Solar, central heating and EV

Forums › Home Workshop DIY › Solar, central heating and EV | Stupid questions

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2391 posts

Uber Geek

#2935185 28-Jun-2022 10:10

sorry to dive in late.

a mate has a few people in his area that have some of those "no money down" type contracts. really good to start with but now they are paying more for their power and the servicing has gone to non-existent. as i understand it you have to buy and sell your power to them. good when solar powers everything you do, but you get stung when you use grid power. i'm guessing they make their money by on selling your power generation and by charging you extra for grid power.

bottled gas is the most expensive energy out there.

the problem with lots of mini splits is the cost. it adds up really quick to the point its cheaper to go ducted heat pump. however ducted systems have their drawbacks especially as its all mounted outside (ie on the wrong side of the insulation).

martyyn

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#2935248 28-Jun-2022 10:27

tweake:

sorry to dive in late.

a mate has a few people in his area that have some of those "no money down" type contracts. really good to start with but now they are paying more for their power and the servicing has gone to non-existent. as i understand it you have to buy and sell your power to them. good when solar powers everything you do, but you get stung when you use grid power. i'm guessing they make their money by on selling your power generation and by charging you extra for grid power.

bottled gas is the most expensive energy out there.

the problem with lots of mini splits is the cost. it adds up really quick to the point its cheaper to go ducted heat pump. however ducted systems have their drawbacks especially as its all mounted outside (ie on the wrong side of the insulation).

I have a funny feeling with solarzero they also cap the amount you can use yourself. So you are effectively generating power for them you could be using yourself. I don't remember where I saw it, or whether it's true, it was just the feeling I had around it.

Bottled gas is still cheaper than wood for the winter.

We don't really have a budget for this. If a solution gives us the convenience and comfort we want we will likely pay the money. I want quality, not cheap, which seems to be an odd way to do anything these days.

The carpet people couldn't believe we chose the expensive carpet, the car upholsterers couldn't believe I wanted it done in leather not vinyl, the mechanics couldn't believe I wanted genuine/OEM parts and not third party knock offs.

Quinny

885 posts

Ultimate Geek

Trusted

#2935252 28-Jun-2022 10:36

martyyn:

We don't really have a budget for this. If a solution gives us the convenience and comfort we want we will likely pay the money. I want quality, not cheap, which seems to be an odd way to do anything these days.

The carpet people couldn't believe we chose the expensive carpet, the car upholsterers couldn't believe I wanted it done in leather not vinyl, the mechanics couldn't believe I wanted genuine/OEM parts and not third party knock offs.

You are me. I have the dual-sided gas fire (Escea DX1500) which I ramp up to get the place toasty, 4 heat pumps with a master controller which means the room I want to be heated is the one heated/cooled AND behind that the Tesla Powerwall and Solar. Honestly, I love it. If I built again the only? is the gas with the way the govt is sending us. Add on $8000 Oled Tv and many more hmm "toys" and yeah. Buy what "Brings you Joy" to quote Marie Kondo (tho I doubt she means it the way I have interpreted lolz)

tweake

2391 posts

Uber Geek

#2935262 28-Jun-2022 11:00

martyyn:

Bottled gas is still cheaper than wood for the winter.

We don't really have a budget for this. If a solution gives us the convenience and comfort we want we will likely pay the money. I want quality, not cheap, which seems to be an odd way to do anything these days.

i think every price checking i've seen shows gas dearer than wood. unless you have access to free firewood. tho gas might be cheaper than wood when people run out and have to buy mid winter at crazy prices. also how many people have both to compare? i bet many fireplaces are well oversized and probably go through far more wood than they should.

unfortunatly many/most markets sell mostly to people who want the bare minimum. just be aware i've struck crowds that advertise top end high quality and they install the same cheap stuff as everyone else.

tweake

2391 posts

Uber Geek

#2935265 28-Jun-2022 11:08

Quinny:

You are me. I have the dual-sided gas fire (Escea DX1500) which I ramp up to get the place toasty, 4 heat pumps with a master controller which means the room I want to be heated is the one heated/cooled AND behind that the Tesla Powerwall and Solar. Honestly, I love it. If I built again the only? is the gas with the way the govt is sending us. Add on $8000 Oled Tv and many more hmm "toys" and yeah. Buy what "Brings you Joy" to quote Marie Kondo (tho I doubt she means it the way I have interpreted lolz)

actually thats not a bad way of looking at it.

to many people act like everyone in nz is in poverty. won't spend $20 to keep warm. house is damp and moldy because they refuse to heat it.

i have three heatpumps and they think i'm extravagant. i much prefer a nice warm home.

Scott3

3964 posts

Uber Geek

Lifetime subscriber

#2935273 28-Jun-2022 11:39

martyyn:

...

Bottled gas is still cheaper than wood for the winter.

We don't really have a budget for this. If a solution gives us the convenience and comfort we want we will likely pay the money. I want quality, not cheap, which seems to be an odd way to do anything these days.

The carpet people couldn't believe we chose the expensive carpet, the car upholsterers couldn't believe I wanted it done in leather not vinyl, the mechanics couldn't believe I wanted genuine/OEM parts and not third party knock offs.

While the comparison to wood might be useful for your current situation, but wood is fairly expensive (if you can't get it free), and is not a realistic option for central heating.

Also consider the risk that the installer has underestimated the running cost of the system.

I calculated the cost of heating with lpg in a prior comment at 23c/kWh. (that doesn't count the annual bottle rental of cira $100).

https://www.geekzone.co.nz/forums.asp?forumid=141&topicid=296198&page_no=3#2935075

Pritty much the only time LPG stacks up for space heating are the following:

Natural gas is not available and one of the following:
You are on a low user power plan, so are paying expensive kWh rates
You are in a part of the country with very expensive power or lines charges (Ruapehu district, Northland etc.)
There is some other limitation (i.e. you are off grid, are maxing out your grid connection capacity, have very unreliable power etc.)

Look up your current power price in kWh. (perhaps check around a couple of power companies to ensure you aren't getting ripped off). If it is less than say 25c /kWh (allowing an extra 2c/kWh to cover LPG bottle rental), you have no reason to go LPG.

If you really want the look / feel of euro style radiators, you can essentially fake it with electric resistance radiators.

https://www.ecogeek.co.nz/shop/1k-lhz-electric-radiator-w-wifi-control-s65dzw

LPG has another couple of issues.

- It's a fossel fuel, so worse for the environment than carbon neutral wood, of our 80% renewable electricity.

- It is probable it will become more expensive as it gets slapped with emmisions fees over the coming decades.

- Climate Change Commission’s draft plan proposed a phase out. This plan is not yet adopted by NZ government, but if it was, it would result in a ban on new gas connections (both natural gas and bottled LPG) from 2025, and discontinuation of existing supplies by 2050. Granted 2050 is 28 years away, but once new connections a banned, it may get increasingly difficult to source the resources needed to maintain your gas boiler.

Note that a gas radiator central heating system doesn't really offer any advantage to a series of wall mounted thermostatically controled heaters.

Options I see as viable:

Electric Resistance heating (oil heaters or wall mounted heaters) with thermostatic controls and timers.
Ducted heat pump central heating
Mini split (high wall / floor console) heat pumps for larger area's, and electric resistance for smaller area's.
Go for the gold plated solution, and retrofit hydronic underfloor heating, fed by a heat pump.

https://www.centralheating.co.nz/assets/resources/Variotherm-Sheet-web.pdf

martyyn

1971 posts

Uber Geek

ID Verified

#2935300 28-Jun-2022 12:06

That's gold thank you @scott3

Gas only came about because the supplier didn't really want to quote on anything else. It's far from our preferred solution.

Those ecogeek radiators look like they would work really well for us. We have the wall space, our room sizes work for what they have and so I've emailed them to see what else they can suggest as they do EV chargers as well.

I even said last night, lets just buy a whole load of oil filled heaters and leave them around the house !

We cant retrofit underfloor heating because we have a 60's house with polished Matai boards and we'd never want to cover them up and we don't really like the noise or air movement from heat pumps. Our European blood is calling for radiators !

Sharesies

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

tweake

2391 posts

Uber Geek

#2935310 28-Jun-2022 12:32

one thing to keep in mind, most places do not have a big enough power connection to the house to heat a house properly with electric resistance heating. in a lot of older i homes i doubt they even have enough circuits inside the house as well. even my small place is 11kw, so ~45amps and the house only has a 60 amp connection.

Scott3

3964 posts

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Lifetime subscriber

#2935314 28-Jun-2022 12:35

If you like the look, and are OK with the price point, then why not? And (assuming your power costs less than 25c/kW) provide both cheaper to install, and cheaper to run option than gas fired radiators.

But as a counter point they are really expensive for what ultimately does the same job as a bunch of oil heaters, or much cheaper wall mounted panel heaters.

https://www.mitre10.co.nz/shop/nobo-oslo-panel-heater-1kw/p/380520

One thing to aware of when installing a lot of resistance heating, it the supply capacity to your home. My home has a 63A (I think) pole fuse, works out to about 14.5kW.

Heat pump fed radiators are still a workable option, but kind expensive as both the heat pump and the radiators need to be over sized vs gas / underfloor systems. Would still easily beat the resistance heaters on efficiency but not by as much as a mini split etc.

On split unit heat pumps, if you want zero air flow, these aren't going to work, but I must say the smaller modern Mitsubishi electric high wall unit at the place we stayed in the weekend is another world to the large older Panasonic heat pump we have in our lounge at home. Could hardly tell the Mitsubishi unit was on.

Another option is floor console heat pumps, some brands are set up to squirt warm air out the bottom and along the floor. Quite nice to stand in front of.

Heat pumps are 3-4 times cheaper to run than a resistance heater.

eonsim

398 posts

Ultimate Geek

Trusted

#2935583 28-Jun-2022 18:50

Another option for heating might be Night-store heaters + Solar power. You should be able to program them to store power while the solar is producing, during free hours or overnight on off-peak charges then release the heat during the morning/evening to help with any heating.

The still only electric heaters so the efficiency is ~1 (unlike heat-pumps at 3-5) but they would allow you to shift power from a decent sized solar array to heat the house during the evening or at peak times.

The most efficient heating is still heat-pumps, though I'd favor a couple of multi-headed units over a ducted heat-pump. That way you can have one unit heat multiple rooms and control the settings for each individual room. That combined with a decent solar setup means you could effectively warm/cool the house through out the day using the power from your panels and assuming your house is reasonably insulated if it's been sitting at a decent temperature all day (heating up it's thermal mass) it should hold that reasonably well.

timmmay

20578 posts

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#2935695 28-Jun-2022 22:05

eonsim:

Another option for heating might be Night-store heaters + Solar power. You should be able to program them to store power while the solar is producing, during free hours or overnight on off-peak charges then release the heat during the morning/evening to help with any heating.

The still only electric heaters so the efficiency is ~1 (unlike heat-pumps at 3-5) but they would allow you to shift power from a decent sized solar array to heat the house during the evening or at peak times.

The most efficient heating is still heat-pumps, though I'd favor a couple of multi-headed units over a ducted heat-pump. That way you can have one unit heat multiple rooms and control the settings for each individual room. That combined with a decent solar setup means you could effectively warm/cool the house through out the day using the power from your panels and assuming your house is reasonably insulated if it's been sitting at a decent temperature all day (heating up it's thermal mass) it should hold that reasonably well.

Some ducted heat pumps have a thermostat in each room and can control the temperature to each room - more here. There are advantages to every option, multi-headed off a single outdoor for example is more efficient as the heated air doesn't travel through big ducts in the ceiling, but they're not as nice to look at and louder than ducted.

HarmLessSolutions

972 posts

Ultimate Geek

Subscriber

#2938988 6-Jul-2022 21:44

Interesting thread with a lot of advice I'd forgotten I'd learnt in designing our own system.

Our story is that following our sale of a previous rural property that we installed 5kW (underrated panels so actually 6kW) of grid tied PV back in 2012 when Meridian were paying a 1:1 buy back tariff. That was never going to last so when they slashed their export rate we bought a Leaf to better use our generation. Still struggled to keep export below 50% of generation even with home workplace allowing daytime EV charging.

Now on another rural property and last year installed 5kW of grid tied PV here. Still got the Leaf with a Polestar2 due to join it next week. This time we included a Paladin diverter in the system which works well and completely displaces grid supply to our HWC. A specialist PV installer in Nelson my sparky put me onto advised strongly against combining battery storage with EV charging as he said it didn't make sense economically.

On both properties we have had 3 phase supply but single phase PV inverters. Currently this is due to physical complications in running all phases from the house to the PV location (on a large farm shed). Again we have transferred as many circuits as possible onto the phase that the PV is connected onto to facilitate maximum consumption of our own generation. This includes a 7kW EV charger, 2 large chest freezers, water supply pump, kitchen appliances and the diverter/HWC. Our heating is by logfire as we have huge sources of firewood on the property.

A couple of tips for budding PVers:

Consider ground mounting your installation, especially if a rural setting provides room to do so. Generation can be adversely effected by dust build up or bird droppings and cleaning is much easier if panels can be reached. PV site location if not on the house can increase cost of cabling as high capacity DC cable is required from panels to inverter and this isn't cheap.
EECA's solar calculator is a good research tool but some extrapolation of results is required for EV charging and other factors.

One question that was asked on another forum was from someone who had "3 phase power and a 3 phase 10kW inverter, but the car only charges off 1 phase. So what's the economy there? I admit to being a bit confused." Is this going to be the same as my situation of feeding into just one phase and if so how will this affect metering? We're billed for just one import quantity despite having 3 phase supply so if the demand on each phase is different are these just totalled to calculate usage?

https://www.harmlesssolutions.co.nz/

tweake

2391 posts

Uber Geek

#2939072 7-Jul-2022 10:57

HarmLessSolutions:

One question that was asked on another forum was from someone who had "3 phase power and a 3 phase 10kW inverter, but the car only charges off 1 phase. So what's the economy there? I admit to being a bit confused." Is this going to be the same as my situation of feeding into just one phase and if so how will this affect metering? We're billed for just one import quantity despite having 3 phase supply so if the demand on each phase is different are these just totalled to calculate usage?

work looked into solar so its something i looked into. the good inverter setups will supply solar power to the phase(s) that has the most load. so if you have a car on charge on one phase the inverter will supply to that one phase.

one thing to watch if your trying to put everything on one phase, 3 phase areas use the different circuits in the house etc to balance the local grid. upsetting that might cause issues for the local system.

CrazyM

110 posts

Master Geek
Inactive user

#2939140 7-Jul-2022 12:09

tweake:

HarmLessSolutions:

One question that was asked on another forum was from someone who had "3 phase power and a 3 phase 10kW inverter, but the car only charges off 1 phase. So what's the economy there? I admit to being a bit confused." Is this going to be the same as my situation of feeding into just one phase and if so how will this affect metering? We're billed for just one import quantity despite having 3 phase supply so if the demand on each phase is different are these just totalled to calculate usage?

work looked into solar so its something i looked into. the good inverter setups will supply solar power to the phase(s) that has the most load. so if you have a car on charge on one phase the inverter will supply to that one phase.

one thing to watch if your trying to put everything on one phase, 3 phase areas use the different circuits in the house etc to balance the local grid. upsetting that might cause issues for the local system.

You are correct in that NZ does not have net metering, so you can be selling power on 2 phases at 8c/Kwh while simultaneously buying on the other phase at 30c/kwh (for example). Makes it harder to self-consume your solar generation and it makes adding batteries even less cost-effective.

Almost no 3 phase inverters will output an unbalanced load (i.e supply power to the phases with the most load). The only examples I know of are the Goodwe ET and the Solax X3 Hybrid. Everything else just evenly distributes your solar generation down all 3 phases. And even with those models the most they can 'unbalance' is 1/3rd of their maximum output (e.g. on the 10kW Goodwe the maximum it can send down one phase is 3.3kW; for example it can split 6kW of generation 3kW/1kW/2kW but it could not split 10kW of generation 6kW/3kW/1kW)

tweake

2391 posts

Uber Geek

#2939143 7-Jul-2022 12:18

CrazyM:

You are correct in that NZ does not have net metering, so you can be selling power on 2 phases at 8c/Kwh while simultaneously buying on the other phase at 30c/kwh (for example). Makes it harder to self-consume your solar generation and it makes adding batteries even less cost-effective.

Almost no 3 phase inverters will output an unbalanced load (i.e supply power to the phases with the most load). The only examples I know of are the Goodwe ET and the Solax X3 Hybrid. Everything else just evenly distributes your solar generation down all 3 phases. And even with those models the most they can 'unbalance' is 1/3rd of their maximum output (e.g. on the 10kW Goodwe the maximum it can send down one phase is 3.3kW; for example it can split 6kW of generation 3kW/1kW/2kW but it could not split 10kW of generation 6kW/3kW/1kW)

thats good to know. sounds like the guys quoting our system where full of crap.

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