ᐅ New Build Photovoltaic System for Semi-Detached House – Quote Comparison

Hello everyone,

I am about to build a semi-detached house (11.50 x 10 m) with a 45-degree pitched roof, no dormers, oriented north-south (meaning each roof half faces west and east respectively).
I have received three quotes for photovoltaic systems, with capacities of 10.8 kWp, 14.0 kWp, and 18.0 kWp, and to be honest, I’m not sure what I actually need or what would be sufficient.
Since my budget is limited, I don’t want to oversize the system unnecessarily.
All three systems include a battery storage unit, with the 18.0 kW option specifying a usable battery capacity of 9.60 kWh.
The household consists of one person plus a small business, and there is a heat pump with underfloor heating installed.

Can someone advise me on what size system I really need and what would be enough? When I ask the photovoltaic companies, of course, each one just recommends what they want to sell.

Best regards,
Flo

As additional information, I currently live in a 105m² (1,130 sq ft) rental apartment and have an energy consumption of about 4,000 kWh (on average over the last 3 years). Now, I’m unsure how much more I will need for the heat pump.

What kind of business is it? Operating 24/7 or just nine to five? What is the electricity demand?
If it’s only during the day, I would drop the idea of a battery storage system. Or if the energy demand is so high that there would be nothing left for the battery.

In general, my opinion is all or nothing. So either you have the budget for a full roof installation (with or without storage, which is great), or if not, it’s better to wait.

By the way, you’ll get very good advice at the photovoltaic “store,” practically “next door.” 😉

PS: What do the quotes say per kWp? (without storage)

nullhorn schrieb:

Who can tell me what I actually need and what’s enough? When I ask the different photovoltaic system companies, of course, each one only tells me what they want to sell.

Check online for the potential energy yields you can generate. Then consider whether a battery storage system really makes sense (I would assume no) and how much you can reliably draw from the storage, especially in winter.

Plot of land: the larger, the better and more cost-effective.

By the way, we don’t know prices or quality. Otherwise, try asking in places where photovoltaic systems are discussed. That’s where the real experts are. I just mustn’t mention the name, or I’ll get banned again 🙄

KingJulien schrieb:

What kind of business? 24/7 or nine to five? What is the power demand?
If it’s only during the day, I would discard the idea of a storage system.

The business is more like nine to five... I print textiles, and the machines run 7 days a week.
I can’t say how much of the 4,000 kW annual consumption is from the business.

So far, I have assumed that installing a storage system is STANDARD these days,
because in the past it simply wasn’t possible, and now the option of storage is technically and economically feasible and therefore used or even required.

nullhorn schrieb:

Until now, I assumed that installing an energy storage system is STANDARD nowadays, because it simply wasn’t possible before, and today the option for storage can and should be used economically (price-wise).

No, energy storage is still not standard, as it is often overpriced. It only really makes sense when subsidized. Calculate what the storage system actually costs and the value of your self-generated electricity. Self-generated electricity is not free—you need the system, the storage unit, accounting for storage losses, taxes on self-consumption, and so on.

nullhorn schrieb:

I can’t say how much of the 4,000 kWh annual consumption is commercial use.

If the consumption includes both residential and commercial use, the total is actually quite low. As a single person working from home with a waterbed, I almost reach that level myself.