Understand my system (England, new house)

Hello

I have bought a new house with a 2.75mw solar array on one side of the roof, installed in 2011 and I can see a sunny boy in the loft.

I believe you can have up to 4mw in a residential setting? Can this be upgraded? Do I need more roof space or can the panels be upgraded?

I believe I am getting a great feed in tariff from 2011 incentives. How can I check this?

Can I upgrade and a battery? Can I draw power at night to the battery and sell the solar to the grid?

Any help, advice and pointers welcome and appreciated

Thanks

Units my good friend, units!!!!

2.75KW. Not MW.

Check with your utility, about your current set up and possibility of upgrading.

Do you have more roof space with good sun?

If you are grandfathered into legacy net metering, you might not save any money if you have to start from scratch even if you double your array output.

740GLE said:

Units my good friend, units!!!!

2.75KW. Not MW.

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Could be a big roof

makemysunnyday said:

Hello

I have bought a new house with a 2.75mw solar array on one side of the roof, installed in 2011 and I can see a sunny boy in the loft.

I believe you can have up to 4mw in a residential setting? Can this be upgraded? Do I need more roof space or can the panels be upgraded?

I believe I am getting a great feed in tariff from 2011 incentives. How can I check this?

Can I upgrade and a battery? Can I draw power at night to the battery and sell the solar to the grid?

Any help, advice and pointers welcome and appreciated

Thanks

Click to expand...

Pictures of the current system and any spec sheets/labels would be good.

The current system could last or it could die within weeks at 13 years old but I'm a novice so what do I know, but personally I wouldn't upgrade anything on it I'd either find a way to integrate it into a newer system or start fresh. But wait for others who are more familiar with the system and have far greater knowledge to comment.

Good luck and welcome to the forums.

ThaiTaffy said:

Could be a big roof

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Really really big if it’s only one side

740GLE said:

Really really big if it’s only one side

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It's only about 8,000 250w panels

Find out exactly the terms of any agreements you have with the power company or tax incentives before you do anything!
And be very careful messing with them. A lot of the deals made in the past are way better that anything you can get today.

Power companies are looking for any excuse to get out of some of those old deals. My parents have a ridiculous deal where they get paid 5 times what they are charged for electricity. They had to get a lawyer just to add a Charger for their Tesla to keep their deal.

Thanks everyone for replies. Indeed, I have the units wrong - not mw!

I've attached a sheet showing the installation, if someone could kindly point out the important parts for me to understand.

There is no additional space for panels on this side of the roof. However, I wondered if the technology has improved to replace/upgrade panels? (Notwithstanding important comments about legal implications and tax incentives)

With regards to the tariffs, the seller left no information about any of this, so it's all new to me. I will call British Gas and/or the original installation company to see if they can provide the legal agreements, presumably.

Does anyone have experience adding batteries to these systems too, especially if you have a good feed in tarriff?

Thanks

You could possibly replace the 8x250W panels with 8x400W to get 3.2kWh, but you'll probably need to upgrade your 2.4kW inverter to a 3.6kW one to handle the additional load. The new panels may be physically slightly bigger.

You would probably need to get the system MCS certified if you did upgrade.

If you are on the old FIT with a really good rate for deemed export you would lose that and go to one of the new rates (default around 4p/kWh, some do 15p or variable rates). FIT allows replacing like for like or similar, but not (as far as I know) upgrading significantly. You almost certainly won't be able to retain your FIT rate if you add batteries.

New residential installations don't have a fixed limit, but up to 3.68kW (16A) you need to apply for a G98 certificate within 14 days of installation. This is automatically granted. If you were to go over 3.68kW (inverter) you would need to apply for G99 which can be expensive, may have output restrictions imposed, are not guaranteed to be accepted, and must be granted before connection. Fortunately G99 doesn't apply to you.

I'd look at the specs for your inverter. It just might be able to handle the additional input, but cap the output at its rated 2.4kW. In that case with just the panels upgraded you would only get 2.4kW max, but you would get that with less sun so overall generation would be higher.

I'm haven't done an upgrade, although if I'd kept my dad's old house I would have looked at replacing his 6x250W panels with 6x440W.

Check the current agreement and the specs on the inverter if you have to swap like for like you could try stick to the current 2.75kw but use modern panels thereby freeing up roof space and add more panels to a separate inverter like the sunsynk hybrid which should in theory work in tandem with your current system, charge a battery and if it was set to zero export shouldn't change your current grid tie output

If my math is correct you have 11 panels on your roof currently if you went with 450w panels you could in theory have 5 feeding your current inverter and 6 powering a new 3kw hybrid as long as they are panels on the higher end of the voc output but as I said you would need to check your current inverters PV input range.

Also side note from the photos you posted earlier it seems your array is only outputting 2.1 amps which seems low how was the weather that day? If you had ample sun you might have issues with corrosion after 13 years on your pv array connections.

The 250w panels will be 1m x 1.4m, 450w will be likely 1m x 1.7m so you will get less on the roof unless there is spare space. Get hold of the FIT agreement before committing to any upgrade but it's looks unlikely to me there is a more cost effective route forward other than adding a diverter to put surplus into hot water depending on the agreement. Some FIT agreements pay export rates on 50% of production regardless of what actually gets exported so the diverter pays for itself very quickly.

If you only get paid for what you actually export then a battery makes no sense as you will be storing at 90% efficiency. With FIT you will be getting more money exporting than storing for later use. Only makes sense once FIT stops or you need to use to cover a powercut.

The SMA Sunny Boy HF is a reliable piece of kit.

According to your doc you have a set of 10 245W panels so a 2.45kw array.

kommando said:

The 250w panels will be 1m x 1.4m, 450w will be likely 1m x 1.7m so you will get less on the roof unless there is spare space. Get hold of the FIT agreement before committing to any upgrade but it's looks unlikely to me there is a more cost effective route forward other than adding a diverter to put surplus into hot water depending on the agreement. Some FIT agreements pay export rates on 50% of production regardless of what actually gets exported so the diverter pays for itself very quickly.

The SMA Sunny Boy HF is a reliable piece of kit.

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Just looked at the photo of op`s roof the panels almost look square, good shout on the size disparity, though I'm not sure they're even 1mx1.4m though the photo could be warping perspective.

ThaiTaffy said:

though I'm not sure they're even 1mx1.4m though the photo could be warping perspective.

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Pic is a pic of a 2009 photo so plenty of room for distortion plus it may be an installers library picture and not the actual panels. To be say 1m x 1m they would have to be very efficient and impossible with the technology available in 2009. Sharp panels in 2009 were 1.3M x 1.0m and 180W, or 245W was 1.6M x 1.0M.

kommando said:

Pic is a pic of a 2009 photo so plenty of room for distortion plus it may be an installers library picture and not the actual panels. To be say 1m x 1m they would have to be very efficient and impossible with the technology available in 2009. Sharp panels in 2009 were 1.3M x 1.0m and 180W, or 245W was 1.6M x 1.0M.

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If you dive over to Openstreetmap and set up an editing account, aerial imagery for most of Britain is good enough to count panels and estimate sizes.

A good proportion of FIT-registered locations are actually mapped.