay to accommodate this, and a few other checks we'd need to do.
Is it possible to have it automatically kick in during a power cut?
No. When a power outage occurs, all systems shut down automatically, and you'll need to manually toggle the switch to enable off-grid mode. So this is not suitable for those who need continuous power without any interruptions.
Will it fully power everything in my house whilst off-grid?
Probably not, but it should be able to cover most things.
Most battery systems can peak up to somewhere between 3kW and 5kW. That means you can use most devices in your house, but you may need to stagger the most power-hungry kitchen items like the kettle, dishwasher & oven. Do note though that things like your oven can use up your charge relatively quickly, as they tend to be on for long periods of time (as opposed to the kettle which is only on for a minute or two).
Devices such as lights, TVs, WiFi boxes, fridges & freezers do not use too much power, so there would unlikely be any issues powering those "background" devices.
You could probably not use electric showers, which have huge power demands, generally above what most batteries can provide.
Again, we are talking here in generalities here for the most common systems and house needs. Please just ask if you want to know more specifics in your own case.
How many batteries do I need?
Alas, that's a piece of string, but we'll do our best to answer.
Power cuts are most common in the winter when solar production is at its lowest, so you would be relying more on the battery side. Batteries normally come in 5kW hr units, and you can get multiple batteries - most people get between 1 and 3 batteries.
An average house in Ireland might use 10 - 12 kW hr per day. So for most people, one battery might cover about half a day, whereas two would likely cover most of the day, especially when you add in the additional solar generation topping up the batteries from your panels. If you want to run for extended periods of time, you might consider more batteries.
Do note though, that this entirely depends on your usage, and of course on how full your batteries were at the start of the power cut.
Potential regulation changes
Please note, after the recent storms this has suddenly become a large talking point, and Safe Electric (the people that set the electrical regulations for Ireland) have said they are reviewing the requirements for changeover switches. This may change the cost and viability of such. We will update this page once any changes are confirmed either way.
How to get started
If you would like to get a solar panel system that'll keep your house powered during a power cut, please just let us know when inquiring, and we can make sure we include a changeover switch in your design. Just get in touch to get the ball rolling.