Solar panels and my electricity bill

[john welsford]

I moved into my new to me house a few days before the shortest day, and we're now a month or so past the longest day of the year. Yes I live in the southern hemisphere.
The house was already fitted out with a rack of solar panels on the roof, about 4000 watts I think, grid tied through a fancy controller that prioritises feeding current to the house, and directs surplus to the grid, while drawing current from the grid when needed.
No storage battery.

I dont need to touch anything, its got its own little brain which manages it all.

The house has an "Infiniti" gas water system, heats on demand, no hot water cylinder, just a pair of 45 kg gas cylinders and a magic box that fires up when I turn the hot tap on so thats a saving on electricity in itself. Yes the gas has to be paid for but the system is much cheaper to run than an electric one.

So hows it performing? Bear in mind that although I live alone I have a big workshop that is so gloomy even in daytime that it needs electric light, and that I have a heap of power tools and machinery that runs on sparks.

My first bill, with my heatpump running full time, 24/7 during the winter, was around US$70 for the month. Now, during summer, I get a credit of maybe US$25 for the month.
We have a standard charge for the use of the "lines", here thats about US$25 a month, so the charge is smaller than the bill suggests, and the credits bigger.

I'm very pleased with it, I've a friend, also lives alone, no workshop to feed, who's winter power bills are in the region of US$175 a month in spite of heating with a woodstove, and in summer his bills are around US$120.

I figure that my system, including the deduction for the cost of the water heating gas is saving me around $1400 a year.
On a small income, thats very significant.

John Welsford

[gypsie]

See also the thread on induction stove tops.

Bills down, greenhouse gases down. Win win win.
Well done!

[JayInOz]

Sky lights for the workshop JW. That and white paint. Just make sure you put the skylight over a bench or whatever and not right where you'll be standing, although it probably doesn't get hot enough down there for it to be a real issue. We had a drenching race in our shearing shed that held over a hundred grown sheep. The row of skylights above it was a blessing- except in the middle of a stinking hot day when the sun was overhead My sister ordered forty six solar panels for the roof of her new house- already has a bunch on her big shed and another array for the bore pump. Off grid so lots of battery storage and a big inverter. She has two enormous rain water tanks filling off the shed and has ordered two more for the house- the roof is going to be huge. One tank- fifty thousand litre poly- will be delivered ready to go. The other steel tank- two hundred and fifteen thousand litres- will be built on site. I suggested a diving board and jet ski for that one but she only buys practical stuff JayInOz

[LeeG]

When my son in law built his 30’x40’ shop he put clear plastic corrugated panels along the top 18” of the 40’ walls under the eaves. It really helps with lighting.

[skuthorp]

With our solar panels, wood heating, pumped water (biggest expense) and a big workshop/studio our total power bill for last year was A$147.00.

[lupussonic]

I thought you were a millionaire boat designer John.

[JayInOz]

Great designer, crappy businessman. Give him a sob story and he'll give you whatever you want

[Canoez]

We have about 7 kW of panels on the roof that generate far more electricity than we use. With the addition of a heat pump hot water heater about two weeks ago that replaced an oil-fired tank unit, the only thing that burns fuel in the house is the oil-fired furnace which only kicks in below 30°F. Very happy with the solar and the decision to lean electric.

[skuthorp]

103F on my verandah today, solar panels working overtime.

[bluedog225]

I finally put lights in my off grid shop, 200 amp hour 12 volt LiFePO4, 15 socket bistro light string with 100 watt equivalent 12 volt led edison lights. 90 watts draw. About 25 hours of lighting if I take up meth. A couple of panels and charge controller on the way.

Now I can work in the evenings. Should have done this. Years ago.

49095959-D82E-4628-A51C-A3C9182D0CA4.jpg

[john welsford]

Sky lights for the workshop JW. That and white paint. Just make sure you put the skylight over a bench or whatever and not right where you'll be standing, although it probably doesn't get hot enough down there for it to be a real issue. We had a drenching race in our shearing shed that held over a hundred grown sheep. The row of skylights above it was a blessing- except in the middle of a stinking hot day when the sun was overhead My sister ordered forty six solar panels for the roof of her new house- already has a bunch on her big shed and another array for the bore pump. Off grid so lots of battery storage and a big inverter. She has two enormous rain water tanks filling off the shed and has ordered two more for the house- the roof is going to be huge. One tank- fifty thousand litre poly- will be delivered ready to go. The other steel tank- two hundred and fifteen thousand litres- will be built on site. I suggested a diving board and jet ski for that one but she only buys practical stuff JayInOz

I've two new windows under construction Jay, one for each end wall, and plan to replace every fourth sheet of roofing with clearlite with a panel of perspex under it to prevent condensation.
I'll get there.

John Welsford

[john welsford]

I thought you were a millionaire boat designer John.

Hah! There is an old saying that applies here, "If you want to make a small fortune as a boat designer, start with a large fortune and keep at it"

More honestly, I had a visitor in from Tasmania today, and he was a real pleasure to meet in person. Its interactions, and people like that, that are the real "payment" for all the work that goes into those drawings. If it were just a few bucks here and there, I'd just go sailing.

John Welsford

[Stiletto]

John, have you worked out what it would have cost you to have the panels installed had they not been on the building when you bought it?

The reason I ask is that when I looked at installing solar some years ago, I found it would take around eight years to break even on the basis of my usage at the time. In every case where fitting a solar array seemed to stack up financially, there was a state or government subsidy.
This was not available in NZ.

I realise that in recent years the cost of solar panels has decreased. Your figures are impressive. Maybe it's time I looked into it again.

[Hugh MacD]

Sounds great, John! I'm hoping to add solar over the next few years, but right now we're doing "Phase II" of the house remodel that we started ten years ago. I just hope I live long enough to go to "Phase III" for the solar panels

[Canoez]

John, have you worked out what it would have cost you to have the panels installed had they not been on the building when you bought it?

The reason I ask is that when I looked at installing solar some years ago, I found it would take around eight years to break even on the basis of my usage at the time. In every case where fitting a solar array seemed to stack up financially, there was a state or government subsidy.
This was not available in NZ.

I realise that in recent years the cost of solar panels has decreased. Your figures are impressive. Maybe it's time I looked into it again.

If there aren’t government subsidies for the panels themselves, does your utility pay for excess generation, or is there any sort of credit for “green” electricity?

Here, we have both state and federal incentives - some are “instant” others come off annual tax filings. We also get credits - SREC’s - for every megawatt of renewable energy generation. It is cash, but varies and is taxable income.

Still, probably worth another look. About 3 or 4 years after we installed our system, a friend had a larger system installed. The cost was about 25% less than our install.

[Jfitzger]

John, have you worked out what it would have cost you to have the panels installed had they not been on the building when you bought it?

The reason I ask is that when I looked at installing solar some years ago, I found it would take around eight years to break even on the basis of my usage at the time. In every case where fitting a solar array seemed to stack up financially, there was a state or government subsidy.
This was not available in NZ.

I realise that in recent years the cost of solar panels has decreased. Your figures are impressive. Maybe it's time I looked into it again.

Considering solar panels are supposed to last 25-30 years I don't see a problem with an eight year payback.

In all likelihood your payback time would be far less. NZ might be different but in the US you can expect your house value to increase by around half of the solar system cost up to around $10,000.

[john welsford]

John, have you worked out what it would have cost you to have the panels installed had they not been on the building when you bought it?

The reason I ask is that when I looked at installing solar some years ago, I found it would take around eight years to break even on the basis of my usage at the time. In every case where fitting a solar array seemed to stack up financially, there was a state or government subsidy.
This was not available in NZ.

I realise that in recent years the cost of solar panels has decreased. Your figures are impressive. Maybe it's time I looked into it again.

I've not done that, but in my RV I have replaced the single 120w panel with two 150s plus put in a later model charge controller, as well as a fridge that is much less of an energy hog than the old one and have never had to hook up to the power since then. Its a very effective system.
I did talk to the company that installed my house system and they told me that in the time since it was installed, only four years back, the price of the panels and controller has dropped by about 25%. Labour cost is higher, but the hardware continues to get cheaper.
These guys supplied the racks, did the fitting to the roof, wired everything including the hookup to the grid and all the programming. They seem pretty good people.

John Welsford

[skuthorp]

The State government provides low interest loans payable over 5 years. The savings on power bills means, in effect, we'll pay it off in well under 3.

[Too Little Time]

I figure that my system, including the deduction for the cost of the water heating gas is saving me around $1400 a year.
On a small income, thats very significant.

I did talk to the company that installed my house system and they told me that in the time since it was installed, only four years back, the price of the panels and controller has dropped by about 25%. Labour cost is higher, but the hardware continues to get cheaper.
These guys supplied the racks, did the fitting to the roof, wired everything including the hookup to the grid and all the programming. They seem pretty good people.

You sound like the salesman not the purchaser.

The fact that you save $1400/year is only important if the cost of money to install the system is somehow related to it.

For me the cost of money is 10%/year. For me to say your system saved any money, the installed system would have to cost less the $14K ($1400/10%). And that does not include the benefit of having the installation money invested where it is liquid and easily converted to cash rather than mounted on my roof and depreciating.

My power bill is about $1400/year - about the same as yours. Expending some effort to look up the cost places the cost for parts above the $14K. So solar is a money loser. At least for me. And that is without storage for charging an EV at night.

[Chip-skiff]

Money is sacred? Clean air is not.

You sound like a lobbyist for the coal industry.

[Canoez]

Having a solar system has been one of the better choices we've made.

It has eliminated our expenses for electricity completely.

We get income from the generation under a state program. Payback was a little over 5 years.

Because we coordinated necessary replacements of household heating and cooling equipment, we have also significantly reduced our annual oil consumption and the associated bill. With changes in the price of oil, that has been a significant savings. We are also happy just to be using less carbon-based fuel.

With the changes in fees, delivery charges and the price rises per kilowatt hour trending upwards it continues to look like a wise decision.

It has been a win-win situation.

[Too Little Time]

Money is sacred? Clean air is not.

You sound like a lobbyist for the coal industry.

While I find it cheaper to buy my electric power from a business that sells power, that business may find solar or wind to be cheaper than coal or gas.

[Dan McCosh]

This house has had a solar-powered heating system since it was built 100 years ago. Doesn't seem to work very well when you don't see the sun for weeks at a time, or at night. Also a problem in the afternoon of a hot day in the summer.

[JayInOz]

We get calls all the time from companies trying to persuade us to buy solar from them. We have resisted thus far for two reasons. First, the old corrugated iron roof on the house will have to be replaced in the next few years- not going to pay somebody to install solar then pull it down and reinstall it. Second, if we go solar we will need battery storage as we would prefer to go off grid. Our biggest power consumer is the submersible bore pump- which has been running for several hours a day during the hot weather lately. Water supplies to our house and garden both run off electric pumps. We also run two fridges, two freezers, electric hot water and an air conditioner. I have a bunch of power tools including two welders which do a lot of work. An ordinary solar power "kit" wouldn't cut it. Our electricity bill at present though is just a tad under two and a half grand a year, and it goes up all the time. It's a big hit on old fart income. JayInOz

[AnalogKid]

At the moment, while it's not raining and sun is actually shining for most of the day, we're finding the amount of solar gain through our roof is too much. The loft space was recently re-insulated, but it still makes the house insufferably hot during the evenings.

I'd be interested to know if solar panels would reduce the amount of heat energy getting stored in the concrete roof tiles. I'd be more keen to find out if I thought would could generate useful amounts of power, but our ridgeline runs north/south, so it would be very hard to get the panels to tilt at the optimum angle to the north without lots of ugly (and storm-vulnerable) framework sitting on the roof.

[JayInOz]

You can build a frame anywhere that suits to mount your panels on. I managed a vineyard for years and my absentee boss was in charge of "worlds best practice" with BP Solar. We had a huge array of panels- all models manufactured by BP and from every other manufacturer selling in Australia. Information from each panel was downloaded constantly and sent to Sydney for analysis. The steel frame the panels were mounted on was placed in an exposed site where it wouldn't be in the way of regular vineyard work but close enough for easy access. It was also high enough to be easily able to get underneath for weed control. By the way, all the power generated went into a couple of huge heat sinks which were cooled by electric fans. And at the same time we paid for electricity from the power company to run stuff on the vineyard JayInOz

[AnalogKid]

Nice idea, but we're talking suburbia here, not an expansive vineyard. There's no location off the roof that wouldn't get deeply shaded for a significant part of the day by trees or the house itself.

[skuthorp]

Our panels are on the big workshop roof adjacent to the house. The place we will move to was bought with solar suitability as part of the criteria about 8 years ago. Likely we will have access to a community battery there as well.

[hawkeye54]

At the moment, while it's not raining and sun is actually shining for most of the day, we're finding the amount of solar gain through our roof is too much. The loft space was recently re-insulated, but it still makes the house insufferably hot during the evenings.

I'd be interested to know if solar panels would reduce the amount of heat energy getting stored in the concrete roof tiles. I'd be more keen to find out if I thought would could generate useful amounts of power, but our ridgeline runs north/south, so it would be very hard to get the panels to tilt at the optimum angle to the north without lots of ugly (and storm-vulnerable) framework sitting on the roof.

How do you heat your domestic hot water ? Would solar hot water panels absorb some of that heat and also reduce your utility cost ?

When I bought this house in 2009 ( South Carolina ) the garage ceiling was uninsulated, and the garage would get close to 100° F in the summer. I insulated the ceiling to R38 and it is now bearable



Rick.

[RFNK]

I've two new windows under construction Jay, one for each end wall, and plan to replace every fourth sheet of roofing with clearlite with a panel of perspex under it to prevent condensation.
I'll get there.

John Welsford

I have 6 sheets of clearish polycarbonate to keep the shed fairly bright. There's never any condensation. Are you sure you need a layer underneath for that?

[RFNK]

At the moment, while it's not raining and sun is actually shining for most of the day, we're finding the amount of solar gain through our roof is too much. The loft space was recently re-insulated, but it still makes the house insufferably hot during the evenings.

I'd be interested to know if solar panels would reduce the amount of heat energy getting stored in the concrete roof tiles. I'd be more keen to find out if I thought would could generate useful amounts of power, but our ridgeline runs north/south, so it would be very hard to get the panels to tilt at the optimum angle to the north without lots of ugly (and storm-vulnerable) framework sitting on the roof.

There's no doubt about it. An extra layer above any roof will reduce the heat of the roof enormously. Solar panels should always be installed to allow airflow under them so if you cover much of your roof with panels, you'll greatly reduce the heat absorbed by your roof and, therefore, the amount radiating from it at night. The only downside would be that you won't have the warmer roof radiating heat in winter.

As far as optimal tilting goes, I wouldn't worry much about that. Find a balance between efficiency and aesthetics and you'll be happy. You might lose a bit of power by not having the perfect orientation so just put in a couple of extra panels to make up for the loss. Plenty of people have panels facing east or west and they still work well.

[john welsford]

I have 6 sheets of clearish polycarbonate to keep the shed fairly bright. There's never any condensation. Are you sure you need a layer underneath for that?

Its been a problem in two of the several places I've worked in that had that arrangement, so as its easier to do when I'm doing the other part of the job, I'll do that.


John Welsford

[Chip-skiff]

How do you heat your domestic hot water ? Would solar hot water panels absorb some of that heat and also reduce your utility cost?

Evacuated tube solar water heaters are really effective where there's enough sun. For hot water at night, you'd need an insulated storage tank and demand or point-of-use boost heaters.

I insulated the ceiling to R38 and it is now bearable.

Guessing you left out the decimal point. R 3.8?