Home Storage Battery

[Tim Falkiner]

Another non car question.

Does anyone have solar panels and a home storage battery?.

I am thinking of investing 4.5k in a GivEnergy 8kw system linked to solar in order to save on bills.

Does anyone have any experience on if savings are possible and how much bills can be reduced by.

Many thanks.

People install solar panel/battery systems to 1 save money 2 give security and 3 save the environment. Different people have different priorities. Generally they are a great idea depending on where you live, what roof you have etc. But appreciate that even a MG ZS EV has a 42 kWh battery so you probably will not have that much left over to charge your car after running your house. And the best time to charge your car is when the sun is up as an 8 kWh battery is designed to run your house over the night. As well, many solar systems are limited to 5 kW and you may only have, say, 2 kW for the car if the house is drawing 3 kW so you will be limited to granny charging.
This is a useful Australian page The Homeowner's Guide To Solar Power And Electric Cars

[ Edited Coulomb: units. ]

 

[Harry]

Another non car question.

Does anyone have solar panels and a home storage battery?.

I am thinking of investing 4.5k in a GivEnergy 8kw system linked to solar in order to save on bills.

Does anyone have any experience on if savings are possible and how much bills can be reduced by.

Many thanks.

Quick answer - I have 3.2kW max generation panels and a 2kWh battery. Charging the car from a standard 3 pin socket on a sunny day when the panels are generating and the battery full cost nothing and I stop when the battery reaches 20%, starting again if and when it is full again. Doesn't answer your question, but if you are at home when the sun is out, it's free topping up. Had my system since 2018 and the payback is improving, plus we run off the battery up to bed time most sunny days. Glad we invested.

 

[ChrisT]

Quick update on this thread, have ordered a Foxess 5.2 kwh battery and hybrid inverter to connect to our 2.3ish kwh solar system. Supplier is Green Building Renewables Doncaster way. They say they have stock of batterys (watch this space) and now waiting for G99 Fast Track Application approval. Apparently some people get charged for this and some don't so will have to see.It was a difficult decision due to cost but hopefully like the panels it will be one that we appreciate in the future.

 

[BarryH]

Quick update on this thread, have ordered a Foxess 5.2 kwh battery and hybrid inverter to connect to our 2.3ish kwh solar system. Supplier is Green Building Renewables Doncaster way. They say they have stock of batterys (watch this space) and now waiting for G99 Fast Track Application approval. Apparently some people get charged for this and some don't so will have to see.It was a difficult decision due to cost but hopefully like the panels it will be one that we appreciate in the future.

You shouldn't need a G99 Approval (Fast tracked or otherwise) for that sized system. A G98 Notification is all that is needed for systems with inverter to Grid rating of 3.8 kW or less. I doubt you have the 5 kW hybrid inverter version of the Fox ESS with the PV and battery sizes you have quoted and more likely you've ordered the same Fox ESS as I have with 3.6 kW Inverter. I've got that 3.6 kW Inverter with 4.8 kW PV (split across two roof aspects) and 7.8kWh storage. I went for the 3.6 not 5 kW version as it didn't require G99 and with a split aspect PV i'm not expecting a peak output to exceed 3.6 kW even at mid-day Plus my base load is 200-350 watts and the inverter can over-drive and deliver into the House up to 5 kW peak (although not into the Grid) for 10 minutes.

 

[ChrisT]

You shouldn't need a G99 Approval (Fast tracked or otherwise) for that sized system. A G98 Notification is all that is needed for systems with inverter to Grid rating of 3.8 kW or less. I doubt you have the 5 kW hybrid inverter version of the Fox ESS with the PV and battery sizes you have quoted and more likely you've ordered the same Fox ESS as I have with 3.6 kW Inverter. I've got that 3.6 kW Inverter with 4.8 kW PV (split across two roof aspects) and 7.8kWh storage. I went for the 3.6 not 5 kW version as it didn't require G99 and with a split aspect PV i'm not expecting a peak output to exceed 3.6 kW even at mid-day Plus my base load is 200-350 watts and the inverter can over-drive and deliver into the House up to 5 kW peak (although not into the Grid) for 10 minutes.

I did query it with the installer and they said because we are adding to an existing system it requires a G99. If I get charged I will investigate further.

 

[BarryH]

I did query it with the installer and they said because we are adding to an existing system it requires a G99. If I get charged I will investigate further.

Some "Distribution Network Operators" (the UK has the Grid is managed regionally by various DNOs and some DNOs are more particular or if there are a lot of SOLAR PV installations in your local substation area) local exceptions can apply. You could always call your DNO and ask if there are special conditions why a small "Hybrid" PV instal might need G99. If you have an AC Coupled install it is a little different since it could be possible in a poorly configured system, that both the PV could be pumping out 2.5 kW and the Battery, via a separate inverter, could be also discharging a further 2 or 3 kW onto the Grid. However, a Hybrid Inverter would be capped at the rated out put no matter the source and therefore G98 which is a notification to the DNO and which doesn't require any decision by the DNO should be the correct approach.

 

[robdjeff]

Remember to factor in the battery and inverter losses when you charge and discharge the battery and that the battery has a finite lifetime (or at least an effectively finite number of charge/discharge cycles). The 75% saving figure quoted above is way out when you factor in these two things.

Other things to bear in mind - the full saving only occurs when you fully charge and discharge the battery every day. If you don't use the whole battery then payback time is longer. If you end up still consuming from the grid later in the day then that electricity is more expensive and your payback time is longer.

Personally, I reserve my battery for charging with free solar energy. That will pay back more in the long run.

 

[busta999]

I reckon it would take around 30 years to recover the cost of a battery installation so bear in mind that for around 4 months of the year there is very little solar generation and the Octopus Go 5p off peak is unlikely to last either. Best option for me was installing an MyEnergi Eddi to heat my hot water instead. As it stands between that and 2 EVs I put virtually nothing back into the grid hence battery option is of no use. Do your own sums carefully before committing. .

I combined multiple measures to significantly reduce energy costs.

Switched my lease car to electric, put in an immersion tank, and added 20kWh of batteries.

The car unlocked cheap rate energy at £0.0825 per kWh, and reduced motoring costs from 25p per mile to 2p per mile, and using the immersion heater has moved it from gas to off peak elec along with a battery powered top up during the day.

This drives an ROI to slightly over 3 years.

The batteries have a 10 year warranty with 100% daily discharge, given I am running just over 50% daily discharge should significantly extend their lifespan.

I cannot advise anyone else on their best way forward, but more than happy with my installation and the return I am getting.

 

[busta999]

Definitely legal in UK. The inverter on many battery systems have two AC outputs. The one sits across the grid as a conventional PV inverter and shut's down when the Grid power is lost and the second called usually UPS or Emergency feeds the essential circuits such as Fridge and Freezer and perhaps lights (assuming you've LEDs you'll be fine). For some Distribution boards, you can arrange the emergency/UPS circuits on one half and the higher load circuits on the other. When mine is installed in the next few weeks I'm having a small Sub-board installed. One provider I had a quote from included a 13A double ganged socket to simply plug my essential whitegoods into.

I am using a Victron Multiplex II 5000va system, and I am using the UPS line into a consumer unit with a line going out to 4 sockets for low wattage critical systems, iOt, broadband/Wi-Fi, home automation, av systems including whole house freeview tuner. The other line goes into a 50ms auto switch that engages if the grid goes down, switches the freezer, lighting, heating and hot water systems over to UPS and back again if grid comes back. The other sockets will drive a Microwave/air fryer during power cuts. Hot water heating only runs at night/manually during a power cut avoiding overloading the inverter.

I have a couple of sockets in the lounge that are connected to a commando socket where the v2l from the car to power Tv/sound systems.

Hopefully won’t need it.

 

[Tim Falkiner]

I have a Powerwall 2 and when I charge the EV I reserve 100% on the Powerwall so I am not using it to charge the car and the car gets charged with solar and grid.

 

[1973solarchap]

I agree, a solar diverter was the step I took before even considering a battery system. Again, a word of caution as many immersion heaters are quite short and only designed to heat up the top 30cm or so of the tank to give enough for a quick shower! My tank only had one of these and lacked the lower heater found in many newer tanks. The solution was to buy a much longer heater which heats all the water in the tank. Also, you must buy a rugged heater element which is designed to be switched on & off a lot - many cheaper ones aren’t and will fail prematurely in such an application. Mine has been working for 9 years.

My diverter is a home made one from a magazine article back in 2013 and works well. I have a remote display of the water temp in the tank which is helpful. My gas boiler is still there but only used when there is a shortage of sunlight or stored power to operate the immersion. I can manually operate the immersion by voice control with an Alexa operated switch which turns on for an hour - this is enough to go from a cold tank to a tank full of hot water. Be careful though as many of these type of switches aren’t upto the job of switching high current loads - I’ve used an intermediate relay which the Wi-Fi switch then operates, in turn switching the immersion load.

Hi, do you have the details of the magazine provided instructions? Sounds like a project coming along. Instructions would be good, or at least a route into getting hold of a back issue of the magazine. Thanks in advance.