Calculation Formula?

[Limpopoboy]

Hey Guys

I forgot to ask in my 1st post is their some diversification factors or formula's you apply in load calculations to things like fridges and or freezers or anything really with a thermostat in them that turn on and off. Even an AC I suppose. As when you add the watts for a fridge freezer for example I have put down xx watts x 24hrs is that correct?

Thanks in advance.

Regards 

Limpopoboy

[Chloe]

You could install an Efergy energy meter in your Db and monitor your usage that way. It would give a  good indication of peak loads and average usage.

[Limpopoboy]

7 minutes ago, Chloe said:

You could install an Efergy energy meter in your Db and monitor your usage that way. It would give a  good indication of peak loads and average usage.

Hi Thanks, but I mean before you install anything. I am talking about the load calculations for appliances etc.. to size batteries and panels

[Chloe]

Make sure your fridges/freezers are A++ because some older freezers can use up to 2kW. We recently replaced a front loader washing machine that used 2.5kWh with a top loader of 350w.

[Limpopoboy]

Hi Guys

 

After working out my usage based on appliances lights etc and some diversification on things like fridge freezers, I totalled 78kWh per 24 hours (some further diversification is possible but not that much as I can see) which seems huge. Its just the 2 of us but that's what it came to, does that seem a lot is my first question?

 

Pool, Cooking AC, Fridge Freezers, Washing machine and dishwasher all included

 

Based on the above how would you calculate battery requirements based on 48v battery system

 

Thanks in advance

 

Limpopoboy

[rectangularBuilding]

78 kWh seems about 10x too much for a residence excluding room heating or room cooling. Although I don't know what daily "pool" consumption is and do you mean swimming pool?

What is "cooking AC"? Cooking air conditioning?

Don't you have existing electricity bills?

My daily consumption is about 6 kWh per day but it's a one person house. A small fridge uses about 1 kWh per day. Peak power on all those appliances that cycle using thermostats has not much to do with daily consumption.

Edited March 6, 2021 by rectangularBuilding

[Achmat]

43 minutes ago, Limpopoboy said:

Hi Guys

 

After working out my usage based on appliances lights etc and some diversification on things like fridge freezers, I totalled 78kWh per 24 hours (some further diversification is possible but not that much as I can see) which seems huge. Its just the 2 of us but that's what it came to, does that seem a lot is my first question?

 

Pool, Cooking AC, Fridge Freezers, Washing machine and dishwasher all included

 

Based on the above how would you calculate battery requirements based on 48v battery system

 

Thanks in advance

 

Limpopoboy

That's a lot 

The only way is to look at an energy meter to monitor your house over a period of time. Simply adding the wattage and possible runtime of appliances is not going to get you an accurate estimate. 

I have 3 aircons, a pool pump and two pumps for my well point water system feeding my house and I'm using on average 45kWh per day with a mac of 60kwh if I run all 3 aircons for most of the day. 

I started with an efergy monitor to monitor my whole house before I decided on going solar. The next step was to try and bring the consumption down by cooking on gas and an evacuated solar tube geyser system. 

I repeat, don't use the rated power of appliances to try and determine and size a solar or battery system. 

 

Edit 

We a family of 4 and it includes a garden flat I'm renting out to a couple and their teenage daughter. 

Edited March 6, 2021 by Achmat

[Achmat]

24 minutes ago, rectangularBuilding said:

78 kWh seems about 10x too much for a residence excluding room heating or room cooling. Although I don't know what daily "pool" consumption is and do you mean swimming pool?

What is "cooking AC"? Cooking air conditioning?

Don't you have existing electricity bills?

My daily consumption is about 6 kWh per day but it's a one person house. A small fridge uses about 1 kWh per day. Peak power on all those appliances that cycle using thermostats has not much to do with daily consumption.

Agreed its too much. 

Daily pool would be the daily consumption of the pool pump and cooking AC would probably mean that he is using electricity to cook and not gas

[Achmat]

One more thing, am efergy is not installed so you are not tampering with anything. 

It's a clamp that goes around the incoming live wire from the electricity meter and it sends the data wirelessly to the receiving unit. 

You can monitor the whole house or attach the clamp to an individual circut breaker to monitor individual circuts. 

[JaseZA]

I'm assuming you don't have a monthly value for your usage from a bill or prepaid? A good ballpark would be averaging that per day. Initially when doing my calcs for our system I just took a photo of our prepaid meter every day for a couple of weeks in the morning and evening to get an idea. We're two and average 12-15kwh per day with a lot of AC usage but no pool.

[Limpopoboy]

14 hours ago, rectangularBuilding said:

78 kWh seems about 10x too much for a residence excluding room heating or room cooling. Although I don't know what daily "pool" consumption is and do you mean swimming pool?

What is "cooking AC"? Cooking air conditioning?

Don't you have existing electricity bills?

My daily consumption is about 6 kWh per day but it's a one person house. A small fridge uses about 1 kWh per day. Peak power on all those appliances that cycle using thermostats has not much to do with daily consumption.

@rectangularBuilding Pool means swimming pool pump on each day for 5 hrs ( estimated).  Cooking AC, comma missed out so Cooking, AC, No we have no electricity bills from Eskom as we are on a pay meter and consume about R900 per month currently without pool, and A/C working. I have no way of telling how many KW/H or units we have used only a Rand figure.

 

I have made some diversification as I said on things like fridges, etc.. what about seasonal things like, A/C , Fans only really running in the summer month hence not daily. What would you consider your peak daily load should or should not include then? I list everything we have and use. daily or not with some diversification on times. But still came up with that large figure something is not right somewhere.

[Limpopoboy]

14 hours ago, Achmat said:

That's a lot 

The only way is to look at an energy meter to monitor your house over a period of time. Simply adding the wattage and possible runtime of appliances is not going to get you an accurate estimate. 

I have 3 aircons, a pool pump and two pumps for my well point water system feeding my house and I'm using on average 45kWh per day with a mac of 60kwh if I run all 3 aircons for most of the day. 

I started with an efergy monitor to monitor my whole house before I decided on going solar. The next step was to try and bring the consumption down by cooking on gas and an evacuated solar tube geyser system. 

I repeat, don't use the rated power of appliances to try and determine and size a solar or battery system. 

 

Edit 

We a family of 4 and it includes a garden flat I'm renting out to a couple and their teenage daughter. 

@Achmat Thanks for the information. I am currently in a rental property with prepaid meter and no pool for example, (no Eskom bills to advise usage and usage will surely change once the house is built) and I am about to build our own house, hence the whole solar questions.

I simply followed the advice here and across the internet, to get my supposed 'peak load' which I admit I am still confused about as to what 'peak load' means as many things we do, we do not use daily,  but maybe every other day like a dish washer or washing machine or seasonally like fans and or Air Conditioning etc..

I was thinking about total solar off grid for the whole house but now thinking about cooking and hot water using LPG and the rest solar. I was a little concerned about putting all my eggs in a solar basket.

[Limpopoboy]

11 hours ago, JaseZA said:

I'm assuming you don't have a monthly value for your usage from a bill or prepaid? A good ballpark would be averaging that per day. Initially when doing my calcs for our system I just took a photo of our prepaid meter every day for a couple of weeks in the morning and evening to get an idea. We're two and average 12-15kwh per day with a lot of AC usage but no pool.

@JaseZA You assume correct. I can take a meter reading but what would that tell me? I use 10 or 30 units a day how does that relate to KW/h or watts or something usable in a calculation? Nothing on the meter tells me anything except a arbitrary figure reducing each day until we buy more electricity.

[Achmat]

23 minutes ago, Limpopoboy said:

@Achmat Thanks for the information. I am currently in a rental property with prepaid meter and no pool for example, (no Eskom bills to advise usage and usage will surely change once the house is built) and I am about to build our own house, hence the whole solar questions.

I simply followed the advice here and across the internet, to get my supposed 'peak load' which I admit I am still confused about as to what 'peak load' means as many things we do, we do not use daily,  but maybe every other day like a dish washer or washing machine or seasonally like fans and or Air Conditioning etc..

I was thinking about total solar off grid for the whole house but now thinking about cooking and hot water using LPG and the rest solar. I was a little concerned about putting all my eggs in a solar basket.

That does change your situation as you have nothing to work from. 

Peak load would be the point where you draw most power. This would determine the inverter size. You can do this by adding the wattage of all appliances that could be on at the same time. Fridges, freezers and aircons are difficult as it fluctuates. My 12000btu inverter aircon goes from 500w to 1.1kw depending on the room temperature. Dishwasher and tumble dryer also fluctuates depending on where in the cycle it is. This is from personal observation of my appliances. 

You could also use a killawat plug to measure individual appliances like your existing fridge. 

Pool pump is a constant draw so it's easy to calculate. Same for lights, geyser, kettle and microwave. 

Graph of my normal usage with the pool pump running for 3 hours from 12:00, 12000btu inverter aircon running from about 22:00 till 08:00 the next morning, geyser peaks at 06:00 and 17:00, 16kg top loader washing machine doing one load, one load with fish washer, domestic ironing for one hour, hairdryer for 15 minutes, chest freezer, fridge, well point pump as I am off grid with my water so it comes on every time a tap is opened. 

Ended up using 40kWh for this day. 

[Limpopoboy]

@Brani We have a Tellumatt meter and all I have is a digital readout of 4 figures ie. Its currently currently reading 204.5 and we use on average 15 units a day. Whatever that will be? You say KW/h though correct?

[Achmat]

2 minutes ago, Limpopoboy said:

@Brani We have a Tellumatt meter and all I have is a digital readout of 4 figures ie. Its currently currently reading 204.5 and we use on average 15 units a day. Whatever that will be? You say KW/h though correct?

Yes. Unit = kWh 

[Limpopoboy]

@achmat thanks

[Limpopoboy]

36 minutes ago, Brani said:

The units that your meter is displaying is KwH 

 

12 minutes ago, Achmat said:

That does change your situation as you have nothing to work from. 

Peak load would be the point where you draw most power. This would determine the inverter size. You can do this by adding the wattage of all appliances that could be on at the same time. Fridges, freezers and aircons are difficult as it fluctuates. My 12000btu inverter aircon goes from 500w to 1.1kw depending on the room temperature. Dishwasher and tumble dryer also fluctuates depending on where in the cycle it is. This is from personal observation of my appliances. 

You could also use a killawat plug to measure individual appliances like your existing fridge. 

Pool pump is a constant draw so it's easy to calculate. Same for lights, geyser, kettle and microwave. 

Graph of my normal usage with the pool pump running for 3 hours from 12:00, 12000btu inverter aircon running from about 22:00 till 08:00 the next morning, geyser peaks at 06:00 and 17:00, 16kg top loader washing machine doing one load, one load with fish washer, domestic ironing for one hour, hairdryer for 15 minutes, chest freezer, fridge, well point pump as I am off grid with my water so it comes on every time a tap is opened. 

Ended up using 40kWh for this day. 

I understand that the peakload is where you draw most power. But this is seasonal isnt it with big draws like pool pump, fans and air cons not working in the winter. How would you account or should you account for that in the calcs?

[Bobster.]

On 2021/02/19 at 5:42 PM, Chloe said:

Make sure your fridges/freezers are A++ because some older freezers can use up to 2kW. We recently replaced a front loader washing machine that used 2.5kWh with a top loader of 350w.

I am constantly amazed by the appliances that are available these days. New fridges, dishwashers even tumble driers are so much more efficient now due to smarter electronics and better motors.
 

[rectangularBuilding]

Just a reminder, the geyser will (or at least should) not involve the inverter or the batteries no matter what kind it is.

For the air conditioning it would be very helpful to have an idea how much is consumed during (future) solar production and how much would be on the (future) batteries.

And preaching again: You can start small with the solar modules and the batteries and add more as you learn.

But your current 15 kWh daily are an OK baseline even if you're currently in a flat. If we only knew how much of that is AC. 

 

 

Edited March 7, 2021 by rectangularBuilding

[Chloe]

1 hour ago, Bobster said:

I am constantly amazed by the appliances that are available these days. New fridges, dishwashers even tumble driers are so much more efficient now due to smarter electronics and better motors.
 

Very true, I have gone from an average of 50 units a day down to 10 units with my geyser permanently on and a gas stove but 3 times the fridges.

[Achmat]

56 minutes ago, rectangularBuilding said:

Just a reminder, the geyser will (or at least should) not involve the inverter or the batteries no matter what kind it is.

 

 

Why? If your system is big enough you can have it on the inverter and batteries. 

I have my 4kw geyser running from my 8kw sunsynk inverter and pylontech batteries without any issues. 

Edited March 7, 2021 by Achmat
Autocorrect issues

[rectangularBuilding]

9 minutes ago, Achmat said:

Why? If your system is big enough you can have it on the inverter and batteries. 

I have my 4kw geyser running from my 8kw sunsynk inverter and pylontech verwoes without any issues. 

OK sounds good. I was thinking too much about my 4 kW sustained inverter.

[Limpopoboy]

2 hours ago, rectangularBuilding said:

Just a reminder, the geyser will (or at least should) not involve the inverter or the batteries no matter what kind it is.

For the air conditioning it would be very helpful to have an idea how much is consumed during (future) solar production and how much would be on the (future) batteries.

And preaching again: You can start small with the solar modules and the batteries and add more as you learn.

But your current 15 kWh daily are an OK baseline even if you're currently in a flat. If we only knew how much of that is AC. 

 

 

@rectangularBuilding   0 of that is A/C currently. We turn the geyser on and off as we need to, only have gas hob and electrical over currently for cook plus a few appliance like halogen cooker and air fryer. In addition in the new property would be pool pump and 1 x A/C probably 

[Limpopoboy]

23 minutes ago, Brani said:

Not always the case. You will pay more per kW the smaller the system is, comparing apples to apples.

Further, Lithium Ion batteries are better value for money than deep cycle batteries. Many people who start small regret buying those and having to replace them in 2-3 years.

 

Of course if the budget does not allow, one has to start small.

My advice would be first reduce consumption as much as possible, then go as big as you can on your own solar production and batteries. 

@BraniI agree about starting small but I am in a little bit of a predicament with that option.. But My concern is do I go all solar while I haveing the mess of house building or HW and cooking LPG with the rest solar during construction? I don't really want to not install gas, then find once the house is built I perhaps should have installed gas.