Is it straight forward to retro fit a battery to an existing solar panel set up and also be able to sustain power during a power cut?

Or do you need to change the inverter and other gubbins?

AFAIK yes you can sustain power during an outage if the controller is set up correctly, Tesla Powerwalls are designed to do exactly that. You would probably need a new controller and the inverter still needs to disconnect on a power cut. Think of it as a UPS for your house.

I’ve only studied the systems and don’t have any practical experience but I’m 99% confident someone who does will chip in.

Depends on how you go about it

Powerwall is the ideal sort of. But there is about 8-12 months backlog if they are even taking orders currently. You want want the current/ future gen life4po not the older NMC units

That’s a one stop bolt on shop for your existing system

There are only a couple of units can do ups and islanding Tesla’s one and puredrives purestorage II DC unit is another to fit that your probably changing your inverter unless

Lots of other batteries can do EPS which requires a manual change over switch and ground spike fitting. An extra 900 quid or so. These can power certain circuits or often just fitted as a single socket above the battery only live when mains is off

If you don’t want to change inverter and can’t get a powerwall your looking at AC units which are stand alone with their own inverter.

Fitted cost of a 10kwh battery currently seems to be about 10grand unless your buying pylontech units which seem to be about the cheapest way in. Telsa came in a bit more than that for 14kwh – gutted as I was quoted 8 when I installed the solar…. But the repay time was silly then – how things change in 2 years. I found cost of going AC or changing inverter were within a couple hundred quid of each other like for like capacity

Be aware that as the standard is presently written, batteries like the Tesla PW that keep your house on during a power cut do not comply with G98.

You need to apply for a G99 connection – which as a manager with a DNO I did.  Relatively painless other than the £260ish fee and I now have an 8kW export agreement too.

A grid tie inverter will not run without a grid connection, you will need another inverter and means of disconnection from the grid I. The event of a powerful for the safety of the line engineers.

A grid tie inverter will not run without a grid connection, you will need another inverter and means of disconnection from the grid I. The event of a powerful for the safety of the line engineers.

That’s one of many ways of achieving the same thing but it is not the only permitted way. Your installer should advise the best way for your budget.

A hybrid grid tie inverter with inbuild g99 islanding being the rolls Royce currently.

Dno application timings and charges are dependant on your DNO. Eg mine doesn’t charge unless upgrades are needed but takes 8-10 weeks

The fee some charge is only to consider your application. If upgrades are required then they send that quote separately…

Interesting thread.

We’ve been considering solar PV for years and a Powerwall recently.

one potential installer said yesterday that they weren’t taking on more business as they were at capacity. They also said that the lead time on Powerwalls was 8-12 months. 🙁

They did suggest that if we were going for it that splitting the install into two stages would make sense given the Powerwall lead time: install PV now and Powerwall when available. Unsure whether that would mean paying any DNO fees upfront or at the time of installation. I suppose upfront in the assessment of the application would be logical.

Another potential installer proposed 30 panels->11kW array. 🤷🏻‍♂️ How that compares to a typical installation.

Price seemed to work out at about £1,000/kW installed.

kind of exciting to be going for it despite supply problems.

G98 is limited to 16A per phase at nominal voltage – that means 3.68kW for your typical house (other houses are available).

At 11kW you need to apply for a G99 connection, but if you can do it I probably would.

That will provide sufficient electricity (not heat) your home and 1-2EVs. Not necessarily at exactly the times you want it.

Storage, heat pumps and EV chargers should be in your thoughts if you’re good for 11kW.  As should import and export tariff choice.

I have an fairly knackered Nissan Leaf which seems to be worth about £3K for resale but came with a 24KW/h battery. Is it possible to remove the battery, scrap the car, and then fit the appropriate controllers/connectors for it to act like a powerwall? I have 2 basic ideas I am considering.

1) Solar panels charge the battery. The battery powers JUST the garage, hot tub and sauna with the existing mains power supplementing this as and when required.

2) The same as above but the battery feeds into the whole house and potentially back into the grid. Charge it up on solar and cheap night time electricity and dump it back on the grid when the price is highest.

Either of these feasible and what kits beyond a spanner to strip the car?

Either of these feasible and what kits beyond a spanner to strip the car?

With he currents and voltages involved I feel your username may be prophetic :->

Storage, heat pumps and EV chargers should be in your thoughts if you’re good for 11kW.

Thanks. Seems like that set up matches fairly well with our ridiculous electricity consumption (12,000 kWh/year) and other factors.

Storage-yes, though in time given supplies.
Heat pump-unlikely, Victorian design even with insulated walls and double glazing etc seems incompatible with an ASHP’s output and the garden is not going to be sacrificed for bore hole drilling.
EVs- got those already though might drop from 2 to 1 late 2023 due to usage.

Heat pump-unlikely, Victorian design even with insulated walls and double glazing etc seems incompatible with an ASHP’s output and the garden is not going to be sacrificed for bore hole drilling.

Which does beg the question, how you going to heat it in the low carbon future?

Not saying I have the answer.

(12,000 kWh/year)

WTAF! I thought we profligate at using 5,500!

Heat pump-unlikely, Victorian design even with insulated walls and double glazing etc seems incompatible with an ASHP’s output and the garden is not going to be sacrificed for bore hole drilling.

Which does beg the question, how you going to heat it in the low carbon future?

We’re in a Victorian terrace in a conservation area, so no chance of being allowed external wall insulation – which is the first thing I’d probably do!

(12,000 kWh/year)

that cannabis farm wont grow on it’s own.

5400 kwh here

We are just about the have more PV fitted in the next 2 weeks. Already have 2kw on our biomass boiler house; house has a large south facing roof which needs retiling (previous owners did the north roof before they sold the house). We are putting 14 390W panels in inset trays with their own inverter. These and the 2kw we already have will will link to a 15Kw Huawei battery system. We already have a solar iBoost which ensures excess generation heats how water before feeding back to grid and we also have solar thermal.
The existing 2kw we have has been pretty reliably delivering 1500 kwh / year for the last 5 or so and we use just under 5000 kwh/yr for the house. We are getting an EV in the new year (delivery times allowing) and are also installing a zappi. My hope is that with all this our utility costs will plummet and we should be able to run the car (an Ioniq 5) for little cost in charging…..

fingers are crossed…

What are the thoughts on suppliers/installers? Lots of bad press about companies folding and owners being left with no warranty.

We toyed with joining the local authorities group buy scheme earlier this year but it didn’t fill me with confidence and the quote we received didn’t seem to offer much discount on market rates. I’m now think more seriously about an install. Do I go local or with a national company like GET or EON?

@Infidel

Out of interest how much have you been quoted for the 14 panels and inverter all in?

I was a little concerned about this. The installer I chose had a series of reasonable reviews on Trustpilot that talked about specifics of the install, and they all seemed genuine.

The main driver behind it was that they could answer some fairly awkward technical questions on the phone during the initial quote, and they were honest about up front costs (as in “we can see that this bit is tricky access so the scaffolding costs will be higher than the headline figure”).

The panels themselves are pretty unlikely to fail (I get the impression that without micro inverters a fault at time of installation will stop the whole string from working), and the inverter itself has a decent reputation.

I’ve worked on the plan that I’ll probably be able to get them back for any issues for a year and beyond that it’s on me.

My colleague at work was looking at the council backed scheme but it was at least 30% more expensive for the same kit.

I used a large local installer for my panels that’s been around for years(since the 80s) and makes its own solar thermal kit….

For my battery I went direct to the manufacturer for their recommended installer for my area.

Folks that installed my panels are Tesla agents and quoted 8-12 months on a powerwall.

Whole job is 20k but the batteries cost as much as the panels and inverter. Cost includes labour as well as moving the existing solar thermal system and servicing it at the same time. Hard to know if that’s good or bad value TBH but I’ve used the company a lot over the years and trust them

I recently registered for the subsidised local council scheme and the quote came through today at 11.5k for 8 panels and a 9.2kWh battery. At that price I am doubting I am getting much of a financial benefit by using the scheme versus just going direct when you consider some of the prices quoted on here, what are peoples thoughts?

Alot depends on access

Example I didn’t need scaffolding for any of my kit.

But if I did it would have been a couple grand more.

There are also variables in the quality of kit. I’d that’s solaredge then it’s good value if it’s growatt it’s poor value.

@johnjn2000 what is the scheme, and where are you?
Still kicking myself for not going with the local council’s Solar Together scheme that I got a quote for 2 years ago… £6k for 12 panels and 3.1kWh battery 🤦‍♂️

@zilog6128 – It is indeed Solar Together and with Hampshire CC or Fareham Borough, can’t remember which

Hampshire CC I suspect, just had my quote, £14k for 16 panels and 6.4 kWh battery

What are you thinking about it @gifferkev? Have you been less lazy than me and done some actual research?

Just as lazy re getting other quotes in. As far as i can see, the kit supplied is the bulk of the cost, scaffolding/installation is a pretty small part of it. They’re not any cheaper than anyone else as far as I can see, so don’t see the cost benefit of the scheme. However, if it get’s the ball rolling and they’ve got a reasonable timetable I’m in. (our actual cost will come down a touch as they seem to have quoted for more panels than can fit on the roof, not a great start)

They’re not any cheaper than anyone else as far as I can see, so don’t see the cost benefit of the scheme.

maybe costs have gone up a lot due to demand? when I got a quote 2 years ago it was extremely competitive!!

Just done the estimate for the same scheme as @johnjn2000 but 16 panels and 9.2Kwh battery . Its growatt kit from the literature and it is coming out at just over £15k. The interesting bit from the quote for me is when bumped to 20 panels and the 9.2Kwh battery the site is suggesting 100% grid independence (and quite a large export amount).