POCO considering charging customers for new transformer.

[Flicker Index]

TOU variable rates would probably be better at incentivizing use patterns that are better for the grid than demand charges.

TOU rates would cause people to run the washing machine, dishwasher, etc. on off-peak hours.

TOU is more about broader scale (think interstate highway congestion management/smog control) demand management where kW demand is much more relevant at local level, such as shift-change rush in a company town.

Imagine you're a cab operator and if someone requests a ride for 6 passengers and you're not allowed to refuse it. That's "local demand". If this was routine, then the capacity is utilized. If this was just once a month, the cab company incurs the cost of always having to have a means of accommodating six passengers at once, like depreciation and insurance on a car that is rarely used. So, industrial customers are often charged for the maximum 5/15/30 min kW demand that occurs over a period of months to a year, depending on the rate tariff.

If the weighing period is 15 minute/1 year peak and the maximum kWh clocked during ANY 15 minute in a one year period is 5kWh, then your demand for that period is 20kW. If the demand charge is $6/kW, that means you'll be paying $120/mo, for the applicable period as determined by tariff, not just that billing period. Alternatively, sometimes the customer can buy their own connection to the canal/medium voltage grid if there's ample capacity on medium voltage network, but not much capacity left on PoCo owned transformer. i.e. customer owned transformer from medium voltage. Who pays the transformer energy loss is determined by tariff.

Suppose you've got a pump station that basically run a 5kW load around the clock. That's 5kW demand and 3,600kWh of billable energy a month. But what about something that uses 1,000kWh in a few days out of the year but carnival calls for operating up to 300kW of load intermittent to run major rides. You bet the festival ground is going to be paying a hefty demand charge for having the capacity always available. That transformer will consume considerable power just sitting idle and it's a fairly expensive piece of equipment that sits idle much of the time. If it was installed to serve an office building, it won't be parked most of the time, but working to convert primary to sellable kWh much of the time.

 

[BarryO]

What are your thoughts?

My thoughts are that electric tankless water heaters are stupid. If you want an appliance that needs that much BTUs on an instantaneous basis, stick with natural gas. If you want an electric unit that's more modern and efficient than older ones, get a heat pump unit.

 

[retirede]

TOU is more about broader scale (think interstate highway congestion management/smog control) demand management where kW demand is much more relevant at local level, such as shift-change rush in a company town.

Imagine you're a cab operator and if someone requests a ride for 6 passengers and you're not allowed to refuse it. That's "local demand". If this was routine, then the capacity is utilized. If this was just once a month, the cab company incurs the cost of always having to have a means of accommodating six passengers at once, like depreciation and insurance on a car that is rarely used. So, industrial customers are often charged for the maximum 5/15/30 min kW demand that occurs over a period of months to a year, depending on the rate tariff.

If the weighing period is 15 minute/1 year peak and the maximum kWh clocked during ANY 15 minute in a one year period is 5kWh, then your demand for that period is 20kW. If the demand charge is $6/kW, that means you'll be paying $120/mo, for the applicable period as determined by tariff, not just that billing period. Alternatively, sometimes the customer can buy their own connection to the canal/medium voltage grid if there's ample capacity on medium voltage network, but not much capacity left on PoCo owned transformer. i.e. customer owned transformer from medium voltage. Who pays the transformer energy loss is determined by tariff.

Suppose you've got a pump station that basically run a 5kW load around the clock. That's 5kW demand and 3,600kWh of billable energy a month. But what about something that uses 1,000kWh in a few days out of the year but carnival calls for operating up to 300kW of load intermittent to run major rides. You bet the festival ground is going to be paying a hefty demand charge for having the capacity always available. That transformer will consume considerable power just sitting idle and it's a fairly expensive piece of equipment that sits idle much of the time. If it was installed to serve an office building, it won't be parked most of the time, but working to convert primary to sellable kWh much of the time.

I understand all that. I was a plant engineer in the early 80s for a plant that used a lot of power, and our monthly demand charges for the entire year were based on our highest peak that occurred between June 1 and September 1. Careful management saved us 6 figures annually.

In the case of residential, the average Joe has no idea what a demand charge is, how it’s calculated, or what he should do to minimize its cost to him. But he can understand something like “your power costs more between 1:00 PM and 9:00 PM.”

 

[kwired]

How does a tankless water heater compare to an EV charger??

sort of different load profile and often different load level.

Yes both will increase demand, though the tankless WH is high demand for short time in most applications where the EV is more of a medium demand but for longer duration.

They need to be able to supply the high demand tankless "on demand" even though total watt hours used for a billing period likely do go down.

They should maybe start issuing demand charges for such loads especially during peak demand periods and that might help discourage the use of them?

I personally don't think they are worth installing, especially in northern half of the US. A typical tank style heater losses are not totally lost during heating season if the unit is inside the heated space and nobody factors that into the total cost of owning and operating their water heater.

 

[Flicker Index]

How do they do it in the UK though? Tankless/semi tankless showers are very common there.
Regardless of where you go, I think there's a time of the day when shower use concentrates.

 

[jaggedben]

My thoughts are that electric tankless water heaters are stupid. If you want an appliance that needs that much BTUs on an instantaneous basis, stick with natural gas. If you want an electric unit that's more modern and efficient than older ones, get a heat pump unit.

Hear hear!

 

[jaggedben]

How do they do it in the UK though? Tankless/semi tankless showers are very common there.
Regardless of where you go, I think there's a time of the day when shower use concentrates.

Electric or gas?

 

[Flicker Index]

Electric or gas?

https://www.mirashowers.co.uk/blog/mira-recommends/kw-ratings-explained these are very common there. I think they're in Latin America also.

Electric.

 

[kwired]

While I’ve never really thought about it, I would have thought water from even a relatively shallow well wouldn’t vary that much in temperature between various places.

I have my own well, submersible with pump around 150 feet deep. Not certain exactly what depth the screens of well casing are at. Year round water temp is about 55F. So one needs to raise temp about 65F if you want 120F water. The higher the desired flow rate the more kW that heater needs to be. I could easily see needing 30 or 40 kW of heater in some situations. Utility distribution, customer equipment and generation facilities all need to be able to handle that load even if it only runs for say 5 minutes. Is less cost for all segments if same water use ended up having heating draw of only 4.5 kW but lasted for say 20 or 30 minutes.

 

[hillbilly1]

https://www.mirashowers.co.uk/blog/mira-recommends/kw-ratings-explained these are very common there. I think they're in Latin America also.

Electric.

In the Dominican they use small 10 gallon tank type for each bathroom, even the master bath. That didn’t work too well for the 100 gallon Jacuzzi tub!

 

[Flicker Index]

Hard to believe an Article 220 load calc shows 18k tankless within existing 1970's electrical-service design plans. Unless it was a custom home, 1970's contractors would have paid a premium for 200A service with 75A of head room for future expansion.

If 200A service really is 2 times over sized, because it was added later without permits, microfiche records would show the original 100A.

I believe new appliances are typically hacked in without building permits, if not to avoid retroactive enforcement of larger remodel hack jobs.

Since existing utility lines are always smaller than building services, and can burn up after expanded occupancy, remodels, & appliance hacks, Cable limiters are one solution for utilities dealing with residential in the wild.

In the mean time, I would expect repeat loss of new cables to be billable, when occupants refuse the building permits that would have notified utility of larger size service requirements.

I feel like they could easily enforce this by putting the permitted amperage in customer account and programming the smart meter. The thermal trip characteristics of breakers are well understood, so if the permit record is 75A service, that could be defined in the meter. If the load profile is outside of what's possible on a 75A service, the meter could be set to notify PoCo of potential unauthorized service upgrade.

 

[ramsy]

If the load profile is outside of what's possible on a 75A service, the meter could be set to notify PoCo of potential unauthorized service upgrade.

That would be the simplest solution.

For meters that wont collect peak data more frequently than every 15 minutes, demand alarms may also be derived from billing history.

Although such reporting measures wont prevent line damage faster than cable limiters, justifying any more equipment & labor cost has proven easier to impose on the customer side.

Just like the NEC sucked up 2-Pole GFCI's, AFCI's, and SPD's, utilities can leverage their NFPA code-panel appointments, to have it both ways if they want.

Using reporting measures to notify code enforcement of permit violations, and substantiate NEC requirements for service upgrades with Cable Limiters, to mitigate fire hazard ignition on rooftops, trees, vault enclosures, and pole transformers, surrounded by combustible landscapes.

 

[Hv&Lv]

How does a tankless water heater compare to an EV charger??

Huge difference. 75 amps vs 25

 

[Hv&Lv]

My thoughts are that electric tankless water heaters are stupid. If you want an appliance that needs that much BTUs on an instantaneous basis, stick with natural gas. If you want an electric unit that's more modern and efficient than older ones, get a heat pump unit.

I agree 100%.
Why did we get rid of strip heat? It costs much more than heat pump or natural gas.

 

[GoldDigger]

The POCO should be happy to sell more power.

They would be happy to just sell more energy. But it costs them for infrastructure to deliver more power.
And for water heating, the amount of energy used per billing period probably does not change much (unless the tankless encourages longer showers) while the peak power increases drastically.
EV charging, on the other hand, increases both energy use and power demand.

 

[GoldDigger]

How do they do it in the UK though? Tankless/semi tankless showers are very common there.
Regardless of where you go, I think there's a time of the day when shower use concentrates.

My experience is that they produce a much lower flow rate than US consumers were used to before flow limiters became mandatory. They are a relatively small load and average out some even with showering or not showering that day even with more popular times of use.

 

[Frank DuVal]

I mean, if everyone installed one of these things and then started their dishwasher in the first hour after peak hours it would be a s#$^# show.

No. As they use very little water compared to hand washing a load of dishes. And... they heat their own water too. You can hook one to a cold water line and it will still heat up and wash the dishes.

OK, I see, even if it only needed water for one minute, all those 120 amp loads in the neighborhood would be on at the same time, not pretty! Sort of a one minute brown out. This is assuming the flow of each dishwasher turned on all the elements, as might be the case in cold water that is cold territory. People on public water here complain their cold water is 70°F in the summer!

 

[Frank DuVal]

My thoughts are that electric tankless water heaters are stupid. If you want an appliance that needs that much BTUs on an instantaneous basis, stick with natural gas. If you want an electric unit that's more modern and efficient than older ones, get a heat pump unit.

Or propane! I'm in the country. I've been tankless for about 15 years, propane fed. Excellent!

My plumbing supplier friend once said you can get a lot more BTUs out of a 1" pipe of natural or LPG than you can get out of a 1" cable. I never did the math....

 

[Frank DuVal]

Larry and I remember the 60 amp services to houses with an "off-peak" meter beside it coupled with a close nipple or so. That off peak meter fed the water heater. The heater would only turn on during off peak hours. So if you had a house of 3 teenagers, someone was getting a cold shower or they learned to shower at night. I always wondered who reset the clocks after a power outage...

 

[gadfly56]

Larry and I remember the 60 amp services to houses with an "off-peak" meter beside it coupled with a close nipple or so. That off peak meter fed the water heater. The heater would only turn on during off peak hours. So if you had a house of 3 teenagers, someone was getting a cold shower or they learned to shower at night. I always wondered who reset the clocks after a power outage...

My last home had something similar. It didn't have a cutoff, but the hot water heater was separately metered.