Number crunching

The net metering I get isn't from the utility's generosity, it is set as state law. Also by that law, the utility doesn't buy any surplus from me, instead just gives credit that can be used anytime through the end of the solar season, March 31. Any unused credit then reverts to the utility for free, just before the next solar season starts kicking into high gear. So there is no financial incentive to overbuild.

Other elements I've benefited from, including approval of the interconnection agreement before installation even began, and allowance to tie in and produce immediately even before either of the inspections, are closely connected to the utility's solar friendliness. That is one benefit of getting service from a public utility that must answer to blue-county politicians. Not all their quirks are beneficial, but this part certainly is.

 

Our Utilities actions are also set by state law. The utility lobby is quite strong in our area as we export power to other states and also the cheap power attracts industry - The states law concerning home solar is greatly influenced ($$$$) by the Utilities.

There are some rumblings of change in the policy - but - if you live where electric is very cheap the compensation or credits are not something to write home about. That will change in the future also as energy continues to increase in price and becomes ever more valuable.

Other than the financials I think having some degree of energy self-reliance and independence with an installed home solar system is priceless.

 

changes to states net metering rules have been giving solar salesman, owners and youtubers a big headache for a few years already.
Add FL and NC to the list of states reducing net metering paybacks and or eliminating paybacks completely for solar owners.

10 minutes on one of NC's biggest utilities
7.6K views 7 months ago #netmetering #solarenergy #solar
youtu.be/NY_i89W_jUQ

In California on April 13, 2023 a big change happened while moving from NEM 2 onwards to NEM 3 which reduced the excess solar payback rate significantly, amongst other California utility time of use changes.
And I've just noticed, so have the youtubes that described the proposal a year or two ago, while looking for links I've watched a year or two ago to post here. So what I seen today in those older youtubes is not the same as what I saw previously.

I get it, solar is big business, and if you want bigger and better solar on or around bigger and better homes, one has to use the bigger is better playbook to meet the goal. And seriously, who doesn't want bigger and batter, well everything ! ytmmv and usually does.

 

Like Leadfoot's home system, and a huge majority of systems in this metro area, mine is a grid-tie system. For the safety of utility workers and the general public, it cannot function when the grid is down. It is entirely about expanding renewable energy and reducing carbon emissions, and needs 'the grid' to function similar to a storage battery. In reality its sends most of my energy to other people immediately, and gives me credits for 'free' energy later from existing sources. It has nothing to do with self-reliance or independence.

Nowadays, it can be upgraded towards that self-reliance goal, to function in a safely isolated island mode during civil emergencies when the grid fails. For me, that would double my system cost: ~$10 for a minimum set of batters (Enphase or Tesla Powerwall), ~$3k for the control to connect to and manage the batteries and provide the 'leader' for the grid-following solar inverters, and at least $4k for other electrical changes to properly accommodate that controller.

Independence? No, this is the wrong climate zone for that. Solar here simply doesn't provide enough energy through winter to supply an all-electric home.

 

Thank you for the explanation of net metering systems.

I was not familiar with them probably because our area would not be a net metering friendly area due to pricing and regulation.

Thanks to the forum and watching you tube videos on the subject - I was able to better understand and learn something.

 

What is your current oil and electricity price? In our area oil currently at $3.28/gal and electricity at $0.28/kWh after 15% solar discount, the cost per kBtu is cheaper for oil. Oil $23.65/MBtu and Heat pump $28.01/MBtu.

This is with 80% efficiency on our aging oil boiler and assumes the highest efficiency near 300% for the heat pump. In a middle of winter when the temp is well below 20f, the heat pump efficiency goes down substantially while oil boiler efficiency actually goes up due to less cycling making the oil heating even cheaper in our area.

Unless I can get substantially cheaper electricity, or the oil price hikes to above $4/gal again, it makes a little financial sense to install heat pump in our home now. But with current incentive on the initial installation cost of whole house heat pump conversion, I am planning to go for the heat pump more for the environmental reason.

 

Yeah, at your rate, the heat pump is going to save you money. My spreadsheet calculator tells me at your rate, you get $24.51/mil Btu for oil and $17.01/mil Btu for the heat pump, again assuming ~80% efficiency on oil burner and near 300% efficiency (COP 3.0) for the heat pump.

You can refer to the following link for a general discussion of the Heat Pump Efficiency Vs Temperature Graph (COP At 0°F To 60°F). While the efficiency drops down to 0F, the difference is COP 3.1 at 30F to COP 2.2 at 0F, so you will not go down to 155% efficiency down to the lowest limit of your system. After reaching below the lowest operational temperature level, it probably will not work at all. But that number depends on the machine. Of course, if the oil price drops below $2.36/gal, then oil becomes cheaper again if your electricity stays the same.

Heat Pump Efficiency Vs Temperature Graph (COP At 0°F To 60°F)

NOTE: It seems the new server is not taking the image file upload now. I can't upload inline figures or photos anymore.

 

Part of what I meant is that if one puts up enough solar panels to cover all winter needs in my climate zone, then one has a HUGE annual over-capacity. A very large capital investment with a huge annual surplus that is mostly wasted, unless tied to the grid to feed back to the utility to help offset the loads of other customers unable to put up their own solar systems. And since ordinary solarized residences in this state don't get compensated for their surplus production ...

Current storage batteries are nowhere near big enough to carry over enough summer surplus to cover winter needs. I can't foresee that ever being economical, compared to transmission lines from sunnier southern climes.

 

Home wind does exist, though it is generally less practical.

 

Yeah, cooling needs are not met with the oil. It would be nice to not have to mount and dismount the window AC every summer. But since our needs for the summer AC is very limited short time usually only a few days during the extreme heat wave, so having a permanent AC system is an overkill. And having a permanent AC (heat pump) may increase our summer AC usage since it is more convenient to use it.

But in our house, even with the whole house heat pump, the oil boiler has to stay for our domestic hot water system. I think I explained to you somewhere that we could not convert our hot water from oil to a heat pump electric hot water system due to our lack of space in the "basement". Using the oil boiler solely for the hot water is very inefficient due to very frequent cycling. So, even if we install the whole house heat pump and 100% of heating needs are met with electricity, our oil consumption will decrease only by ~33%. Not a very cost-effective nor environmentally friendly solution.

That may be true. But one thing I am concerned about the heat pump system is its longevity. What I read is that average heat pumps last for ~15 years with a range of 10-30 years. If it lasts 30 years, then I don't have a problem, but if it needs to be replaced every 10 years, that is not a plausible replacement for the iron-clad oil boiler that can last basically a lifetime. Almost any element of the oil boiler parts are replaceable. Our oil boiler is over 35 years old now, and it is still going strong. Yeah, I have had a few pieces replaced, but it never cost me more than a few hundred dollars, and it never needed to be replaced completely. I really wonder what the real-world average lifespan of heat pump systems and maintenance (repair) costs are.

 

I hope both replacements led to significantly better efficiency and cold weather performance, to levels not available back then.

With numerous other household appliances having shorter lifetimes these days, I'm crossing my fingers that my heat pumps will have reasonable lifetimes. My first is now 14.75 years old, and showing no hints of any problems. But with that not being a reliable indicator of remaining life, as failure can happen with noticeable warning, I'm keeping an eye on the market for replacement ideas with somewhat improved performance.

The same applies to my 10.5 year old heat pump water heater, which has already outlived its traditional predecessors. And even greatly outlived its manufacturer. Today's HPWHs are very significantly improved, and manufacturers now have track records to show.

 

The resistance heater is the most expensive way too heat almost anywhere unless electricity is free. Using your rate of $0.17/kWh, it will cost you $49.83/mill Btu compared to $17.01/mill Btu fo HP and $24.51/mill Btu for oil at $3.40/gal.

We used 1500W space heaters to supplement our oil heat set at 58F last winter when the oil price was near $6/gal. The result was that we cut down monthly oil use by about one half. But our monthly electricity use went up almost 50%. But that turned out to be roughly $300 saving on oil and about $150 extra spending on electricity, netting $150 saving per month.

 

After mentioning heat pumps to a friend, I learned that at least at her second house, residential electricity is almost free: $0.027/kWh.

Cheap enough that after a couple cryptocurrency miners moved in and caused significant disruption (e.g. forcing the utility to make costly distribution upgrades just for them, then quickly going bust and closing when Bitcoin values plummeted), they created a special commercial crypto rate schedule.

 

We've talked about many compelling energy subjects in this thread.

One item I haven't seen discussed is energy consumption avoidance. The best way to cut energy consumption may be by design and passive energy construction, capturing and storing energy passively that is applicable to any climate.

Passive Solar Homes in Cold Climates (6 Design Examples) (attainablehome.com)

Embracing Sustainability: What Is a Passive House? (turbotenant.com)
"A passive house creates a comfortable and consistent interior climate without an active heating or cooling system. It achieves this by combining key features such as high-quality insulation and ventilation."

Would enjoy building a house with this concept in mind. That ship has sailed for us but it is quite interesting to still plan and keep up with the concepts.