Quotes & pricing
Why quotations differ, how to compare them properly, what should be included and how to tell whether two prices actually represent comparable systems.
Solar questions answered
Confused about solar? Start with the question you actually need answered.
Solar homeowners are often given completely different advice about panel numbers, batteries, inverter sizes, tariffs, savings and what their property really needs.
This library is being built around the real questions homeowners ask when they are trying to make sense of it all.
Real homeowner questions
Plain-English answers
Scottish solar focus
Start here
The biggest problem: every solar quote says something different.
One company recommends 10 panels. Another says 18. One wants to fit one battery. Another recommends two. The inverter sizes are different and the prices may be thousands of pounds apart.
That does not necessarily mean somebody is wrong.
It does mean you need to understand what each company is actually proposing before comparing the price.
Questions we are answering
The Tom Solar Q&A library.
Solar panels & roofs
Panel numbers, roof direction, shading, usable roof space, north-facing panels, panel wattage and why two companies may produce completely different roof layouts.
More answers coming.
Battery storage
How much storage a household really needs, whether two batteries make sense, usable versus nominal capacity and how tariffs affect battery sizing.
Inverters & grid connections
Inverter sizing, clipping, hybrid systems, MPPTs, G98, G99, export limits and why grid approval can influence the final design.
More answers coming.
EVs & heat pumps
How electrified heating and transport change household demand, solar sizing, battery requirements and the opportunity to use surplus generation.
More answers coming.
Installers & warranties
What to ask before signing, workmanship protection, equipment warranties, certification, installer claims and what should appear in a properly specified proposal.
More answers coming.
Savings & payback
Generation estimates, electricity-price assumptions, export tariffs, self-consumption, payback calculations and why financial projections from two companies can look completely different.
More answers coming.
Surveys & system design
What should actually be checked before deciding how many panels, what size battery and which inverter a property should have.
A useful rule
The equipment should be the answer — not the starting point.
Solar discussions often begin with equipment:
✓ How many panels?
✓ Which battery?
✓ What size inverter?
✓ Which manufacturer?
But those answers depend on questions that should come first.
✓ How much electricity does the household use?
✓ When is that electricity used?
✓ How much usable roof space is actually available?
✓ What directions do the roof sections face?
✓ Is there significant shading?
✓ Is there an EV?
✓ Is there a heat pump?
✓ What electrical and grid constraints exist?
Once those facts are understood, the equipment choices become much easier to explain.
Real evidence
Answers are stronger when we can show why a real system was designed that way.
Tom Solar also publishes anonymised case studies using genuine system-design information.
One Central Scotland example involved a four-bedroom home using approximately 8,725 kWh of electricity a year, with an air-source heat pump, electric hot water and an EV.
In that situation, a twenty-panel array, substantial battery storage and a larger inverter had a very different justification from the same equipment being proposed for a low-consumption household.
Common questions
Some of the homeowner questions this library will tackle next.
How many solar panels do I actually need?
Why maximum roof capacity and sensible system size are not always the same thing.
What size solar battery do I need?
How electricity demand, solar generation, tariffs and household behaviour affect storage requirements.
Do I really need two batteries?
When additional storage can be justified and when it may simply leave expensive capacity underused.
Is a bigger solar inverter better?
Why inverter size should be considered alongside array capacity, strings, MPPTs, batteries and grid limits.
Are north-facing solar panels worth installing?
Why orientation matters but does not always provide a simple yes-or-no answer.
What is the difference between G98 and G99?
Why inverter output and grid-connection requirements can influence domestic solar design.
Is solar worth it with a heat pump?
How seasonal generation and high winter electricity demand change the calculation.
Is solar worth it if I have an electric vehicle?
How EV charging can create useful flexible demand for daytime solar generation.
Why are solar payback figures so different?
The assumptions behind import prices, export tariffs, self-consumption and electricity-price inflation.
Have a question?
If it is confusing you, there is a good chance somebody else is asking it too.
The Tom Solar question library will continue to grow around the problems homeowners actually encounter while considering solar, batteries and wider home electrification.
If your own quotations leave you unsure what system your property genuinely needs, start with an independent assessment rather than trying to guess which sales proposal is right.