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How much energy does your inverter/BMS use?
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Magnitio
Posts: 1,207 Forumite

I guess this is a question more aimed at hybrid inverters. Given the poor weather for generation at the moment, the amount of energy consumed by the inverter and BMS to keep them operating becomes more apparent. It is even more noticeable when there is no cheap-rate electricity to charge the battery (Agile rates for me at 35p 24/7 mean no point in charging). From what I can deduce, the Huawei inverter and BMS consume on average 40-60W, though it's difficult to isolate the electrical consumption from the inverter conversion losses. This means any generation of less than 1kWh per day results in negative nett output. Interested to hear what others experience with their setup.
6.4kWp (16 * 400Wp REC Alpha) facing ESE + 5kW Huawei inverter + 10kWh Huawei battery. Buckinghamshire.
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According to its own stats, our invertor put 290 into the battery in November and dispensed 226 back out. This covers pretty much all our usage 19 hours a day bringing our base consumption down from 300-400w to about 50-100w (so about 250-350w) for most of those hours but obviously also covering some larger loads, total output about 7-8kwh per dayI think....0
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Deleted_User said:This is something that I'd been looking into a couple of weeks ago.
Essentially, the bigger the inverter the more energy it will use (although some are more efficient than others).
Specs will often say things like "80% efficient" or "85% efficient" - but that's under optimal usage.
I have solar generators so I have a variety of inverter sizes to choose from. But using the biggest, 2.2kw as an example.
The inverter without fan is 22w, with fan 32w.
If you're running a 2kw air frier an additional 22w is trivial.
However, if all you're running is a fridge for 24 hours (consuming a total of 700wh) you need to add the overhead of 528wh for the inverter. If your house is warm in summer and the fan is on all the time that would increase to 792wh. So the inverter would use more energy than the appliance!
If you have a home backup/grid connected system I'm not sure how it works. But it's possible in theory for your inverter to use almost all of your winter solar - your battery could well go flat whilst the inverter is idling.
In my case the solution is to be selective about what runs off solar in order to get the most out of it. We tend to save up solar in the battery and use it for high draw appliances - not high enough to put the fan on, but high enough (and short duration) so that the 22w inverter isn't eating up valuable energy.
I don't know if that's possible in a grid tied system.HiThe issue the OP is raising for discussion is predicated on current 'poor weather' which is having an effect on the ability to run the installation from solar ...It doesn't matter whether you have the portable solution you have or not, you have the same basic issue ... lack of sunlight to charge the batteries, however, what you're also missing is that in order to make your portable solution(s) affordable, compact & light enough to actually be portable a number of compromises were necessary .... for example, your fans will be necessary to offset internal space & the substantial passive heat-sinks that many inverter systems have ....Again, you seem to be valuing watts derived from solar as if they have a purchased value, and looking into the relative efficiencies based on this, however, where most would be concerned if the overhead of operating an inverter/BMS setup was significant, they simply see this as a necessary overhead without which they wouldn't have a battery system that actually works, think of it as the overhead of operating the control circuits of a freezer even when the compressor isn't running - without the controls circuit it either wouldn't do anything, or be very inefficient.Most looking at this technology in the UK will have a grid connected system and simply be looking at reducing their electricity imports ... most will likely have solar, some may only be looking at various forms of arbitrage, however, the important consideration is that they're unlikely to want to run around manually turning their systems on & off whenever they deem it necessary to save a few watt-hours of energy per day, especially so if the cost of those watts is either effectively zero (with PV) or totally offset by the savings available through leveraging TOU tariff differentials .... because physics denotes that something isn't strictly 100% efficient, it doesn't mean that the marginal cost of operation isn't greater than 100% and that's the difference in perception that needs to be considered.HTH - Z
"We are what we repeatedly do, excellence then is not an act, but a habit. " ...... Aristotle3 -
HiThere you go on efficiency again .... efficiency is either relative (ie against other systems), relevant (if there are significant costs involved) or simply irrelevant (because of necessity or convenience) ....Try this thought experiment ... it's been dull today therefore the PV generation has been low, so low that half of what's been generated has and will be consumed by the inverter if it's switched on ... tomorrow will be different, the forecast is for bright skies so the PV should do well .... although the electricity generated both days effectively has zero marginal cost, the proportion of stored energy available today which is available to power devices is considerably impacted by the baseload overhead of the inverter itself .... should I be concerned with theoretical physical efficiencies, switch the inverter off and sit in the dark tonight and claim that it's all in the name of utilising what's there efficiently, in the knowledge that (due to a better generation:overhead ratio) overall efficiencies will be better tomorrow (ie a spreadsheet exercise)... or ... use the energy collected today to sit in the light tonight, thus using both the capital invested & the system marginal cost efficiencies to their best advantage, which equates to improved comfort at a massive marginal cost of ... <wait for it>... £zero ...Remember, you are not off-grid (yet), you are on grid with a variety of portable back-up batteries ... above that your levels of inefficiencies as described are heavily impacted by the ratio of the baseline energy consumption of your system(s) against the ability for your relatively small PV setup to charge the batteries you have within the confines set by the low maximum charge power rating of each individual unit ... if you were able to double the installed PV, the ability to raise the SOC on a daily basis would benefit, therefore the energy overhead of maintaining the batteries & cooling the system as a proportion of total energy concerned would fall, this is the inefficiency that you see & are describing, as such it's something you could improve if you wanted to ....As I see it, you continue to fail to recognise that when considering efficiencies, it's the capital employed in your setup that has been inefficiently applied .... for the storage capacity you have, far too much has been apportioned to the integrated energy transition elements (inverters & charge controllers) to the detriment of the energy source itself (PV panels) and the energy storage element (batteries) ... don't get me wrong, I like the idea of portable backup battery systems for emergencies & mobile applications, however, they're not really designed to operate as the main source of a household's energy provision in an off grid setting which raises a number of concerns revolving around long term use, including potential scaleability & related costs - all things that a well specified domestic scale inverter/PV/battery setup shouldn't cause concern over, whether grid tied or off grid ...Anyway, food for thought ....HTH - Z"We are what we repeatedly do, excellence then is not an act, but a habit. " ...... Aristotle1
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I was just interested in how much other installations consume. Not the efficiency of the DC/AC/DC conversion, but the continuous power usage when the inverter and BMS are on. It's not information that was available for the kit I have installed, but can have a significant impact at this time of year. scarter actually provided an answer "inverter without fan is 22w, with fan 32w", though her setup is not necessarily relevant to most people on here as far as I can tell.6.4kWp (16 * 400Wp REC Alpha) facing ESE + 5kW Huawei inverter + 10kWh Huawei battery. Buckinghamshire.0
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Magnitio said:I was just interested in how much other installations consume. Not the efficiency of the DC/AC/DC conversion, but the continuous power usage when the inverter and BMS are on. It's not information that was available for the kit I have installed, but can have a significant impact at this time of year. scarter actually provided an answer "inverter without fan is 22w, with fan 32w", though her setup is not necessarily relevant to most people on here as far as I can tell.4kWp (black/black) - Sofar Inverter - SSE(141°) - 30° pitch - North LincsInstalled June 2013 - PVGIS = 3400Sofar ME3000SP Inverter & 5 x Pylontech US2000B Plus & 3 x US2000C Batteries - 19.2kWh0
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Deleted_User said:Magnitio said:I was just interested in how much other installations consume. Not the efficiency of the DC/AC/DC conversion, but the continuous power usage when the inverter and BMS are on. It's not information that was available for the kit I have installed, but can have a significant impact at this time of year. scarter actually provided an answer "inverter without fan is 22w, with fan 32w", though her setup is not necessarily relevant to most people on here as far as I can tell.
Essentially, from what I was able to discover via Google, the bigger the inverter the more energy it costs to run.
The reason I expanded further is that most systems (grid tied and generators) are advertised in terms of 'percentage efficiency'. A lot of people seem to think that this is a constant - but it's not. (EDIT: FWIW, mine was advertised at 88% efficient - but that is entirely subjective because without knowing the load under which it achieved 88% efficiency it's meaningless).
The running cost of the inverter is constant. So obviously there's a big difference in efficiency between running the inverter for 10 minutes to run appliances that consume 2.2kw and running the inverter constantly to power a 10w lightbulb.
Therefore, in winter when solar is scarce and people are trying to be efficient in their energy usage inverter efficiency is going to plummet. In summer when solar is abundant and people are running more appliances, efficiency of the inverter will go up. So the reverse of what you need!!
I'm guessing that the app only measures the inverter round trip loss & the other 10% is the battery round trip loss.4kWp (black/black) - Sofar Inverter - SSE(141°) - 30° pitch - North LincsInstalled June 2013 - PVGIS = 3400Sofar ME3000SP Inverter & 5 x Pylontech US2000B Plus & 3 x US2000C Batteries - 19.2kWh1 -
Deleted_User said:1961Nick said:Magnitio said:I was just interested in how much other installations consume. Not the efficiency of the DC/AC/DC conversion, but the continuous power usage when the inverter and BMS are on. It's not information that was available for the kit I have installed, but can have a significant impact at this time of year. scarter actually provided an answer "inverter without fan is 22w, with fan 32w", though her setup is not necessarily relevant to most people on here as far as I can tell.
Say for example you generate 300wh of solar energy on a winter's day - it's stored in your battery.
A lot of people spend a great deal of money adding more solar panels in an attempt to generate more solar in winter. But if you have a big inverter costing perhaps 40w to run - over 24 hours that's 960w!! Nearly 1kw a day.
So rather than adding more solar panels to gain 1kwh of solar in winter, you could achieve the same result by using your inverter more efficiently.
So for example, use the mains to run your fridge, lights, tv etc and ONLY switch the inverter on to run a high power appliance - a 2kw air fryer running for half an hour will consume 1kw of solar energy with only a 20w getting used to run the inverter. You effectively free up 1kw of solar to power your appliances without having to spend a penny adding more solar panels.HiWhat you seem to be missing is that 1W used in a 11W light has the same marginal value as 1W consumed in a 2kW air fryer, so where's the value in micro-managing demand against supply when the grid is available ... it's only when source is constrained through power outage or lack of PV generation that it makes any difference, but then again most with grid connected systems wouldn't have your concerns because their systems are designed to do automatically what you're attempting to do manually and they're doing so with panel arrays which are likely considerably larger than your own setup ...Okay, so to efficiencies .... many grid & not grid connected systems (incl mobile homes etc) utilise Victron inverters, so let's take a quick look at a spec to see what's published ... (Link - Multiplus-II GX) ... looking at their 3kW variant we can see that the following self consumption conditions apply ...- Zero load power - 11 W (normal power consumption excluding load/inverter efficiencies)
- Zero load power in AES mode - 7W (automatic energy saving mode power consumption when AC power is not actually needed, but still immediately available when called on)
- Zero load power in Search mode - 2W (power consumption in a sort of standby mode where parameters can be set to enter this 'monitoring/sleep' mode if the load is <parameter threshold and wake the system up if load>another threshold, but there will be a delay)
How you configure these thresholds depends on the situation required, but they are used in off grid setups such as caravans, mobile homes, remote log cabins, boats etc all over the world ... most likely too in grid connected systems when there's a power outage ...This is what one of the larger systems is capable of .... I suppose the closest AUTOMATIC setup to your manual switching proposal would be the search mode as you're obviously not concerned by the time to get to the Bluetti system to switch it on ... so your direct comparison for your own circumstances wouldn't be a constant 40W resulting in 960Wh/day, it's be closer to 48Wh/day .... moreover, the 22W/32W you raise as the background self-consumption of your larger units (vs Victron 11W) is just for one .... and you have already stated you have 5(?) of them in various sizes!The systems you have are ideal if you need them to be portable or as an emergency backup ... however, their limitations mean that they are not ideally suited to scaleability without duplication of expenditure ... your comparison of your ability to run your portable inverters in a more efficient way by switching them off comes at the cost of having invested in multiple small inverter circuits which are limited in scope by their maximum charge rates & voltages, and therefore the maximum number of solar panels ..... if, in the future, you were to find you need more solar energy provision, you'll need more panels and more inverters and more batteries, effectively at a linear scaling cost to what you already have, whereas someone with the example Victron unit may only need more panels resulting in a marginal component based investment, which for a DIY off grid setup could be in the region of ~£400/kWp ...HTH - Z"We are what we repeatedly do, excellence then is not an act, but a habit. " ...... Aristotle0
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