Need advise - Heatpump or Solar Expansion

[daniemare]

Hi All - Need opinions
 

My heatpump of 8 years have packed up in Decemebr. Will cost R17,000 before installation. Currently running element. 
 

Some facts. 

My heatpump used +- 1.5 kw/h

My geyser now use +- 4kw/h

I run the geyser for an hour before solar production

I run the geyser for 30 min at 12:00

My current system

1x5kw Inverter (geyser not on essentials)

10.8kwh batteries

4kwh PV 

Now my options. 
1 - Replace Heatpump

2 - Buy another battery (3.6 kw @ R10k used) plus 2kw of panels for difference. 
 

I am based i Stellenbosch. During summer I had a positive experience with element. But winter will drop ambient lower and I will struggle loading my batteries during the day.

I do not have any battery capacity left when my geyser turns on for morning heating, so that is at R3/kw. 
 

Can’t decide. Your opinions welcomed. 

[Bobster.]

And extra 3.6 kWh of battery will give you enough stored energy to run the geyser for something less than an hour. (geyser consumes 4 kW, battery probably provides a useable 3.2 kWh). 

I have a heatpump for my water heating. My timings are similar to yours. I run it on backed up side of the DB and I have 10kWh of battery. I NEVER run the heat pump after 3pm. Because the draw is lower and the water heating faster, I get away with the heat pump on the backed up side as long as don't go too crazy with appliances in the kitchen. 

That's what works for me. I haven't been without hot water for getting on 5 years now.

So, on the basis that it works for me, I'd spend the money on the heatpump. Do a little research first. I would expect that things have improved over the last 8 years and so you will be able to get a pump with the same heating capability but that uses less power.

A heatpump is one of those things where you have to spend now to save down the line (though 8 years is a bit short, you'd expect more like 10, and mine is 13 in a couple of months). Since you have PV already, your savings will be not as great, though I'm guessing that every now and then your battery runs down and you have to fall back on to the grid. But what it will save you is ability to run off of power stored in the battery and to get through power outages and still have hot water.

Edited April 15 by Bobster.

[daniemare]

2 hours ago, Bobster. said:

And extra 3.6 kWh of battery will give you enough stored energy to run the geyser for something less than an hour. (geyser consumes 4 kW, battery probably provides a useable 3.2 kWh). 

I have a heatpump for my water heating. My timings are similar to yours. I run it on backed up side of the DB and I have 10kWh of battery. I NEVER run the heat pump after 3pm. Because the draw is lower and the water heating faster, I get away with the heat pump on the backed up side as long as don't go too crazy with appliances in the kitchen. 

That's what works for me. I haven't been without hot water for getting on 5 years now.

Thanks Bobster.

I know we have the same Goodwe Inverter.

My current use is 5-6kwh (measured average) a day on the Geyser since loosing my heatpump. 1kwh is covered by solar currently.  My experience on my old heatpump is 1:3 COP in practice. So I can save 66%. Call it 70% for newer tech.

That is a saving of 3.5kwh per day (summer experience) or R10 a day, R3,650 a year. @R20k quoted cost that is 5,5 year payback. 

So initially my thinking was exactly as you explained, just replace the thing.

But then I started wondering.  If I still spend the R20k, but on solar expansion. (R10k on used battery I can get and am comfortable with, rest on 2kw panels and maybe a new smaller rated geyser element). My thinking is I can still save on the heating bill, maybe 40% and not 70%, BUT I have more excess solar for cloudy days, or summer running the aircon.

My savings might actually be better.

Hence why I am fishing for opinions

Edited April 15 by daniemare

[Vaal]

How soon is your battery charged in the morning?

What is your base load during the day?

I've got 5.3kw of panels, but my base load is about 400w/hr after my battery is full. 

I changed my geyser element from 3kw to 2kw and now I heat it up from 11h00 to 1600 to max available on the thermostat (about 72 °c ) 300L of hot water which gets heated even more by the sun after the thermostat stopped.

My problem is that a heat pump can only heat water but a bigger PV system can heat water and power the rest of the house. 

[Arandoza]

The other positive about adding a second battery and more panels is one assumes it would reduce the number of cycles counted by both batteries, as they now both share the load and work half as hard, in the early morning before sunrise , and don't do any work once the sun is up.

Our Evacuated tube geyser has a backup element 2kw on it and it takes longer to heat, but is more gentle on the batteries, when there is little or no solar. Also when there is more than enough pv we burn the excess power by powering the geyser If it needs it.

Presently we have two 150l EvacGT geysers in series, only the first one can be electrically heated, but they are getting onto 10 years old and one of them is probably going to need replacement, i am currently considering replacing the first geyser with a standard one, as it will give more more roof space for PV and one can still mount the traditional geyser underneath or below the panels or existing second EvacGT geyser, while still feeding the second EvacGT geyser with no electrical backup.

[daniemare]

2 hours ago, Vaal said:

How soon is your battery charged in the morning?

What is your base load during the day?

I've got 5.3kw of panels, but my base load is about 400w/hr after my battery is full. 

I changed my geyser element from 3kw to 2kw and now I heat it up from 11h00 to 1600 to max available on the thermostat (about 72 °c ) 300L of hot water which gets heated even more by the sun after the thermostat stopped.

My problem is that a heat pump can only heat water but a bigger PV system can heat water and power the rest of the house. 

Base Load - 500W. SoC starts at 30%, but I can't get it currently to 100% (see below regarding to small PV).  But I get to 90% when PV rpduction stops at 17:30-18:00.  (This includes an 1/2 hour of geyser heating and 1 hour of kitchen undercounter geyser heating). Reach 30% at 00:00 - 02:00 depending on evening activity.

Problem is, I do not have good data on my Self Consumption ratio for the last while due to the changes in my system planned and unplanned.

Summer months 2023: Heatpump YES with 7.2kw Battery, 2.4kw PV           50:50

Summer months 2024: Heatpump NO with 10.8 kw Battery, 2.4kw PV  still 50:50

Winter months 2023: Heatpump YES  with 7.2kw Battery, 2.4kw PV           30:70

The PV is low yes.  Due to me upgrading as I got good deals on batteries, it lagged, but this saturday I am adding another 1,8 to get to 4.2kw PV. Expect the Summer months to improve to 60:40, but winter, with my limited knowledge, that is a guess at best, but hopefully I maintain 30:70.

 

So I see my scenarions as

1 - I can have Batteries 10.8kwh and PV 4.2kw PLUS Heatpump

2 - I can have Battries 14.4kwh and PV 6.2kw NO Heatpump

3 - Save the money, Batteries 10.8kw and 4.2kw PV NO Heatpump

Maybe 3 is the way to go untill I have some winter data.

[Scorp007]

1 hour ago, daniemare said:

Base Load - 500W. SoC starts at 30%, but I can't get it currently to 100% (see below regarding to small PV).  But I get to 90% when PV rpduction stops at 17:30-18:00.  (This includes an 1/2 hour of geyser heating and 1 hour of kitchen undercounter geyser heating). Reach 30% at 00:00 - 02:00 depending on evening activity.

Problem is, I do not have good data on my Self Consumption ratio for the last while due to the changes in my system planned and unplanned.

Summer months 2023: Heatpump YES with 7.2kw Battery, 2.4kw PV           50:50

Summer months 2024: Heatpump NO with 10.8 kw Battery, 2.4kw PV  still 50:50

Winter months 2023: Heatpump YES  with 7.2kw Battery, 2.4kw PV           30:70

The PV is low yes.  Due to me upgrading as I got good deals on batteries, it lagged, but this saturday I am adding another 1,8 to get to 4.2kw PV. Expect the Summer months to improve to 60:40, but winter, with my limited knowledge, that is a guess at best, but hopefully I maintain 30:70.

 

So I see my scenarions as

1 - I can have Batteries 10.8kwh and PV 4.2kw PLUS Heatpump

2 - I can have Battries 14.4kwh and PV 6.2kw NO Heatpump

3 - Save the money, Batteries 10.8kw and 4.2kw PV NO Heatpump

Maybe 3 is the way to go untill I have some winter data.

Some things do not line up for me. If you have 4kW of PV they can generate up to 20kWh a day on average. You are now using about 7kWh a day. Funny you battle to get the battery fully charged. I assume you don't use more than about 6kWh after sunset. 

New heat pumps have a 4-6 Cop. Getting a heat pump without more PV or battery means you can use about 3kWh less than now. Thus you only use 4kWh per day for total consumption. 

Why do I favour a heat pump. I have my ITS now for over 13yrs and I have never had to use the geyser element. It has never been connected. This is my best investment made to date. 

Fitting a new heat pump while all pipes are already there to your current pump should not take longer than 2 hrs labour at ???? rate per hour. 

Summary. With already excess battery power and PV for your load profile I don't see a need for more PV(extra wasted PV) extra battery nice to have if you need more storage for bad days of rain/cloud. 

Edited April 15 by Scorp007

[daniemare]

26 minutes ago, Scorp007 said:

Some things do not line up for me. If you have 4kW of PV they can generate up to 20kWh a day on average. You are now using about 7kWh a day. Funny you battle to get the battery fully charged. I assume you don't use more than about 6kWh after sunset.

I do not have 4kw PV yet. Will have from this Saturday. Currently only have 2.4kw. 
 

I use 20-22kwh per day of which I generate 50%. (Use to be 16-18 before my heatpump went)
 

But you make a good point. I am first going to see hiw my system performs when I have 4.2kw PV. 
 

Then make the call. 

[Scorp007]

1 hour ago, daniemare said:

I do not have 4kw PV yet. Will have from this Saturday. Currently only have 2.4kw. 
 

I use 20-22kwh per day of which I generate 50%. (Use to be 16-18 before my heatpump went)
 

But you make a good point. I am first going to see hiw my system performs when I have 4.2kw PV. 
 

Then make the call. 

Good. I just saw in your 1st post you mentioned CURRENT SYSTEM as PV 4kW.

I agree with the other post of getting the element down to 2kW but that is at the expense of longer run time to have the geyser more inverter friendly. My 1.5kW on average heats faster than the 3kW element on a 150L geyser. 

[Bobster.]

On 2024/04/14 at 10:34 PM, daniemare said:

I do not have any battery capacity left when my geyser turns on for morning heating

I heat water early in the morning. On a bad morning my battery will have 55% SOC when the heating starts, and about 43 when the run finishes. I have 10kWh of battery. Can you cut back on your overnight useage? That will give you more flexibility and better protection for the worst case IE no grid early in the morning and no/low PV.