Solution for a day's usage of over 200 kWh

Hi - first post here. I have been watching Will's YouTube videos for months. I just moved into a new to me home. The electrical utility is different and has quite expensive summer rates. I think my power needs greatly outweigh my ability to have enough panels or batteries to cover my total needs. Peak usage each day is in the afternoons when it is the hottest (I live in the Atlanta, GA area). I also have an EV that I charge between 2 and 4am. I have some days that I exceed 200 kWh and used 6900 kWh last month. Part of my problem is a pool pump that isn't efficient and I'm sure the house could be insulated a lot better. Three 4 ton heat pumps and an electric water heater to boot.

My summer rates are over 0.14 per kwH over 1000 kWh. If I had an "EV plan", it would be .02 per kWh to use power between 11pm and 7am. Not sure what the next step would be as I need to charge a lot of batteries overnight or have some type of hybrid approach. If you had a similar situation, I would be interested in your approach.

I realize my house is too big, so just getting that comment out of the way I am trying to find a way to tame my power bill before I retire in a few years.

60HzShuffle said:

Hi - first post here. I have been watching Will's YouTube videos for months. I just moved into a new to me home. The electrical utility is different and has quite expensive summer rates. I think my power needs greatly outweigh my ability to have enough panels or batteries to cover my total needs. Peak usage each day is in the afternoons when it is the hottest (I live in the Atlanta, GA area). I also have an EV that I charge between 2 and 4am. I have some days that I exceed 200 kWh and used 6900 kWh last month. Part of my problem is a pool pump that isn't efficient and I'm sure the house could be insulated a lot better. Three 4 ton heat pumps and an electric water heater to boot.

My summer rates are over 0.14 per kwH over 1000 kWh. If I had an "EV plan", it would be .02 per kWh to use power between 11pm and 7am. Not sure what the next step would be as I need to charge a lot of batteries overnight or have some type of hybrid approach. If you had a similar situation, I would be interested in your approach.

I realize my house is too big, so just getting that comment out of the way I am trying to find a way to tame my power bill before I retire in a few years.

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Just to put it into perspective, that rate would be heaven to have here in California.

If you have access to significant amounts of city water, one possibility to reduce the demand is to use water evaporation on the roof to keep the heat from coming into the house in the first place. You can probably cut your air conditioning demand by 50% using this method.

As you noted, electricity pricing is very time dependent, and it is common for power to cost 2 - 3x more during the peak temperatures of the day. (nominal 4 - 7 pm. in the summer )

Go outside during this part of the day and look at how the sun is hitting the outside walls and portions of your roof at this time of day. That is where you will want to install solar panels - so they are off setting the peak demand power.

Gotcha, I am probably going ground mount at some point. I am thinking i can do 20 panels off the back of that face South to Southwest with decent sunlight for 6 to 8 hours a day. My thought was to install solar and a battery system to operate lights, appliances (and maybe the water heater) while leaving the HVAC, EV charger and other high loads on the "grid panel". Seems like cons to everything as I would like to have an option for emergency power too.

Yeah, we're 50.5c/kWh here haha. If you can get on an EV plan at 0.02/kWh, and that's not something that expires soon, my 2c (pun intended?) is skip the solar, get as many batteries as you can afford, charge them during those hours and use them to power the home the rest of the day.

I'll also say on the pool pump, we got a variable speed, if you set it up right, it uses less than half the electricity, pays itself off quicker than most other "efficiency investments"

IMO, there is not a lot you can do energy efficiency wise to bring your bill down. Enjoy the home.

60HzShuffle said:

leaving the HVAC, EV charger and other high loads on the "grid panel"

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For my house this is 80% of the loads. These are comfort loads that are non-negotiable, as in kWh usage is not going down. I will still drive to work and get groceries, I will still keep the house at 78. I do recommend you get something to track usage off each circuit breaker like an Emporia Vue, and gather data.

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I hear its best to be energy efficient before going solar, but this is harder than I thought.

I'm finding a lot of stuff is you need to buy to find how much you'll save. There's some things I can control and my family still hasn't forgiven me for saving 20% on my electric bill by one summer putting the AC at 80 instead of 78.

I peak at about 160 kWh in a day with a 4 ton and 5 ton AC. Mini-Spits are not an option for me because needing central air, but I can go with a high SEER 20.5 inverter Air Conditioner, but finding out how much that will save me energy wise is difficult. Based off SEER ratings, I think I would save $500 a year off it, which replacing two units would take decades to recover the money.

I hear about roof insulation, but for those who've done it can't quantify to me how much they've saved. They just don't keep track of the data. I'm not ready to dump money into something that I'm not how much it will save me.

Someone told me he saved half on his electric bill by changing windows, but he actually had just moved in and in the first hot month of they year, switched them, so I don't know what he saved half from.

I did get a thermal camera, but this hasn't told me anything I can use about my house. I see things like when I shut the curtains less cold air escapes. I saw that the thing like the part of the window that most of the heat leaves from is the metal frame. I also saw I seem to have pretty good insulation in my house, but I'm losing a bit of cold air through the wooden rafters that are vertical through the walls.

60HzShuffle said:

nd used 6900 kWh last month. Part of my problem is a pool pump that isn't efficient and I'm sure the house could be insulated a lot better. Three 4 ton heat pumps and an electric water heater to boot.

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OK so before focussing on the supply side, some work done on the demand side will help.

Proper insulation, draft proofing and window treatment (e.g. external shading, double glaze, blind/curtains) will make a big difference to the thermal performance of the home and can cut cooling energy demand significantly. This will likely be your biggest energy demand item and so should be a priority.

The pool pump can be replaced with a variable speed model - they are way more efficient. And pool pumps can be programmed to run when power is cheapest. My VS pool pump uses about 25-30% of the energy my old single speed pump did. And running it at the time of cheapest energy (which nowadays is when solar PV is generating) resulted in pool pump energy costs falling to 15% of what it was when we moved here.

Electric water heating also has options.

If the water heater is old / nearing end of life then consider swapping it out for a heat pump water heater. they will use ~ 1/4 of the electrical energy of a regular electric water heater. There may even be incentives where you for doing so.

Much like the pool pump water heater operation can be timed to run when power supply is cheapest (be it from your own solar PV or from off-peak energy). The basic principle is to have a tank large enough to be heated once a day when energy is cheap so that it can supply hot water for the rest of the day. Hot water tanks are cleverly simple - the water naturally stratifies into hot on top, cold down low with very little mixing in between, which is why you can heat it over a matter of hours once a day while still have hot water supply 24 hours a day.

My own tank (315 litre resistive element) uses a PV diverter which cleverly diverts whatever excess PV generation there is to the water heater's resistive element. We also heat it at super off-peak times if the solar PV is insufficient. Our water heater operational cost is now about A$30/year (about US$20/year).

Pool pumps and water heaters do also have the option of having dedicated off-grid PV but to me it's better to have PV capacity available for any demand rather than be confined to one job.

But on the supply side:
Keep in mind that getting to zero grid draw is not necessary with your own system. The idea is to use it to reduce your energy supply costs but in a cost effective manner. Often the first half of the reduction in grid energy draw can be done fairly easily and relatively cost effectively but it gets harder and less cost effective to close the gap to 100% self sufficient. This is why reducing demand to begin with is so helpful. But for sure consider options that make sense in you area - that will vary by location. Here grid-tied PV is cheap, easy and encouraged but that's not the case everywhere.

Of course if you have the option do some energy supply shopping. It's different everywhere - we have several dozens retailers and hundreds of plans options (it's actually quite complicated!). You mentioned possibility of having access to cheap energy periods because you have an EV. We have that too, we get free energy 2 hours a day 12-2PM, so I load up the EV, off-grid home battery and if needed the water heater plus that's when the dishwasher and clothes washing get done.

Good luck with it. While our consumption is not at your levels, this is how our grid imports have tracked over the years:

I have a very similar profile for our primary residence (177kwh/day). 4 and 5 ton central AC, pool pump (36kwh/day), EV, entire house is electric. We can’t grid tie so offgrid it is and no way I can cover all power usage. Finished putting most of our cabin offgrid so now starting home with what I learned.

Currently getting my critical load panel installed which has been a PITA but found a way forward. I’m moving all electric outlets, lights, pool pump for now to the panel. An 8kw inverter, 30kw battery and ground mount should manage the peaks based on a year of Emporia Vue data. Outside of summer months pool pump run time is reduced to coincide with less solar production. Will run this way for a while and see what, if anything I can move off next. The best part is a good amount of my home will be available if grid is down so taking it as a win, pool pump I need to figure out how to auto shut down with out grid so it doesn’t use battery but think a good inverter can do this like a Solark or even Midnite The One with its multi purpose.

60HzShuffle said:

My summer rates are over 0.14 per kwH over 1000 kWh. If I had an "EV plan", it would be .02 per kWh to use power between 11pm and 7am.

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GEORGIA POWER TIME OF USE – OVERNIGHT ADVANTAGE SCHEDULE: “TOU-OA-13”
Basic Service Charge......................................................................................................$0.4603 per day
Energy Charges:
On-Peak kWh................................................................................................................ 28.6083¢ per kWh
Off-Peak kWh.................................................................................................................. 9.7663¢ per kWh
Super Off-Peak kWh....................................................................................................... 2.0996¢ per kWh
Minimum Monthly Bill: Basic Service Charge plus Environmental Compliance Cost Recovery,
plus Demand Side Management Residential Schedule, plus Municipal Franchise Fee.

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You will get hit with 28c between 2-7pm on-peak when you need air con. You need to do financial cost/benefit analysis of grid-tie vs. offgrid battery system. I suspect regular grid-tie would make best sense.

AntronX said:

You will get hit with 28c between 2-7pm on-peak when you need air con. You need to do financial cost/benefit analysis of grid-tie vs. offgrid battery system. I suspect regular grid-tie would make best sense.

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Agree with analysis before choosing. Even getting a week of hour by hour usage would be helpful to decide. If PoCo doesn’t provide that detail get an energy monitor.

200KWHR of battery is ~$50K, spend a fraction of that first on measuring and controlling your load, and increasing your efficiency and insulation.

Using EG4 powerpro batteries, cost is about $257 per kWh. Saving 7 cents a day per kWh, that is about 7 year payback assuming you get the benefit of the tax credit. Savings during summer peak rates pays for inverter and installation.

You don't need all 200kWh since some of that goes into the EV and consumed at night.

Start with 84 kWh (6 batteries) and increase as needed. I would plan for space for 10 batteries. Consider 3 growatt sph 10000tl-hu-us for the inverter.

Unfortunately, GA Power does not have a concept of different rates at night. From June 1 through Sept 30th, you are 14.2 cents after 1000 kWh regardless (unless on that "EV" plan). Outside of that time period is is 7.something cents per kWh. So now that I am typing it out, grid-tie really may make the most sense. I will get the biggest output from panels when my power bills are the greatest, in the summer months and offset the costs sooner. The panel for the pool equipment is right off the meter, so that one is a bit tricky to "offgrid" anyway but doable. That said, I will not have an emergency backup until I start putting in batteries.

AntronX said:

You will get hit with 28c between 2-7pm on-peak when you need air con. You need to do financial cost/benefit analysis of grid-tie vs. offgrid battery system. I suspect regular grid-tie would make best sense.

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This is interesting too. That looks like $20k in batteries plus the inverters and installation. I guess that would be two batteries feeding each inverter? I have two electrical panels with 200 amp service (400 amp total) coming into each, so how would that feed each panel??

DIYrich said:

Using EG4 powerpro batteries, cost is about $257 per kWh. Saving 7 cents a day per kWh, that is about 7 year payback assuming you get the benefit of the tax credit. Savings during summer peak rates pays for inverter and installation.

You don't need all 200kWh since some of that goes into the EV and consumed at night.

Start with 84 kWh (6 batteries) and increase as needed. I would plan for space for 10 batteries. Consider 3 growatt sph 10000tl-hu-us for the inverter.

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You could pit one inverter between the meter and Main panel for each, or parallel two inverters that would feed both main panels (before the split from the meter).