Quote for solar PV

Cottage_Economy

Could I get some opinions/thoughts on the following quote please. Am awaiting a second quote for comparison, due imminently, but have been given a ballpark figure. I won't say who it is at this point.

Both suppliers can get the systems fitted and certified before the end of March.



Supplier 1

4.2kWp

14 x QCells 300
Solis 3.6 Inverter (5 year manufacturer warranty)
Renusol on roof mounting system with Solar Limpets
AC electrical equipment
Scaffolding/access equipment
Deposit insurance cover
Installation, testing and handover
MCS Registration and certificate
5 year insurance-backed workmanship warranty

Total + 5% VAT
£5512.50

Total Energy Output 3,553kWh

Electricity saving: £341.09
Exported electricity income: £93.09
Income from Feed-in Tariff: £134.66
Total annual benefit: £567.848

20 year forecast: £18,477.56 (3% inflation and 7% fuel inflation)(based on 16p kWh and 60% use of PV on site.)

***


6kWp

20 x QCells 300
Solis 6.0 Inverter (5 year manufacturer warranty)
Renusol on roof mounting system with Solar Limpets
AC electrical equipment
Scaffolding/access equipment
Deposit insurance cover
Installation, testing and handover
MCS Registration and certificate
5 year insurance-backed workmanship warranty

Total + 5% VAT
£6667.50

Total Energy Output 5075kWh

Electricity saving: £487.20
Exported electricity income: £132.97
Income from Feed-in Tariff: £192.34
Total annual benefit: £812.51

20 year forecast: £26329.81 (3% inflation and 7% fuel inflation)(based on 16p kWh and 60% use of PV on site.)

***

Supplier 2 (ballpark)

4kWp
£4750

5.83kW
22x 265W full black panels
£6,163.00

6.16kW
22 x 280W full black panels
£6,499.00.

Doesn't indicate if this is +VAT.

****

We use 4,100 kWh annually (smallholding so run a bank of freezers and also have a large fishtank running 24/7) so asked for a quote for both the standard 4kWp and 6kWp. Panels going on a long run of south-facing barns with little, if any, shade, even in winter. We are rural so use heating oil and cook on electric. Two out of three residents are home all day so can easily plan to stagger electrical-based tasks to maximise use of an energy generated.

Our electricity supplier is Ecotricity and we pay 17.42p kWh.

The house had an EPC rating of D when we bought it 2.5 years ago so could do a bit better on basic energy saving. We've had a new oil boiler fitted last year, we have all new controls for that and on the water tank in the airing cupboard. Already had very deep loft insulation. No idea about cavity walls and a few too many of our lights run on halogen bulbs so could look to switch some of those.

pinnks

I am sure others will pile in with thoughts but the first thing that strikes me is that the suggested own consumption looks a tad high for both 4.2 and 6kWp and especially the latter. This links to the suggested 60% own consumption which again is too high in my view.

I appreciate that you have a heavy base load with those freezers running but even so 60% own consumption is difficult to achieve. I have 5.25 kWp as noted in my signature below. Annual consumption is about 3,600kWp and typical generation about 4,400kWp. I have two diverters to sweep up otherwise exportable generation. The first powers the immersion heater and 1.8kW of under floor heating (one at a time, so water first and then floor). The second powers an oil-filled radiator with anything not being used by the first diverter. We cook electric and stagger our use of hungry devices. We have a larder fridge, larder freezer and a second normal size freezer in the garage. Even so we "only" achieve 60-63% own consumption. Exclude the diverters and we are around 30-35% own consumption or 1,300kWh or £225 at 17p.

Adding the extra generation capacity will not have a linear effect on own use. It will help in winter as you will not generate all you need anyway, so every little helps and you will need to import less but in summer you will simply export more. I would still go for the higher capacity if you can but don't assume a linear increase in savings.

Generally people on here suggest about £150 per year saving on electricity but with the current increase in pricing that is perhaps more like £200. Given your potentially higher base load you could edge that up but much more than £250?

Hope this helps
:beer:

Martyn1981

Hiya CE. I think pinnks has nailed it. We generate about 4,000-4,500kWh pa, and have reduced leccy import from about 3,000 to 1,500, so a saving of 1,500kWh and approaching £200.

Your higher consumption will mean greater savings, and my gut guess (just a guess) would also be around £250pa.

Supplier one is assuming the same percentage of consumption with the bigger system, but in reality, as you go bigger, you'll export more and more of what you generate since any time the smaller system was generating 'too much' the bigger system would simply be exporting more.

Prices wise, have to admit they all look good, and most importantly I can see that as you go bigger, the costs don't go up proportional to size, for instance installer one adds 1.8kWp [edit - not 18kWp] for 'only' £1.15k. So that all looks fair and reasonable.

Personally, and this decision is squarely yours, I'd go big. The extra costs less (so to speak), and in the long run you'll find ways to make use of more generation, perhaps a leccy car in the future, a battery to store excess when costs come down, and even a small ASHP (air con unit) to heat parts of the house, when boiler use is marginal.

Looking good.

PS, get rid of the halogens today. The payback on LED's v's Halogens will be a few months, in one year you'll have made money. Don't wait for them to die, take em out the back today with a shovel, and do the kind thing, put em out of your misery!

pinnks

I agree with Mart on the LED point.

We had loads of halogen lights, e.g. ceiling lamps with 5 spots at 30W each or 150W replaced with 5 LED spots (TP24.com have some really nice ones which look like to old 12V halogens but they are still a bit expensive compared to larger outlets) at 3.5W pumping out the same sort of overall amount and quality of lighting.

We have replaced all lights with LED (other than one room), either retrofitting or replacing lamps and have reduced our overall maximum lighting wattage from 30kW to 3kW, so a net 90% saving.

Indeed, I now moan and groan when I use the downstairs loo light as it is still 3 x 7W CFL, whereas replacement lamps could be 3.5W each and a new fitting could reduce that still further...


HTH

Crowmann

It is entirely possible with a suitable diverter to achieve 80% plus on site usage.

I know this because that is exactly what happens at Crowmann Towers.

Cottage_Economy

Thanks Pinnks and Martyn. My gut feeling was that they were about right based on what I've been reading here over the last few years.

I'm going to ask the installer to request DNO raise the export cap. I know it is unlikely so it is on the basis of nothing ventured, nothing gained. Apparently it takes 1-2 weeks to get a response so that could be ticking away in the background while I wait for my installation date, which looks to be the third week of March for both suppliers. If unsuccessful, add on £75 for the capping device. Also, I thought about asking for the inverter warranty to be extended to 10 years. Apparently that is inexpensive to do.

I have the option to go a bit higher, possibly another couple of panels, but is it worth going higher if I don't get the cap raised? Yes, it will help in the winter but could be overkill in the summer as I could be wasting far more than using or exporting (and I wonder if the quoted inverter would need to be changed as a result). Also, not sure if you have to start the application process again if the cap is raised on the basis of 6kWp, or whether DNO will accept the installer simply updating the figures to include the extra panels retrospectively? One installer told me he has no way of knowing what the result would be - it is a simple yes/no with no information. So I wouldn't be told "yes, you can do up to 6.5/7/8". Just a flat yes or no to the applied 6.

I thought about batteries, but I'm inclined to agree with one installer who said the technology is too expensive and we would be hard-pressed to get payback with our energy usage patterns. Maybe they will come down in price over the next few years.

Agree with usage concerns and the payback time is off as far as I'm concerned. I was thinking payback could be 12-14 years, something in that order.

I know we could do better on our energy usage behaviour, especially bulbs. I'm going round the house to do a light bulb audit shortly to see what we need to buy.

We will be getting an electric car next year as 95% of our journeys are local, (just an older secondhand one with a good battery integrity) so that will be a good chunk of money we won't be spending on petrol anymore and we'll charge it during the day. We will still need a part-time load lugger for the car and animal trailers though so that expense will still be there.

We have been given the option of the iBoost but a) it is uncertain whether we can have it as the cupboard sensor may be too far away from the receiver in the barns and b) we barely use the hot water to have the immersion on for the panels to be diverted to. The water is on for a 2-3 hours in the morning and evening, and none of us take long luxuriant hot showers or baths, we're all in and out in record time. I understand it is supposed to save us some oil, as the boiler wouldn't be firing to heat the water, but as far as I can see given when we use the hot water the panels wouldn't be generating anyway...or am I missing something?

Cottage_Economy

Crowmann wrote: »

It is entirely possible with a suitable diverter to achieve 80% plus on site usage.

I know this because that is exactly what happens at Crowmann Towers.

So how are you set up to achieve that?

Crowmann

iBoost plus - the later one with two outputs.

One to the immersion (that only takes around 3Kwh), the second to a large storage heater that can take upto 24Kwh.

Throw in base load of around 150w plus fridges / freezers plus dishwasher washing machines and all that's sent back is the surplus - never more than 400w at peak plus the margin of around 75w the iBoost typically works to.

The only time this changes is when the storage heater is off - four months of the year. Even that might not happen this year as a hot tub is being considered - the heater will take the surplus in those four months.

Cottage_Economy

Crowmann wrote: »

iBoost plus - the later one with two outputs.

One to the immersion (that only takes around 3Kwh), the second to a large storage heater that can take upto 24Kwh.

Throw in base load of around 150w plus fridges / freezers plus dishwasher washing machines and all that's sent back is the surplus - never more than 400w at peak plus the margin of around 75w the iBoost typically works to.

The only time this changes is when the storage heater is off - four months of the year. Even that might not happen this year as a hot tub is being considered - the heater will take the surplus in those four months.

To be honest, I'm not sure how much value the iBoost will be to us.

If we could get it (assumes the sensor in the house can communicate with the diverter in the barn), I'm switching on the immersion heater permanently to be powered by the panels when there is a surplus watts above a certain level, rather than having my oil boiler heating the water up for 2-3 hours between first thing in the morning and during the evening.

What power source is the immersion heater drawing from when the panels are not generating?

We currently don't use our immersion heater at all so my brain is having a problem working out how switching it on so the panels can power them during the day will save us money if something else (grid power) has to keep the water temp up so we can have hot water when my husband gets up at 5am.

I'm missing something here...

mmmmikey

Cottage_Economy wrote: »

I'm missing something here...

Hi - what you're missing is that once you've heated the hot water in the cylinder it should stay hot a long time, so if you get it piping hot in the morning when the sun's out it will still be hot in the evening when you want to shower. Depending on size of panels, how big and well insulated hot water cylinder is and how much hot water you use, you may well find you don't need to use any oil at all for hot water heating in the summer months

Cottage_Economy

Without wishing to stir a honest's nest of opinion, I'm also trying to consider what the impact would be if solar power users end up paying penalties for being low grid users as a result of OFGEM's targeted charging review. It is going to do something, just don't know the scale of it.

If the savings up on this thread are going to be more realistically £200-£250 for me a year plus FITS, and a charge wipes out the FITs benefit and maybe a bit more, is it still worth me spending a lot of money on this system?

Would I be better changing my energy usage behaviour, putting all LED bulbs in, replacing energy inefficient devices, maybe scheduling the washing machine and dishwasher to run at night, investing in a portable solar pack to charge small devices like laptops etc during the day as I am at home and can do that, purchasing a secondhand electric car now , etc., etc.

I should add if I put the money directly into DH's additional pension we would get the tax uplift from HMRC on that straight away. He's of an age where he could access it if he needed to, so it is not 'locked' away as such.

This is a tougher decision than I thought it would be...