Solar Panels

Benny2020

Over 30% of my generation goes into hot water before you even begin to think about general household usage.

drsquirrel

minorman said:

My only 2 realistically useable roofs face roughly east / west.  I cannot put it on the flat south side wall of the house or on the garage flat roof (propped up) without getting planning permission which my neighbour would probably object to  .  My biggest electrical load is anytime from lunchtime to 10pm so I put in the west facing roof as the one of choice.  I would think 4 kW max is probably the limit as I am not sure but I think the limits were 4kW before restrictions kick in but they might have changed the rules..  

They can object to it, but doesn't mean you won't be allowed. Unless there is good reason it will likely be allowed.

I am hoping they start reducing any restrictions (and I do mean ANY) on solar installs.

QrizB

Benny2020 said:

Over 30% of my generation goes into hot water before you even begin to think about general household usage.

Unless your house is all-electric, the 30% that you're using to heat water is only worth 7.5p/kWh. That's going to push your payback time out.

Benny2020

Already got my money back after 7 years. Only 12 kwh generated today, 5.1 into hot water and still generating 539 watts.

Benny2020

Also try putting 5 kwh of gas into your hot water tank and see how much hot water you get.

Petriix

We use practically zero hot water at home. No more than £100 per year worth of gas. Your figures will be massively distorted if you're treating every kWh diverted into hot water as a unit of peak electricity saved. I suspect that you're keeping your airing cupboard nice and warm for minimal benefit.

Rather than measuring how much you're able to waste, a more realistic measure of savings is how much you're able to avoid importing based on sensible usage.

gefnew

That is why proportional diverters with multiple output relays really work with solar and dedicated outlets to use spare generation. Not just water heating but space heating or any resistive load. So that baseload is always used first. 

QrizB

Benny2020 said:

Already got my money back after 7 years. Only 12 kwh generated today, 5.1 into hot water and still generating 539 watts.

If you're saying you got your money back in reduced gas and electricity bills, I want to see your maths.

If however you're saying that you got your money back because in 2015 you qualified for FIT payments, you're being deceptive by not disclosing that since people reading this thread today won't receive those.

Your misleading statement:

Benny2020 said:

A 4kw system should produce 4000 kwh a year, if you use half then thats £560 a year so 10 years payback before you factor in using more with a diverter, future energy rises and SEG payments. 

... only applies IF you are such a high electricity user that you can substitute 2000kWh/yr of your current electricity consumption with solar, all in daytime and mainly in the summer. And you've explicitly excluded any diversion to heat HW from that.

Benny2020

Well I used to import 3300 and now i import 950. And yes I get around £800 a year in FIT payments.
I understand that if I didn't get the free hot water each day I would use much cheaper gas to do the job.
But which ever way you look at it my consumption of electricity and gas from the grid has fallen since getting panels and that's a good thing all round.

[Deleted User]

drsquirrel said:

minorman said:

My only 2 realistically useable roofs face roughly east / west.  I cannot put it on the flat south side wall of the house or on the garage flat roof (propped up) without getting planning permission which my neighbour would probably object to  .  My biggest electrical load is anytime from lunchtime to 10pm so I put in the west facing roof as the one of choice.  I would think 4 kW max is probably the limit as I am not sure but I think the limits were 4kW before restrictions kick in but they might have changed the rules..  

They can object to it, but doesn't mean you won't be allowed. Unless there is good reason it will likely be allowed.

I am hoping they start reducing any restrictions (and I do mean ANY) on solar installs.

You can have as many solar panels on your roof as you like provided you comply with planning rules. That isn’t the issue. The issue for your DNO is the amount of electricity that your panels can potentially export. Installations below 16 amps per phase, do not require DNO approval just notification. Anything more than 3.86kW export per phase requires DNO sign off. The DNO will look at your local electricity infrastructure and it may impose an export limit which can be as low as 3.86kW. I have a 6.5kWp array and a battery. My export limit has been set at the site limit of 11.5kW (the AC battery inverter is treated as a potential generator).

Any export limit is managed by the inverter. If for example, you had a 7kWp array and a 5kW export limit and you were charging an EV, then you would be able to benefit from the full 7kW. However, if there was no house or other load, the inverter would limit solar production to the 5kW export limit.

As part of its approval for large arrays, the DNO may also insist on a 3 phase connection which you would have to pay for. Sadly, our ageing Grid infrastructure is not capable of managing renewable loads. For example, the voltage at my local transformer has recently had to be ‘tapped’ down from 256 to 243 volts.