I’m putting a new off grid solar system into my home in Spain. I’ve owned the home since October and it came as a small surprise to learn it needed changing immediately. As such, I’m on a step learning curve.
I have estimated my optimal needs to be around 30kw a day (although current usage is about 20kw), with between 5 and 10 hours of usable solar radiation a day (on the worst day in the last 15 years this dropped to 2 hours).
I have 3 quotes, and I would welcome any insight on how best to evaluate their merits.
Hi
I’m an off-grid system designer in Australia and first it seems all of the systems are well undersized for your situation, in particular on the solar side. Quality solar panels are cheap compared to batteries so it is regular practice to oversize the solar array to account for days of bad weather and reduce generator runtime. (do you have very limited roof space?)
It’s hard to follow the quotes you posted but I’m guessing the 3 three columns are the three quotes. The first (left) is way off and specifies a 24V inverter/battery which is crazy for a system of this size. The second (middle) is better at 48V lithium battery but undersize on the battery, although being a lithium BYD battery it should be modular so it can be increased in size later. (The BYD B-Box Pro would be a much better choice for off-grid)
The third looks to be sized correctly on the battery ( I can’t read spanish well) but undersize on the solar. All three specify Victron Quattro inverters and controllers which is great quality gear.
Finally I would be looking at reducing your energy consumption as much as possible (rather than increasing) and using the most efficient appliances available,
One more question. Did any of the solar companies provide you with a ‘load table’? A load table lists all of the appliances and estimates daily energy consumption, maximum demand and time of use.
Yes, you are right that there are 3 quotes with one column each (I could only attach one photo as a newcomer to the forum). Sorry about the Spanish, I should have thought about that, but you did great in translating.
The battery in the middle quote i think is a gel battery. In the right quote in understand that it is for self managing lead acid battery (brand is called black bull) . My concern on the middle quote is the size of the generator and with the right quote that I will need to replace the batteries in 5 years (whereas gel should last 10 years?). Am I right?
I did my own assessment on consumption and I came up with the following. The property is 4 bed, 3 bath with a pool.
I don’t see any generator listed in the second (middle) quote? You would need a minimum 10kVA diesel generator for your installation based on the load table provided.
The second quote does specify the BYD lithium battery (not gel) and I just noticed that it listed a quantity of 2 10kWh batteries which is not bad (ignore my previous comment). The BYD B-box lithium battery system is a good choice as it is very efficient and can be charged rapidly. Many off-grid systems are now using lithium systems like this due to the many advantages.
You are right! Apologies, I was getting my quotes mixed up. So it would seem that if the middle quote had a back up generator of over 10kw, or the right quote had better batteries, I should be in a reasonable position?
Hi guys, I wanted to say a massive thank you for your support. We spent EUR30,000 on the system and 1 week in and so far so good. We have a 14kw generator, 24 lead acid batteries and 18 solar panels. We had a bad weather day this week and even that didn’t seem to dent the system and what we are producing. Thank you all for your help and guidance.
