Adding battery to existing solar PV system - any thoughts/advice please.

QrizB

Screwdriva said:

Have you considered?
1) An EV (even a cheap one) to gain access to the Intelligent Go EV tariff? 7p from 11:30pm to 5:30am every day. This tariff works well with the PW3 and you'll still have access to their 15p export rate. 

You'd need £2k for the EV and £1k for the charge point, unless you spend more-than-£3k and buy a IOG-compatible vehicle and use a granny charger. I don't see the OP benefitting by £3k quickly enough for this to be worthwhile, unless they were planning to buy an EV regardless.

(Cheekily, I guess you could do it for £1k by fitting the charge point and getting a neighbour to charge every couple of weeks. A neighbour of mine gave me 10kWh for free when he wanted to test his newly-installed charger - it was going to be less but we had a second beer before remembering to unplug!)

JKenH

Hi

1) Yes, I was looking on Auto-trader last night. I already have a Zappi charger having owned EVs for 3 years in the past. I’m not sure whether I could recover the cost of insurance and RFL let alone depreciation from having an EV tariff but again this isn’t really about saving money. I’m really tight when it comes to certain expenditure but profligate when I want to be.

2) Yes, but no. My wife likes having an airing cupboard and complained when I insulated the HW tank too much. I see installing a heat pump hot water cylinder as being very disruptive. Because we have two hot water cylinders at opposite ends of the house to cut down having to run off gallons of water, I would have to install two HP HW cylinders. 

Good to know I can program Agile cheap slots into the PW3. Every night I reset the immersion heater controller with the best Agile slots.

JKenH

QrizB said:

Screwdriva said:

Have you considered?
1) An EV (even a cheap one) to gain access to the Intelligent Go EV tariff? 7p from 11:30pm to 5:30am every day. This tariff works well with the PW3 and you'll still have access to their 15p export rate. 

You'd need £2k for the EV and £1k for the charge point, unless you spend more-than-£3k and buy a IOG-compatible vehicle and use a granny charger. I don't see the OP benefitting by £3k quickly enough for this to be worthwhile, unless they were planning to buy an EV regardless.

(Cheekily, I guess you could do it for £1k by fitting the charge point and getting a neighbour to charge every couple of weeks. A neighbour of mine gave me 10kWh for free when he wanted to test his newly-installed charger - it was going to be less but we had a second beer before remembering to unplug!)

My son is on IOG with a Nissan Leaf and a Quasar charger. He says he can’t get the charger to work with IOG but he gets the cheap rate anyway. 

I don’t want to bung my drive up with a Mk1 Nissan Leaf thank you. I wouldn’t mind a Fiat 500e but as my wife has a (petrol) Kia Picanto which she loves it wouldn’t get much use. Our Picanto does 3k miles a year and the Golf 8k of which my daughter accounts for 3k miles when she comes back from abroad twice a year to stay with us and visit friends. I’m currently averaging around 57mpg and got 69mpg on a 135 mile run home from our Norfolk holiday so it’s hard to make a case for switching to an EV. 

I yearn for an EV but can’t justify one (I can’t justify a battery or more panels either but I want them). Cars are money pits. Things break on them whether EV or ICE. I really want a classic Jaguar but my head says no and it also says no to a Tesla Model 3, cheap as they might be now. I try to manage my life to avoid stress and that means being very sensible about not owning cars I don’t really need. I forget all these hard learnt lessons of course until my very sensible wife reminds me.

NedS

JKenH said:

Good to know I can program Agile cheap slots into the PW3. Every night I reset the immersion heater controller with the best Agile slots.

I don't know how many slots the PW3 will allow you to enter - I doubt it's 48, but who knows. This is why I suggested earlier breaking it down into more manageable blocks where prices may be similar for a few hours. You know you don't want to import when the price is over 15p as you can store and use your solar for that, so any periods over 15p can effectively be 'peak rate' on most days and it doesn't really matter whether you tell the PW it's 50p, 99p or 200p as the result is the same - I'm not buying at that price. 

There are 4 'rates' you can set/use - Super Off-Peak, Off-Peak, Mid-Peak and Peak, and for each 'rate' you set the buy price (import) and sell price (export) in pence. For Cosy, I only use two rates (peak and off-peak) and set the off peak to 15p/15p and all other times to peak at 200p/15p. In other words, I only want to import electricity during the off peak times, but you can export at any time as it's always 15p. I exaggerate the difference in price so the App can be in no doubt what to do.

Note the app will not accept a buy price lower than the sell price, which really confuses those on cheap overnight EV tariffs (e.g, 7p/15p overnight), so you would have to enter the same price for both import and export.

JKenH

Update: 

It’s all been very quiet for a couple of months while Northern Powergrid considered the DNO application. I wasn’t optimistic but I have now heard that my proposed PW3 plus an additional 5kW of panels has been approved with a new export limit of 11.04kW up from 7.3kW. Let’s say I am pleasantly surprised as previous informal enquiries had received a negative response. I have to say a big thanks to @Screwdriva and his contacts for making this happen. Installation won’t now be until the New Year. I can’t wait but I will have to. It will give me a chance to experience an Agile December.

Screwdriva

Given the triple aspect nature of your roof, I would hope you are able to achieve roughly 13kWP of generation via additional panels, which should make for a very lucrative generation period when on Intelligent Flux. 

It's a pleasure to serve this helpful community - Congrats on an incredibly rare result! 

QrizB

JKenH said:

I wasn’t optimistic but I have now heard that my proposed PW3 plus an additional 5kW of panels has been approved with a new export limit of 11.04kW up from 7.3kW.

That's a result!

I'm glad it's all working out for you

JKenH

QrizB said:

JKenH said:

I wasn’t optimistic but I have now heard that my proposed PW3 plus an additional 5kW of panels has been approved with a new export limit of 11.04kW up from 7.3kW.

That's a result!

I'm glad it's all working out for you

Thanks, yes it is. In practice, because the panels are over 3 roofs and therefore subject to shading, I doubt my solar generation will ever much exceed 9kW but it gives me plenty of scope for exporting in the 4pm to 7pm slot. The contractors are though going to have a look at my existing panels which are only performing at about 85% of their potential so there is the potential to squeeze out another 1kW. 

I have no real idea which way electricity prices will go in the future but I am expecting continued volatility and more scope for dynamic pricing and arbitrage. I  doubt though I will ever make a profit on my latest investment but I am enjoying SKIing.

After a misunderstanding regarding my availability I have now been given an installation date of 8/9th December so that’s an early Christmas present for me.

Screwdriva

JKenH said:

I doubt my solar generation will ever much exceed 9kW but it gives me plenty of scope for exporting in the 4pm to 7pm slot. The contractors are though going to have a look at my existing panels which are only performing at about 85% of their potential so there is the potential to squeeze out another 1kW. 

I hope you won't mind my humbly suggesting you delete all faulty panels and consolidate the remaining working panels on one single aspect (West). Then, add as many new 500w bifacial panels on both aspects (South and East) as possible. Given the relatively low cost of panels and your DNO allowance, I'd be aiming to maximize generative potential of that roof (and aesthetic uniformity) if it was my home.

JKenH

Thanks @Screwdiva. Yes, that does make sense. I was just concerned that with the faulty panels being on 2 elevations of a two storey roof the scaffolding cost would be quite high for the extra generation I would be gaining. I will see what the contractors say when they investigate.

Just out of interest why do DNOs opt for a 11.04 kW limit. I worked out it is 3 x 3.68 so it would make sense if I had a 3 phase supply but my house is only single phase.