which to persue - elec dryer or water heater?

autoxsteve
autoxsteve Solar Expert Posts: 114 ✭✭✭✭
in Energy Use & Conservation #1
I'm very pleased with my solar system and have been turning my electric meter backwards every day so far (29 kWh produced yesterday and I'm planning for over 30 from June - Sept). That being said I am doing some research on whether I should replace my gas dryer with an electric dryer or replace the water heater (gas with electric) to take advantage of the extra electricity.

Since the government has not developed an energy star or rating system for these two appliances, there is more work to be done here to choose the right approach.

Anyone got any info that can help?
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #2
    Re: which to persue - elec dryer or water heater?

    seems like the same question

    http://forum.solar-electric.com/showthread.php?t=2695
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #3
    Re: which to persue - elec dryer or water heater?

    Short answer... If you have enough solar power (assuming grid tied) to power your drier/water heater with solar electric power, you can do it. There was one person in my area (according to my solar installer) who sized his system to power an all electric home. Was expensive to install all of those solar panels, but it works fine.

    Cost / Efficnecy wise--it would be better to install solar thermal system for hot water heating (80% efficient collectors vs the 12% or so of solar electric), plus the cost, just for the solar thermal system is probably 1/3 the cost of capturing and using the same amount of power with a solar PV system.

    Lastly, it also depends how Net Metering and Time Of Use metering works in your area... In my area (northern California), we have tiered rates and if you use Time of Use metering--using a whole bunch of power at night and generating a whole bunch of "excess" power during peak times will still put you into higher electrical tiers (say you use 300 kWhrs off peak and generate 300 kWhrs on-peak--in PG&E's system, that would put us in the 600 kWhr rate tier--which increases both our off peak and on peak rates... Instead of putting us in the zero kWhr base tier one would think)... Amazing how Grey areas in rate plans seem to be exploited to give the power company the most money.

    None of how this works for TOU rate plans is explained in our Tariff system--and people a few years ago where fighting it--so it may be different now (I don't use/generate that much power to have it affect me at this time). But it may affect your bill if you are able to shift loads in a TOU net metering rate plan.

    If you do not have TOU and just net metering--you will be fine.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • rickeolis
    rickeolis Solar Expert Posts: 110 ✭✭✭✭
    #4
    Re: which to persue - elec dryer or water heater?

    I'm getting a gas dryer to replace my electric.
    This is a good summary from another poster:
    "If you hadn't been convinced to go propane already, here is yet another way of showing how gas would be better - With gas, the fuel is burned directly to make heat, in a relatively efficient burner, probably 80% plus, so nearly all the potential energy in the gas will end up in your laundry. There are also essentially no "transmission losses" - all the gas coming out of the tank goes into the dryer (we hope...)

    With a generator, you have multiple conversion steps, with heavy losses at almost every one. First you burn the gasoline in an IC engine - I forget the exact numbers, but this is not very efficient, lots of thermal losses. Then you take the mechanical energy and spin a generator with it in order to make electricity, again heavy losses. If you feed the electricity to a battery bank, you get even more losses at each step of powering the charger, charging the batteries, and then powering the inverter. If you power the dryer directly, you still get more losses from transmitting the power over the lines. The final step of converting the electric into heat IS efficient, but that's not saying much in light of the earlier losses. I've seen figures saying grid power only about 30% of the energy in the fuel actually makes it to outlet in your wall, I doubt that a gas generator would be any more efficient.

    Gooserider"

    -Rick-
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #5
    Re: which to persue - elec dryer or water heater?

    You pose an interesting question. If your goal is to reduce your bill to as close to zero as possible you may have one option. If on the other hand your goal is to be as efficient with the use of energy (net) as possible you have another option.

    In option A you could use an electric dryer powered by your excess pv capacity. Domestic hot water, backed up with electric from your pv could also be used.

    On the other hand if you choose option B: I think your best bet would be to use solar (heat) for domestic hot water, with gas demand backup. Hang the laundry out, and barring that, use gas for the dryer, with the motor etc powered by your pv. Your excess pv capacity is then used in the most efficient way IMHO, even if it doesn't yield the smallest bill to you, net/net.

    Let us know,

    Icarus
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #6
    Re: which to persue - elec dryer or water heater?
    autoxsteve wrote: »
    to take advantage of the extra electricity.

    You need to bank your summertime surplus, to offset your short winter days. At least I need to, to keep my annual billing close to zero.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • autoxsteve
    autoxsteve Solar Expert Posts: 114 ✭✭✭✭
    #7
    Re: which to persue - elec dryer or water heater?

    Just an update. I got my first full month solar electric bill. It is $1.71.

    I pushed 322 kWh back on the grid in that time. Here is my thinking. A water heater or electric dryer both use about 5kW of power when they are running.

    So, I'm figuring that we do 4 - one hour loads of laundry a week, then the power used for the dryer is: 4 *1 *5kW = 20 kWh per week, and that adds up to about 90kWh per month.

    Seems like an electric dryer is a no brainer. Regarding the water heater tho, that I know less to nothing about.

    Anyone got any useage info on how many kWh per month an electric water heater uses for a family of 3-4?
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  • Windsun
    Windsun Solar Expert Posts: 1,164 ✭✭
    #8
    Re: which to persue - elec dryer or water heater?
    rickeolis wrote: »
    There are also essentially no "transmission losses" - all the gas coming out of the tank goes into the dryer..

    Gooserider"

    -Rick-

    You know, that is so obvious, I wonder why it is never mentioned in the gas vs electric heat debates.
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