Which is afforable to install solar hot water system or heat pump?

poetadams · January 8

Hi
I have had a water heater for 10 years and decided to buy a new one. Which is better a Solar or Heat pump hot water system my mom likes solar hot water systems because our climate is warmer in our place.

Any suggestion is appreciated

Thanks

EBEBRATT-Ed · January 8

A lot depends on how much hot water you use and where you are located. Heat pump water heaters are an option. Some love them. Some (including me) are skeptical that they are a throw away appliance,,,,like a window air conditioner. They can be repaired if need be but is it worth it. And they are expensive rebates may be available in your area.

Solar is another option. Same thing with rebates

Larry Weingarten · January 8

Hi, In the systems help center you'll find an article "Another Solar Myth Bites the Dust", that I wrote. It might be of some use.

Yours, Larry

kcopp · January 8

What type of water heater do you currently have? Gas or Electric?
Is it currently working?

ethicalpaul · January 8

I’ve had both. Solar hot water will never pay for itself. A heat pump water heater should and is way easier to install

hot_rod · January 8

Check for incentives or rebates in your area. If you can get $1000. for a HPWH install the answer becomes clearer

www.dsireusa.org

Larry Weingarten · January 8

Hi, @ethicalpaul said: "I’ve had both. Solar hot water will never pay for itself. A heat pump water heater should and is way easier to install". This depends completely on what assumptions are made. The solar system I wrote about cost about half of what conventional solar does, took about six person hours to install, takes care of 90% of the hot water needs, and requires nearly zero maintenance. It is not a cold climate system, but in temperate or warm climates, it likely beats HP in terms of life-cycle cost. I don't know how to make an inexpensive cold-climate solar water heater, but it's worth pondering.

Yours, Larry

ethicalpaul · January 8

Mine was cold climate--I used vacuum tube collectors and a collector loop with antifreeze in it, that went through a controller into an indirect tank. The kit was $3000 and it took me maybe 20 hours to install.

hot_rod · January 8

I think the economics can work out for ST if you can build, or at least install the system yourself.
And you have a consistent DHW load for it.

I have about $2600. into this 56 sq ft collector and tank. Plain water drainback, Resol control.

It a partially cloudy day here 25°, light wind. My tank and radiator attached to it are running just under 120F. With a plate HX I could generate DHW easily with that temperature.

I have one simple moving part, a Grundfos SS circulator. So much less potential for breakdown and $$ repair compared to a HPWH.

I think the tank will be the weakest point of HPWH. Wholesalers tell me 6 years is about average for any glass lined tank around here. Although less stress in a HP tank compared to a fired tank.

ethicalpaul · January 8

Always keep your important books and electrical distribution under your water tank!

hot_rod · January 8

ethicalpaul said:

Always keep your important books and electrical distribution under your water tank!

In an aluminum drain pan pvc to the floor drain below

ethicalpaul · January 8

The photo might be deceiving me, but the pvc doesn't look piped. But trust me, I'm no one to judge! I have some precarious stuff myself

hot_rod · January 8

Correct you are, the PVC drain in the pic is actually from the boiler condensate.

Not planing on the pan failing and the only thing non replaceable is my System Syzer wheel, although the wheel itself is plastic.

The non replaceable books are on a shelf up above the boiler. These may be the only original Heatway tech books in existence.

ethicalpaul · January 8

Hey look at those sweet sight glasses!!!

jumper · January 9

Well maybe in long run most economical is both?
Solar collector to source heat pump heater.
If collector can produce 80° then heat pump should be super efficient.

ethicalpaul · January 9

The collector can produce way hotter than that, but not economically, and I think having both would be even less economical.

Hot_water_fan · January 9

Solar thermal is extremely niche in the US. It can work great. But the market has left it behind. HPWHs are also pretty niche and are newer and seem to be ascending, but definitely are not reliable as they need to be yet. If you want solar, solar PV is the best bet.

ethicalpaul · January 9

but definitely are not reliable as they need to be yet

What is the failure rate compared to, say, electric resistance ones? Are those numbers known?

kcopp · January 10

I would like to hear back from the OP @poetadams about what they have and why the need to replace?

hot_rod · January 10

$$wise, running what you have until it leaks would be a suggestion.

If an average family spends $300 per year for DHW, you can see why the solar thermal is such a long roi.

If it is not strictly a $$ decision, solar thermal can cover 50% of your DHW load in most any part of the
US.

Since the solar needs a back up, the hpwh would be the most efficient appliance for that.

Most solar systems will have a 50 gallon or larger tank, so you will have plenty of stored hw between a solar and hpwh.

If your utility puts power in sale at off peak times, then the hpwh starts to look really good.

You could series the tanks, solar feeds through the hpwh. So the hpwh is always seeing the preheated solar input

ethicalpaul · January 10

That's what I did with my resistive electric heater (fed the solar tank into it). You're absolutely right, it works! But the ROI is baaaaad. But I loved installing it and I liked watching the controller turn on the pump when the collectors would get hot, heating the tank.

jumper · January 11

ethicalpaul said:
The collector can produce way hotter than that, but not economically, and I think having both would be even less economical.

You have to consider how many btu s your solar collector harvests at each temperature. So solar thermal had better economic results for pool heating than DHW. And a heat pump produces more btu per kwhr when it lifts less degrees.

ethicalpaul · January 11

This isn't a pool heating application but OK

hot_rod · January 12

I believe @jumper point is the lower the operating condition of any thermal collector the higher the efficiency. A pool collector in an ambient condition close to the fluid supply can approach 90% efficiency
This graph and formula let’s you enter the numbers and determine the collectors efficiency.

poetadams · February 7

Hello All

thanks for your time and effort I appreciate you guys for giving your comments it made me decide to buy a solar hot water system its good for the environment and easy to install with a good percentage of rebates

Cheers!

Which is afforable to install solar hot water system or heat pump?

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