Question The electric home questions

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I am undecided regarding installing rooftop solar on my house. However, I will remove my last two appliances that consume natural gas (water heaters and HVAC) when they need to be replaced. My circuit breaker box already has the maximum number of circuits attached, and it does not have an automatic disconnect from the outside lines which would be required for a solar/Powerwall installation. I assume that the existing circuit for the air conditioners would be adequate to provide power to a heat pump or electric furnace, but a new line would need to be installed for an on-demand electric water heater.



Any advice as to how to proceed with breaker box upgrade if I changed out the box/appliances first and then installed the solar system later? I want to avoid upgrading the box only to need to swap it out for a new box with a solar installation.
 

SR22pilot

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I think you are confusing several things. The disconnect goes outside the house and disconnects the solar so lines aren’t live from the solar. The panel inside is a different thing. I had a separate inside panel installed as part of my solar installation but could have avoided it. However, it gave me the space to wire the heat pumps and hot water which I did later. The gas company even removed the meter when I disconnected.
 
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I left out one important fact: my line to the utility pole is maxed out too. To add a current-hungry appliance like an on-demand electric water heater, I have been told that the utility company will need to come out and provide a higher amp connection between the utility pole and the house. I was planning to have the disconnect installed at that time. I don't know if municipal code would allow me to avoid a utility line upgrade if solar+battery storage capacity could reliably cover the expected deficit.



Also, I already have two circuit breaker boxes installed. The second was added when I installed EVSE for our electric cars.
 

JasonF

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I don't know if municipal code would allow me to avoid a utility line upgrade if solar+battery storage capacity could reliably cover the expected deficit.

It absolutely will not, and it shouldn’t. The one thing that will kill your solar panels and inverter is a huge surge like a single 30 kilowatt load suddenly switching on.

A secret I found out from several plumbers on Youtube is that unless you’re a commercial installation with 3 phase power, you will probably never save enough energy to recover the cost of installing an electric on-demand water heater. They use somewhere between 20 and 30 kilowatts (not watts) to operate. That’s like charging 4 Teslas at once, or running two extra air conditioners. The small “savings” you get is from it not running to keep water hot in a tank, but as it turns out, tank water heaters are actually pretty good at being efficient at doing just that. They also tend to require more maintenance than a tank - you have to have scale cleaned out and the seals checked yearly, or it will grenade itself. Tanks you can pretty much ignore for 15 or 20 years and they’ll be fine.

I would just get a regular tank water heater - and if you want to save a little more, get one with a heat pump that will suck some of the heat from around it (a hybrid one is even better, so it can save some energy but also keep up with demand). That would be 8 to 10 kw for standard electric, or 1 to 2 kw for heat pump, and either would fit into a 240 volt 30 amp circuit breaker, and neither will kill your solar system or inverter.

As for the furnace, if you already have air conditioning, a heat pump will simply replace it completely, and require no extra circuits. It’s just an air conditioner with a reverse cycle.

And on the box upgrade...if you stick with a tank water heater and heat pump, you probably don’t need a box upgrade. If it comes with the solar installation or is cheaper to do while the electrician is there anyway, go for it. However, remember that replacing that box doesn’t give you more amp capacity, it just gives you more physical space for circuits. If you’re already up against the limits of the mains feed, you might have to upgrade it next time you add something - but that will be significantly cheaper if you already have the box upgraded.
 

Ed Woodrick

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I left out one important fact: my line to the utility pole is maxed out too. To add a current-hungry appliance like an on-demand electric water heater, I have been told that the utility company will need to come out and provide a higher amp connection between the utility pole and the house. I was planning to have the disconnect installed at that time. I don't know if municipal code would allow me to avoid a utility line upgrade if solar+battery storage capacity could reliably cover the expected deficit.



Also, I already have two circuit breaker boxes installed. The second was added when I installed EVSE for our electric cars.
You made the options pretty easy with that statement. If you don't have the capacity, you will need to increase the size of your service, which may or may not be possible and may have a significant cost of implementation.

It is part of a home's design when the electrical system is specified. If there is gas service to the house and an area commonly uses gas, then those services are installed as gas and the electrical system not sized to handle the service. Some areas, East Tennessee with TVA as the provider was commonly designed as an All-Electric area and all services on a home made electric. But as electricity prices increased, many new homes in the area are now being built with gas and electric, not requiring as large of an electrical service as an all electric house.

There are services that I DON'T want to be electric, stove tops and dryers are some. My generator is definitely not supplied with electricity.

Also, having gas and electricity can help being redundant, since electricity is significantly less reliable than gas.

In short, going fully electric may be expensive for some homes, and isn't always the most comfortable solution. And don't assume that solar or batteries will run your air conditioner (or heat) or charge an EV.
 

msjulie

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Warning kinda long post

Here's more personal anecdotal experience - we just finished renovating a house and the remaining gas bits are the stove top (preference for some cooking) and gas fireplaces - ornamental mostly though they can provide a quick local temp bump.

The gas hot water heater is gone, the gas hot air furnace is gone, the gas clothes dryer is gone. Basically I'm not a fan of natural gas (or whatever it's current propagandized name is today) and was trying to get rid of it all together. Can't dissuade the chef in the house that gas cooking isn't the best so compromise was required.


We have fairly large solar install and 2 batteries (luckily all purchased/gone live winter 2018 for max tax break).
Hot water heater : Rheem hybrid https://www.rheem.com/innovations/innovation_residential/hybridsavings/
Stackable all electric washer/dryer (full size): LG
Heat/AC: https://daikincomfort.com 5 inside units (that's a lot actually) and 1 main outside unit
One Tesla Model 3 that charges from a nema 14/50 outlet in the garage off-peak (if it ever drives anywhere these days)

To be fair, the climate here has fairly narrow temp range, mid 40s to low 90s at the extreme and good breezes and it's mostly just 2 people and some dogs but also a home office which is a real power hog (many spinning drive enclosures, too many computers).

Electric service was upgraded to allow for 2 nema 14/50 outlets in the garage as the plan is the other car will someday be full electric.

This was a long term plan, the warranty on the inverters is 25 years, solar panels something like that as well. We have 1 year of living with this setup and it's all Covid stay-at-home so less car charging but 99% occupancy with computers running, etc

So far our first PG&E true-up is -$362 meaning even with an all electric house we still produce more than we use. As mentioned, it's a bigger system but it was important that we come as close to breaking even as possible with power use as I am a greenie. But equally important is the area is known for PG&E brown outs as well as just frequent downtime and the batteries are set up to drive important lights, the internet equipment :), the office and the refrigerator so we can in theory last a bit that way, not dependent on flashlights etc

The folks that installed the solar installed the inverter such that load shift is automatic (if PG&E is down, batteries come on < 2 seconds). The issue for your electrical box is not just breaker availability as there are options there https://www.thespruce.com/tandem-breakers-vs-double-pole-breakers-1152748 but the total load on the system; there are calculations based on every active circuit being used at the same time. Prior, we would exceed system limit if we ran everything and charged the car at the same time but that never happened and we did upgrade the service surprisingly not as pricey as we feared.

So that's a lot to read sorry, but if the budget can handle it I'm all for as much solar (and batteries) that you can feel comfortable with as it's both a good environmental move but I also honestly believe the stability of the grid isn't necessarily going to get better anytime soon around here, and perhaps worse?


cheers
 
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Thanks to all. Very valid points.



My household already does well with electric glass top stove. Regardless of going "zero-emissions”, nothing could be easier to clean. A razor blade and Bar Keepers Friend can quickly clean even the biggest mess. We swapped out the range that came with the house when we had small children.



The grid in Houston is reliable, and the price of electricity is relatively low. Our "free between 8pm and 6am" electricity plan along with charging cars/running dishwashers after hours brings down the average rate even more.



We have three electric cars, but only a single NEMA 14-50: we use it for whichever car needs to charge the quickest. Otherwise, charging off 110V/12 amps provides about 50 miles of range overnight. I drive about 500 miles per week, but only about once per week do I need to bring my long-range model 3 back up to 90% with the NEMA 14-50.



I will probably talk to an electrician about running a new line to provide power to tank electric water heaters so it will be ready when we replace the current gas ones (likely in less than 5 years). Once this is in place, it should streamline solar installation whenever that happens.
 

SR22pilot

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In my previous house I had a top end gas range. It was very expensive and looked like something in a professional kitchen. In my current house, I replaced a so so gas range with a Bosh induction. I much prefer the induction. It boils water much faster. It has great simmer control. It is very easy to clean. It is very energy efficient.

I converted a gas water heater (45) to a Rheem heat pump unit (81 gallon). Based on the yellow stickers on the side, the new unit costs about a quarter of what the gas unit costs to run. It was not cheap but it was the last thing on gas.

Even in the summer I would have a $45 or so bill for gas. Usage would be about $9 and the rest base fees. I love being off of gas. Yeah, I can’t use the gas logs in the fireplace but I hadn’t used it anyway.
 
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jlquinn

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I hope it makes sense to continue this thread rather than start a new one.

I just installed solar and powerwall - the system isn't even operational yet. But I've also been thinking about the other source of carbon generation in my home, an oil hydronic system.

I'm lower NY so winter is an issue (though not as bad as VT). I have oil boiler, indirect water heater, hot water high temperature baseboard, as well as AC in the upper floor only. As far as I can tell, there are no decent options to reuse the existing heat distribution system with heat-pump based heat production. It seems that heat pumps, whether A2W or W2W, only output low temp (120F), which isn't enough to drive existing radiators. And the AC ducts are only in the attic.

The best option today looks like mini-split systems, but I think there would need to be a bunch of heads to get warm air distributed well throughout the house.

Is anyone aware of reasonable options for oil boiler system replacements?

Cheers
Jerry
 

JasonF

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jlquinn

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When I've looked at geothermal heat pumps, it seems that they require ductwork to use. I only have high-temperature baseboard radiators.
 

garsh

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When I've looked at geothermal heat pumps, it seems that they require ductwork to use. I only have high-temperature baseboard radiators.
  1. Radiators are really inefficient compared to heat pumps.
  2. Depending on how large your house is, you might be able to get away with installing a couple of ductless mini-split heat pumps instead of a whole-house ducted heat pump.
  3. But I don't think anybody is selling geothermal mini-splits - all mini-splits are air-sourced AFAIK.
 

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