Solar Panel & Battery Quote Advice

Martyn1981

@Screwdriva Just thinking, but an alternative to reducing panel numbers, could be to limit the output of the Tesla PW3 (if chosen) to the DNO limit. I know that would mean clipping when the battery is full, and generation exceeds the limit, but may be acceptable. And of course, clipping would be less (and less) in the winter months.

@McKnze21 This may sound odd, but as the panels themselves are the cheap part of PV installs, it may be worth considering. Happy to bore you with more thoughts and examples if interested. But as Scredriva says, best to find out what you can, and can't do first with the DNO.

Screwdriva

Martyn1981 said:

@Screwdriva Just thinking, but an alternative to reducing panel numbers, could be to limit the output of the Tesla PW3 (if chosen) to the DNO limit. I know that would mean clipping when the battery is full, and generation exceeds the limit, but may be acceptable. And of course, clipping would be less (and less) in the winter months.

The PW3 automatically self limits generation based on household demand -> battery recharging -> max permitted grid export in that order. As an example, an 8kWp array with a 4kWh export allowance will generate only 4kWh + base load + any appliance consumption only, even in ideal conditions, assuming the battery is full.

kumarana

Solar PV System

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You told us you can fit 12 panels on your roof.

£3,716

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We recommend a battery of 5.2 kWh for you. Why?

£3,559

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		Selected
Advantages in the first year	Solar only  12 panels	Solar + Battery  12 panels + 15.6 kWh
Energy bill savings	£649	£1,299
Earnings with an export tariff	£378	£82
Electricity generation	5,608 kWh	5,608 kWh
Usage of your own electricity	2,467 kWh (35%)	4,935 kWh (70%)

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Solar PV System£3,716

Battery Storage System£3,559

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£7,695

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Is this too good to be true. This is from solar together partnership with Medway council

Qyburn

Screwdriva said:

The PW3 automatically self limits generation based on household demand -> battery recharging -> max permitted grid export in that order. As an example, an 8kWp array with a 4kWh export allowance will generate only 4kWh + base load + any appliance consumption only, even in ideal conditions, assuming the battery is full.

Can you set an absolute output limit on the PW3, as well as export limit?  Just out of interest as our Solaredge predates the PW3.  Our DNO initially offered 7kW maximum system size, 4kW export. 

Screwdriva

Qyburn said:

Can you set an absolute output limit on the PW3, as well as export limit?  Just out of interest as our Solaredge predates the PW3.  Our DNO initially offered 7kW maximum system size, 4kW export. 

As shared above, once you set the export limit, the PW3 scales system generation to match 1) household demand -> 2) battery recharge -> 3) grid export, in that order. When the battery is full, the absolute output = household demand + export limit. 

In your example, assume your battery was full, and your household is using 300W in total, the PW3 would scale production down across one of more strings to precisely 4.3kWh.

Hope this makes sense? 

Screwdriva

kumarana said:
Is this too good to be true. This is from solar together partnership with Medway council

In my experience, council schemes are typically the lowest end of components brands, often installed by the worst types of installer. 

What's your annual electricity consumption in kWh? 

QrizB

kumarana said:

Is this too good to be true. This is from solar together partnership with Medway council

6kWp of solar PV for under £4k is a pretty keen price, yes.

5.2kWh of battery storage for £3600 is less convincing, considering it's potentially under £2k of parts (example here) and the installers will alreay be on-site.

Qyburn

Screwdriva said:

Qyburn said:

Can you set an absolute output limit on the PW3, as well as export limit?  Just out of interest as our Solaredge predates the PW3.  Our DNO initially offered 7kW maximum system size, 4kW export. 

As shared above, once you set the export limit, the PW3 scales system generation to match 1) household demand -> 2) battery recharge -> 3) grid export, in that order. When the battery is full, the absolute output = household demand + export limit. 

In your example, assume your battery was full, and your household is using 300W in total, the PW3 would scale production down across one of more strings to precisely 4.3kWh.

Hope this makes sense? 

Thanks but that doesn't quite answer the question. Using my initial figures as an example can the PW3 be set so that total output (house plus export) is limited to one figure, say 7kW. And export is limited to a different lower figure say 4kW.

Screwdriva

Qyburn said:

Thanks but that doesn't quite answer the question. Using my initial figures as an example can the PW3 be set so that total output (house plus export) is limited to one figure, say 7kW. And export is limited to a different lower figure say 4kW.

The export limit is the only number that can be "fixed". The inverter size for the PW3 is software programmable so in your case, would be set to 7kW.

Martyn1981

QrizB said:

kumarana said:

Is this too good to be true. This is from solar together partnership with Medway council

6kWp of solar PV for under £4k is a pretty keen price, yes.

5.2kWh of battery storage for £3600 is less convincing, considering it's potentially under £2k of parts (example here) and the installers will alreay be on-site.

I thought the very same.

But, the next part suggests the battery is 15.6kWh. And that is exactly 3x the previous figure, so could be a typo, or perhaps they meant 5.2kWh battery packs?

So the battery seems to be either too expensive, or perhaps too cheap, unless subsudised?