PV Panels for me?

[paulc313]

Sorry I know this has been done to death and the same questions have appeared in this forum but I thought I would ask anyway. 

 

I like the idea of PV panels, however after reading through this it appears that many people have said that if quotes are high - 4k - 6k PV it is not worth it financially. 

 

I'm about to do my loan application for renewables, getting an ASHP and potentially PV panels. We were thinking of putting them on our workshop roof which is much bigger than our new build. This is the quote I got:

 

 

 

 

 

The workshop is in Aberdeenshire and faces directly south west. There are four of us in total and due to our circumstances it's likely that there will be one of us working from home every day during the week, most probably 2days both of us working from home. So could potentially get dishwasher/washing machine on etc mid day. Plus we will be using laptops/monitors/tv's on during the day as well. 

 

So I was wondering if you could tell me if it is financially worth it? How long will it take roughly to pay the sum back from savings? 

 

Thanks

 

Paul

[ToughButterCup]

8 minutes ago, paulc313 said:

...

So I was wondering if you could tell me if it is financially worth it?

...

 

Is finance the only consideration? Because if it is, the answer is likely to be ... no... But if you take a wider perspective, then the answer may become ... yes. 

And thats the route we took. Yes, emotion comes into the calculation. 

 

Overall, if pay back is the only consideration, then self-building is one of the hardest possible routes to take. Unless you are already in the business.

[ProDave]

My view is you are very unlikely to use all you generate from an 8kW PV system.  Unless you are installing battery storage (another topic for debate) I see little point going beyond 4kW

[paulc313]

@ProDave So we have too many panels and too much electricity being generated?? Even with a south west direction and ASHP?

 

 

[pdf27]

4 minutes ago, paulc313 said:

@ProDave So we have too many panels and too much electricity being generated?? Even with a south west direction and ASHP?

Crudely, you're unlikely to be generating PV at the same time as your thermostat will be calling for heat. Most of the year you're using the grid as a giant battery with a round-trip "efficiency" (ratio import:export costs) of about 30% on one of the better tariffs, more like 0% on one of the Big 6 tariffs.

Views differ on what is worthwhile and isn't - personally I'd be reasonably happy with that system and cost, but I'd also be fine with a payback of >10 years and doing a fair bit of work on load-shifting and time of use tariffs. I certainly wouldn't consider it a good investment from a purely financial point of view however.

[SteamyTea]

First thing to do is run the setup through PV-GIS.

https://re.jrc.ec.europa.eu/pvg_tools/en/#MR

Then compare that to current usage (you can read a meter every hour to get a feel for what is going on.

Battery storage, at the moment, is a nice toy to play with, but probably not worth it.

But storing electrical energy as thermal energy probably is worth it. Especially if you can reduce the capital cost of an ASHP.

There will be times when you over produce, and times when you under produce, but that is just a calculation to find out the overall ideal system and storage size.

 

Look up the prices of DIYing a system. Probably much cheaper.

Edited April 7, 2021 by SteamyTea

[ProDave]

I have a 4kW system on an E/W split (hopefully to lengthen generation time rather than optimise total output)

 

I manage to self use about 90% of what we generate, by using the big appliances one at a time in the middle of the day (use a timer if you are out) and by dumping surplus to the immersion heater rather than let it export.

 

The small amount we do export is usually when there is no load to use any, and the generation is >3kW so more than the immersion heater can absorb.

 

In the shoulder seasons the ASHP will help use some but for all the summer that won't be heating the house.  I also time the ASHP so it only starts heating the DHW at 11AM when there is plenty of PV generation to use.

 

I assume the quote you had was from an MCS installer?  do you feel confident to install the panels on the roof yourself then just get an electrician to connect them?  That will be a lot cheaper.

 

Even my DIY installed system will have a payback of 6 years based on how much we are self using.

[Lots2learn]

This is a subject I am wrestling with at the moment.

We have had quotes of about £7400 for a 12 x 380 Q cell system with solaredge inverter and givenenergy 5.2 kw battery.  If we opt for PV panels only it would be about £2400 less.

We have an all electric house, although we have gas up to the back door, running an ASHP and MVHR system into a highly insulated and airtight house.  Having been in for about 8 months we are going to be using about 6500 kWh pa.  We have provision for a fast charger in the garage but do not yet have an EV.

Like everyone else the reasons for considering this are trying to do "the right thing" but I'm struggling to justify to myself for paying a premium to have a warm feeling.  I calculate the breakeven point will be 11-12 years based on increases to power costs of 6% pa, this is around the time when the inverter is likely to require being replaced.  Another benefit would be to reduce our exposure to a power cut by having the battery fitted through an emergency power supply switch to run a reduced house circuit board.  To cover this eventuality alone the simplest and cheapest solution would be to have a quality back up battery connected to the mains or a portable generator that could be back fed through the ring main.  We have lived in this area for 18 years and have only rarely had short power outages.

So the pros are:

Hedging against ever increasing power costs.

Some insurance against power cuts (this could become increasingly significant as supply struggles against demand).

A warm fuzzy feeling.

Cons

High initial cost.

A long payback which might be beyond the point we will be living here.

Supporting an industry which seems to be overcharging for the supply, fitting and certification of kit.  I am not at all inclined to fit this myself!

Most of the kit is from China which has questionable human rights particularly linked to the industrial area which is closely associated with solar manufacturing.

 

Am I missing anything here?  The sums are likely to change with ever developing technology, are we about to see a step change in this technology?  To those who have had systems fitted by a MCS certified company, are you satisfied, are the sums going to work based on what the system is actually doing against the predictions?  Any recommendations, we live near Cambridge?

 

[Thorfun]

3 hours ago, Lots2learn said:

I calculate the breakeven point will be 11-12 years based on increases to power costs of 6% pa, this is around the time when the inverter is likely to require being replaced.

if the solar panels are guaranteed for 25years then a 11-12 year payback period sounds good to me as that means a further 12 - 13 years of free electricity!

 

and yes, I understand that the inverter might need to be replaced and maintenance may be required but that will be the case with any form of energy, right? yearly gas boiler servicing for one example.

 

for us the payback period is irrelevant as it's worth it for the warm fuzzy feeling but I am very happy if we can get that payback in the period you suggest. and we're also going for a battery system as I want to be able to use all that free electricity (once it's reached payback period) at night once the sun has gone down when we need it to run the lights, TVs, electronic device charging etc.

 

There are definitely 2 camps on this forum about Solar PV and battery storage and if they're 'worth it' from a financial point of view. some say 'no' and others say 'it's more than the money'. both camps are right in their own way and everyone has to make the decision on what is important to them.

[SteamyTea]

5 hours ago, Lots2learn said:

I calculate the breakeven point will be 11-12 years based on increases to power costs of 6% pa, this is around the time when the inverter is likely to require being replaced. 

What sort of 'pay back' would that same outlay earn you from the bank, even on a 10 year deal?

You will save more energy, and possibly cash, getting an EV now.  8000 miles in a car that does 50 MPH is about 7,000 kWh, and costs about £900 at £1.25/litre.  An EV will use about 2,500 kWh (0.3 kWh/mile) and cost about £450 at 18p/kWh.

A £3,000 bathroom never gives you a payback, nor will a £300 one, or a £10,000 one.

Edited May 28, 2021 by SteamyTea

[TonyT]

I’m all for PV, and have had mine since 2011.

 

I think you need to think about the future too, so inverter location?

maybe in a plant room/garage somewhere that in the future you could add batteries or diverters and make it easy to cable up.

 

you won’t get be able to install that size of install without prior permission if it’s grid connected So maybe worth dealing with that first

[joth]

5 hours ago, TonyT said:

maybe in a plant room/garage somewhere that in the future you could add batteries or diverters and make it easy to cable up.

 

Aside from still relatively uncommon DC coupled battery, neither the diverter or battery needs to be next to the inverter.

 

I'd site the inverter based on:

- simplifying the routing of DC cabled from the panels to inverter,

- minimizing the length of feed from meter head to inverter, 

- cool temperature.

 

For us, these all happened to be the garage anyway ?

 

[TonyT]

Ageee, but I said this in regards to make it easier to cable up.

 

so if they are in the same room or in the same wall it’s a doddle with  little or no disruption 

[SteamyTea]

1 hour ago, TonyT said:

Ageee, but I said this in regards to make it easier to cable up.

And reduce the losses, they are 3% on the AC side, and the meter have to be close to the main meter to get more accurate export readings (though this may not be important now)

An Inverter can also chuck out quite a bit off heat in the summer, so you have to consider cooling.

It can also chuck out a bit in the winter, so make use of that if you can.