Debate switching to solar power

[mickri]

When I was living on my sailboat I went solar to keep my batteries charged instead of running the diesel engine on the boat. This was a total off the grid situation. My experience may not be a good comparison to a house. I was in Mexico most of the time and then in San Diego. I did not find that slight shading like the shade from the back stay going across a panel made much if any difference in the amount of power that the panels generated. The biggest problem for an off the grid set up is battery storage. You can never have too much battery storage. The batteries require constant maintenance. Primarily keeping the terminals clean with good connections and keeping the batteries topped off with distilled water. The old standard lead acid batteries are the best bang for the buck.

To get a good estimate on power usage you need to keep track of how much power you use on a daily basis. This is important in determining the size of the battery bank. Then you need to estimate how many days in a row that you won't have sunshine. Multiply the number of days times your daily power usage. Multiply this by 4. Why do you need 4 times your estimated power need. The batteries in an off the grid system will never be at full charge. 80% charge is typically. You also never want to drain your batteries below 50%. Doing so will damage the batteries. A battery bank will not except a charging rate of more than around 25% of the size of the battery bank in amps. Even this will be hard to achieve. For example I had 400 amp hours of battery capacity on my sailboat. I never achieved a charging rate of more than 25 amps per hour and that was with my diesel engine using a 105 amp alternator. The solar panels never produced more than around 15 amps per hour going into the batteries. No matter how may amps you system may be capable of producing the charge controllers will not allow more than the battery bank can accept to be transmitted to the batteries.

This is just the start of what is involved with living with an off the grid system. You will have to change your life style if you go off the grid.

Based upon my experience I would never have an off the grid system in a home. A grid tied system with at most a generator backup IMHO is the way to go.

If at all possible I would not mount the solar panels on the roof. The supports for the panels require lots of holes through the roof. Everyone a potential leak point. Also if your roof and the solar panels are not in sync life span wise, you will have to remove and reinstall the panels to replace the roof. Another cost to factor into the calculations.

I was a real estate appraiser for most of my working career. Although it has been many years since I did that, I was never able to actually measure an increase in value from solar panels. I still follow value trends watching sales in my area and still can't attach a value to solar panels on a home. I think the reason for this is the life span of solar panels. The closer you get to the end of the life span solar panels may even turn into a negative due to the cost to remove and replace the panels.

As has been mentioned above what your utility company is mandated by law in your area to compensate for the power you generate will have have a big impact on the cost effectiveness of a solar system. California requires the utility to give you dollar for dollar credit up to the amount of electricity that you use and pay you at a reduced rate for any excess that you pass onto the grid. Not many states are this pro solar.

 

[mattthemuppet2]

based on your location your monthly bill should be around $80/mth or about $1000/yr. A fairly standard 5kW install (9-10,000kWh per year depending on location etc) seems to be coming in around $3/W give or take after rebates and incentives, which comes to $15,000. If that takes your bill down to zero per month, you'll take around 15 years to make your money back. Payback time shortens with higher electricity costs, higher feed-in tariffs or better net metering rules, more generous Federal (ha!) or state subsidies and rebates and so on.

Our use is similar, from $60 to 150/mth depending on time of year, and our neighbours are always moaning about how miserly our city power company is - net-metering with $0.016/kWh paid for the excess - that it didn't make financial sense. I'd rather spend some of that money on more attic insulation and a more efficient AC, then invest the rest.

 

[MikeInOr]

Every time I try to pencil out a solar electric installation I can never make the economics work. Solar electric installs seem to be more about making a statement than actually saving money or even saving electricity.

A few years ago I inherited a bit of money and looked into a solar electric system. I live in the high desert region of Central Oregon which should be one of the better return on investment areas for solar electric. The pay back time was going to be longer than 10 years... on paper. I am confident my actual milage would vary from the paper esitmate... and NOT in my favor. It just didn't make sense.

Instead I added a centrally located (great room - kitchen, dinning room and living room) high efficiency (Highest efficiency Fuji) mini split AC / heat pump system. Not having natural gas all my heating is electric. The mini-split lowered my electric bill about 20% for summer and winter. I was all excited to get the government and electric company kick back until I found that a mini split is only eligible if I had the system installed by a "qualified contractor". Well the "qualified contractors" best price was $9k to install their 18seer 12000 btu mini split. For get that! Instead I purchased the 26 seer 12000 btu Fuji mini split and installed it my self for just under $2000. I didn't get the tax credits but I still came out way ahead. And quite frankly the two different HVAC guys I talked to didn't impress my at all... i.e. the thought of them butchering my house kept me awake at night. If you are in the mini-split AC buisness should you know atleast as much about mini-splits as your customers?

I absolutely LOVE the mini-split. We are much more comfortable while saving real money and electric power. My central AC hasn't been on since we installed it. My next project will be to install a 3 head mini-split in our 3 bedrooms.

If I ever do install a solar system: 1) I will install it myself. 2) It will almost definitely be a solar hot water system as it will be by far the best bang for buck with the quickest pay back considering I do not have natural gas service.

 

[davidcarmichael]

Net metering is not always dollar for dollar especially if you have a TOU (Time-Of-Use) tariff. It may depend on when you generate the power.
If you have an old roof then often the installer will suggest you replace the roof at the same time. Solar systems generally come with a 25-year warranty and I assume most roofs should last that long.
If you examine your last 5 years of bills and the total is low then the chance that you will benefit from solar is also much lower. However you should never make the mistake of trying to generate all of your usage from solar panels. That is just a waste, especially if you have a tiered electricity tariff where the first few hundred KWh are priced at a low level. You want just enough solar generation to stay in the bottom tier all of the time except for short periods when the weather is very hot and you use a lot of A/C. There definitely is a sweet spot and a good installer will help you find it.
It had not occurred to me that you might not have gas for water and home heating. That does change some of the calculations as using solar power for water heating is a pretty poor choice.

 

[kb58]

On the site I recommended above, some of them are electrical engineers who've installed their own systems. They did a TON of monitoring and computations, finding that solar is a real mixed bag as far is being a net positive. There's cost of the equipment, installation cost (if not done yourself), daily exposure, equipment reliability, degradation over time, electrical pricing tiers, time of use (TOU) policies, etc.

Their strong advice is a bit surprising: consider simply using less power instead of installing solar. This is extremely telling, having people who "been there done that" came to the conclusion it may not be worthwhile.

 

[mickri]

I think that a solar hot water system makes a lot of sense. Especially if the solar panel is lower than the water heater by about 2 feet. As water heats in the panel it will naturally rise up the pipe and into the tank while at the same time sucking cold water from the bottom of the tank. You actually have to be careful because the water will get really hot. So hot that you can get scalded by the water. I used solar to heat water on my sailboat and I had to keep the tank under shade cloth that filtered out most of the sun.

You have to be really careful if you enter into a TOU contract with your utility company. I have read about people having higher electric bills after installing solar with a TOU contract.

 

[BGHansen]

My in-laws put in a 7.5Kw roof top system a year ago. Cost was just over $40K on a 5.99% note (they didn't read the fine print and were surprised by the interest rate). They live in Southern Michigan and without the AC on had a $26 bill last month. But the payment on the loan is something like $220 a month so really haven't seen a benefit yet. They're both about 80 and might not hit the cross-over point during their lifetimes.

Biggest problem is Michigan is about as cloudy as Seattle, so like real estate, think location, location, location. He commented on July 4 that he probably wouldn't do it again. But that's based on our climate. You might get a little more sun in Chicago so it'll pay off.

Bruce

 

[Larry42]

Solar hot water makes a lot of sense. I've traveled a lot and there are large areas of the world that have simple hot water systems, often jury rigged. They require no electrical and very little maintenance. In my climate they would be more complicated due to our low temperatures that get to -20F. As for electric solar, I ran the #s before we bought our house, 19 years ago. A total looser, but things have improved. I live in tornado alley with lots of high winds and hail. Our house is on its 3rd new roof, (4 if your count the first one) several new windows and new siding due to hail. I'd like to know how the solar panels fare with those conditions. How do insurance companies view solar panels? Lots to consider!

 

[kb58]

Oh, and another thing to consider. There are two types of DC-AC converters. One system uses a large single unit, typically near the power meter on the side of the house. The other type uses "micro converters", where one is attached to each panel. The latter type can cause a lot of radio interference, so if you're out in the country such that you count on through-the-air TV, radio, or ham radio, the former may be your only choice.

 

[davidcarmichael]

I think that a solar hot water system makes a lot of sense. Especially if the solar panel is lower than the water heater by about 2 feet. As water heats in the panel it will naturally rise up the pipe and into the tank while at the same time sucking cold water from the bottom of the tank. You actually have to be careful because the water will get really hot. So hot that you can get scalded by the water. I used solar to heat water on my sailboat and I had to keep the tank under shade cloth that filtered out most of the sun.

You have to be really careful if you enter into a TOU contract with your utility company. I have read about people having higher electric bills after installing solar with a TOU contract.

Solar water heating for your home is a non-starter if you have a gas supply and as long as gas is ridiculously cheap. The repayment period would probably be longer than you will live.

We only moved to a TOU electricity contract after we bought a Tesla. TOU makes A LOT of sense when you have an electric car. However pretty much every utility in every state is going to go there eventually whether you like it or not.

So far, thanks to our solar panels we are running 100% off-peak which has reduced our overall electricity per-KWh cost by more than 22%. This is because all of the daytime off-peak is handled by solar, some of the nighttime off-peak is reduced by daytime solar over-production, and all of the (manually limited) on-peak time is covered too. In fact this month we have negative numbers of KWh used on-peak. To give you an example we are likely to buy 550 KWh this month at the off-peak rate (it is hot and we do use A/C) and our solar system is producing a total of about 500+ KWh this month, so our final bill is more than halved.

I agree wholeheartedly with all suggestions about saving energy, within reason. As with all engineering problems there is a sweet spot that you have to find and many building codes expressly prevent you from modifying existing homes to improve efficiency. And don't get me started on home owners associations.