Solar Panels

Bowsa

Is there anyway a Mod could move this to the green group please? 

MSE_ForumTeam5

Moved as suggested

Hexane

Bowsa said:

Typical annual usage is 3,161.5kwh is what we’re projected so looking at it I would need ~12 panels to make that before thinking about Charging a battery or selling back to the grid? 

It doesn't work like that. A significant part of your annual usage will be in the dead of winter, when no amount of panels (regardless of batteries) will suffice to meet your entire needs on a second by second basis. Meanwhile on midsummer's day your panels will start generating before 6am and carry on until 10pm, there's only so many laundry loads and dishwasher loads you can do in a day so what are you going to do with all that power?

We have 23 panels which means at ideal moments in early September days like today we can still have the tumble dryer and dishwasher both running simultaneously and still not need to buy any electricity from the grid to do it, even without batteries. But it also means we end up selling a lot of what we generate back to the grid.

12 panels is a good install and is very worthwhile. Going larger can also be worthwhile (so long as you aren't borrowing money to do it) but of course requires more roof space and also involves some extra complications negotiating with the DNO, which is why some (lazy?) installers won't recommend more than 12.

If you already have a hot water tank with an immersion heater then a solar diverter controller (iBoost or eddi) only adds a few hundred pounds to the cost. By contrast, batteries add thousands to the cost so opinions there are still divided. Some batteries also allow you to power your house during power cuts which may appeal to many.

If your house is any higher than a bungalow, make sure you get anti-pigeon mesh.

Exiled_Tyke

As I've put on the 'is it worth getting a battery' thread I'm currently getting an annual return of around 18% on my battery.  Prior to the crisis, a lot less but still just about worthwhile.  

Personally I've never had a problem with pigeons.  There's loads near us but they prefer the trees to the PV panels. 

Hexane

Bowsa said:

13 sounds like quite a lot, this is where I am struggling as I don’t know how much energy to expect…..

12 x 350W panels will generate just over 4kW under ideal conditions (a cool but cloudless midsummer day) but on typical installs the inverter will limit that to 3.68kW.   (Note: panels of 400W or more are now commonly available.)

If you're generating 3.68kW then you can be running your tumble dryer on full blast (3kW) and then whatever other LED TVs, radio, internet router, alarm clock, laptop, phone chargers, the clock on the oven etc., at the same time all for free. But if you then turn on a 3kW kettle as well then you are going to be several kW short so you will be paying for the shortfall by buying energy from the grid.

So your choices are either:
1. accept that for that small amount of energy you're going to have to pay
2. accept that you're going to have to wait for the tumble dryer to finish before boiling the kettle
3. pay extra for a bigger solar generation system
4. pay extra for batteries suitable to supplement generation in that situation
5. some combination of the above

if it's a cloudless midsummer day then maybe you won't need to use the tumble dryer anyway though!

For comparison purposes, the heating cycles on our dishwasher and washing machine both draw about 2kW each (but not for especially long periods of time), a top-end games console or gaming PC or a big plasma TV might draw some hundreds of watts each, and most laptops, phone chargers, internet routers etc draw basically negligible amounts of power for these purposes.

The heating element on our electric oven draws 3kW when heating up to temperature or heating to return to temperature.

An electric car charger can typically use 7kW ...

Exiled_Tyke

The heating element on our electric oven draws 3kW when heating up to temperature or heating to return to temperature.

Am I the only 'nerd' that gets the oven hot and then turns it down slightly before starting the rest of the cooking (on an induction hob)? 

Alnat1

Those in the trees are probably wood pigeons, great big things. The ones that tend to nest under solar panels are rock doves, the original ancestors of the city centre type birds that get referred to as pigeons. The various colours of town pigeons were bred in by humans. That sort like solar panels too though.

Hexane

Exiled_Tyke said:

The heating element on our electric oven draws 3kW when heating up to temperature or heating to return to temperature.

Am I the only 'nerd' that gets the oven hot and then turns it down slightly before starting the rest of the cooking (on an induction hob)? 

I hadn't actually thought of that (and in theory it is wasting some energy), but we do try to run the microwave in the gaps where the heating element on the cooker isn't active. (The hob is still gas.)

Hexane

Alnat1 said:

Those in the trees are probably wood pigeons, great big things. The ones that tend to nest under solar panels are rock doves, the original ancestors of the city centre type birds that get referred to as pigeons. The various colours of town pigeons were bred in by humans. That sort like solar panels too though.

Ah, finally I understand the difference! We've had a few wood pigeons locally for a long time, but putting out food for songbirds has had the side effect of also attracting some city pigeons or rock doves as well. So still glad we have the mesh.

Martyn1981

Hexane said:

Bowsa said:

13 sounds like quite a lot, this is where I am struggling as I don’t know how much energy to expect…..

12 x 350W panels will generate just over 4kW under ideal conditions (a cool but cloudless midsummer day) but on typical installs the inverter will limit that to 3.68kW.   (Note: panels of 400W or more are now commonly available.)

If you're generating 3.68kW then you can be running your tumble dryer on full blast (3kW) and then whatever other LED TVs, radio, internet router, alarm clock, laptop, phone chargers, the clock on the oven etc., at the same time all for free. But if you then turn on a 3kW kettle as well then you are going to be several kW short so you will be paying for the shortfall by buying energy from the grid.

So your choices are either:
1. accept that for that small amount of energy you're going to have to pay
2. accept that you're going to have to wait for the tumble dryer to finish before boiling the kettle
3. pay extra for a bigger solar generation system
4. pay extra for batteries suitable to supplement generation in that situation
5. some combination of the above

if it's a cloudless midsummer day then maybe you won't need to use the tumble dryer anyway though!

For comparison purposes, the heating cycles on our dishwasher and washing machine both draw about 2kW each (but not for especially long periods of time), a top-end games console or gaming PC or a big plasma TV might draw some hundreds of watts each, and most laptops, phone chargers, internet routers etc draw basically negligible amounts of power for these purposes.

The heating element on our electric oven draws 3kW when heating up to temperature or heating to return to temperature.

An electric car charger can typically use 7kW ...

One other option (not being picky, great list) is to spread the load out over a longer period.

Explanation for non-PV'ers:  So for instance, put the tumbly on low heat setting, and get a travel kettle. I have a 1kW kettle (birthday present / joke from Wifey years ago), use it all the time, as it boils one mugs worth, so no wasted heating. The lower but longer load solution helps to prevent or minimise import but spreading demand out and trying to keep it within the amount being generated.