To MCS or not to MCS

[SimonSays]

Have to ask though, is a North facing array worth the expense? What's a back of the envelope payback calculation look like?

It's a good question and I didn't include the expected generation, which is around 2.2MWh/yr. There are a few Youtubers recording data from their north facing arrays, and it seems they can be surprisingly useful.
The best quote I have for the whole work £4,970, including MCS. I could probably sell both my existing 3.6kW and unused 5kW inverters to recoup a little.
If we assume (we know what that makes) it's only "offsetting" purchase of IOG cheap slot energy then the generation is "worth" £154/yr. The value is of course worth slightly more than that though as it'll increase export during sunny months.

So, I think it comes down to three choices

• roofer to install panels from City Plumbing, around £3200, DIY inverter swap, get Octopus Energy Services to approve - £250, inform DNO myself
• commercial installation including MCS, around £4200
• do nothing, leave itch unscratched

[resybaby]

So £3450 personal work to do, organising, and no cert vs £4200 watch someone else do the lot and sup cuppa with cert and no agro organising or risk.

Not really in keeping with the idea of the forum/hands on/get stuck in approach but my hat would be on the later (funds permitting). Having first of course done the math on the yield/payback etc.

Just my twopenneth.

[Gareth J]

Have to ask though, is a North facing array worth the expense? What's a back of the envelope payback calculation look like?

It's a good question and I didn't include the expected generation, which is around 2.2MWh/yr. There are a few Youtubers recording data from their north facing arrays, and it seems they can be surprisingly useful.
The best quote I have for the whole work £4,970, including MCS. I could probably sell both my existing 3.6kW and unused 5kW inverters to recoup a little.
If we assume (we know what that makes) it's only "offsetting" purchase of IOG cheap slot energy then the generation is "worth" £154/yr. The value is of course worth slightly more than that though as it'll increase export during sunny months.

So, I think it comes down to three choices

• roofer to install panels from City Plumbing, around £3200, DIY inverter swap, get Octopus Energy Services to approve - £250, inform DNO myself
• commercial installation including MCS, around £4200
• do nothing, leave itch unscratched

With even your cheaper option having a 20+yr payback, this would answer the question for me. If you have the money to invest and want to do some renewables, surely money and resources are better spent elsewhere? Is there a current ripple turbine/solar buy in option? More batteries? Shares in octopus?

All that said. I get it, I've done a PV project here with little thought about the payback - mostly just because the roof was there and easy to access/do DIY.

[Joeboy]

We achieve around 750kWh per year per 1kWp from our best Southfacing panels. At our last secondhand purchase session we paid the equivalent of £276 for the micro inverters and panels per 1kWp.

Assuming we export it all as an add on and raked about in the scrap pile for some timber and cable to install.

It's 750 x 15p =£112. That's 2.5 years payback. Knowing this now and enjoying living it I'd definitely pursue mcs on a new install and leave the diy stuff until registered and on an exporting contract. It is surprising how much can be added on via outbuildings.

The guys further South will destroy the 2.5 yr payback time I'd think?

Just posting that up for thought.

[Gareth J]

I'm wondering if Octopus would

• notice this
• care

What do you guys think?

These are interesting questions that remain unanswered. Either those who are doing it don't want to publish the fact online. Or no one is doing it here.

Gut feeling is that they will have some level of checking. @15p, there is a small incentive to run a diesel generator to spin the meter backwards and get paid for it. While they may not mind a bit of unregulated extra PV, the negative publicity of it potentially being found out that the "green" company is paying for even a few non regulated generators running on whatever will burn is incentive for them to be at least a bit on the case.

If one were to try to add an under the radar array, export limiting it to not exceed the original MCS capacity is surely advisable.

[SimonSays]

If one were to try to add an under the radar array, export limiting it to not exceed the original MCS capacity is surely advisable.

On the longest and sunniest days, starting with full batteries and being out of the house, I found it necessary to be discharging the batteries from quite early in the day as otherwise it ends up being a bit of a fight to discharge them before the IOG cheapslot starts if I'm not paying attention. Often I'd be maxing out the 3.6kW inverter before mid-day despite only having a 3.2kWp array.

Octopus haven't said anything so far. That's no guarantee that they won't in future of course.

[Gareth J]

If one were to try to add an under the radar array, export limiting it to not exceed the original MCS capacity is surely advisable.

On the longest and sunniest days, starting with full batteries and being out of the house, I found it necessary to be discharging the batteries from quite early in the day as otherwise it ends up being a bit of a fight to discharge them before the IOG cheapslot starts if I'm not paying attention. Often I'd be maxing out the 3.6kW inverter before mid-day despite only having a 3.2kWp array.

Octopus haven't said anything so far. That's no guarantee that they won't in future of course.

Yeah, interesting example. Presumably you've registered the increased generator capacity with DNO? If so, in theory, I guess Octopus would be able to cross reference this and see that it tallies with your export amounts. Feels unlikely though somehow.

[SimonSays]

On the longest and sunniest days, starting with full batteries and being out of the house, I found it necessary to be discharging the batteries from quite early in the day as otherwise it ends up being a bit of a fight to discharge them before the IOG cheapslot starts if I'm not paying attention. Often I'd be maxing out the 3.6kW inverter before mid-day despite only having a 3.2kWp array.

Octopus haven't said anything so far. That's no guarantee that they won't in future of course.

Yeah, interesting example. Presumably you've registered the increased generator capacity with DNO? If so, in theory, I guess Octopus would be able to cross reference this and see that it tallies with your export amounts. Feels unlikely though somehow.

I have G98, so allowed to export up to 3.68kW. And as I said at the beginning of the thread, our DNO have automatic approval for up to 5kW on G99 post installation, so could in theory replace the 3.6 unit with the 5kW I have in storage and inform the DNO within a calendar month.

Perhaps that could be a step forwards? - ie, tell Octopus the existing inverter needs to be replaced, query if they'd worry if I replaced it with the 5kW unit, see if they spot the increased export from battery.

[resybaby]

Simon, think id start with getting the 'no quibbles' automatic upgrade to 5kw confirmed in writing from the DNO, before going to Octopus. That way you have your ducks already in a row before you contact Octopus and are future proofed from both organisations viewpoints being different or changing in the future.

Looking at this from another route. If allowed to export 3.68 (or 5.0 for that matter) surely the maximum you could export would be:-

3.68 x 24 = 88.32 or
5.0 x 24 = 120kw

Neither without exceeding the ability of your inverter. Obviously you'd need a suitable battery to export 24/7, so would Octopus even worry if you export upto those figures anyway, considering they have no idea on your actual storage?
You could after all have lots of storage as well as dc charging (nobodys concern) directly to the stack to supplement generation as well.

All i can see them picking you up for would be exceeding the 3.68 or 5kw thresholds at any given point in time via the smart meter.

Should add i dont export, am not with octopus and am more green than cabbage looking at most of this malarky.

[SimonSays]

Simon, think id start with getting the 'no quibbles' automatic upgrade to 5kw confirmed in writing from the DNO, before going to Octopus. That way you have your ducks already in a row before you contact Octopus and are future proofed from both organisations viewpoints being different or changing in the future.

The approval has come through from UK Power Networks. It's a really simple application process through their portal. They want some commissioning diagrams once the work is complete but we'll cross that bridge when it comes to it.

I'll put a call into Octopus tomorrow hopefully they'll verbally confirm and I'll ask that they put confirmation into an email.