Ive had solar for a year and now the utility company charges a demand fee... not cool.

[Zwy]

I believe this is the problem some companies are trying to solve with smart home management panels and load control panels.

Emporia is starting to integrate Demand management.

I prefer using MyEyedro for viewing consumption and can drill down easily for load details without downloading to Excel which Emporia does. But when it comes to integration, Emporia does have those features.

I have been installing some Shelly products and found they seem to be moving to integration of load management.

 

[Zwy]

I tried a big old diode to cut the power in half on my dryer heating element but it really did not work well at all, the dryer buzzed like crazy and the whole electrical system was grumpy.

I remember that!

 

[Hedges]

Again, was that diode on water heater driven by inverter?
I'll bet the inverter didn't like that.

Grid, you'd just be a gnat on elephant's back.

 

[Zwy]

For water heater, low wattage and more energy storage seems like the way to go. Larger tank and/or higher temperature + tempering valve. 80 gallon? 120 gallon? More than one? Tanks are cheaper than batteries, and cheaper than one-off programming/implementation of control systems. I went for 120V and a timer.

Went down to the home improvement store last night and picked up a heat pump water heater for a dump load. It was about $200 off on sale and it has the 11% rebate to boot. With the 30% tax credit, I figured why not? I have the choice to run the resistive element or the heat pump.

I'm leaving my propane water heater in place and will plumb the HPWH in series ahead of the propane WH. I doubt I will use much propane but come winter, I might want to limit loads.

 

[wattmatters]

Demand charge could be much more. Is that charged on every kWh, or only on kWh above a threshold like 5kW?

It's not charged on kWh at all. It's a demand charge, not a consumption charge.

The lower consumption tariff does look good on paper... but when they hit you with power cost adjustments each month that are typically over 2 cents per... you start to realize that the lower tariff is mainly to look good to customers of other power companies comparing one company to the next.

To be clear, I'm not defending the charges, just explaining how they work.

What prices do people see for home AC batteries, which can shave these peaks?

In my case I'm estimating I'd need to spend ~A$5.5-6k in extra inverter and battery capacity + sparky support in order to shave ~$500-600/year off the bill (a combination of peak shaving and reduced grid consumption). It's not that appealing frankly. I'd love to do it from a fun/hobby POV but not sure I can justify it.

This past two years has been a bit wild with inflation killing us. Our home insurance quote went up to $18k (and accordingly I have changed what is insured). When we moved here 8 years ago it was ~$2k.

 

[zanydroid]

I'm leaving my propane water heater in place and will plumb the HPWH in series ahead of the propane WH. I doubt I will use much propane but come winter, I might want to limit loads.

What are the tradeoffs between the two different ways of sequencing the WHs?

 

[Zwy]

What are the tradeoffs between the two different ways of sequencing the WHs?

Longer recovery time with the heat pump with limited daytime PV hours. I might want to dump all excess solar I can into the water heater so the resistive coil can be used for that purpose.

If you are referring to series vs parallel water heater connections, the idea is primary heating of water is desired with the heat pump/resistive water heater to cut propane use. I have excess PV available most days of consecutive sun and the system is not grid tie so use it or lose it. Using series will have a minimum water temp with the propane water heater last in series and increase the storage capacity when using as a dump load.

 

[Hedges]

It's not charged on kWh at all. It's a demand charge, not a consumption charge.

I'm slipping on units. Somewhat.
Is there a maximum continuous kW level that avoids demand charges?
That is, a certain amount of kWh per 15 minutes, if that is the time window?

My ark welder might be very high kW, but only 30 seconds at a time laying a bead, then change the rod.

To be clear, I'm not defending the charges, just explaining how they work.


In my case I'm estimating I'd need to spend ~A$5.5-6k in extra inverter and battery capacity + sparky support in order to shave ~$500-600/year off the bill (a combination of peak shaving and reduced grid consumption). It's not that appealing frankly. I'd love to do it from a fun/hobby POV but not sure I can justify it.

10 year break even could be OK for PV and inverters, because they have long life.
I'd rather not do that for a battery that could wear out. Or a car that could get totaled after front-loading energy expenses by paying extra for an EV.

Speaking of PV, that's the ticket. For water heating, if that is your peak load, it could be fed PV direct, not touching AC lines so no need for "Sparky"

This past two years has been a bit wild with inflation killing us. Our home insurance quote went up to $18k (and accordingly I have changed what is insured). When we moved here 8 years ago it was ~$2k.

Ouch, that's ballpark what full medical coverage costs us.

Home insurance went up quickly from about $600 to $1500 (for 1000sf house with shake roof) after fires in another area. Different house 1600sf or so, asphalt shingle, is similar $1500.

California doesn't let insurance companies freely adjust premiums to match risk or losses, so they may have raised rates across the board rather than selectively where risks were high. Many have exited the market, not writing new policies.

 

[Ampster]

Is there a maximum continuous kW level that avoids demand charges?

There are probably regional differences. My SCE rate plan has no limit on the continuos kW level except for the practical capacity of the service panel. In my case it is a 50 Amp meter for house loads and I installed a 14-30 receptacle for EV charging and that would work out to be 5.7kWs. It turns out my tenant is not using that receptacle but using a 20 Amp 120 volt receptacle so that is only 1.9 kWs. He must be using it less lately because my latest bill shows maximum demand at 1kW and only a $2.70 charge even though the rate shows as $6.23 per kW for the demand charge. I will look at other months when the demand charge was as high as $30 per month.
EDIT: I looked at the August bill and the highest kW for that month was 2kW but the rate was $16.43/kW so the fixed fee for that month was $32.86 on top of kWh charges. I just put solar on a contigious building and both meters are on NEM 2.0 Aggregation so my kWh charges for those buildings will be minimums but will include NBCs and the demand charge.

 

[wattmatters]

Is there a maximum continuous kW level that avoids demand charges?

Not usually.

It's just based on the highest interval reading for the period in question. Depending on where you are that might be a 15-min or a 30-min interval. They will be the standard metering intervals, e.g. 18:15-18:30, or 17:00-17:30 and not 17:42-18:12.

The kWh for that interval is then converted to an average power value for the interval. e.g. 2.3 kWh for a half hour = 4.6 kW.

My ark welder might be very high kW, but only 30 seconds at a time laying a bead, then change the rod.

Because it's based on an average power for the metering interval (be it 15 or 30 minutes), ephemeral peaks are not going to make much difference.

In some cases the intervals included for calculating peak may be restricted to certain times of day and/or days of week. For example in my region the demand is calculated on the peak occurring during the 5-8PM interval on weekdays. So my actual peak demand could be in the middle of the day, but the network doesn't care so much about that as there is so much spare solar capacity in the system they actually want the load. It's only during peak evening periods they care.

 

[wattmatters]

10 year break even could be OK for PV and inverters, because they have long life.
I'd rather not do that for a battery that could wear out.

Yeah, plus have to be sure we'll be staying here that long. I'd like to think so but if the costs and workload become to onerous then we may choose to downsize.

I could probably sell a few things like the generator since it's just not needed now I have the car's V2L. Might get ~$2k for that.

 

[zanydroid]

If you are referring to series vs parallel water heater connections, the idea is primary heating of water is desired with the heat pump/resistive water heater to cut propane use. I have excess PV available most days of consecutive sun and the system is not grid tie so use it or lose it. Using series will have a minimum water temp with the propane water heater last in series and increase the storage capacity when using as a dump load.

OK, so the idea of having the propane tank second is so that you get extra storage tank to use? Doesn't the propane water heater tank have high standby losses unless it's fancy? Since any fuel-fired boiler is going to need extra insulation effort compared to an electric or HP system.

How do you keep a propane heater tank where the propane heater is off at a safe temperature?

How about:
- Instant propane
-> HPWH
-> Insulated storage tank

 

[wattmatters]

How about:
- Instant propane
-> HPWH
-> Insulated storage tank

I'd be putting the instant propane last in a hot water supply chain. Then it only needs to fire if the incoming water temp is insufficient.

 

[Zwy]

OK, so the idea of having the propane tank second is so that you get extra storage tank to use? Doesn't the propane water heater tank have high standby losses unless it's fancy? Since any fuel-fired boiler is going to need extra insulation effort compared to an electric or HP system.

I can throw a blanket on it if needed. It is a powervent, not like the propane water heaters with the open flue.

How do you keep a propane heater tank where the propane heater is off at a safe temperature?

That is a contradiction to the questions above.

If you are referring to Legionaries, if the water temp coming in is 140°F, I doubt that will be a problem. It would be different if tanks were in parallel.

How about:
- Instant propane
-> HPWH
-> Insulated storage tank

I have a instantaneous propane in the shop. It's ok, takes too long to get hot water at a sink but if I need hot water over an extended period it works great for that.

Why would you heat with propane ahead of the HPWH? That defeats the purpose of the HPWH. I'm looking for a dump load for excess electricity. It may completely supply all the hot water needed during certain times of the year as a bonus. The idea is to shift propane use to excess electricity when available. I'm currently heating my house basically with free excess electricity.

As this thread is about demand fees, one thing about using a HPWH with increased storage is excess electrical generation used to heat water can reduce that demand charge. Heat water when other high demand items are not running. The increased storage results in choosing when hot water is heated without running out and with the propane in series allows for a minimum water temp when usage has been higher than average or excess PV generation is minimal for extended periods.

 

[SunDave]

Went down to the home improvement store last night and picked up a heat pump water heater for a dump load. It was about $200 off on sale and it has the 11% rebate to boot.

Menards. If you know, you know.

 

[Zwy]

Menards. If you know, you know.

Today is the last day on sale. It is a good deal, I can control it from my phone which allows me to choose which way I want to dump power to it. This time of year I'm heating the house with electric and still getting batteries fully charged by noon to 1 pm. House is 80°F and nowhere to go with excess power.

I often wonder if I should have grid tied first, then added off grid system.

 

[zanydroid]

If you are referring to Legionaries, if the water temp coming in is 140°F, I doubt that will be a problem. It would be different if tanks were in parallel.

If nobody is home using the water you would have to leave the propane storage tank thermostat on to reheat. That sounds complicated/I don’t understand the details.

If it is an instant propane after I get how it works.

Yeah I don’t see an advantage to instant propane before. I do see some advantage to a small instant resistive before since that allows backup extra power to be injected into the HPWH tank. If there is a lot of excess solar turn on the small instant resistive.

 

[Zwy]

If nobody is home using the water you would have to leave the propane storage tank thermostat on to reheat. That sounds complicated/I don’t understand the details.

Propane thermostat is set slightly lower than the HPWH. The idea is to heat with electric as much as possible but if needed the propane will heat if needed. It is best to have the propane cycle once in awhile too, this ensures it operates when desired.

The propane water heater is maybe 8 years old or less. I don't see a reason to remove it but wanted a dump load to heat water. Come next winter, I might want to use the propane as primary. I am adding some PV this summer so will not know until winter how much excess I may have in winter. This gives me some flexibility.

If it is an instant propane after I get how it works.

Yeah I don’t see an advantage to instant propane before. I do see some advantage to a small instant resistive before since that allows backup extra power to be injected into the HPWH tank. If there is a lot of excess solar turn on the small instant resistive.

I can always turn on the resistive in the hybrid water heater if I have a large amount of excess PV and getting near the end of the day. This allows storage of excess PV.

Installing a small instant resistive only works if you have water demand. I want to store the excess energy for when I can use it, just like a battery.

 

[Danke]

Menards. If you know, you know.

Been on that 11% Menards treadmill for years. 11% back, spend it at Menards only, another 11% back, etc. etc…. Smart marketing, keeps you coming back.

At Home Depot and Lowe’s I get a 10% off for military veteran. Only problem is Menards usually beats their prices.

 

[Zwy]

Been on that 11% Menards treadmill for years. 11% back, spend it at Menards only, another 11% back, etc. etc…. Smart marketing, keeps you coming back.

At Home Depot and Lowe’s I get a 10% off for military veteran. Only problem is Menards usually beats their prices.

I bought all my 10AWG THWN at Manard's with the 11% rebate. Lowe's and HD couldn't touch it.

I used to get the HD 10% discount for military, then they went to the app and I quit buying much there. I think Lowe's went the app too. Put an addition on my house back when I did get the discount.