Solar PV for Newbies Questions

Forums › Home Workshop DIY › Solar PV for Newbies Questions

tdgeek

29755 posts

Uber Geek

Trusted

Lifetime subscriber

#233836 5-May-2018 10:22

I have solar HW and want PV, and I've learnt a lot from here. I have some basic questions. My concern is getting PV then realising later I shoulda done this or shoulda done that.

Say I decide to install a base setup for now. 5kW or 7kW or 10kW. No battery. Home is 5BR, built in 2010/11. Solar HW 300L cylinder. Gas cooktop. Two heated bathroom floors

Hope this may be useful for others too

1. Can I easily have more panels added to what I have without having to get an extra full install for the new panels?

2. Can I easily get a battery added without a whole re-do of the PV wiring? I realise there would be extra components required.

3. If my power provider doesnt do export, does that matter? I use EK at the moment.

4. If we get an EV, can that just be wired in so I can charge at home without any major electrical work? The switchboard is in the garage.

5. Can the EV connection in the garage be used so that I can use the EV battery for the home? Yes can do, or no, or major wiring costs?

6. If I had a battery, can I tell the PV to prioritise the battery or the house or the car. The Sun, the usage, and the battery level in the car or home battery may mean that different days I may want different directions for the generation.

7. I assume I would have a panel that shows current generation, current PV usage, current grid usage,home battery level.

Thanks in advance

wellygary

8345 posts

Uber Geek

#2008370 5-May-2018 12:06

Without a battery your heated floors are going to be pretty much exclusivily grid powered, i.e the times/seasons you want to use them will have little PV potential

If you want to alter the configeration in the future, you should install wiring to allow it from the beginning,

You only want to have to drill/run wires once, having to go back to retrofit connections can be a PITA and can be really difficult if there are pinch points where you having limited options for running wires,

Jase2985

13466 posts

Uber Geek

ID Verified

Lifetime subscriber

#2008397 5-May-2018 12:54

1. yes but it depends on what your inverter is rated at, a 5kwh inverter will only take 5kwh of panels so if you want more than this then you need a new/second inverter. you would base the system size on the load you intend on powering. realistically you need to know your base load during the day and if you haver the ability time shift some of your loads, like washing or dishwasher to during the day when you are generating power.

2. relatively easily as it just need to come off the inverter to the batteries. make sure you have an inverter capable of this and also one that allows you to use the batteries when the mains go off. most do this but there are still the odd one around that doesn't do this.

3. depends, do you want paid back for power you export? makes sense to as it can offset any usage when you are not generating power. and most people oversize the system so even at at 8-10c buy back you can lower your bill. i would be going for a company that allows export and has low night rates so if you do need power at night its cheap.

4. again depends on what type of charger you want, a 16a socket wouldnt be to hard to add, but anything bigger may be a bit more of a challange.

5. Can the EV connection in the garage be used so that I can use the EV battery for the home? Yes can do, or no, or major wiring costs? i don't believe there is any scope for this at the moment and i think it comes down to the car/charger not the house.

6. generally its house first, battery second, export third. most inverters are like this but you can get some that you can manually set. but i dont know why you would want it any different.

7. yes most show this and most will have an app or web portal that you can go to, to see whats happening.

tdgeek

29755 posts

Uber Geek

Trusted

Lifetime subscriber

#2008640 6-May-2018 11:12

wellygary:

Without a battery your heated floors are going to be pretty much exclusivily grid powered, i.e the times/seasons you want to use them will have little PV potential

If you want to alter the configeration in the future, you should install wiring to allow it from the beginning,

You only want to have to drill/run wires once, having to go back to retrofit connections can be a PITA and can be really difficult if there are pinch points where you having limited options for running wires,

Yeah, tab\\he floors are not relevant as they cant be time shifted

tdgeek

29755 posts

Uber Geek

Trusted

Lifetime subscriber

#2008642 6-May-2018 11:18

Jase2985:

1. yes but it depends on what your inverter is rated at, a 5kwh inverter will only take 5kwh of panels so if you want more than this then you need a new/second inverter. you would base the system size on the load you intend on powering. realistically you need to know your base load during the day and if you haver the ability time shift some of your loads, like washing or dishwasher to during the day when you are generating power.

2. relatively easily as it just need to come off the inverter to the batteries. make sure you have an inverter capable of this and also one that allows you to use the batteries when the mains go off. most do this but there are still the odd one around that doesn't do this.

3. depends, do you want paid back for power you export? makes sense to as it can offset any usage when you are not generating power. and most people oversize the system so even at at 8-10c buy back you can lower your bill. i would be going for a company that allows export and has low night rates so if you do need power at night its cheap.

4. again depends on what type of charger you want, a 16a socket wouldnt be to hard to add, but anything bigger may be a bit more of a challange.

5. Can the EV connection in the garage be used so that I can use the EV battery for the home? Yes can do, or no, or major wiring costs? i don't believe there is any scope for this at the moment and i think it comes down to the car/charger not the house.

6. generally its house first, battery second, export third. most inverters are like this but you can get some that you can manually set. but i dont know why you would want it any different.

7. yes most show this and most will have an app or web portal that you can go to, to see whats happening.

Thanks Jase for the detail

1. Cool, I will research what my load might be. I think we can get creative with timeshifting. Laundry and dishwasher are a given. Any use of slow cooker, or all all day slow roast helps. Winter heating can pre warm the house, so that grid power is reduced

2. Great

3. Is there a problem if I am not on an export provider, and I have excess generation? House is powered, battery is full. What happens to the generation when there is no where for it to go? Or does it go back to the grid anyway, even though there is no buyback if my provider doesnt support that?

6. Yes, on reflection thats the only order thats needed.

Thanks again

richms

28218 posts

Uber Geek

Trusted

Lifetime subscriber

#2008644 6-May-2018 11:37

Jase2985:

6. generally its house first, battery second, export third. most inverters are like this but you can get some that you can manually set. but i dont know why you would want it any different.

Grid first is often used in countries with crazy subsidies. Some inverters will even charge the batteries and then invert to the grid from that when your consumption is low enough that you could export.

Richard rich.ms

logo

647 posts

Ultimate Geek

Trusted

#2008653 6-May-2018 12:09

I thought if you got a system with microinverters you could simply add more panels at any time?

Is solar a no brainer yet? I've been toying around with the idea for ages but have always put it off for one reason or another.

richms

28218 posts

Uber Geek

Trusted

Lifetime subscriber

#2008661 6-May-2018 12:30

logo:

I thought if you got a system with microinverters you could simply add more panels at any time?

Is solar a no brainer yet? I've been toying around with the idea for ages but have always put it off for one reason or another.

Still need to get approval from the grid operator. And they go by the total amount of inverters, so even if they both point different ways and will never max out at the same time, its still the total kW of inverters that you need approval for, not the max that it will output during the day.

Also the enphase ones use power line communication which seems pretty problematic, I have to have the gateway in the garage for it to talk to those inverters, in the house its just constant errors. So when I add panels to the shed, will probably need another gateway for those ones. Or run a feed from the shed to the garage or something.

Richard rich.ms

Sharesies

Trade NZ and US shares and funds with Sharesies (affiliate link).

Aredwood

3885 posts

Uber Geek

#2008730 6-May-2018 13:54

logo:
I thought if you got a system with microinverters you could simply add more panels at any time?

Is solar a no brainer yet? I've been toying around with the idea for ages but have always put it off for one reason or another.

It is a long way from being a no brainer for everyone. If you have high baseload power consumption, meaning that you can directly consume most of your production, then yes get solar.

Otherwise you are sinking lots of capital into a system with uncertain payback. As a lot of that payback is riding on future electricity policy changes. Main one being scrapping of the low user regulations based plans. Which would mean cheaper KW/Hr costs but higher fixed costs.

Consider getting the EV first. As petrol costs more than grid power. And when I got a quote for a solar with battery system for my house, it was over $15K. You can easily buy an EV for that money.

And lots of solar inverters had silly things like only being able to output 1KW when the grid was not available. And having really long transfer times. So you can't even use your expensive solar and battery system as a UPS for your computer's.

Jase2985

13466 posts

Uber Geek

ID Verified

Lifetime subscriber

#2008822 6-May-2018 17:53

tdgeek:

Thanks Jase for the detail

1. Cool, I will research what my load might be. I think we can get creative with timeshifting. Laundry and dishwasher are a given. Any use of slow cooker, or all all day slow roast helps. Winter heating can pre warm the house, so that grid power is reduced

2. Great

3. Is there a problem if I am not on an export provider, and I have excess generation? House is powered, battery is full. What happens to the generation when there is no where for it to go? Or does it go back to the grid anyway, even though there is no buyback if my provider doesnt support that?

6. Yes, on reflection thats the only order thats needed.

Thanks again

1. crudely you could use your power bill if its updated hourly, im using a specific device to do this so i have a history of my base load which at the moment is about .6kwh. could be reduced more by having more efficent appliances and not having the desktop server running all day.

Here is an image of the data you get from it:

3. im not 100% with what happens there, i would assume it would just be given to the grid for free as you cant stop the panels from making power and it would have to go somewhere.

logo:

I thought if you got a system with microinverters you could simply add more panels at any time?

Is solar a no brainer yet? I've been toying around with the idea for ages but have always put it off for one reason or another.

Micro inverters yes. you can, and depending on the size inverter on a standard system, they seem to be between 5 and 7kwh, you can as well

problem with a micro inverter system is its dc-ac-dc for a battery system where as a normal system is dc-dc so reduces conversion losses.

No brainer, not yet, its getting closer and closer to becoming so as panels inverters and batteries get cheaper but not quiet yet. and there will be a point where there might be no export payback so you get nothing back from exporting.

Jase2985

13466 posts

Uber Geek

ID Verified

Lifetime subscriber

#2008823 6-May-2018 17:57

@Aredwood most inverters, and solar battery systems will offer between 3 and 5kwh worth of battery backed up power these days. does mean it has to be separately wired in your house.

Aredwood

3885 posts

Uber Geek

#2008884 6-May-2018 19:27

Jase2985:
@Aredwood most inverters, and solar battery systems will offer between 3 and 5kwh worth of battery backed up power these days. does mean it has to be separately wired in your house.

@Jase2985 I was referring to the inverter capacity when there is no grid power. It doesn't matter how much battery capacity you have, if you can barely use it during a power outage.

Jase2985

13466 posts

Uber Geek

ID Verified

Lifetime subscriber

#2008888 6-May-2018 19:35

@Aredwood again like i said most are rated for 3-5kw output when in battery mode.