Is my roof too small for solar panels, what to do?

Scot_39

Have you though about ground mount if there is no tree coverage at the bottom of the garden to increase the total panel kWp.

Or maybe just a solar pergola - an open pergola type structure with flat mounted or maybe even slightly angled roof - using panels as the "tiles" - over part of the patio or garden space ?

Or the conservatory roof if strong enough and not transparent for sun light etc ?

Uncle_Cuddles

https://forums.moneysavingexpert.com/discussion/comment/82127183#Comment_82127183

Yes, 9000kWh of each (gas water and heating, and hob).

I have thought about getting the same set-up - battery storage supported with plug-in solar. We already manage our usage around the Agile cheap rates, which used to be fairly consistently low or free overnight, but lately have been not so much. The EV usually gets charged of a weekend when it is usually cheaper, so for example I charged it to 100% over yesterday and today on negative rates and that will safely last me well over a week.

We went on holiday and our baseload was 5.57kWh per 24 hours (0.24kWh per hour).

What battery would you recommend?

lohr500

I went with the expensive option at the start of last year.
A 13.5kWh Tesla Powerwall 3 and Gateway.
For a number of reasons really.

Firstly, our base demand over the 17 hour peak period is higher at around 12kWh, so I wanted enough capacity to cover this. Your baseload is a lot less, so I suspect a 5kWh battery would cover you for most of the time. (Espacially with a small boost from plug in solar).

Secondly, I liked the idea of a ten year parts and labour warranty as it was a significant investment.

Thirdly, the PW3 is capable of providing a max output of around 11kW so no worries over handling short term spikes greater than 5kW.

Fourthly, although we don't suffer frequent power cuts, the Tesla setup does provide true off-grid backup. I think since we had the system installed, we have had four or five power cuts, a couple of which lasted several hours. This wasn't a deal breaker for me, but it is good to know we have coverage for several hours when power cuts do occur.

Finally, it already has the built in DC to AC inverter needed to add solar at a later stage saving cost on any future upgrade.

The 800W plug in solar has helped to reduce the demand on the battery through this summer and with no changes to the battery configuration, any surplus solar generation is flowing back into the battery to charge it.
In the 4 months starting May, It has generated around 370kWh.

If you are considering plug in solar and want a fully approved setup rather than a DIY approach, I would be tempted to wait for a few months as I think prices will fall. Also, solar generation drops off significantly through the winter months.

In terms of battery choice for your required capacity, I don't think I can comment with any real knowledge/experience. I made the decision at the start of last year based on our needs, but the battery storage landscape is changing rapidly and prices are falling. Hopefully other forumites will chip in with their thoughts on this.

Scot_39

Are you sure your comparing apples with apples with your 12 kWh for 17hrs.

I maybe getting confused having come in late - but wasn't the OPs 5.5 kWh base load whilst home empty - but the OP's annual average 25 kWh - based on their 9000kWh pa for both fuels - so electric.

Is that 12kWh base load for 17 hours - as in empty as per the 5.6kWh figure - or average load when occupied between cheap EV or E7 rates (24-7 for E7=17 etc).

(Even that 5.6kWh is very high - around 2000kWh per annum - 80% of median, 25% higher than lower quartile Ofgem 2026 lowered TDCVs)

I worry that the OP's 25kWh per day average (9000 kWh annual on both electric and gas) might be seasonal as well - maybe electric heater of some form (given high electric and low gas cf median let alone upper quartile tdcv balances). As the balance seems abnormally flat.

Uncle_Cuddles

https://forums.moneysavingexpert.com/discussion/comment/82127160#Comment_82127160

That worries me too so I have just locked into a fixed rate at 7.28p / kWh. Tracker is currently around 8.74p.

lohr500

https://forums.moneysavingexpert.com/discussion/comment/82127699#Comment_82127699

The 12kWh I quoted is my average daily usage over the 17 hour peak period.

But as I said in my post, based on his/her reply, the OP's average day time usage is a lot less (0.24kWh), hence my comment that I suspect a 5kWh battery would cover their daytime usage.

My assumption is based on the premiss that they can't get any solar panels on the roof so going for a battery only solution which is charged up overnight at the cheapest available off-peak tariff could be a good solution.

Given the reducing capital cost of batteries though, I guess it would make sense to go for a higher capacity to future proof the system. And to give more flexibility if cheap off-peak charging hours were only available for 5 hours, not 7.

Scot_39

but my point is that it isnt - its only 5,5kWh empty 24/7 and c25kWh averaged from annually using 9000kWh pa electric normally

And that empty 5.5x kWh would be 2000kWh pa - 25% more than the lower quartile cap tdcv and 80% of tge new median.

I cant really understand why quite so high - but can guess say for 6 adults there might be say 1 or 2 very large fridge freezers and older models of tge us double door variety can be quire inefficient / wasting energy in summer, but adding 2-3 kWhs of heat in winter etc.

The 9000 annual more than double the new higher qaurtile cap tdcv of 3800kWh, but the OP has an even larger number of adults - 6 adults - in a 4 bed ? (3+loft) property - then Ofgem attribute that too.

Even allowing for an ev its still quite high - and they try to charge that only at weekend - so maybe not high mileage.

The ops 17 hr daytime normal occupied use could be near double your 12kWh if empty base typical of night use - less if exclude ev - but agile rates often cheap mid afternoon now thanks to GW of grid solar (maybe c15GW of thd June 22.8 GW total)

9000/365=25, minus 7x5.6/24 = 1.6kWh of base estimated night load = 23.4kWh daily 17hrs use. Shifting ev to night will impact that depending on mileage.

born_again

https://forums.moneysavingexpert.com/discussion/comment/82127370#Comment_82127370

My average unit cost on IOG is around 14p kWh Which is a saving of 14p kWh over std unit rate that I would be paying with a non smart charger & non EV tariff.

As OP already has a charger, then the cost could be far less that £1K, due to less work involved.

QrizB

My average unit cost on IOG is around 14p kWh Which is a saving of 14p kWh over std unit rate that I would be paying with a non smart charger & non EV tariff.

Sure, but compared to regular Octopus Go the saving on IOG is only about 1p/kWh (1.5p on the fixed version of Go, 0.6p on the variable one). And the OP could get Go with their current EV charger.

It's similar with other suppliers; EON Next Drive is 1.6p/kWh more expensive than the equivalent Next Drive Smart, for example.

Uncle_Cuddles

https://forums.moneysavingexpert.com/discussion/comment/82128251#Comment_82128251

My unit cost on Agile is about 16p over the last 3 months. My adult kids do tend to live in their rooms watching TV, on gaming PCs or consoles late into the night. Lots of washing and a tumble dryer (heat pump although we do use the washing line). The energy usage is probably higher than it would be because I do tend to take advantage of negative rates when they are available, doing washing, drying or using electric heating or cooling or putting the hot tub on at these times - if we took that out then the usage would be lower but the unit rate would be higher. You can see from the below the purple spikes of high usage alight to the low or negative cost days (apart from when I had to charge my car before my holiday).