Solar for Dummies.

You pretty much have 90% of the answer yourself Ackwell (love the name btw).

So batteries are measured in "Kilo-Watt-Hours" or "kWhr" for short. You can basically think of it as "units" of electricity. To use your example, your 1Kw heater would use "1Kw in 1 hr".....which is "1kWhr". So a battery which is rated for 8kWhr capacity would be able to run that heater for 8 hrs. Or if the heater was 2Kw, then it could run that for 4 hrs, etc.

There are two sides to the argument about batteries and payback. I'm firmly in the camp that batteries do have a positive payback, but (and this is important) it very much depends on your "usage profile". How many units do you use per year, when in the day do you use those units, etc. No sense in buying a huge battery as it will never pay for itself , or take 20 years .....unless you consume a lot (more than 4000-5000 units / year). Conversely super small batteries tend to have a longer payback too as the capacity per €€€ that you get isn't as favourable.

There is a sweet spot I believe somewhere about 5Kwhr capacity for batteries that 80% of people will see them payback in 10 years or so, assuming you qualify for the €600 grant. Again, depending on your usage others will see payback as short as 7-8 years, while others will be 11-12 years.

Aside: Your question about the "night tarrif" is a good one. Many people, including myself charge the battery up using the night rate in winter, and then during the day use the battery to power things when the electricity is more expensive.

Everything can be upgraded, barring the "inverter" (the device which converts the DC from the panels to AC which your house uses). So if you do plan on expanding your system down the road , you should ensure that you get a biggish inverter from the get go. Something around 5Kw-6Kw will see you right.

That said, adding additional panels after initial installation is typically more expensive. When you think about it, having 2x guys come out and install 10 panels is a fixed fee, and to put on 12 panels instead of 10 probably would be 400-500 extra..... but to get them to come out a year later and add 2 more.... you end up paying that fixed "call out charge" so ....maybe this would cost €800-900 (I'm guessing) to get those 2x panels on later.

So it's probably best to try and "overspec" the panels from the get go. If you can avoid people going onto your roof you'll be better for it.

Batteries/adding hot water diverters are all easily added later, but again, it's a little complicated as there are grants to get gained and normally (normally) it's cheaper to do it right from the start. I appreciate that not everyone has all the money in one year to put in the system they'd like - so sometimes it's necessary to split

Gotcha. Yeah, you can add years later down the road, although many installers won't touch another installers work. Some of it with good reason, as if the original installers were "cowboys" then they may inherit a problem someone else made years ago. Then you are looking to the new installer thinking that they did something bad, but really it was the original guys.. Then again, sometimes ..... they are just being dicks :-)

Really though whatever about batteries, EDDI, Harvi's, Zappi's (for the car), I'd max your panels as much as you can from the get go. Panels change, and ideally you want to get the same panels as you have already got up there. Couple of years later, and they simply may not be making the same panels anymore as technology has moved on. It's not a complete crap show if you can't get the same of course, but ideally they work better when all the resistenaces are the same and if you have different makes/models it can make a difference.

Yup - sound logic there too. However, if you can go for 5Kwp of panels and 5Kwhr of a battery, that system should see you right for the foreseeable furture . Yeah, you can add to it later, but it's a solid good spec that will do most of what you need. IN about the €7-8K mark (assuming you qualify for a grant)

Don't overlook that a 5kw system (i.e. with 5kw of panels) will only produce that power on a bright sunshiny day, with the sun hitting the panels at a good angle and in the spring / summer / autumn.

Many of us have many more panels than that installed so that you get maximum allowed (by size of the inverter) in less than ideal conditions. For instance, I have a 5kw inverter but 6.1kw of panels. So on a great summers day I'm maxed out at 5kw (actually a little more than that as the inverters are not precise) but on a cloudier day in the summer I can still hit 5kw and in early spring and late autumn I'm still pushing 5kw even when the sun is lower in the sky etc.

The general advise here would be to put up as many panels as you can fit / inverter will take (i.e. my inverter will take around 24 panels total on 2x strings).

Meter vs consumer unit has nothing to do with ability to use solar. You need an EV charger that can detect the amount of excess solar going to the grid and modulate the power it is consuming.

Power flows in both directions through cables. To have solar panels you need an inverter. The inverter is connected to your house power - your house power is (presumably) connected to the national grid.

Your house already has power cables running all over the place :)

Ah right, so it's just the net of neutral over live. Maybe I've the wrong idea about Solar, if I want to power say the kettle in the kitchen, how does the power from the solar get to the kettle without going through the consumer unit?

OK so the invertor will have to run directly back to the consumer unit, and this is where I get a little unsure as my EV charger doesn't come off that consumer unit. For me this is more than academic as I wonder if someone with an EV really needs a battery.

The question of "Do I need a battery if I have an EV?" has come up a few times too.

I'm not sure there's a right/wrong answer here. Depends on a number of factors, which you'll have to answer yourself and then draw your own conclusions.

For example, will the car be in the driveway when it's sunny? With working from home, this is normal for many of us, but if your using the EV to drive into the office, obviously you'll be exporting a lot when it's sunny outside and the car is in the company car park and not at home.

Similarly, even if the car is at home....great you'll be able to soak up the excess. EV's get (roughly) 5Km for every 1Kwhr, but if you fill the battery on Monday and it's also sunny on Tuesday.....will you have driven 50Km or so to "free up" 10Kwhr or so capacity from the battery.

Depends on the circumstances. My own gut feeling is that most people with an EV do need a moderate sized battery (5Kwhr) or there abouts, but that's just my own opinion.