Utility Costs: Difference between revisions
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*Industry standards - 80 gal heater - 21 gal recovery rate per hour with 9kW. [https://www.lowes.com/pd/American-Water-Heater-Company-80-Gallon-Tall-3-year-Limited-4500-Watt-Double-Element-Electric-Water-Heater/1000213693] | *Industry standards - 80 gal heater - 21 gal recovery rate per hour with 9kW. [https://www.lowes.com/pd/American-Water-Heater-Company-80-Gallon-Tall-3-year-Limited-4500-Watt-Double-Element-Electric-Water-Heater/1000213693] | ||
*Max gallons recovered with 18 kW electric - 42 gal/hr - or 250 gallons per day. | *Max gallons recovered with 18 kW electric - 42 gal/hr - or 250 gallons per day. | ||
*Perhaps the large 80 gal heater is the way to go as a basic, off-the-shelf unit running on solar. Keep it on only during the hottest sun time. | *Perhaps the large 80 gal heater is the way to go as a basic, off-the-shelf unit running on solar. Keep it on only during the hottest sun time. Heat loss of a hot water heater is 1-2.5 kWhr/day - [https://www.viessmann.co.uk/heating-advice/how-long-does-water-stay-hot-in-tank#:~:text=As%20an%20estimate%2C%20the%20water,form%20of%20insulation%20you%20have.]. This means that if it took 4 hours to heat the 80 gallon tank at 9kW - then it took 36kWhr, so daily loss of 2.5 kWhr means it would take 14 days for all heat to be lost? That means, we lost 1/14 * 50F = 3.5F per day? If we went to 110F, then after 3 days we are still at about 100F! | ||
Revision as of 16:46, 19 November 2020
Between $141 and $266 for lowest to highest states per month for gas and electric. See nice map at [1]
This means that in the design of the Seed Eco-Home, we put in the extra effort to make electrical costs less over lifetime. We can also strive to make those costs 0 up front via energy loans.
Basics of high PV profile - use 20kW.
Invest in concrete pipe (it leaks [2]) for water storage when sealed and insulated.
Transcending the System - Calculations
- 20kW PV - raw cost of $7k, down to $5.8k in bulk.
- Water from 59F to 110F (15 to 44) - 30C rise. For 250 gallons.
- Industry standards - 80 gal heater - 21 gal recovery rate per hour with 9kW. [3]
- Max gallons recovered with 18 kW electric - 42 gal/hr - or 250 gallons per day.
- Perhaps the large 80 gal heater is the way to go as a basic, off-the-shelf unit running on solar. Keep it on only during the hottest sun time. Heat loss of a hot water heater is 1-2.5 kWhr/day - [4]. This means that if it took 4 hours to heat the 80 gallon tank at 9kW - then it took 36kWhr, so daily loss of 2.5 kWhr means it would take 14 days for all heat to be lost? That means, we lost 1/14 * 50F = 3.5F per day? If we went to 110F, then after 3 days we are still at about 100F!