Solar panels / batteries / cheaper energy at night

The cost of the inverter and batteries (which currently are actually as dear as solar panels) and installation used in the way you describe is not cost effective. You would never recover the capital outlay with just the difference between high and low tariff charges (usually 10pm to 8 am)
To have enough battery power to run a house during the day and evening before low tariff kicks in, in the manner you describe would require something like £15k -20K (nearer the latter) batteries plus inverter (it still has to be able to switch between incoming grid and battery with or without solar panels,) They would ultimately need replacing after about 10 to 12 years.
If you have £10k to spend you either get solar for free daytime electricity, or batteries only (which would not provide sufficient storage to run your house during the peak hours anyway).

Your solution makes no sense on a cost/benefit analysis basis

I speak with some authority on this as I have done a lot of research and very recently had the consultant round for an entire morning who is project managing our PV installation and went through our bills in fine detail to size and advised on the best solution based on our consumption and usage. Our system is costing just short of 20k euros with the hybrid hot water and heating and that is with a 50% tax relief on the bill... We should recover the full cost with 6-7 years even without taking fuel cost inflation into account. I fully appreciate we are lucky that we are able to afford the initial outlay with only a small supplementary loan but many sources of low cost loans are available, for which the monthly repayments are offset by the lower gas and electric bills. Even a full loan with the interest payments would have reached break even within 10 years (Calculations showed we will have virtually zero electric bills due to the buy back clause) and our gas bills (LGP) will be around 70% lower. (of course this varies from household to household and how well a house is insulated).
Even with a small restored and well insulated farmhouse bills are skyrocketing and we spend over 4K (euros per year currently) on gas, electric and wood burners and that is due to increase by about 15%, Hence we are going PV.

 

Yes, obviously, solar with batteries is better than just batteries. That’s a given. What you are ignoring though is that some people cannot have solar for various reasons (roof not suitable, mortgage company/landlord won’t let them etc.) SuperTyke is asking if, in that case, batteries are worth it. You might still think that they aren’t, which is fine, but that needs to be decided based on solar not being an option.

 

It really doesn't The cost of batteries is per KW plus inverter is roughly equivalent to PV panels. To get batteries to run a house for the entire peak period especially in winter requires a huge capital outlay.

 

Absolutely makes no sense.. even a single Tesla latest PV costs around 10K with inverter and installation . There is no way that can be recovered simply by the difference between low tariff and peak and, if you try to use it to heat water, cook , use washing machines, fridge freezer, TV etc,. a single one has sufficient capacity to do so.

 

A number of social housing providers are trialing/implementing it. My team in my previous role installed them for Gentoo Housing, Leeds City Council and Northampton Council.
It does require a massive outlay, but if you’re saving 3/4 on your electric bill of £120 per month you’ve got £5000 back in 5 years.

 

And that’s assuming the price of electricity is static (see what I did there), where in reality it doubles every 9 years

 

I dont see how you can save 75% on an electric bill with battery supplement to grid supply alone. Even if the off peak tariff is 20p per Kw hour cheaper how can you possibly save 75% on the total bill with a single battery (even the most efficient battery (Tesla Powerwall) is insufficient to provide more than a short period of peak usage? In any case 5K savings in 5 years would not produce any saving on the capital cost over 10 years and the battery life for PV and inverters are is quoted at around 10 years even with average inflation since that sizeable chunk of investment could yield a decent return. Yes I know current fuel inflation is through the roof but that will not continue for 10 years. Also the cost of panels although they may not come down, will probably be lower than inflation once the supply chain issues are fixed.

Can you send me the calculations that demonstrate how you arrive at 75% savings? I would be interested to see them. at 75% savings it makes PV +batteries solutions obsolete because even that does not guarantee 100% self dependency at twice the outlay. I am very sceptical re your figures. I will also raise it with my consultant who has being doing PV for over 20 years and see what he thinks.

 

Please see the link to EDFs website https://www.edfenergy.com/electric-cars/tariffs

I don’t know what you are paying per kW but this is 4.5p.

if you can charge up a correctly sized battery at 4.5p/kW and use it during the day when it’s roughly 28p/kW I’d say that works out at 1/6 of the cost. even if your battery is only 90% efficient you’re making a massive saving.

And the higher the price of electricity, the faster the return on your initial investment.

 

Am I reading that right? In a small, well insulated property in the med you're spending around £300 a month on gas and electric?

 

Yep around 2000 euros per year for gas GPL price is astronomical and we don't have town gas. That is only heating half the house to UK standards in winter with the underfloor. The rest we burn through about 300 euros using wood oven in the kitchen and Woodstove in the living room. Electric is around 150 euros per month. Most Italian houses are very cold in the winter as many only have woodstoves. Bear in mind just cos it is the Med it still gets cold. We get winds direct from Siberia in wintertime down the East side when the wind is from the North. The snow on the mountains we can see from our house has only recently gone altogether in spite of mid 30s temperatures for the past few weeks. We have been snowed in here more than once even with the 4x4.

 

Ah so you are talking about charging a car. Not the same as the size of battery needed to run a house though.

 

Blimey. I'll stick to Barnsley

 

The tariff is how much it costs between certain hours… whether you charge a car or a battery it makes no difference? There’s no limit on how much electric you can use.
They just marketed the tariff as being suitable for car users.

 

Do you mean 6kw? 600 watts is not very much at all.

 

No, lol, i mean exactly what I wrote, I have 600w of solar.

 

He's on a boat not a super yacht

 

Does my maths make sense now?
You have 12kW of batteries.
If you use 12kWh in the day it costs you £3.36 per day based on 28p/kW
If you can charge your batteries up from PV it's free! Get in.
If you charge them up at off peak grid prices of 4.5p/KW it's £0.54 per day.

30 days x £3.36 = £100.80 per month
30 days x £0.54 = £16.20 per month.

That's £84.60 per month less.

Lets take this 12kW system https://homeenergygroup.co.uk/product/lux-hybrid-12kw-battery-storage-system/ at £7295

That's paid off in 7.18 years, assuming that electric stays at the same price.

If batteries have a life of 15 years you then have another 7.82 years where you save another £7938.

If electric has doubled in price in 7.18 years you basically save £16k.

 

Even cheaper system with access to Octopus Agile tariff. https://homeenergygroup.co.uk/product/lux-power-ac-12kw-ac-battery-storage-system/
Octopus Agile is capped at 30p/kW in the day and 7.5p/kW at night.

12kW at 30p/kW = £3.60/day
12kW at 7.5p/kW = £0.90/day

30 days at £3.60 = £108
30 days at £0.90 = £27

Cost of system = £6550

Paid off in 6.73 years.

 

Likely to be a 10 year lifespan on LiFePO4 batteries, not 15.