Solar Wind Installation Piha
I spoke to you today on the phone about setting up my house in Piha for solar and/or wind.
I would be interested in seeing a few different options to run a small 2 bedroom house (gas hob) washing machine, dryer, Hot water and basic household electronics. I would also like to know about what sort of maintenance is involved.
Your power usage :
Washing machine – 1.5 kWh / day .
Dryer – 1.0 kWh / day
Hot Water – 8.0 kWh / day
Lights – 2.0 kWh / day
TV / Computers – 2.5 kWh / day
Kitchen appliances – 1.5 kWh / day
Total Daily Usage – 16.5 kWh / day
Estimate daily power cost : Daily Connection Charge (.375 + .16) – $0.56
Unit Cost (0.268 X16.5) – $3.96
Monthly Bill (4.96 X 30 ) – $148.80
You would be a low user ( less than 22.0 Kwhr a day )
Using gas hobs would have saved 5 Kwhr a day.
Home heating is achieve with a wood burner.
Generation cost of solar and wind :
Solar: To produce 1 kWh a day requires $1000 investment in solar panels
You would require an investment of $16,500 in solar panels to supply your daily usage.
Wind: The RB900 wind generator can produce 2 kWh a day in low wind conditions ( average 4 m/s).
For Piha I would expect the RB900 to produce 4 kWh a day (average 6 m/s)
You would require 3 wind generators an investment of $12,000
These cost do not include the cost of inverters, solar controllers, batteries and installation.
If hot water is removed from the equation you can reduce your usage and hence your investment by half.
Islanded installation
Cost: ( Solar Panels 16,000, Controllers 3,000, Inverter 3.000, Batteries 2,500, Installation 2,000 )
Estimate Total Cost: $26,500
Cost of borrowing @ 8 % over 20 years = monthly payment $221.66 ( Total Interest Paid $26,697.59 )
With a monthly power bill of $148.80 you have a net cash outflow of $72.86
If hot water is taken out of the equation:
Cost: ( Solar Panels 8000, Controller 1000, Inverter 3000, Batteries 1500, Installation 1000 )
Estimate Total Cos : $14,500
Cost of borrowing @ 8% over 20 years = monthly payment $129.65 (Total Interest Paid $16615.57)
Power bill drops to $98.40 monthly and you have a net cash outflow of $31.25
Cost estimates are for this exercise only and may vary depending on your choice of products and setup.
The savings are considerably higher as power cost will increase every year.
Cost of batteries will be higher as they may need replacements every 5 years.
If economy bulbs are used throughout lighting cost can be reduced to 1 kWh a day
Cost of borrowing is lower if combined with your mortgage.
Islanded Solar and Wind Combination
Cost: (Solar Panels 10,000 Controllers 1000 Inverters 3000 Batteries 2500 Wind Gen 4000 Installation 1000)
Estimate Total Cost: $21,500
Cost of borrowing @ 8% over 20 years = $179.83 ( Total interest Paid $21,660.31 )
With monthly power bill of $148.80 a month you have a nett cash outflow of $31.03
Wind and solar combination is the best option as wind is stronger when sunshine hours are lower.
Wind is very variable and production can range from 0 to 16 kWh a day.
On days when too much is produced the excess can be diverted to heat the hot water.
Solar and Wind Grid Connect System
Cost: (Solar Panels 10,000 Wind Generator 4000 Grid Connect Inverter 4000 Installation 2000)
Estimate Total Cost: $ 20,000
Cost of borrowing @ 8% over 20 years = $167.29 ( Total Interest Paid $20,149.12 )
Monthly export to grid $132.60 a month. Nett cash outflow $ 24.96
No battery banks required results in minimal maintenance cost for system installation.
Full credit for excess power generated on very windy days.
Grid connect inverter has built in MPPT circuits for both wind and solar generation.
Assume prepower is used so no daily charge is incurred and all power used is fully compensated by export.
Green Plug Option (Lights and One Power Plug)
Say you only want to use solar power for your lights and one power plug – 2 kWh.
Cost: (Solar Panels 3000 Controller 500 Inverter 400 Batteries 400 Green Plug 700 )
Estimate Total Cost: $5,000
Cost of borrowing @ 8% over 20 years = monthly payment $41.82 ( Total Interest Paid $5,037.28 )
Monthly power savings is $16.20 and you have a nett cash outflow of $25.62
The green plug will switch to mains power when your batteries are low.
The Final Analysis
The best option is a mix solar and wind grid tie solution.
No on going cost of battery bank
Very low maintenance cost
Power cost is calculated at low user rate of 26.8 cents a unit. If this is increased to 30 cents the return increases to $148.50 a month for export power.
You should get a net cash inflow within 5 years.
Calculations is done over 20 years to reflect expected life of the generation equipment though they would last longer than that.
