Solar Panels UK - is it worth it?

[PITA]

Not in my experience - lights flicker for a second, things like the tv will usually switch off. I have my broadband router & a few other bits on a very small UPS, otherwise even a powercut for a few seconds results in a 2-3 minute wait for the internet to reconnect. The oven clock doesn't seem to reset (and kept on cooking my cake last time we had a short powercut)

Same...

But I have noticed something...

If the Grid is a 'clean' cut off... then the Gateway swapover is seamless.

But... if it's a fuse failing somewhere and the Grid 'fluctuates' then we get a dirty swapover. Which can cause lights to flicker or stuff to reset.

So we now have an internal UPS on office equipment to bridge this uncertainty.

Other than that, the Gateway 2 is brilliant... plus it can be used to wire in EV Chargers, so it free's up places in your Consumer Unit.

 

[Avendit]

Stuff...

All super helpful, thanks. Even the AQ devices as I went on a voyage last week to check what 'too tight' might actually mean and how to measure for it. Bugger all definitions out there other than humidity once you get rid of any CO risk.

My EPC does suggest a 2.5kw solar install, so good to know additional generation goes directly on the score card. Might be able to get to a B with that .

 

[Fred2]

But I have noticed something...

If the Grid is a 'clean' cut off... then the Gateway swapover is seamless.

But... if it's a fuse failing somewhere and the Grid 'fluctuates' then we get a dirty swapover. Which can cause lights to flicker or stuff to reset.

So we now have an internal UPS on office equipment to bridge this uncertainty.

Other than that, the Gateway 2 is brilliant... plus it can be used to wire in EV Chargers, so it free's up places in your Consumer Unit.

coincidentally I queried a bad failover with them a few days ago & got a reply from tesla today, partly to say that (as you observed) the type of grid failure may impact the swapover, but also pointing out several issues with how the wiring had been done (how tesla know all this I don't know - perhaps they require the installer to take photos that are reviewed in case of any issues) and instructing the installer to fix them

 

[init6]

Is there an equivalent that can take the location, azimuth and slope and give you some typical daily estimates, but in KWh? This (mostly awesome tool) gives you really nice data for the year, but only does irradiance per m^2 for the daily data. Like, I caaan stick it all in excel, but I'm pretty sure to get a unit wrong eventually...

Does this give you what you need? (solar newb so may have misunderstood this)

PVWatts

Estimates the energy production and cost of energy of grid-connected photovoltaic (PV) energy systems throughout the world. It allows homeowners, small building owners, installers and manufacturers to easily develop estimates of the performance of potential PV installations

pvwatts.nrel.gov

You can download an hourly csv.

 

[Yachtsman]

Is there an equivalent that can take the location, azimuth and slope and give you some typical daily estimates, but in KWh? This (mostly awesome tool) gives you really nice data for the year, but only does irradiance per m^2 for the daily data. Like, I caaan stick it all in excel, but I'm pretty sure to get a unit wrong eventually...

It will take your EXACT location, just zoom into the map & pinpoint your house then enter PV size, azimuth, roof slope etc, accept 14% l. The estimation is per month & can be downloaded as CSE. If you have more than one roof enter figures for each then add & chart the results in excel

 

[Avendit]

It will take your EXACT location, just zoom into the map & pinpoint your house then enter PV size, azimuth, roof slope etc, accept 14% l. The estimation is per month & can be downloaded as CSE. If you have more than one roof enter figures for each then add & chart the results in excel

Conclusions reached: Excel is single threaded and doesn't like it when you drop a years worth of hourly data into the wrong field of a pivot table.

What beutiful data tho, thank you. When you don't drop the data in the wrong places, you get pretty pictures like this:

 

[Mrklaw]

newbie here although I’ve had solar for maybe 10 years its a ‘free’ system where we get to use spare electricity but the installers get the exports. In theory I think that means we should try and use a battery to leverage the output as much as possible but its only a tiny array - 2.9kw I think so probably not a lot of excess especially now I’m wfh fulltime?

Is the general aim (balanced vs cost) to try and use battery to store excess and then feed back into the house to fill out the gaps early/late when the solar dips below house load? And top up with off peak if needed? I’ve seen solar calculators but is there somethign that can also then estimate your house load (eg if you have octopus half hourly readings), and estimate a battery or other options to smooth things out?

 

[PITA]

newbie here although I’ve had solar for maybe 10 years its a ‘free’ system where we get to use spare electricity but the installers get the exports. In theory I think that means we should try and use a battery to leverage the output as much as possible but its only a tiny array - 2.9kw I think so probably not a lot of excess especially now I’m wfh fulltime?

Is the general aim (balanced vs cost) to try and use battery to store excess and then feed back into the house to fill out the gaps early/late when the solar dips below house load? And top up with off peak if needed? I’ve seen solar calculators but is there somethign that can also then estimate your house load (eg if you have octopus half hourly readings), and estimate a battery or other options to smooth things out?

Yes, exactly that.

Our Solar Array can be producing 5kW of power constantly for some time during Summer.

That's a lot of power, and you can't always use it all immediately.

So having a lot of battery storage, allows you to store that excess power to use when the Sun goes down. Continuing through the evening.

Another way of doing it without battery storage, is an export tariff that equals your import tariff. So if you can sell your power at 5p and buy it at 5p... then you're using the Grid as your storage battery.

The two main things with storage batteries is

1) kW capability. How much power can your battery deliver at maximum demand.

If the battery can only deliver 5kW maximum at any one time... anything over this has to be got from somewhere else (solar generation or Grid). So understand what your homes maximum demand might be, as an example...

Showers : 8kW
Heat Pumps : 2.5kW
Induction Hobs : 2kW
Hair Dryers : 2.5kW

2) kWh Capacity. This is how much Energy can be stored in your battery. The more energy you can store, the longer you'll be able to run power off it.

Storage capacity can be used for downloading cheap rate electric overnight. Ideal in Winter when Solar Panels are quiet. We buy our electric at 5p per 1kWh and can store 27kWh overnight. This gives us a days worth of cheap power during Winter, topped up by a small amount of solar power.

In Summer, the storage is filled with Solar Power, so we become completely self-powered from April...

 

[PITA]

I bought two Tesla Powerwall 2 storage batteries because they offer a 10kW power discharge capability. This means I can run an 8kW shower off them, or a 7kW car charger etc... without pulling from the Grid at peak rate costs.

They also have 27kWh storage capacity which is enough to get me through 3/4 of a day at cheap electric... or backup our house from blackouts.

You can buy 'Energy use' meters which tell you what your house demand is. I then went through our house to get each appliance power consumption ratings. To find out what my maximum loads would be.

I do it occassionally as a game with our Grandkids, so they appreciate how much power items use... they were shocked at how much an electric shower uses compared to a TV, didn't have a clue... fun when you ask them to guess which uses the most power.

 

[Avendit]

Working out our consumption, I used a set of cheap wifi meross plugs to rotate around all the obvious consumers in the house to measure base load and understand what causes spikes in usage etc. A slow but informative process.

I have since ordered one of these, tho still waiting for a sparky to come and fit it. I don't do inside the distribution board.
Emporia Smart Home Energy Monitor... https://www.amazon.co.uk/dp/B08CJGPHL9

 

[phil4]

Having seen how bad the controls are for the tesla for scheduling charging (set a start, or and end... but not both) is control of Powerwalls equally hit and miss?

 

[PITA]

Having seen how bad the controls are for the tesla for scheduling charging (set a start, or and end... but not both) is control of Powerwalls equally hit and miss?

Maybe our use case is weird then, because I find it perfect.

I plug the car into the Zappy Wall Charger, then on the Tesla in-car display I set the scheduled charging time to start at 00:30 - set it once and leave it set like that.

In my Tesla App, every day I set the kWh and 32amp charge limit on how much energy I want to add... then it charges the car at 00:30 start time until the charge quota is achieved.

If I want to just add-hoc charge during the day, I just press 'start charging' button in the app... and it takes the power from the Powerwalls (stored sunshine)

On the Powerwalls...

In Summer I'm on Self-Powered mode, so the solar panels fill up the batteries and power the house. Backup threshold set at 8%

In Winter I'm on Time-based control, so the Tesla Artificial Intelligence fills the batteries overnight from Grid, and learns how much Solar we can expect the next day to compensate any spare storage needed.

It all works great, for us anyways.

 

[scdoubleu]

Having seen how bad the controls are for the tesla for scheduling charging (set a start, or and end... but not both) is control of Powerwalls equally hit and miss?

No. You can define your peak and off-peak periods, plus their price per unit.

 

[scdoubleu]

Note that the Powerwall's Time-based control "AI" is not particularly clever. It will reduce the amount of kWh put into the battery during off-peak if there is a run of sunny days. If that run is followed by an overcast day then you can run out of stored off-peak energy well before the end of the day.

Then the "AI" will be more likely to fill its boots during the next off-peak period. This is all well and good if the next day is cloudy again. If sunny, then you don't have much spare capacity to make good use of the extra solar.

This is pretty much the scenario here this week. Tuesday/Wednesday were not particularly sunny, but Powerwall charged to around only 70% both preceding nights because Sunday/Monday were reasonably sunny. We drained the Powerwall by about 6pm Wed/Thu, so it charged to 100% last night. Today is forecast to be pretty sunny. If we're not careful, we'll end up exporting excess solar.

The "AI" is probably ok for benign climates like California, but is far less "smart" when it comes to predicting day to day UK weather. It would be nice to have a control to override the AI from time to time.

 

[Avendit]

Note that the Powerwall's Time-based control "AI" is not particularly clever. It will reduce the amount of kWh put into the battery during off-peak if there is a run of sunny days. If that run is followed by an overcast day then you can run out of stored off-peak energy well before the end of the day.

Then the "AI" will be more likely to fill its boots during the next off-peak period. This is all well and good if the next day is cloudy again. If sunny, then you don't have much spare capacity to make good use of the extra solar.

This is pretty much the scenario here this week. Tuesday/Wednesday were not particularly sunny, but Powerwall charged to around only 70% both preceding nights because Sunday/Monday were reasonably sunny. We drained the Powerwall by about 6pm Wed/Thu, so it charged to 100% last night. Today is forecast to be pretty sunny. If we're not careful, we'll end up exporting excess solar.

The "AI" is probably ok for benign climates like California, but is far less "smart" when it comes to predicting day to day UK weather. It would be nice to have a control to override the AI from time to time.

What it actually needs is access to a forecast. But that probably requires £££ for a subscription.

 

[HenryT]

Is the AI not turn offable?

 

[scdoubleu]

Is the AI not turn offable?

The AI is active in Time-based mode only. The other mode is Self-Powered, where it charges using excess solar only.

You can force the Powerwall to start charging immediately from the grid by raising the standby reserve, but the charge rate for this is limited to about 1.7 kW.

 

[RedMod3]

Is there any manual that explains how the Powerwall 2 can be controlled; I should be getting my first Powerwall and the extra solar panels within 2 weeks and I'd like to understand how to set-up teh system. Ideally, I'd like to set the % full of the Powerwall each night, but the user manual is no use.

https://www.tesla.com/sites/default/files/pdfs/powerwall/powerwall_2_ac_owners_manual.pdf

 

[phil4]

Is there any manual that explains how the Powerwall 2 can be controlled; I should be getting my first Powerwall and the extra solar panels within 2 weeks and I'd like to understand how to set-up teh system. Ideally, I'd like to set the % full of the Powerwall each night, but the user manual is no use.

https://www.tesla.com/sites/default/files/pdfs/powerwall/powerwall_2_ac_owners_manual.pdf

I'm earlier doors than you... wondering if I should go with Givenergy or some such... found this might be useful (albeit might be a bit out of date now):

 

[phil4]

It doesn't appear that you can set a "target" percentage as such.