Net Zero House and 200A Service or More

[canadarox12]

I am building a net zero house in Edmonton Canada, which will not have a gas service to it. It will have a 13kW solar array and I want to pre-wire it to support two future EVs. Sadly this new neighbourhood only has 100A services to their lots. There will be an electric heat pump, with auxiliary heating unit for our winters, forced air electric hot water tank, HRV, electric stove and electric washer/dryer.

I will purchase a Model 3 or a Model Y, and my spouse will either have a PHEV or EV as well. I know we need to upgrade the main service to the lot, which so far quotes are around 15-20K directly from the power corporation. This includes trenching, ripping up sidewalk, materials and upgrading the transformer.

My question is will 200A be enough? Also how best to do it, so far the idea was to just run individual lines from the breaker panel in the basement to the garage for the circuits, one on each side of the garage. Another option would be to do a sub-panel in the garage. The garage is an attached one as well.

Thanks for your replies!

 

[goto10]

For an all electric home with potentially two EVs 200A sounds a bit low to me, but you'll want to do a load calculation to be sure.

We're building a new home right now with with a gas furnace and water heater and the load calculations said 200A was borderline for us with a single EV. We have decided to go to 400A to provide enough headroom for any potential future needs such as a second EV and electric heat pump / water heaters. We had to pay to upgrade the transformer though the power company only charged us $3,300 for that. The transformer is luckily already on our property so there weren't extra costs for trenching, tearing up sidewalks, etc.

Other incremental costs to install 400A instead of 200A which included impact fees, an upgraded meter head, etc. added up to about $4,000 more.

 

[canadarox12]

For an all electric home with potentially two EVs 200A sounds a bit low to me, but you'll want to do a load calculation to be sure.

We're building a new home right now with with a gas furnace and water heater and the load calculations said 200A was borderline for us with a single EV. We have decided to go to 400A to provide enough headroom for any potential future needs such as a second EV and electric heat pump / water heaters. We had to pay to upgrade the transformer though the power company only charged us $3,300 for that. The transformer is luckily already on our property so there weren't extra costs for trenching, tearing up sidewalks, etc.

Other incremental costs to install 400A instead of 200A which included impact fees, an upgraded meter head, etc. added up to about $4,000 more.

For a difference of only 4k that seems well worth it. I know a couple electricians, will see what they say. Did you do a subpanel in the garage, or just a circuit to it?

 

[goto10]

For a difference of only 4k that seems well worth it. I know a couple electricians, will see what they say. Did you do a subpanel in the garage, or just a circuit to it?

We haven't made final plans on how we'll distribute the power. I'm leaning toward a subpanel in the garage but I'll discuss with the electrician and see what he recommends.

 

[canadarox12]

We haven't made final plans on how we'll distribute the power. I'm leaning toward a subpanel in the garage but I'll discuss with the electrician and see what he recommends.

Okay.

One method I am leaning towards is to use Clipper Creek's Share2 chargers off one 80A circuit. As I get home before she does I would get the full draw (even with the model 3 only with a 40A onboard charger), then when she comes home and plugs in her car we each share 40A. This way it cuts the total load nearly in half. Going from a suggested main service from 230A down to 190A. This is after all of the mechanical systems and kitchen appliances added.

 

[TLej]

I would think a bit about exactly how much current you need for charging; I charge my S overnight at 40A and only in rare circumstances am I charging for longer than 4 or 5 hours (charging from 40% to 80% takes 4 hours at 40A). Given that the 3 is more efficient than the S, it probably charges at 15%/hr at 40A, and unless your spouse is getting a Tesla or a Mission E, nothing else can charge at even that rate at the moment. I get the future-proofing idea, but unless you both have long commutes you can alternate charging days, or one of you can charge from 10 p.m. until 2 a.m. and the other from 2 a.m. until 6 a.m. and you both wind up fully charged every morning. You might be able to get by on 40A and share it.

Rather than giving Epcor another $20k, how much would it cost to install battery storage for your PV system? Might be able to do that instead, although it sounds like your loads are going to be high enough you need to upgrade to 150 or 200A service anyhow.

I assume you’re using a hybrid water heater (i.e. heat pump with electric); any thought of a solar water heater instead?

I have electric dryer, stove, air conditioning, and a 50A circuit all on 100A service. No issue as the loads are staggered because I charge starting at 1 a.m. when nothing else is running.

 

[SSedan]

I have a 40yo 2400sq bi-level home near Green Bay WI bought with baseboard electric, electric hot water, electric range, and when I moved in even 90watt incandescent in the cans in the kitchen........
200amp service last winter I upgraded from baseboard electric to Fujitsu minisplits 2 outdoor units 3 indoor on each, bathrooms, laundry room and utility room still on baseboard electric, and then last summer I bought the Tesla which I charge on a 30amp circuit, Been fine and this house is NOT well sealed.

A newer home I think will be fine even with 2 EVs so long as you are not trying to charge both at high rates at the same time on a cold day while someone is showering..............

My house still has some single pane windows and when I changed the service door to the garage there was ZERO insulation around the door jamb, wind just blew thru, the trim was all that slowed it down.

If I get by on 200amps I think you will too.

I do not even schedule charging of the car, it charges soon as I get home to make use of the already warm battery so it is charging while cooking dinner and doing dishes.

 

[SageBrush]

I am building a net zero house in Edmonton Canada, which will not have a gas service to it.

Are other homes in the 'hood also without NG heating and limited to a 100 Amp panel ?
I ask because a well insulated and tight home is going to have electric loads way below standard code.

Net zero is one thing, but does it approach the passivhaus building standard ?
I'm guessing you aware of the these differences since you are installing an HRV, but hopefully you have an energy analysis that includes load calcs. Then you can figure in the EVs.

 

[canadarox12]

I would think a bit about exactly how much current you need for charging; I charge my S overnight at 40A and only in rare circumstances am I charging for longer than 4 or 5 hours (charging from 40% to 80% takes 4 hours at 40A). Given that the 3 is more efficient than the S, it probably charges at 15%/hr at 40A, and unless your spouse is getting a Tesla or a Mission E, nothing else can charge at even that rate at the moment. I get the future-proofing idea, but unless you both have long commutes you can alternate charging days, or one of you can charge from 10 p.m. until 2 a.m. and the other from 2 a.m. until 6 a.m. and you both wind up fully charged every morning. You might be able to get by on 40A and share it.

Rather than giving Epcor another $20k, how much would it cost to install battery storage for your PV system? Might be able to do that instead, although it sounds like your loads are going to be high enough you need to upgrade to 150 or 200A service anyhow.

I assume you’re using a hybrid water heater (i.e. heat pump with electric); any thought of a solar water heater instead?

I have electric dryer, stove, air conditioning, and a 50A circuit all on 100A service. No issue as the loads are staggered because I charge starting at 1 a.m. when nothing else is running.

I have received a quote for a Powerwall which would be roughly 14K installed. Even without the EVs our loads would require a higher service than the 100A which will require a similar cost as the material is the smallest portion of the cost.

I would have to look into solar water heating. Could be an option depending on how much space the single slope roofline has after the solar array is designed.

While it won’t be an issue for load, when the electrician pulls permit they have to consider the chargers as continuous loads.

 

[SageBrush]

While it won’t be an issue for load, when the electrician pulls permit they have to consider the chargers as continuous loads.

Meaning they presume people are too stupid to stagger their loads.

 

[canadarox12]

Are other homes in the 'hood also without NG heating and limited to a 100 Amp panel ?
I ask because a well insulated and tight home is going to have electric loads way below standard code.

Net zero is one thing, but does it approach the passivhaus building standard ?
I'm guessing you aware of the these differences since you are installing an HRV, but hopefully you have an energy analysis that includes load calcs. Then you can figure in the EVs.

Nearly all homes have a NG connection for space and water heating. Many neighbourhoods are on a 100A with some now reaching 200A.

Yes the building will be approaching passivhaus standards. We are striving for under 0.5 ACH at 50 pascals.

Once we finalize our first version of drawings we will have an energy model done on them to determine the needs and effective r-values.

 

[canadarox12]

Meaning they presume people are too stupid to stagger their loads.

This is required in the Canadian electrical code. They are aware people will stagger it but they won’t want any skin in the game either.

 

[Rocky_H]

While it won’t be an issue for load, when the electrician pulls permit they have to consider the chargers as continuous loads.

Meaning they presume people are too stupid to stagger their loads.

Wow. No, that has nothing to do with that. You're mixing up concurrent load with continuous load. Concurrent is talking about being used at the same time as something else, and there is a provision in a load calculation to choose one or the other if two loads are not going to be running at the same time, instead of having to add them both.

But the continuous load comment has to do with how NEC rates the current draw versus the rating of the circuit. It is because of how the wire size is set for an amount of heating for shorter periods of use, not continuous. For short term loads, the circuit can draw up to 100% of the rating. So a 30A dryer circuit can actually have a dryer pulling 30A, because the heating element cycles on and off. Same with an oven pulling 50A from a 50A circuit. But car charging circuits don't cut in and out in 5 minute intervals like that. They stay on for hours at a time, and if it were pulling 100% of the circuit rating, the wires are not sized to handle that long term amount of heating. So the continuous use provision in NEC means that for whatever constant current you will be pulling, you need to allocate 125% of that as the circuit rating in your breaker and wiring. So the comment was just mentioning that the circuit will be provisioned in the permit and load calculation for a higher amount than whatever current will be flowing to the car.

 

[SageBrush]

You're mixing up concurrent load with continuous load. Concurrent is talking about being used at the same time as something else, and there is a provision in a load calculation to choose one or the other if two loads are not going to be running at the same time, instead of having to add them both.

Oh ... good.
Thanks for the correction

 

[ai4px]

Just for you solar people wanting a power wall.... SolarEdge makes a StorEdge 7.6kw Solar 220V inverter that works with the LG Chem battery... it is 10kwh and cheaper than power wall. Just food for thought.... I think you can simply parallel more of them.