Hybrid solar with grid tie on Hawaii?

[BenHawaii]

My brother has two houses on Maui and they encountered significant stonewalling when they inquired about a grid tie system solar system. Ultimately they bypassed the Maui utility which I think is controlled by HECO. They got a building permit for solar and batteries and are running in self consumption mode only using the grid for backup. Follow the advice above from scrambler and you should be fine.
Because of the high rates on the Islands and the stonewalling by HECO it is not hard to justify a system. Only the battery size is the cost that has to be justified based on the value you place on backup. In some circumstanes it can beat the cost of propane for running a generator. I would keep the generator for rainy days.

Helco and HECO are monopolies except for those of us that have grid service and a solar system that depends on them just for extra power needs. Yes, I think that is the question we need to ask, "how much do we value having backup?"

[BenHawaii]

15kWh/day is only 5,475 kWh per year, so not huge.

You need to determine if that may change drastically in the future, like if you add electric cars...
First goal is to determine the total energy (kWh) you should aim to produce per year.

In addition to the target kWh per year, you will need to determine where the panels will go (roof, ground...) so you can determine their orientation (south, SE, SW...) and their tilt.
One you have these numbers, you can determine the size your solar array (how many kW of panels) using the PVWatts Calculator (nrel.gov) site.
You enter an array size like 5kW, your location, Orientation and tilt, and that will give you the yearly kWh that 5kW array can produce.
You then just increase or decrease the array size to meet the yearly goal


The next step is sizing the battery (capacity in kWh). To do that, you need to figure out a few things.
- How long are outages usually.
- During what season / periods are they usually happening
- During the seasons / periods identified above, what kind of weather can you expect, sunny days, light clouds, heavy clouds...
- What are the essential loads that would have to run during evening and night, how long would they run during that period. Keep in mind you probably wont be running any super heavy loads (like AC or charging cars) on the battery.
- What are the extra load that would need to run during the day and for how long.

The minimum battery size will be defined by the energy needed for one evening / night.
Then you can make sure the Array daily production based on season and period will be enough to both fully recharge the battery, and provide the extra load capacity during the day.

If you can provide all the above, we can help figure out what battery sizes would be best.

Thank you for the feedback. Visited pvwatts.nrel.gov and based on location, second story 45 Deg NE facing roof mount and a 5kW array the tool reported 6,030 kWh per year.

My goal is to have battery capacity to power current evening power usage needs and reduce power bill. Evening usage is 8.5 Kw (which includes fridge and chest freezer that don't run constantly), with inverter that will auto switch over to grid if batteries can not supply power needs.

[Ampster]

My brother has two houses on Maui and they encountered significant stonewalling when they inquired about a grid tie system solar system. Ultimately they bypassed the Maui utility which I think is controlled by HECO. They got a building permit for solar and batteries and are running in self consumption mode only using the grid for backup. Follow the advice above from scrambler and you should be fine.
Because of the high rates on the Islands and the stonewalling by HECO it is not hard to justify a system. Only the battery size is the cost that has to be justified based on the value you place on backup. In some circumstanes it can beat the cost of propane for running a generator. I would keep the generator for rainy days.

[scrambler]

15kWh/day is only 5,475 kWh per year, so not huge.

You need to determine if that may change drastically in the future, like if you add electric cars...
First goal is to determine the total energy (kWh) you should aim to produce per year.

In addition to the target kWh per year, you will need to determine where the panels will go (roof, ground...) so you can determine their orientation (south, SE, SW...) and their tilt.
One you have these numbers, you can determine the size your solar array (how many kW of panels) using the PVWatts Calculator (nrel.gov) site.
You enter an array size like 5kW, your location, Orientation and tilt, and that will give you the yearly kWh that 5kW array can produce.
You then just increase or decrease the array size to meet the yearly goal.


The next step is sizing the battery (capacity in kWh). To do that, you need to figure out a few things.
- How long are outages usually.
- During what season / periods are they usually happening
- During the seasons / periods identified above, what kind of weather can you expect, sunny days, light clouds, heavy clouds...
- What are the essential loads that would have to run during evening and night, how long would they run during that period. Keep in mind you probably wont be running any super heavy loads (like AC or charging cars) on the battery.
- What are the extra load that would need to run during the day and for how long.

The minimum battery size will be defined by the energy needed for one evening / night.
Then you can make sure the Array daily production based on season and period will be enough to both fully recharge the battery, and provide the extra load capacity during the day.

If you can provide all the above, we can help figure out what battery sizes would be best.

[BenHawaii]

Aloha,
So happy to have found this forum and that different solutions to energy generation are divided into separate sub forums. We live on Hawaii, on the rainy side, and are investigating a hybrid system. However, after reading the sticky message "Hybrid Solar, grid tied solar pv with batteries" relating to the extra cost vs financial benefit, I see we need to do more research.
We have to consider that we are on a remote island in the Pacific. There is one electric company that relies on ships to bring fuel. Shipping to Hawaii is strictly regulated by the Jones act so which makes us further vulnerable to fuel price spikes. If shipping traffic is disrupted there are minimal fuel reserves on the island. We also wanted to reduce our electric bill, possibly to just the minimum monthly customer charge of $25, since we are tied to HELCO. Having been through multiple hurricanes, with one resulting in no power for 10 days,did not have a generator at the time), self sufficiency is a consideration. We currently heat house water with propane and have propane stove. Of course, we know that propane supply could also be disrupted, so alternatives are a consideration down the road.

I have a basic understanding of small off grid systems. Wanted to get some advice on considerations for a whole house hybrid system. Home is 2,000 Sq feet 4 bed 3 bath. Currently just two of us, but have the space for our parents to visit or possibly live with us if they need to. But for now we are aware of conserving power, mostly LCD bulbs, energy star appliances. I know that going completely off grid would not be a wise financial investment. So buying some power, when batteries or panels can not supply our needs, seems more cost effective.

15 Kwh daily average
Purchased power rate .344 per Kwh

Energy inventory shows 4,000 watts total need, if everything was being used at the same time. A typical evening shows that 1700 watts might be used per hour, but I don't know how to calculate a true usage taking into consideration that this includes a refrigerator and chest freezer, that are not always running. If we had company staying here the possible evening usage could increase to 3,000 watts per hour. But company is not a regular occurance. Thinking we need to install panels that can generate 5,000 watts, under optimal sunny conditions.

Thanks
Ben