Should I invest in solar PV panels, a home energy storage battery... or both?

  • 25 January 2022
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I've been considering getting solar PV installed but I'm now wondering if the money would be better spent on batteries. I want to reduce carbon and also save money. We use between 30 and 50 kWh per day in winter (depending on the weather and if we charge the car). This will reduce in summer but our water heating is still electric.

 

Solar PV - our roof isn't ideal for panels. We're in the South East and might manage to fit 3.5kW facing ESE. There is some shading so we will have the extra cost of optimised panels.

 

Batteries - if we just had a battery we could charge at low rates and use the electricity during the day. A simple setup would use a tariff such as Octopus Go to charge at a fixed time overnight. A more sophisticated setup would link to Octopus Agile to decide the best time to charge.

 

I should add that we currently have a time shifting heating system as part of a trial. This charges heat batteries during low demand periods. The system has some problems so it's possible that we'll reconfigure it at the end of the trial and remove the heat batteries.

 

Should we fit both solar PV and a battery or forget the solar and buy a bigger battery? Or something else?

 

Your ideas and suggestions please ☺️


29 replies

Userlevel 7
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Just to be aware although things change all the time on tariffs... I am sure things will change. 

I don't think you have an EV? 

I would do some hunting on tariffs that are now available to charge a battery if you don't have an EV.

In theory Octopus Go is only available if you have an EV, but you can use to charge a battery if you have an EV. 

"Our Octopus Go Tariff is designed for customers who either own or long-term lease a battery electric vehicle or a plug-in hybrid vehicle that they'll be charging at home, so you need one to join. If you sign up without one, or you're in the process of getting one, we'll be here to help find you another tariff that's more suitable for your setup in the meantime"

The agile tariff basically doesn't work right now as there are usually no 30 minute price plunges when energy is cheap on the tariff. Octopus are trying to protect agile customers from very high spikes so the average rate is not really  competitive

Perhaps @Jess_OVO or @Tim_OVO could comment on ovo tariffs for battery owners?

Am sure others can comment on the benefits of having solar and batteries based on their experience. 

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We have a Phev, so would qualify for Octopus Go.

 

The failure of Agile to cope with the recent uncertainty and high prices does make these sort of decisions harder. But TOU tariffs are a popular discussion point so you have to hope they will get sorted out.

Userlevel 7

A fantastic question that I’m keen to understand better myself. 

 

@Jeffus makes a really good point that the tariff is key. Plans like Octopus Go and OVO Drive are for EV drivers. If I understand correctly, OVO Drive’s Anytime add on is currently a unique proposition for ‘type of use’ EV charging. However we’re trailing a similar tariff for heat pumps. Nothing for energy storage for me to confirm…. yet. However as you have an EV (PHEV), you have options here. 

 

The next thing is the return on investment (ROI) of solar PV vs storage, when combined with available and future tariffs. Or, is a combination of energy generation and storage the key. For this, we need first hand experience:

 

@EverythingNeedsAUserName@hydrosam and @sylm_2000 might be well placed for Solar ROI, and @Bev has been considering storage to combine with their solar generation. 

 

@Sean T and @mrmhf AND @dnshorto have all posted recently around storage, so are well placed to advise you here if they have any time. 

 

I’m hoping that @M.isterW is one of thousands of households that are considering these big changes. Investing in your house with green tech now can pay off if done right. Doing nothing or replacing like for like carbon intensive technologies is the alternative. Hopefully some knowledge sharing can help you with your decisions. 

 

I’ll dump some related threads here in case it helps anyone:

 

 

 

 

Userlevel 6
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@M.isterW - an excellent question indeed!


I have solar PV for over 8+ years and I joined the bandwagon slightly late to miss out on the lucrative FIT a decade ago (but then the solar PV were more than double the price). Anyway I find that whilst solar PV are an attractive net zero initiative the SE UK (where I am based as well) is not in Spain or Italy to maximise the returns in less than 10 years. Additionally there has been some discussion about risk to roof if you have a rather old property. 

As a viable alternative, the batteries now combined with TOU tariff can easily commercially competitive. I would say the cost of installation is almost the same however the only risk with batteries is the tariff you’re not in control of. A typical domestic solar PV will typically produce 4KW in a year which is not sufficient but consistent year-on-year allowing you to negate some of the increased energy costs. 

In my view, a smaller footprint solution with similar returns might be a better solution.

 

 

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I have a 3.3 kw system which generates about 3.5Mwh per year. Payback will vary but for me it was about 7 years, but the expected lifespan of the panels is >30 years. Excess generation gets dumped to my hot water tank which takes some of the work off of the heat pump, but not that much in the winter, especially with weather like we have at the moment. 

Now I have a heat pump, a battery is appealing but the capacity needs to be big to help significantly, yesterday the heat pump used about 30kwh, typical seems to be 15-20kwh per day, and the lack of variable tariffs makes a battery less attractive, I’ve struggled to find one. Over the winter when I really need the battery to be charged by the solar PV I have rarely have a day where I have had much excess generated to charge a battery, so most would need to be topped up from the grid.

I can’t find any suitable tariffs that make sense with a battery. The Drive tariffs @Tim_OVO mentions are not available to me because you need to be a dual fuel user and I’ve ditched gas 🙄, but I have an EV… 

@Tim_OVO a segway to this thread, is the heat pump tariff you are trialling going to be trialled with those on the heat pump trial? I’m happy to look at it. 

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We have a Phev, so would qualify for Octopus Go.

 

The failure of Agile to cope with the recent uncertainty and high prices does make these sort of decisions harder. But TOU tariffs are a popular discussion point so you have to hope they will get sorted out.

Yep lets hope the market overall evolves so agile type tariffs can play a part.

For me the current Go rates would be as follows. With enough batteries it should be possible to pick up a good chunk of cheap electricity overnight while you waited for ToU to evolve. 

Unit rate (04:30 - 00:30):

30.83p/ kWh

Unit rate (00:30 - 04:30):

7.50p/ kWh

Standing Charge:

24.01p/ day

Prices include VAT.

 

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SolarEdge PV since October 2015. 4kW nominal but facing East and West in Durham. Average annual production 3.1MWh. Payback (generation, export and actual saving from reduced consumption) will Payback the £6500 cost in about 8.5 years. 

Today was sunless, we had 1.22kWh. In the 4 summer months we average about 15kWh a day. 

I looked at the cost / benefits of batteries about 2018 and couldn't make it pay. Technology may have improved at the same time fuel costs are rising, but unless it works in a power cut, I don't see the point. Even our panels cannot power the house if the external power is lost. I fear that may matter more in future.

 

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@EverythingNeedsAUserName You mention that your panels are facing east and west. Does that mean you have two banks of panels facing in different directions?

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You could try the loop app

https://loop.homes/

It attempts to simulate the impact on adding solar and batteries to your home based on your actual energy usage taken from your smart meter and your actual tariff details 

Free to use.

 

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@EverythingNeedsAUserName You mention that your panels are facing east and west. Does that mean you have two banks of panels facing in different directions?

Yes. 6 panels east, 8 panels west. If I'd only been able to put them on one side, it would have been West as we continue to get the evening sun and perhaps that would be most use of electricity.

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@Jeffus loop looks impressive but expectations may need to be tempered because in reality production is very lumpy and may not match the generic power calculations.

Two successive days in July ie mid summer show very different stories.

 

 

Our 5th January had heavy cloud with the sun suddenly breaking through in the morning. 

 

Our 6th January had almost nothing generated. 

 

Userlevel 7

Good thread this one, I feel like storage+solar needs more consideration though... @Transparent @dnshorto @malc_smith @Graham110011 @Sean T @JoeC @f0rtune and @osborner have this green tech combo. Would any of you ever recommend one without the other? 

 

a segway to this thread, is the heat pump tariff you are trialling going to be trialled with those on the heat pump trial? I’m happy to look at it. 

 

We’re running (or we’re about to start) a trial in the Manchester area involving compatible heat pumps with a type of use tariff. Please note that for any future trial or proposition, your heat pump will need to be IoT enabled. Robin Abraham referenced this in our last online event, the transcript of which we hope to publish in the coming weeks.

 

We don’t have much information about this trial yet, @hydrosam but I’ll make sure to share anything with you when I see it!    

Userlevel 5
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a segway to this thread, is the heat pump tariff you are trialling going to be trialled with those on the heat pump trial? I’m happy to look at it. 

 

We’re running (or we’re about to start) a trial in the Manchester area involving compatible heat pumps with a type of use tariff. Please note that for any future trial or proposition, your heat pump will need to be IoT enabled. Robin Abraham referenced this in our last online event, the transcript of which we hope to publish in the coming weeks.

 

We don’t have much information about this trial yet, @hydrosam but I’ll make sure to share anything with you when I see it!    

It’s a shame the heat pumps installed last year under our trial weren’t IoT enabled, seems like another trick missed there. 

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Has OVO published a list of compatible IoT heat pump configurations/equipment ?

Or is this a specific piece of equipment that OVO will provide or sell?

@Tim_OVO 

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What does IoT mean please ?

Userlevel 7
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IoT - Internet of Things. It's connecting stuff that isn't a "computer" to other things via the internet. Think of internet connected fridges that order more cheese when you've eaten it all.

 

Or a heat pump that feeds data to your electricity provider.

Keep in mind that you also need an extra inverter to charge the battery. There are some batteries that have their own inverter integrated, but you might be better off buying several modular batteries (how many depends on how much storage capacity you need) and a single charger. In most cases, this is the cheaper option. Also, having one inverter for each battery means more devices that are prone to failure.

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Hi I have just had Tesla storage battery fitted.. How it work you have 13.5 kWh battery. You can charge from solar or the grid. Grid charging can be set to charge at cheap times. If you have power cut battery still run house. You can fit up to 10 batteries 135kwh.  The only problem is cost my single powerwall 2 cost £9800 to fit.

Userlevel 6
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Another thread find and I feel the option of another debrief to be penned. 
We have had solar PV since 2009 which paid back in 9 years (without counting lower energy costs). Last year we added battery storage and I’ve been experimenting with various uses to maximise the benefit and also test the reduction of peak time use. 
It works well, once you’ve got over a few niggles as there are very few people who seem to be fully conversant with an install, setup and operational control, coupled with the difference with active, reactive power and flows into and out of the grid as needed. We’re also looking into an input from a community wind farm to add another feed - although once in place I might have to move to a wind farm partner supply. 

Userlevel 7
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I forgot I'd started this thread.

 

We now have solar PV and a battery, and I'm very pleased with our choices so far.

We have 5.2kW of panels split east/west. They give a good spread of generation during the day and I'm expecting that to improve a lot during the summer as we should get electricity produced well into the evenings. They run into a hybrid inverter which also connects to a 6.5kWh battery. I pondered over the size of battery for some time because they're expensive and there's a point at which the cost can't be justified. So far the battery capacity seems okay. Even in the sunny days at the end of September the battery allowed us to use almost 100% of our generated electricity, although that will change in the summer.

 

Having seen how much other people have been paying for solar panels recently, our system was a complete bargain. The solar PV market has gone crazy with high demand and rising prices. It's made it a lot harder to recommend them to friends and family.

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As we were ‘fitting’ into the FIT scheme at the time, our arrays are 3.75kw split east and west which actually gives a good spread through the day. It is a Enfinity system but I didn’t have a remote monitor at the time. 
We added 4 modular batteries with a separate (add on) inverter (LuxPower) giving 9.6kw of storage but expandable. 
There were several problems with the battery installation as the clamps were chopped and reconnected against the manufacturers advice. This gave interference until I remade the connections which shows in bad feedback to the controller (now sorted) making the connection sum jittery. 
My latest discovery is to restrict the switching at low battery levels otherwise there is more chance of feeding back to the grid as power switches on/off in the house. 
All very interesting and useful!

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What do you think about vertically mounted panels ? We have an unshaded south west facing gable end which gets the full force of the winter sun. It seems a shame not to use it. Our south east facing roof would be the main site for panels but the north west side is unsuitable.

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Panels perform best when they're perpendicular to the sunlight. The further away from that you are the less they produce. Our roof isn't very steep so production is good in summer, when the sun is high, but drops off a lot in winter when the sun is low. A steeper roof would be worse in summer but better in winter.

 

If you have vertical panels they're never perpendicular to the sunlight so you'll never get maximum output. But they could do quite well in winter with a low sun.

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Winter is the time we’d need more output for the heat pump - sounds like it’s worth considering.

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You could mount the panels on angled brackets @juliamc if there’s enough room - that might help

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