Anyone oversizing their system installation now for a future electric vehicle?

[jflorey2]

So, for those who've installed recently or soon, are any of you oversizing your installation now for future plans (electric vehicle, etc.)?

On our first system, we got approval and a rebate reservation for a 2.1kW system (9 panels) based on our loads. We quickly upgraded that by adding another 3 panels to bring it up to 2.8kW, which maxed out the inverter. It covered all our loads. (no EV)

When we moved to our next house, it came with a 10kW system. We quickly replaced all the incandescents with LED lights, replaced the electric dryer with a gas one and installed programmable thermostats and found ourselves with a large surplus every month. We then bought an EV (a Leaf) and now we are slightly overproducing.

[SolarFamilyGuy]

On our first system, we got approval and a rebate reservation for a 2.1kW system (9 panels) based on our loads. We quickly upgraded that by adding another 3 panels to bring it up to 2.8kW, which maxed out the inverter. It covered all our loads. (no EV)

When we moved to our next house, it came with a 10kW system. We quickly replaced all the incandescents with LED lights, replaced the electric dryer with a gas one and installed programmable thermostats and found ourselves with a large surplus every month. We then bought an EV (a Leaf) and now we are slightly overproducing.

Do you get a lot of sun where you live? Just wondering? In two weeks I am having a 9.8kwh system installed onto my roof only because of the epic incentives that Washington State give out. I figured that my system will recoup my upfront cost in 5-6 years and still have many kw's left over to carry my home through the winter months. In Washington we get diffuse sun and the panels are specifically engineered for this kind of weather and, in theory, produce just as much as the same system in other states. But I will not know until I actually have it up and running. Having a oversized system is actually a good thing for most homes. Even if the incentives were to disappear tomorrow all over the nation, I can still produce more than my house can consume most months of the years. The whole purpose of having solar installed is to be energy independent right?

[jflorey2]

Do you get a lot of sun where you live?

We are in Vista (southern Ca) where we average about 5.5 equivalent hours of sun.

Even if the incentives were to disappear tomorrow all over the nation, I can still produce more than my house can consume most months of the years. The whole purpose of having solar installed is to be energy independent right?

Well, I think the purpose of most people's solar power systems is to reduce their electrical bills. Very few solar power systems allow people to be independent of the grid. For most people that's a large additional cost with a small additional benefit.

[SolarFamilyGuy]

I understand. According to the government map I was looking at yesterday, we up North get 5 hours per day of sun average. It will be interesting to see when it gets installed.

[sensij]

I understand. According to the government map I was looking at yesterday, we up North get 5 hours per day of sun average. It will be interesting to see when it gets installed.

To get a good idea of what your system may produce, I would suggest that you spend some time with PVWatts, especially the documentation. With some basic understanding, you can look for nearby systems on PVOutput.org to see actual production data.

Here is a map of PVO systems near Seattle.

http://www.pvoutput.org/listmap.jsp?sid=31255

[SolarFamilyGuy]

To get a good idea of what your system may produce, I would suggest that you spend some time with PVWatts, especially the documentation. With some basic understanding, you can look for nearby systems on PVOutput.org to see actual production data.

Here is a map of PVO systems near Seattle.
http://www.pvoutput.org/listmap.jsp?sid=31255

I have actually been to that web page. I actually talked with a guy who went with a 9.5 kWh system two miles up the road. He has the same setup as I will get with the same installer. Even on a cloudy overcast day he was producing around 26-30 kWh every hour. If I did my math correct, my home is much smaller than his and sips energy. I have a very strong feeling that I will produce all day every day.

[sensij]

I have actually been to that web page. I actually talked with a guy who went with a 9.5 kWh system two miles up the road. He has the same setup as I will get with the same installer. Even on a cloudy overcast day he was producing around 26-30 kWh every hour. If I did my math correct, my home is much smaller than his and sips energy. I have a very strong feeling that I will produce all day every day.

That sounds overly optimistic. What is your zip code, and what array azimuth/tilt are you planning?

[bcroe]

I actually talked with a guy who went with a 9.5 kWh system two miles up the road. He has the same setup as I will get with the same installer. Even on a cloudy overcast day he was producing around 26-30 kWh every hour. If I did my math correct, my home is much smaller than his and sips energy. I have a very strong feeling that I will produce all day every day.

With really excellent sun, 9.5KW of panels will produce 9.5KWH of energy each hour; with losses delivering
under 9KWH. CERTAINLY NOT 25-35. Now add clouds and output might reduce to the 10% to 50% range,
depending.

As for panels that produce just as much under clouds as not, THEY DON'T. If they did I would be using
them, and somebody would be getting the Nobel Prize for defeating the laws of physics.

Heat your northern house with solar, it can be done. Your house would need to be extremely efficient
to do it on 10 KW of panels. I do it with a lot more panels and a heat pump. Better do some more
numbers to see what is possible; my results were pretty much in line with calculations. Bruce Roe

[Samsolar]

Oversized but not for EV

I needed a ~6kW system and installed an 8.4 kW system.

Doing a self install brought the cost down to just under $1/W installed after rebates ($2/W before), so building larger than I needed was not too hard to justify.

My plans over the next year include a heat pump water heater which will save about 200 gallons of oil per year. Yes, payback on this is getting longer and longer with every penny that oil drops, so I may defer this a bit.

Another change will be to replace a thru wall mounted 1972 vintage air conditioner when it fails (or perhaps sooner). It will be replaced by a mini split which will be much more efficient, much quieter and have the added ability of heating to use up excess kWh in the winter instead of selling back to to my utility at the avoided cost rate. The AC unit is only used 3 or 4 weeks out of the year, so replacing it just to save electricity is a bit tough to justify.

Another consideration was panel degradation. Sizing for 100% of your needs today knowing that 20 years from now you will not produce enough to meet your needs unless you reduce your energy consumption by an amount equal to your panel degradation.

Last but not least, a growing family ensures that my electric usage will be trending upwards despite conservation efforts!

[Alchete]

I have actually been to that web page. I actually talked with a guy who went with a 9.5 kWh system two miles up the road. He has the same setup as I will get with the same installer. Even on a cloudy overcast day he was producing around 26-30 kWh every hour. If I did my math correct, my home is much smaller than his and sips energy. I have a very strong feeling that I will produce all day every day.

I think you mean to say 26-30 kW / day. He'd be producing 9.5kW / hour, at most -- as given by his system rating. Given 4 - 5 hours of sunshine in the north, he'd be producing 30-45kWh / day, roughly speaking.

So, back to my original post, come to find out, my town runs its own utility, and as such, in MA, it sets its own rules. That means that they don't limit the size of the customer's solar install to a percentage of the usage bill, but do cap it at 10kWs. Great!

Unfortunately, in MA, the net metering rules apply differently in towns that have their own public utilities. In my town, I'm getting charged 11c/kWh for electricity and 5c/kWh for delivery = 16c/kWh. For net metering purposes, I'm only reimbursed the 11c/kWh. So, I'd lose 45% right off the top, compared to other towns who have private utilities and who must pay full value for electricity including delivery charges. What a waste. Typical antiquated government bureaucracy.

We have a grand total of SEVEN people in my town with solar panels -- in a town of 30,000. Another town in MA also with 30,000 people and a town-run power company (that pays only 50% for generated power) has ONE person with solar panels. What an absolute joke.

So I now need to decide if the extra year or two this adds to my breakeven is worth it.

[Alchete]

I needed a ~6kW system and installed an 8.4 kW system.
Another change will be to replace a thru wall mounted 1972 vintage air conditioner when it fails (or perhaps sooner). It will be replaced by a mini split which will be much more efficient, much quieter and have the added ability of heating to use up excess kWh in the winter instead of selling back to to my utility at the avoided cost rate. The AC unit is only used 3 or 4 weeks out of the year, so replacing it just to save electricity is a bit tough to justify.

I replaced three in-wall air conditioners, one of which dates at least back to 1970, with a 15 SEER central A/C unit, and saw my electric bill drop from 8000kW/year to 5700kW/year. I'd say at 80%-90% of that drop was due to the central A/C unit. It'd be even better if you can incorporate a heat pump with it.

[Mb190e]

I'm wondering if this is somewhat crazy or if it's worth thinking a few years ahead at install time...

My usage last year was approximately 5700kWh.

If I fill my south facing roof with panels, I can get ~7.8kW of panels, which would equate to a yearly output of 9000kWh. It' also brings the cost/watt down due to installation costs.

So, I'd potentially be running a surplus of ~3300kWh/year. But, I'd lock in the federal and state tax credits, and MA is an SREC state, so I'd start collecting SREC money for my electricity generation.

My plan is to get a Tesla Model III (or equivalent) in late 2017 or whenever it ships.

In MA, according to my research, there is no feed-in-tariff system to buy the electricity, but net metering credits never expire. So, I'd potentially be running a large surplus for ~2 years, until I get an electric vehicle, at which point I'd likely go negative and start drawing them down (depending on my yearly mileage).

Oversizing the system would also open up other options, such as converting other appliances to electric. In my case, I already have an electric stove, but I'm about to replace a 70 year old oil burner with a gas furnace & indirect hot water storage. However, having a surplus of electricity would allow me to potentially consider an electric hot water or even electric heating of some sort. I haven't researched electric heat yet and am guessing the efficiencies are horrendous, which would add up quickly in the Northeast over the winter.

So, for those who've installed recently or soon, are any of you oversizing your installation now for future plans (electric vehicle, etc.)?

I did this exact thing when installing my system about a year and a half ago my annual usage was 6,100 kWhs. We installed I think it's 128% of our usage (8.1kW 9,200 kWhs) with plans on adding a heat pump and using the air conditioner which we've never used before, we added the heat pump last fall I figure it's offset about 400 gallons of propane heating on the fringe seasons. Plus I like the idea of being a little oversize so as the panels degrade I still can cover 100% of my usage.

[DanS26]

........... However, having a surplus of electricity would allow me to potentially consider an electric hot water or even electric heating of some sort. I haven't researched electric heat yet and am guessing the efficiencies are horrendous, which would add up quickly in the Northeast over the winter.............

Take a look at the Steffes ETS (electric thermal storage) systems. They make whole house and room sized systems. Now I do not think the whole house systems are practical or cost effective but the room sized systems make a lot of sense. Just heat the space you're in rather than the entire house.

The Steffes units are well built and are timer controlled so that you can charge the unit only in the daytime using your excess power. The power is converted into heat and stored in ceramic bricks and released as you wish by thermostat control. They also come with a module to sense the outside temperature and thus control how much charging occurs.

Yes resistance heat is inefficient but if used to heat a room or small work space it is ideal and will soak up a lot of that excess power. I installed one in my wife's work shop and I get kudos all winter long for that little project. This fall I will install another in the living room area.

[Alchete]

I did this exact thing when installing my system about a year and a half ago my annual usage was 6,100 kWhs. We installed I think it's 128% of our usage (8.1kW 9,200 kWhs) with plans on adding a heat pump and using the air conditioner which we've never used before, we added the heat pump last fall I figure it's offset about 400 gallons of propane heating on the fringe seasons. Plus I like the idea of being a little oversize so as the panels degrade I still can cover 100% of my usage.

Excellent! So how has your town been handling your positive net metering credits for a year and a half? Are you getting paid for them, or have you been accumulating a surplus that you hope to draw down someday?

[Mb190e]

Excellent! So how has your town been handling your positive net metering credits for a year and a half? Are you getting paid for them, or have you been accumulating a surplus that you hope to draw down someday?

Last year by solar PV array was up and running on May 1, My true up month is March going into October I had a surplus of about 3000 kWhs. Due to the low production and heavy snow over the winter months, we used all of our surplus and I actually got a bill for somewhere around $8. I currently have 3800 kWhs in the bank. Anything left over in March I will get paid for like .03-.05¢ a kWh