Solar PV and Tesla Battery

  • 3 December 2020
  • 11 replies
  • 148 views

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Its taken a while to happen but we now have 17 solar PV panels on our 2 roof piches (SSE/NNW orientation and 15deg pitch) and and a Tesla battery to store any surplus.  The PV project had to wait until we'd upgraded the thermal efficiency of our roof, which was costly and time consuming, as our house has no loft space for convenient installation of insulation.  So to insulate has required a roof strip and replacement.

Take away from the PV installation:

  1. Shop around suppliers for advice you are happy with and a good price.  Get at least 3 quotes.
  2. Use an MCS certified Installer. You are likely to need this for insurance / mortgage / SEG tariff purposes.
  3. Tell your house insurer.
  4. For roof installation you'll need scaffolding so consider doing any other work required on your roof at the same time.
  5. Aim to install as much generating capacity as you can afford and the roof will allow.  You're likely only doing this once . Consider the benefit vs cost of higher capacity panels.
  6. You or your supplier will need permission from your DNO for connecting your inverter to the Grid. They will agree to capacity upto about 3.6kWh.  Approval for anything higher will depend on the status of your local sub station.  
  7. Allow plenty of lead time for:: i. The installer to schedule the work. ii. The DNO to make up their mind - you should be able to check this online.
  8. Panel prices and capacities are quite volatile.  Check for any changes between quotation and installation.
  9. Look at warranties for panels  inverter and the work.  The panels will have separate product and performance warranties.  While the panels should have an expected 25 year lifespan its quite possible you'll need to replace the inverter after 10 - 12 years. Consider extending the inverter warranty if its less than 10 years as standard.

And the key question I still have is what will the PP SEG tariff offer for any surplus capacity that my system generates.


11 replies

Userlevel 7
Badge +8

Hi @matthewr 

PP will not be offering SEG payments until 2021, this FAQ is 5 months old but may give a bit more information

https://community.purepla.net/payments-31/feed-in-tariffs-and-smart-export-guarantees-10316

Just to add that you don't have to go with your energy supplier for SEG, you can use any company that offers it, so you can shop around for the best deal

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Yes.  And with a Tesla battery the Octopus Tesla tariff looks very attractive.

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Its taken a while to happen but we now have 17 solar PV panels on our 2 roof piches (SSE/NNW orientation and 15deg pitch) and and a Tesla battery to store any surplus.  The PV project had to wait until we'd upgraded the thermal efficiency of our roof, which was costly and time consuming, as our house has no loft space for convenient installation of insulation.  So to insulate has required a roof strip and replacement.

Take away from the PV installation:

  1. Shop around suppliers for advice you are happy with and a good price.  Get at least 3 quotes.
  2. Use an MCS certified Installer. You are likely to need this for insurance / mortgage / SEG tariff purposes.
  3. Tell your house insurer.
  4. For roof installation you'll need scaffolding so consider doing any other work required on your roof at the same time.
  5. Aim to install as much generating capacity as you can afford and the roof will allow.  You're likely only doing this once . Consider the benefit vs cost of higher capacity panels.
  6. You or your supplier will need permission from your DNO for connecting your inverter to the Grid. They will agree to capacity upto about 3.6kWh.  Approval for anything higher will depend on the status of your local sub station.  
  7. Allow plenty of lead time for:: i. The installer to schedule the work. ii. The DNO to make up their mind - you should be able to check this online.
  8. Panel prices and capacities are quite volatile.  Check for any changes between quotation and installation.
  9. Look at warranties for panels  inverter and the work.  The panels will have separate product and performance warranties.  While the panels should have an expected 25 year lifespan its quite possible you'll need to replace the inverter after 10 - 12 years. Consider extending the inverter warranty if its less than 10 years as standard.

And the key question I still have is what will the PP SEG tariff offer for any surplus capacity that my system generates.


Great post - thanks

Where abouts do you live and who was your installer?

 

Is SEG tariff needed? What if your local generation just nets off your own demand?

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Yes.  And with a Tesla battery the Octopus Tesla tariff looks very attractive.


Only open to those with a Tesla car.

Userlevel 7
Badge +11

@matthewr 

What’s the storage capacity of the batteries?

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From Tesla webpage:

https://www.tesla.com/en_gb/powerwall

  • Capacity13.5 kWh
    100% depth of discharge90% round trip efficiency
  • Power7kW peak / 5kW continuousSeamless backup transitionPure sine wave output
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Yes.  And with a Tesla battery the Octopus Tesla tariff looks very attractive.


Only open to those with a Tesla car.


There are 2 tariffs. The first, at 8p/kWh for import and export, requires a Tesla car, a Tesla battery and solar PV.  The second  at 11p/kWh only requires the Tesla battery and  solar PV.  And there is no standing charge on either.

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In answer to Ohit's other questions:

  1. I live in Wiltshire and am in DNO SSEN's patch.
  2. The installer was SunGift, who are based in Exeter but that distance evidently didn't cause them or me a problem. Their presales and delivery were excellent. I'd thoroughly recommend them for consideration on anyone's shortlist.
  3. You don't “need” an SEG tariff.  Without one any surplus exported will benefit the Grid but not you. You can sign up to supply and SEG tariffs with separate providers.  I don't yet have an SEG tariff and as you can see in previous posts I'm considering what PP will offer but also looking at the Octopus Tesla tariff.
Userlevel 7
Badge +11

From Tesla webpage:

https://www.tesla.com/en_gb/powerwall

  • Capacity13.5 kWh
    100% depth of discharge90% round trip efficiency
  • Power7kW peak / 5kW continuousSeamless backup transitionPure sine wave output

Thanks, I wasn’t sure if it was installation specific hence the question.

Badge

In answer to Ohit's other questions:

  1. I live in Wiltshire and am in DNO SSEN's patch.
  2. The installer was SunGift, who are based in Exeter but that distance evidently didn't cause them or me a problem. Their presales and delivery were excellent. I'd thoroughly recommend them for consideration on anyone's shortlist.
  3. You don't “need” an SEG tariff.  Without one any surplus exported will benefit the Grid but not you. You can sign up to supply and SEG tariffs with separate providers.  I don't yet have an SEG tariff and as you can see in previous posts I'm considering what PP will offer but also looking at the Octopus Tesla tariff.


Great, thank you.

Hey Matthew - sounds like I’ve ordered the same as you - 17 panels and a Tesla battery to Wiltshire.

One question, you say that you had to increase the thermal efficiency on your roof before installation. I’m now nervous that there’s something major I don’t know. Would you be able to go into more detail there please? Why did you need to upgrade it? My house is 1985 and likely unmodified since construction so I’m eager to know your experience. 

 

Many thanks!

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