TL;DR

PV system works, it contributes to lower electricity bills, it lowers greenouse gases production, it contributes to energy independency and shows the middle finger to the Hormuz strait and all involved. But it intruduces additional thinking & tinkering. Overall, our home runs on 90% low-carbon electricity (combined PV-grid).

(I’m aware it also contributes to issues related to rare materials extraction, but that’s not the topic of this post)

(I’m also aware I’m writing this from the privileged position. A (too big) amount of people can’t afford PV)

Some data

Setup

• PV: 12,7 kWp
• Inverter: 12kW
• Battery: 20 kWh
• Export limit: 1,5 kW
• Electricity is used for everything: heating, cooling, cooking, (and for several months now, driving).
• Individual home, 60yrs old, good insulation, a bunch of people and pets.
• No net metering, but monthly calculation. The grid operator buys excess electricity for about 1/2 of the import price.

Production/consumption

• Timeframe: 1. 7. 2025 – 1. 7. 2026
• Total solar production: ~10 600 kWh
• Total grid import: ~4300 kWh
• Total grid export: ~1600 kWh
• Total house consumption: ~13 300 kWh

Energy production and consumption by months

Legend:

• Yellow: consumed solar
• Cyan: consumed battery
• Blue: grid import
• Pink: battery charge
• Magenta: grid export

Or, summarized:

Biggest consumption (individual device): heatpump, 4300 kWh (interestingly, almost identical consumption as total yearly grid import).

Some balances:

Costs:

Total costs of electricity:

• 2024-2025 (without PV): 1900€
• 2025-2026 (with PV): 770€ (this also includes 3 months of e-driving, that would cost ~500€ in diesel).

That is 1130€ / less costs per year.

Pessimistic ROI prediction(driving excluded) would be approx 10 yrs.

If I add also reduced cost for driving (charging mostly with excess solar), then ROI will be 5 yrs.

Prices of electricity will probably rise, therefore ROI will be further decreased.

Cooling

Cooling is basically ‘free’. ACs consumed 100 kWh/month (Jun.), ran when was sunny and directly consumed PV electricity. I’m writing this because of all public debates, if AC should be used at all. I think ACs are the best case to use in combination with PV (if there is excess of solar energy).

Heating

Heating is most ‘problematic’ energy consumer. It consumes most electricity in Nov.-March, when the PV production is low and grid import is needed. Nevertheless, PV lowered our heatpump consumption approx. by half (in comparison with prev. year).

What would further contribute to electricity cost reduction:

• bigger export limit

Small amount of electricity that was exported to grid was used to lower electricity bills in summer months. 5 kW export limit would already be great – it would help to reduce bills also in autamn and spring months (when there is still enough PV production, but it is capped). But the grid is old and the operater will not upgrade it in next 10 years.

I’m out of ideas what else could I do to lower the energy costs. I already optimized the consumption and improved losses (insulation).

What is good:

• Partial energy independency (67% in total). Nevertheless, in case of emergency, we could be 100% independent of grid (UPS mode), but the house would probably be a bit chilly in winter.
• Family members became aware of the energy consumption – now they consider the weather, SoC of battery, etc. before turning on big consumers (washing, dishes etc.)

What is challenging:

• More thinking:
  
  • Before PV, I never spend a single thought about electricity. I turned it on and never asked myself if it makes sense.

  
  

• Additional learning:
  
  • I had to learn a bunch of new concepts related to PV (zero export, )
  • New Home Assistant integrations, entities, calculations, automations

  
  

• Dealing with new kind of issues:
  
  • Buggy ev-charger firmware in solar only mode required I had to adjust some parameters on inverter to smooth charging power (dealer and producer are slow with updates).
  • Grounding issues of the panels caused some main electricity meter trips and disconnects. It took a few days to figure it out.
  • Additional insurance costs for the equipment.
  • Complexity of the whole setup (There is absolutely no need to tinker with PV system if you don’t want to. But I have to. You know, some people just must know what all these knobs and parameters do.)

  
  

• New kind of background fears:
  
  • What if all this equipment fails? What if it caches fire? What if… (I know a lot of these fears are ungrounded. For example, my previous pellet stove had a much bigger chance to catch fire. It failed every few days, I had to constantly tinker with it. Every year, there are at least 10 chimney fires in my muncipality. But anyways, new junk, new fears, I can’t do much about it, I’m overthinker. Nobody taught us about these things. Our parents only knew how to chop wood and make a fire. )