Fairly new to this. Just passed inspection and currently waiting for PTO. I was looking through my past year energy usage and looks like I used about 6,800 kwh annually. Tesla recommended a 5.78 kw system for my house and according to Tesla, this system should produce about 9,600 kwh annually. Is this too much for what I need? I’m thinking I could of gone with a smaller system and still would of been okay?
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Is my solar panel system too big?
- Thread starter Carbonfiber
- Start date
Much of the cost of the system is fixed so reducing size may not reduce the cost that much. Also, summer weather is getting hotter and longer. So the amount of electricity we use for A/C today will likely rise in the future. Additionally, power rates will continue to rise, so the less power you can consume the better.
I agree with @jboy210. It also depends on the rate trends and how much of a hedge against erosion of NEM benefits you want. Are you with SCE? The economic benefit of overproducing may not be much but the ability to service future needs may be priceless. My next conservation investment will be replacing my natural gas fired furnace with a heat pump that will change my consumption patterns. The A/C portion may become more efficient but the higher winter electric for heat pump will be offset by reduced natural gas consumption.
charlesj
Active Member
If your power company approves this oversize, take it. PG&E would not as they limit to 110% of previous usage.
And, if you have battery backup, it should las mush longer in an outage if weather conditions during outage allows, sun.
And, if you have battery backup, it should las mush longer in an outage if weather conditions during outage allows, sun.
Use the excess to mine bitcoin.
It's Tesla approved.
It's Tesla approved.
Then track your bills and don't worry about generating too much electricity. The rates are going up and the time periods are becoming less favorable.
If your power company approves this oversize, take it. PG&E would not as they limit to 110% of previous usage.
And, if you have battery backup, it should las mush longer in an outage if weather conditions during outage allows, sun.
PG&E approves applications that exceed 110% if you say that you planning on increasing your usage.
A lot of us that charge had a drastic reduction in usage over the last year but plan to go back to the usage from the year before when we start commuting again. That said, I'll probably never commute again and work from home from this point on.
Silicon Desert
Well-Known Member
yes, this ^^^. And to add that over the years, the output from your system will gradually reduce. After 10 ten years, you might see a 8-10 % loss depending on your type and brand of modules.
Uncle Paul
Well-Known Member
Believe that people with excess generation tend to use it. They keep the AC/Heat at more comfortable levels, leave on lights for ambience and tend to obsess less about their electric bills.
If something is "free" people tend to use more of it.
If something is "free" people tend to use more of it.
Electrph
Member
definitely "oversize" .. i went conservative and i'm already going to be ordering another powerwall and more panels moment PTO approved .. much more economical to get all 1st time or "oversize" .. not to mention hassle going thru inspection / another PTO (i assume ?) / possible more strict system size limits from elect utility etc etc
much rather be in your position
much rather be in your position
OP, you are on SCE, you need to produce more than you use to get not get charged too much. The reason is that the solar generation period is during the day until about 4pm and you get paid the lowest rate ($0.26 to $0.27/kWh) by SCE. When you have to use the energy after 4pm (no more solar generation), you have to pay the highest rate ($0.37 to $0.43/kWh) unless you have powerwall or battery.
So you will need to over produce by about twice the energy you needed for evening prime time usage (lights, TVs, electric oven, etc...) from 4pm to 9pm to get the lowest bill possible.
(4pm - 9pm) energy usage x 2 + (rest of the time) energy usage = your solar generation if you want the lowest bill possible.
So you will need to over produce by about twice the energy you needed for evening prime time usage (lights, TVs, electric oven, etc...) from 4pm to 9pm to get the lowest bill possible.
(4pm - 9pm) energy usage x 2 + (rest of the time) energy usage = your solar generation if you want the lowest bill possible.
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I do not have battery or powerwall.
Has anyone been able to generate enough energy to cover the the electricity bill?
Silicon Desert
Well-Known Member
yup, we do that on occasion (more AC, but NOT more heat). Electricity isn't that expensive up here anyway.
Silicon Desert
Well-Known Member
On our other home, we don't as it doesn't make economic sense to do it there. I think you know that it depends on a LOT of variables as to whether or not it makes financial sense to add enough module to cover the cost completely.
currently on tou-c. I have enough panels that I will have a zero true up, and my house is 99% electric, and large.
Our 12.75 kW system will generate between 2-10 kW from 7AM to 6 PM in June. Our house uses approximately 1-8 kWh during those hours. In addition to the solar, we also have Powerwalls that picks up the load when the solar drops to cover the evening and overnight. Our June electric bill dropped from $500 to $50.
I installed solar on a newly purchased home so there was no history. I told the installer what size system I wanted and that I would be charging two EVs. I had already applied for the EV rate so PG&E already had that documentation. I also explained that I was replacing the existing gas fired water heater and installing an electric dryer. I got the system size I wanted but too late I realized that the the DC to AC ratio was 1.5 to 1. I don't know if that was a constraint imposed by PG&E, but the system has performed well with respect to pvwatts model and installer guaranty.
Currently you can't generate enough to cover all your monthly charges as you have to pay about $0.02 to $0.03/kWh for non-bypassable charges. So you will probably pay about $13 to $20 a month even if you over produce. At the end of 12 months, you get a check back for over production at about $0.03/kWh.
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