DIY Solar

[solar]

With rising electricity costs i'm thinking of self installing solar which for a 6KW 16 panel system, i'm estimating £5k cost and possibly a 5-6 year return on investment

Annual use is approx 7000 KWh, south facing roof with room for 16+ panels

Installation/wiring of the panels looks straight forward, and being a spark i can install the inverter/isolators/CU as necessary in the garage

However i'm not MCS certified so could i
1. Connect it to the mains, if not how could i use the generated solar power for the house? (i'm not planning on using batteries as the return on investment is poor)
2. Export any unused power to the grid without MCS certs and get paid?
3. If i can export to the grid, being a 6KW system i presume the easiest option is to put a limiter in place to limit the export to 4KW but then i wouldnt be able to make full use of the 6KW for the house?

Estimated returns using the calculator from https://great-home.co.uk/solar-export-guarantee-seg-calculator/

 

[Murdoch]

Why do you think you need a 6KWH system.

We have a 4 kwh system and its great.

If you are using 700o kwh - on what - thats a lot

Do you have a hot water tank and immersion heater?

 

[ProDave]

The fly in the ointment might be for > 3.68 kW inverter, you need PRIOR approval from the DNO and there might well be a network upgrade cost to pay.

A more typical system with 4kW of panels and an inverter limited to 3.68kW output does not need prior notification, you fit it and then notify the DNO.

You are MUCH better off installing on the basis of self usage. If that is your plan then you can truly DIY install it. At 27p per kWh from tomorrow you are FAR better maximising self use by time shifting usage to the middle of the day than being paid an insulting 5.5p for what you do export. And in order to claim that insulting export, you have to pay extra and have an MCS installer supply and fit the kit. That will likely cost you double or more what you could buy and self install for.

The other advantage of a smaller system is much easier to self use almost all that you generate.

 

[binky]

I would always recommend maximizing the array, but you will need to apply to DNO prior to installation on. G100 application. Most inverters have export limitation which can be set up on installation.

 

[solar]

Why do you think you need a 6KWH system.

We have a 4 kwh system and its great.

If you are using 700o kwh - on what - thats a lot

Do you have a hot water tank and immersion heater?

The cost difference of the panels from a 4kw to 6kw is only around £1000 so number crunching it makes more sense to maximise the system for faster ROI and future proofing

i work from home and have network servers running 24x7x365 which push my annual use up by approx 3000 KWh

no immersion, hot water tank is heated from the boiler

 

[solar]

The fly in the ointment might be for > 3.68 kW inverter, you need PRIOR approval from the DNO and there might well be a network upgrade cost to pay.

A more typical system with 4kW of panels and an inverter limited to 3.68kW output does not need prior notification, you fit it and then notify the DNO.

You are MUCH better off installing on the basis of self usage. If that is your plan then you can truly DIY install it. At 27p per kWh from tomorrow you are FAR better maximising self use by time shifting usage to the middle of the day than being paid an insulting 5.5p for what you do export. And in order to claim that insulting export, you have to pay extra and have an MCS installer supply and fit the kit. That will likely cost you double or more what you could buy and self install for.

The other advantage of a smaller system is much easier to self use almost all that you generate.

I have read some posts detailing that’s it may be sytaight forward to get approval from the DNO for systems >4kw , from what I read you detail the kit that will be installed along with basic diagrams so worth considering.
the problem I have will be the MCS sign off so I need to find out more about this.

Fully agree self usage would be my preferred solution so I could nearly come off the grid, however the battery costs are extremely high and number crunching I would be lucky to recoup the additional battery costs before they failed.

i have skim read about people using diy battery systems but would much prefer to use a solid tested battery but may be worth researching diy setups

 

[binky]

You don't need MCS anymore.

 

[binky]

Fully agree self usage would be my preferred solution so I could nearly come off the grid, however the battery costs are extremely high and number crunching I would be lucky to recoup the additional battery costs before they failed.

i have skim read about people using diy battery systems but would much prefer to use a solid tested battery but may be worth researching diy setups

Coming off grid is a non starter with your constant energy demands. Batteries, also easy to fit. Get a hybrid inverter that does the solar and batteries. 10 kw of battery can be had for around £5k. Wholesale prices.

 

[ProDave]

You don't need MCS anymore.

You do if you want to claim the insultingly low "smart export payment" which the OP mentioned.

 

[binky]

MCS registered installers are quoting stupid prices, so definitely not worth the pittance the likes of Octopus offer

 

[Murdoch]

i work from home and have network servers running 24x7x365 which push my annual use up by approx 3000 KWh

I think you are expecting too much input from your solar

Our lowest generation last year was about 55 kwh in December, our highest was 484 kwh in April

You estimate your servers use about 3000 per year is about 8 kwh per day or about 0.34 kwh per hour

Should you consider battery storage?

 

[user 31423]

I'm just a casual observer of this thread as only vaguely thinking of solar. I assume the batteries that are used are lithium. One of the big advantages of lithium batteries is their low weight. This is not a consideration for a static installation so could lead acid batteries be used instead, at presumably much lower cost?

 

[binky]

I'm just a casual observer of this thread as only vaguely thinking of solar. I assume the batteries that are used are lithium. One of the big advantages of lithium batteries is their low weight. This is not a consideration for a static installation so could lead acid batteries be used instead, at presumably much lower cost?

lead acid maybe cheaper, but, lack the charge cycles of lithium, so overall lithium does work out cheaper in the long run. It's also not so easy to find a battery charger for lead acid, as all the soalr units are designed to work with lithium.

 

[revor]

I have 6kW system plus battery and would not be without the battery. At first thought it would take to long to get the £400 it cost me for the MCS but now costs of energy have soared the return will be sooner. From figures I have seen quoted for a battery the cost over the lifetime is in the region of 12p to 15p per kWh so investing in a battery you are effectively buying forward electricity. This last week I have consumed less than 1kWh from the grid. Also last month I switched from fixed 5.5p export from Octopus to the variable export tariff linked to wholesale price and first month got kWh average of 23.69p/kWh which was more than what my consumption rate was (20.38p/kWh ). My consumption was £19 including daily charge but got £57 for my export. All will change from today no doubt.
I could see from my graphs that I was clipping out a lot at the 3.68kW limit so last evening sent application in to my DNO (SP) to see what if I could increase the limit and had very quick reply this morning that up to 5kW is allowed without a witness test and I did not have to pay any costs. If I required to export more then would incur a charge of £750 +VAT plus cost of any work. I do not think there will be many occasions that I would exceed the 5kW.
So I would not write off a battery nor MCS until you have looked further into it. Could you team up with an MCS registered installer who will let you do the work and get them to give you after checking an MCS certificate? If later you think of adding a wind turbine it is extremely difficult to link with a Li battery system because of the complexity of the charging architecture. So a LA alternative I believe is much easier to accommodate. Also look for a inverter and battery combo that is tried and tested as a system as the inverter will have firmware compatible with the battery BMS.

 

[solar]

thanks, I havent written anything off yet as i'm just in research stage to see if this is viable / worth doing

what size battery have you got installed and do you know the approx cost price of the battery?

 

[revor]

what size battery have you got installed and do you know the approx cost price of the battery?

10 kW 8 useable approx £5K

 

[binky]

Also last month I switched from fixed 5.5p export from Octopus to the variable export tariff linked to wholesale price and first month got kWh average of 23.69p/kWh which was more than what my consumption rate was (20.38p/kWh )

who are you getting the export rate from- is that an Octopuss deal?

 

[solar]

I am an Octopus customer but would need MCS certification in order to export to them.

If i could pay an MCS installer £300 to sign off it may be worth especially if the variable rate is as high as you're receiving @ 23.69p but not sure how long that would last so i'm looking into battery storage too

 

[revor]

who are you getting the export rate from- is that an Octopuss deal?

Yes had been getting just 5.5p (now 7.5p I think) since last May until I read on a forum that someone was getting 17p on variable but since then prices gone up. Swapped over end of Feb. Also found via forum (good are they not) that if you get FIT you can also get export. I don't get FIT but I enquired of Octopus if that is true as I have a friend who could benefit. Was told that FIT is a generation payment and export is just that a payment for measured export for which you need a smart meter. The payment rate fluctuates by time of day in 1/2 hr intervals greater the demand the higher the payment linked to wholesale price. you can have FIT from one provider and get export from another so it seems.

 

[binky]

Yes had been getting just 5.5p (now 7.5p I think) since last May until I read on a forum that someone was getting 17p on variable but since then prices gone up. Swapped over end of Feb. Also found via forum (good are they not) that if you get FIT you can also get export. I don't get FIT but I enquired of Octopus if that is true as I have a friend who could benefit. Was told that FIT is a generation payment and export is just that a payment for measured export for which you need a smart meter. The payment rate fluctuates by time of day in 1/2 hr intervals greater the demand the higher the payment linked to wholesale price. you can have FIT from one provider and get export from another so it seems.

That's really interesting, as that makes a massive financial difference. Does the rate you pay for importing leccy vary over the day also?