What size of MIC (kVa) for new build house for EV

ECO_Mental

Hi,

Building a new house out in the country and am I just looking to get my ESB connection. What size of MIC should I get to be some way future proofed for EV charging, I don't have an EV yet but planning to in the next year or two.

My house will have Air Source HP, MHRV and I will be putting in solar PV, 3KWp min but probably as much as I can.

Looking as the ESB site 16 kVa I think is the new minimum I think I should get if I am planning to get an EV. But ESB have 20 kVa or 29 kVa options. There isn't a 3 Phase line near me but can I get 20 kVa or 29 kVa on a single phase, but again are these over kill but I want to be future proofed as best as possible.

I have this cross posted in the Electrical forum but then though the EV charging will be the main consumer of power in the house into the future so I posted here as well. many thanks

Gumbo

ECO_Mental wrote: »

Hi,

Building a new house out in the country and am I just looking to get my ESB connection. What size of MIC should I get to be some way future proofed for EV charging, I don't have an EV yet but planning to in the next year or two.

My house will have Air Source HP, MHRV and I will be putting in solar PV, 3KWp min but probably as much as I can.

Looking as the ESB site 16 kVa I think is the new minimum I think I should get if I am planning to get an EV. But ESB have 20 kVa or 29 kVa options. There isn't a 3 Phase line near me but can I get 20 kVa or 29 kVa on a single phase, but again are these over kill but I want to be future proofed as best as possible.

I have this cross posted in the Electrical forum but then though the EV charging will be the main consumer of power in the house into the future so I posted here as well. many thanks

Standard ESB connection will give you 7kw charging in the future, similar to every other house in Ireland.

If you can, and costs are not prohibited, then I’d try get 3 phase installed. This would mean you can utilise the 22kw charging speeds of some chargers out there and be full every night during night rate hours.

unkel

How much does it cost extra as a one-off to get 20kVa or 29kVa? And did you enquire about the extra cost of getting 3-phase? Could be extremely expensive, could be relatively cheap. Handy to have for sure for future proofing your house. Charge your car 3 times as fast if the car allows it, most cars don't (but some do, like mine and the car of the above poster, which can charge at 32A / 3 phase - 23kW) but it looks like a lot of cars will be able to charge at 16A / 3 phase going forward - 11kW and you will be able to generate and export far more solar PV, etc.

16kVa is fine for a household with one EV (or more, but just one charging at any one time) and a heat pump, as long as you don't have electric showers

graememk

20+ depend on the MV network in your area,

It could be the standard price (ie the 16,kva) or more.

Esb won't give you a price until you send the form in, they just refer you back to your electrician for requirements.

I think 16,kva look for 25mm tails, don't know what size you'd need for 20 or 29. If it's bigger, then getting a consumer unit with big enough terminals in it becomes an issue unless you go for an industrial board.

KCross

ECO_Mental wrote: »

Hi,

Building a new house out in the country and am I just looking to get my ESB connection. What size of MIC should I get to be some way future proofed for EV charging, I don't have an EV yet but planning to in the next year or two.

My house will have Air Source HP, MHRV and I will be putting in solar PV, 3KWp min but probably as much as I can.

Looking as the ESB site 16 kVa I think is the new minimum I think I should get if I am planning to get an EV. But ESB have 20 kVa or 29 kVa options. There isn't a 3 Phase line near me but can I get 20 kVa or 29 kVa on a single phase, but again are these over kill but I want to be future proofed as best as possible.

I have this cross posted in the Electrical forum but then though the EV charging will be the main consumer of power in the house into the future so I posted here as well. many thanks

Its a pure cost-benefit decision.

16kVA will be more than enough to run your HP and charge 2 EVs overnight on night rate unless you are doing insane mileage on both cars everyday.

Upgrading to single phase 20kVA+ will be of limited benefit and really down to the extra costs as to whether it’s worth it or not for the rare edge cases where you need to charge quicker at home versus just visiting a rapid charger on the road.

imo, getting 3 phase would be a better benefit as you can export more Solar excess and get a 3ph HP which tend to last longer.

Again, it’s all down to what ESB are going to charge you for the uprated MIC but 16kVA will work fine.

Whatever you decide, get the EV cables run now while you are building. That’s the hardest part of installing the charge points.

ECO_Mental

Just filling in the the online application for the new connection through the ESBN system and going into the Connection Capacity section and they ask you do you have a heat pump and are you planning to have EV charging. If I select EV charging it automatically selects 20kVa or 29 kVa and 3 Phase. No option for 12kVa or 16 kVa.

If I say I am NOT EV charging then I can select 12 or 16....

Is this a new policy in ESBN

pauldavis123

16kva 3 phase is only a grand.

They use 100a fuses in the 16kva and the 29kva so I'm not sure what the difference really is of you never want to upgrade from 29kva.

KCross

ECO_Mental wrote: »

Just filling in the the online application for the new connection through the ESBN system and going into the Connection Capacity section and they ask you do you have a heat pump and are you planning to have EV charging. If I select EV charging it automatically selects 20kVa or 29 kVa and 3 Phase. No option for 12kVa or 16 kVa.

If I say I am NOT EV charging then I can select 12 or 16....

Is this a new policy in ESBN

That must be a relatively new thing. It was always just a case of you needed to get 16kVA if you ticked the HP box.

The charges for each MIC are laid out here (page 3)
https://www.esbnetworks.ie/docs/default-source/publications/approved-statement-of-charges-2020-2021.pdf?sfvrsn=224533f0_69

The unknown bit is where they say "+ MV Network Charges". That could be very little or huge money and those MV charges only apply when you go to 20kVA+.

A 1ph 16kVA connection is €3500. A 20kVA connection is €2400+MV charges so there might not be much in it and then its better to have the 20kVA.... depends on those MV charges though.

pauldavis123 wrote: »

16kva 3 phase is only a grand.

They use 100a fuses in the 16kva and the 29kva so I'm not sure what the difference really is of you never want to upgrade from 29kva.

Are you specifically referring to 3ph there?
I have a 1ph 16kVA connection and it has an 80A fuse. A standard 12kVA connection typically has a 60A fuse and the 100A fuse is for 20kVA+

pauldavis123

KCross wrote: »

Are you specifically referring to 3ph there?
I have a 1ph 16kVA connection and it has an 80A fuse. A standard 12kVA connection typically has a 60A fuse and the 100A fuse is for 20kVA+

Yeah, three-phase has three 100A fuses, 80A in domestic single alright.

Manion

Apologies for resurrecting this thread, it's actually one of the top linked on google when searching MIC power supply.

After reading around and looking at my fuse board. It would appear I've a 80a mains fused and a 63amp consumer unit. House is a new build with a HP from 2016.

A few questions:

Can I assume that if I have an 80a mains I already have a 16kVA enhanced supply.

What exactly does that get me? My understanding is that a 16kVA will allow me to use more power at the same time. So for instance charging two EVs or an EV and HP at the same time with plenty left over?

pauldavis123

https://www.boards.ie/discussion/comment/118131669#Comment_118131669

The kVA in is somewhat meaningless, it's more about the conductor size going into your unit. I have an old 8A supply in the city centre but it's fed by 25mm square conductors with an 80A main fuse.

That 8A supply pulls 40kW in the winter no problem. I rang ESB Networks after an ECIR about this a while ago and was basically told if the main fuse has not blown there is no problem.

More kVA means more ability to draw more power. The weak link is the 80A fuse. ESB Networks will replace it once but will complain the second time according to a spark I spoke to.

pauldavis123

Three-phase is the way to go, €2k to install but they will limit it soon I would say once EV's kick-off.

Standard three-phase is 3 x 100A connections compared to a single 80A for single phase.

Manion

Is this something you've actually done? That pricing doesn't seem realistic.

graememk

https://www.boards.ie/discussion/comment/118131669#Comment_118131669

I have a 16KVA supply and the fuse in my consumer unit (well its in the meter cabinet) is 80A. My main tails are 25mm2.

I got my supply upgraded for the farmyard thats connected to the house.

the_amazing_raisin

https://www.boards.ie/discussion/comment/118131669#Comment_118131669

I have a 16kVA connection with 6kW heat pump and 2 EVs with 2 chargers

It isn't an issue for us because the chargers have load balancing built in, or rather one of them does

The chargers share the same 40A fuse. The Leaf only charges at 16A so the Zappi will monitor the load on that circuit and slow down the charging speed of the ID.4 so as not to overload the circuit

Similarly the Zappi monitors the house's usage and will slow down if the heat pump is drawing a lot of power

When we replace the Leaf the next car will probably draw 7kW, so we'll probably replace the EO with another Zappi as they can do better load balancing that way. The EO can also do load balancing but the version we have is too old for that

Manion

Ok so it's really about supporting more concurrent load as opposed to faster charging, though obviously if you have to limit the current that will slow things down.

pauldavis123

https://www.boards.ie/discussion/comment/118132518#Comment_118132518

https://www.esbnetworks.ie/docs/default-source/publications/esb-networks-dac-statement-of-charges.pdf

Page 8

pauldavis123

You will need a new distribution board as well

Manion

https://www.boards.ie/discussion/comment/118132904#Comment_118132904

OK, I take it you didn't get this done then or you got it done business? Page 8 listed business charge at 2,430.00. Page 5 has the charge at €3,790 including vat + MV Network Charges. I'd assume I would need an electrician as well, and given what I'm paying for a days work installing a charger and writing a cert, it's hard to imagine I'd have change out of 5K.

KCross

https://www.boards.ie/discussion/comment/118131669#Comment_118131669

 

Can I assume that if I have an 80a mains I already have a 16kVA enhanced supply.

Yes but you cant assume your "tails" is rated for 80A. You'd need to eyeball that cable. 25mm² is what you need to see there.

What exactly does that get me? My understanding is that a 16kVA will allow me to use more power at the same time. So for instance charging two EVs or an EV and HP at the same time with plenty left over?

Standard domestic has 60A so if you have an 80A main fuse and your consumer unit also has an 80A fuse then you have an extra 20A to "play with".

Two EV's at full charge rate would be 60-64A and then the heat pump would be another 10-20A depending on the rating of the heat pump. So you wouldnt have "plenty left over" but you have enough to just about run all 3 together at full tilt, which is then where you would use load sensing charge points so that they would reduce their rate to keep the overall house load under your 80A fuse rating.

In practice you wont have two EV's charging all night every night unless you are doing very high mileage on both, so the load sensing is there just as a protection and wont actually affect your ability to have two fully charged cars everyday.

graememk

https://www.boards.ie/discussion/comment/118132966#Comment_118132966

Over thinking this a bit, a lot of charge points have load balancing built in. So the it will slow the charge to not over load your connection.

Manion

https://www.boards.ie/discussion/comment/118133108#Comment_118133108

I'm not really able to eye ball the cable thickness and there appears to be no writing on them. The thing is we've an AC system which is 6.5A, Induction Hob, Dryer, Heat pump and now a EV Charger on the way. It's mainly just piece of mind to know how close we are to hitting our MIC.

Manion

https://www.boards.ie/discussion/comment/118133121#Comment_118133121

Some folks are happier to live in ignorance I guess than others. The charger I'm getting has an adaptive fuse so I'm not worried about tripping anything, I'd just like to understand better the options and what different things get me so I can have an informed conversation with the installer.

KCross

https://www.boards.ie/discussion/comment/118133262#Comment_118133262

You might be able to see the meter tails in your attic?

ESB will tell you for sure tomorrow anyway if you call them and your electrician will be able to tell too.

the_amazing_raisin

https://www.boards.ie/discussion/comment/118132713#Comment_118132713

You're right, a lot of it comes down to resource management. The load balancing can slow down the charging, a bit, but it's very rare that we need to charge both cars at the same time anyway

Even still, if we push up to the 40A limit for the circuit, that's 9.2kW. Over the 9 hours of night rate, that's 82kWh. On average that's probably around 435km of range

Divided between both cars that's still 200km per car per night. If you regular daily commute for both cars is more than this, then you'll need more power

Even then, you can charge a couple of hours at the day rate if needed, it's worth balancing the costs against the cost of upgrading your supply

The heat pump might not have a major impact depending on the power draw. Ours is a 6kW output so pulls around 1.5kW of electricity. I think with the immersion or backup heater it's closer to 3kW for short bursts

We haven't had any issues of overloading with the Leaf. We'll see how it goes this winter with both cars but I don't forsee any issues

Manion

OK, so it turns out after contacting ESBN that I've a standard 12kVA supply. The CU Main fuse is 80A rated but based on the supply the fuse at the meter must be only 60A. She sounded a bit vague about whats really involved in doing an upgrade, suggesting I may need new cables running back to the CU, as per above. Anyway, I maybe getting way a head of myself on this, I hardly expect to be driving from 100% to 0% every day.

the_amazing_raisin

https://www.boards.ie/discussion/comment/118140507#Comment_118140507

I've found the folks on the ESBN customer help aren't really knowledgeable about the engineering involved and can't help with any technical stuff. They told me I need a new meter when switching to a Day/Night meter, even though I've a newer digital meter which can do all of the readings already

My house has an 80A fuse in the meter and 63A on the CU as well. Not sure what the logic behind that was, might be standard but could also be that the electrician probably had a box of 63A MCBs in the van

It does mean I'm limited to 63A, but if the meter tails support it I also have the possibility to increasing this to 80A if needed (or a but less, since I assume I'll want some buffer between the CU fuse and the ESB one)

graememk

https://www.boards.ie/discussion/comment/118140617#Comment_118140617

For 16 kva your supposed to have 25mm² cables from the meter to the consumer unit.

KCross

https://www.boards.ie/discussion/comment/118140507#Comment_118140507

The CU Main fuse is 80A rated but based on the supply the fuse at the meter must be only 60A.

That sounds a bit dodgy. If correct it means you can pull more than the ESB fuse and hence easily blow it. Either your electrician put in the wrong fuse or that ESB person on the phone hadnt a clue what they were talking about and you actually have an 80A meter fuse.

KCross

https://www.boards.ie/discussion/comment/118140617#Comment_118140617

My house has an 80A fuse in the meter and 63A on the CU as well. Not sure what the logic behind that was, might be standard but could also be that the electrician probably had a box of 63A MCBs in the van

Mine was done the same way and I think it is just down to a lazy electrician not having the uprated CU.

I got mine changed to "unlock" the extra 20A.... after all, thats why I paid extra for the enhanced supply so why have it limited to 60A like that. I regularly go up to 60A so I'm glad I did uprate the CU.

pauldavis123

https://ie.rs-online.com/web/p/cartridge-fuses/1818876/

Do NOT do this!

Manion

https://www.boards.ie/discussion/comment/118142634#Comment_118142634

I'm probably inferring something I shouldn't, all they confirmed was the power supply is 12Kva. I assume that means the Meter fuse is 60A to protect the network. At least now I'm armed with the right questions to ask to electrician when he comes.

graememk

https://www.boards.ie/discussion/comment/118133262#Comment_118133262

They look, at a glance like 16mm2 tails. and being on a 12kva supply confirms it.

Did you have a photo of your consumer unit in another thread? I think thats just a switch, not a MCB. (is there another box in your meter box?)

Manion

For those interested, I was onto ESBN today regarding a smart meter and they told me the main fuse is 80amp but the supply is definitely just 12Kva. So that's pretty conclusive that fuse and MIC don't match up one to one.

ECO_Mental

Just for your info I got my new connection over the summer and specced a 16 kVA connection and ESBN put in a 100 Amp fuse. My main isolator on the CU board though is 80A....I dont have any EV's at the moment so not going near it, but planning to over the coming years. I have prewired for 2 charging points and I have a heat pump etc. I probabaly wont have two EV's charging any time soon so I think I have the capacity.

graememk

https://www.boards.ie/discussion/comment/118275016#Comment_118275016

That tallies with what I'd been told too when I got my supply upgraded, the esbn fuse is 100amp but the mcb on the house is 80amp

Manion

The charger we got installed came with a smart energy monitor on the mains supply. We've an air to water heat pump on a 32 amp breaker. So far we've not gone over 3kw usage at any one time. Feels like there is loads of head room for 7kw charging without the upgrade, though the upgrade is easier now that the main fuse board is in the meter cabinet.

loopymum

https://www.boards.ie/discussion/comment/118275931#Comment_118275931

3kw seems very low. I have a zappi & the hub. I regularly see mine flying up. We don't have any gas though & everything is electric.

Say oven is on

The base in our house is 0.6 kw usually.then throw on a few things

Oven 2.2

HP 3kw

Immersion 3kw

Microwave 2.2

Ring on the hob 1.3

Tv & a few computers 1kw +

I have seen my zappi load manage a good few times even during the night. Washer, dryer & dw & car charging & hp. turn on the kettle & it will drop down. Otherwise I would be paying ESB 1500 to upgrade

Manion

That's fair enough, most of our appliances are A+++ rated (except the dryer). It might be spiking up when we turn on the kettle or the like, but our steady state seems pretty low.

CHorn

Been a while but resurrecting as seems closest to my Q, what I worry about is future-proofing for 2EVs and HP with everything going to Electric.

I’m just doing a sanity check on the electricity supply proposed for a new build- 16kVA Enhanced. Please correct me if I’m wrong but this’ll mean we have a 100A fuse on the ESB side and an 80A fuse on the house side. The idea being the 80A fuse trips first and the customer can figure out why, if the 100A fuse goes the ESB will want to know why (and charge you to correct it).

That means we’ve got 80A to play with as CONCURRENT power use within the house. If we’re looking to future-proof the house, probably best to look at what’s going to happen down the road with 2 x EVs being charged at night. Worst case scenario is a below zero winter night where the heat pump will be running full blast. That’s 32A (16kW heat pump), and 2x32A with 2x7.4kWh EV chargers running. Now I know the EV chargers can balance the load (i.e. turn down/off if too much total current is being drawn), but that may mean you wake up in a warm house with an EV uncharged.

We’d also plan to run the dishwasher, washing machine and tumbler dryer in off-peak hours too (10 each =30A) to take advantage of lower rates. So with heat pump on and ONLY 1 EV charger, we’re still looking at a potential 94A draw, even before adding in lights and minor appliances.

So max concurrent draw at night to use night rates is potentially 126A (3x10A Appliances, 2x32A EV Chargers, 1x32A Heat Pump). Should we not opt for the (1 Phase) 29kVA with the 160A fuse (and 125A fuse on customer side)? I don’t think there’s a significant difference in cost between the two (16kVA versus 29kVA): https://www.esbnetworks.ie/docs/default-source/publications/esb-networks-dac-statement-of-charges.pdf

If it turns out we can go lower on the heat pump spec (say 12kW), this may change (down to 20A?). Also I haven’t even considered the power shower in a garden office (30A), a desktop PC (10A) that can use or anything to do with the hot water or rads/underfloor heating in the house (I'm assuming latter is related to heat pump?), just items I can fairly confidently say will all be running at the same time.

3 Phase not an option. Will 16kVA Enhanced cut it, or should I go to 29kVA? Or am I missing something or doing something desperately wrong with my #s? Thanks.

KCross

Or am I missing something or doing something desperately wrong with my #s?

^ This

There is lots wrong in your post and understanding of the HP and EVs and fuses etc.

The 16kVA connection will suffice. I’ll write you a full explanation tomorrow.

Manion

Other than the EV chargers the rest of your appliances will not draw the max current continuously. I wouldn't down grade your Heat pump, it will draw most power at start up and shut down. Ours is rated to 32 amp, typically drawing about 8 amps at start up in the morning and quickly settling down to half that. It might draw 32 amps I guess if it had been off and house temperature was freezing.

Your office shower doesn't factor in unless you plan to be out there showering in the night, even then in that highly rare instance the load balancer will briefly drop power to the EVs.

Fuses and breakers work by have a max continuous load threshold and a max instantaneous load.

As the other poster said, you don't need the 29Kva supply.

zg3409

Another factor in calculations is what is daily commute. I used to do 110km a day which worked out average 20kWh energy needed per car per day, so in less than 3 hours car would be refilled at 6/7kW charging rate. If you have a 9 hour night rate it should be possible to charge 2 cars on typical commute. It would be rare both cars would need a full charge and need to be 100% full the next day. You can set one charger to be priority over the other one to ensure one car can get more. Even just starting charging with priority car first should do that.

As said dishwashers and washing machine only use high power while heating water which may only be 10 minutes of the wash cycle.

We may be forced into smart meters with 2 hour low night pricing typical. Will you be forced smart meter on new build?

You may want to consider solar during planning. You would need massive solar to power heat pump in winter from sun during daytime. However solar is relatively cheap compared to long term bills.

Do you know the annual cost difference on different supplies?

Personally I would be worried about cost of heat pump. Electricity is crazy expensive now. I would want my house ideally passive rated (using sun through windows to warm house) and have house a+++ rated.

the_amazing_raisin

I can assure you that 16kVA will be enough because I'm in almost the exact situation you describe for the past year and have never had an issue with the cars not being charged

ECO_Mental

HI I'm the OP of this tread and I am a year into my house now and I got a 16 kVA connection and it is more than enough, I would highly recommend getting the 16 kVA connection and it does give you the wiggle room. I am all electricity and I have one EV at the moment.

See below here a day last week where I had the Car charging, I had the dishwasher timed to go on at 2am and the Heat pump when through its once a week legionella heating routine.. I nearly tipped 13 kW import during the night so the 12 kVA might have struggled

Regarding EV charging I agree if you charge about 2 hrs every night that should keep you topped up in the car for the average mileage (I do about 40- 60km a day in the EV) so if you had two you could easily schedule the charges not to overlap. Even then I am sure two charging at the same time with a 16 kVA connection you would be alight. 80 Amps is about 19kW so there is plenty of room (if my math's is right..)

FYI...ESB Fuse is 100amp

Manion

https://www.boards.ie/discussion/comment/119798619#Comment_119798619

I'd guess it's the convenience of not having to think about actively managing what you put on when. Though I don't thing there is any issue anyway.

Regarding concerns about heatpumps, it's not really a subjective thing. It's a new build and you have to heat it somehow. A heat pump should provide you an efficiency of 300% in a new build. Gas cost have increase as well. Taking gas prices at 12.617c per kWh if you can get your average electricity for less than 50 cents, you're winning. Keep in mind that you also have a Gas standing order, are you even allowed put a gas/oil boiler into new builds?

People are often shocked when they get a heat pump because their electricity builds are much larger but forget they aren't getting a gas bill at all.

KCross

https://www.boards.ie/discussion/comment/119798216#Comment_119798216

You need to look up "electrical diversity".

All of your post is calculating based on everything being on and drawing max power at the same time. In reality it wont happen. Thats not to say you dont need to take some precautions (load balancing etc) but the point is you dont calculate your MIC based on everything being on at the same time.

16kVA Enhanced. Please correct me if I’m wrong but this’ll mean we have a 100A fuse on the ESB side and an 80A fuse on the house side

The ESB fuse could be 100A. It could also be 80A but I think they are installing 100A now. It gives you access to 80A at your consumer unit either way. Note also that the ESB fuse wont just pop at 80A. They are designed to last beyond 80A to account for load spikes when things like HP's turn on and very short bursts.

That’s 32A (16kW heat pump)

Thats a rather large heat pump for a new build. Unless its a massive house (400m²+) it looks like overkill to me. Somewhere between 6-12kW would be more normal, particularly for a modern A rated build.

2x32A with 2x7.4kWh EV chargers running. Now I know the EV chargers can balance the load (i.e. turn down/off if too much total current is being drawn), but that may mean you wake up in a warm house with an EV uncharged.

Its unlikely you would wake up to an uncharged car unless you are doing huge mileage every day in both cars. In reality you will be charging them a couple of times a week and on random days. On the rare occasion where both need a big topup on the one night let the load balancing do its thing and you will still get 100kWh+ into the 2 cars over the 9hr night rate. e.g. You have an 80A fuse, 60A used by the 2 cars for 9hrs, so that's 124kWh. Thats two long range cars charged from 0-100% and you still had 20A to spare for the HP so the cars might ramp down by a few amps to just keep you under 80A. It wont change the end result much and its unlikely you would be going from 0-100% on both anyway.

We’d also plan to run the dishwasher, washing machine and tumbler dryer in off-peak hours too (10 each =30A)

Those appliances are pulling 10A for a tiny portion of their full 1-2hr cycle. Im not sure they would even pull 10A. When they are rinsing, spinning etc they use very small amount of power. When they are heating the water for a few minutes they peak, but that's only minutes, not hours (i.e. electrical diversity). So, those appliances wont materially affect your ability to have a charged car in the morning.

So with heat pump on and ONLY 1 EV charger, we’re still looking at a potential 94A draw

I'd say closer to 50A in reality.

Should we not opt for the (1 Phase) 29kVA with the 160A fuse (and 125A fuse on customer side)? I don’t think there’s a significant difference in cost between the two (16kVA versus 29kVA

The costs are likely to be much higher for the 29kVA but very much dependent on your local grid supply. The key thing in the ESB charges document is where it says "+ MV Network Charges". Those MV charges could be many thousands if they have to run extra supply specifically for you. The only way you would know is by asking them to give you a quote for it and they would visit your site and match that to the grid. I'd be willing to bet it will be thousands, particularly if you are in a rural setting with not much grid around you.

If it turns out we can go lower on the heat pump spec (say 12kW), this may change (down to 20A?)

Yes, you should definitely be looking at that. My 12kW HP is rated for 20A but some are variable rather than a set rate whenever its running so its not drawing 20A all the time and it will also be cycling on/off as required.

Also I haven’t even considered the power shower in a garden office (30A), a desktop PC (10A) that can use or anything to do with the hot water or rads/underfloor heating in the house (I'm assuming latter is related to heat pump?), just items I can fairly confidently say will all be running at the same time.

Again, diversity... will the shower be running while the cars are charging? And a shower will only be running for minutes anyway so again, not a big deal. The cars will rate down while the shower is running if it happens to coincide..... rating down for 5,10,20mins over a 9hr period is just background noise.

I doubt your PC is taking anything close to 10A. Unless you are crypto mining with it or something! Again, diversity will be at play here, the PC wont be doing much at night, presumably.

Will 16kVA Enhanced cut it, or should I go to 29kVA?

16kVA will cut it.

I have all of what you have described above. It works fine on 16kVA. I do occasionally hit the limit and the charge points rate down as required. Plenty to spare over the 9hr night rate.

If you are still a bit unsure and want to future proof what you could do is wire the house to take the next step up (20kVA) but only get 16kVA from the ESB. If you find you have issues you can then relatively easily upgrade the ESB side without having to upgrade the house "tails" and consumer unit etc. Thats a discussion you'd need to have with your electrician.

Manion

Fair point, you should right size your heat pump, too big and you'll have it knocking on and off frequently.

CHorn

Thanks so much to all for the answers, HUGELY helpful. And @ECO_Mental if a picture is worth a 1000 words, that graph of yours surely is. If I can ask how did you generate it and what are you (and anyone else who cares to comment) using to monitor your consumption like this?

ECO_Mental

I use Home Assistant on a Raspberry

https://www.boards.ie/discussion/comment/119801272#Comment_119801272

I use Home Assistant (HA) on a Raspberry Pi4b . I use 3 ShellyEM's to log 6 circuits on my main consumer board. The data from the ShellyEMs is pulled into HA and those graphs are generated using Grafana on HA...

If you are not measuring you are not managing!

Manion

Hey @ECO_Mental did you have any issues with installing multiple ShellyEM units on the one home network?