Solar, Wind or Micro Hydro: Compare the Resources on Your Own Plot

A sunny roof, a windswept gate and a lively stream can all look promising. They do not tell you how much electricity a system would deliver, whether permission is achievable or how well production would match your household’s needs.

You do not need to choose equipment during your first walk around the plot. Your first job is to identify worthwhile options, document uncertainty and decide which professional assessment would answer the most useful question.

Start with the job you need electricity to do

Write a short brief before comparing technologies. Are you reducing daytime imports, charging tools in an outbuilding, supplying an off-grid cabin or protecting essential appliances? Include measured daily consumption, peak demand and the months when energy matters most.

A summer irrigation system and a winter household have very different requirements. Annual generation alone can hide this mismatch. Likewise, a grid-connected installation does not automatically provide power during an outage: confirm the intended backup arrangement separately.

Record the location of existing electrical supplies, possible cable routes and any distance between the resource and the load. Include access for installation and future servicing. These details belong in the comparison even when the natural resource looks excellent.

Make one shared site record

Sketch your boundary, buildings, trees, slopes, watercourses, neighbouring properties and candidate equipment positions. Give each position a simple label. Photograph it from safe ground and note the date, viewing direction and anything uncertain.

Mark missing information as “unknown”. Do not convert it into a favourable assumption. A sensible first shortlist may contain only one technology, with the others parked until better evidence appears.

Solar: assess the usable space and its shade

List each candidate roof or ground area separately. Record its approximate dimensions, direction, slope and nearby obstructions. Observe shade at different times and consider winter sun angles, leaf growth and neighbouring structures.

The European Commission’s PVGIS service can support an initial production estimate. Save the location, array size, orientation, slope and loss assumptions with the results. Review monthly output as well as the annual total.

Check how the chosen model handles local shading. The JRC’s documentation for PVGIS 5 explains that its calculated terrain horizon does not account for nearby houses and trees. A model therefore needs an appropriate site check; a tidy result is not proof that your proposed roof is unshaded.

Use our shade-mapping guide to organise observations. Keep resource suitability separate from structural suitability: a bright roof may still need reinforcement or a different mounting approach. See questions for an installer about a lightweight shed roof.

For your comparison sheet, request expected monthly electricity at a clearly stated measurement point, such as the inverter’s AC output. Ask which losses and shading effects are included, and which remain provisional.

Wind: investigate the air the rotor would meet

The useful wind resource is at the proposed rotor location and height. Buildings, trees and terrain affect airflow; a gusty corner can be turbulent rather than productive. A regional map is a screening tool, not a measurement of your exact installation position.

The US Department of Energy’s Small Wind Guidebook discusses hub-height conditions, obstacles and on-site measurement. It recommends at least a year of measurements to capture seasonal variation when undertaking a measurement campaign.

Annual output depends on the wind-speed distribution and the turbine’s power curve, not its rated wattage multiplied by every hour of the year. Ask what evidence supports the yield estimate and how turbulence, downtime and electrical losses are treated.

Prepare a wind-site log before requesting a quote. Include candidate positions and access constraints without erecting a mast yourself. Our roof-mounted versus pole-mounted wind guide provides related siting questions.

For the shortlist, write the unresolved question precisely: “Can a feasible mast position reach a useful resource here?” is more actionable than “Is this a windy area?”

Optional further reading: view the separate energy-information offer (affiliate link). We have not tested this product or verified its claims; it is not a substitute for a resource assessment.

Micro hydro: check head, usable flow and the seasons

For conventional head-based micro hydro, head is the vertical energy difference available to drive the turbine. Gross head describes the site’s elevation difference; net head allows for hydraulic losses. Flow is the volume of water passing each second.

The Department of Energy’s turbine overview explains why head and flow influence turbine selection. A long stream is not necessarily useful if the available fall and flow are inadequate. Free-flow kinetic turbines are a different technology and also need specialist assessment.

Record seasonal conditions from safe banks and collect any existing flow or survey records. Do not enter fast water, modify a channel or improvise a weir to obtain readings. Commission suitable measurements if the site merits investigation.

The whole stream’s flow is not necessarily available to your turbine. Ecological requirements, other water users and licence conditions may restrict diversion or require shutdown during low flows. Ask for a flow-duration assessment showing how often different usable flows are available.

A small continuous output can accumulate useful energy, but multiplying it by 365 days would assume uninterrupted water availability and operation. Dry periods, debris, maintenance and operating restrictions must appear in the annual estimate. The DOE’s historical Microhydropower Handbook covers the underlying head, flow and power principles; it is not current UK regulatory guidance.

Compare monthly energy at the same point

Ask each assessor for monthly estimates using a common boundary: for example, electricity reaching your AC distribution point. Record whether cable losses, conversion, battery storage and downtime are included. This avoids comparing one system’s gross output with another’s usable delivery.

Make a twelve-row worksheet, one row per month. Add household demand, each candidate’s expected generation, the portion likely to be used on site and the expected shortfall. Label modelled figures, measurements and assumptions distinctly.

Consider a purely hypothetical plot where demand is highest in December. A strong annual solar estimate does not answer the winter question. A hydro estimate based on a wet November visit cannot establish summer reliability. A wind estimate based on a distant weather station needs its location and height differences explained.

Monthly totals are still insufficient for off-grid reliability. Check short difficult periods and overlapping shortages. Our three-day reserve plan for essential appliances shows how to examine a low-generation spell without treating hoped-for production as guaranteed.

Check practical and permission constraints early

For each option, list mounting or civil works, cable routes, access, maintenance tasks and who will service it. Ask for itemised estimates that include the supporting works, controls and professional fees. A low equipment price alone is not a complete project comparison.

Confirm planning, land rights and electrical connection requirements for your actual location. For hydro in England, the Environment Agency’s guidance says most schemes need a water-resources abstraction or impounding licence, and other permissions may also apply. Environmental protection and other water users form part of the assessment.

Those rules are specific to England. Use the relevant authorities for Wales, Scotland, Northern Ireland or another country. Owning a stream bank does not establish that a proposed scheme is permitted. Get advice before paying for detailed construction plans.

For readers exploring broader energy ideas, the optional energy-information promotion (affiliate link) is separate from the surveys and permissions discussed here. It does not demonstrate that any technology will work on your land.

Choose the next assessment, not the biggest promise

Use a simple decision record rather than a numerical score that hides major obstacles. A missing permission route cannot be cancelled out by a good-looking generation estimate.

A hybrid system may improve the match between production and demand, but it also adds integration and servicing requirements. Ask whether the second resource fills a measured gap and whether that benefit justifies the extra work. Two uncertain resources do not automatically make one dependable supply.

Frequently asked questions

Is solar always the best starting point?

It is worth screening where suitable space exists, but the right first investment depends on your plot and purpose. Clear evidence should determine which option receives a detailed assessment.

Can a stream power my whole home?

Only a head-and-flow assessment, operating constraints and demand comparison can answer that. Even adequate daily energy does not necessarily meet short appliance power peaks without suitable supporting equipment.

How long should I observe the plot?

A first walk can identify questions immediately. It cannot establish year-round performance. Use seasonal records and appropriately designed professional measurements for investment decisions.

What should I send an installer?

Send your site sketch, dated photographs, energy-use brief, available records, candidate locations and a list of unknowns. Ask for a clearly scoped assessment with stated assumptions before requesting a final equipment specification.